Hip Surgery: A Practical Guide [1 ed.] 9789811593307, 9789811593314

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Changqing Zhang Editor

Hip Surgery A Practical Guide

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Hip Surgery

Changqing Zhang Editor

Hip Surgery A Practical Guide

Editor Changqing Zhang Department of Orthopaedic Surgery Shanghai Jiao Tong University Shanghai China

ISBN 978-981-15-9330-7    ISBN 978-981-15-9331-4 (eBook) https://doi.org/10.1007/978-981-15-9331-4 The printed edition is not for sale in Mainland of China. Customers from Mainland of China please order the print book from Shanghai Scientific & Technical Publishers. © Springer Nature Singapore Pte Ltd. and Shanghai Scientific and Technical Publishers 2021 This work is subject to copyright. All rights are reserved by the Publisher, whether the whole or part of the material is concerned, specifically the rights of translation, reprinting, reuse of illustrations, recitation, broadcasting, reproduction on microfilms or in any other physical way, and transmission or information storage and retrieval, electronic adaptation, computer software, or by similar or dissimilar methodology now known or hereafter developed. The use of general descriptive names, registered names, trademarks, service marks, etc. in this publication does not imply, even in the absence of a specific statement, that such names are exempt from the relevant protective laws and regulations and therefore free for general use. The publisher, the authors, and the editors are safe to assume that the advice and information in this book are believed to be true and accurate at the date of publication. Neither the publisher nor the authors or the editors give a warranty, expressed or implied, with respect to the material contained herein or for any errors or omissions that may have been made. The publisher remains neutral with regard to jurisdictional claims in published maps and institutional affiliations. This Springer imprint is published by the registered company Springer Nature Singapore Pte Ltd. The registered company address is: 152 Beach Road, #21-01/04 Gateway East, Singapore 189721, Singapore

Preface

Before the description of the surgery of the hip, I would like to detail some experience and ponderation during the diagnosis and treatment of osteonecrosis of the femoral head. Back in 1999, it occurred to me that whether it can be possible to broaden the application of microsurgery to the treatment against both common and rare diseases? Once a breakthrough happens in clinic, it would not only promote the development of associated disciplines, but also benefit a significant number of afflicted patients. Based on this careful deliberation, I tended to focus on the effective treatment of osteonecrosis of the femoral head. Nowadays, artificial joint technology has been significantly developed; hence, it is obviously necessary for young and most middle-aged people to preserve their hip joints for the functional recovery towards normal stage based on the clinic demand and efficacy. The free vascularized fibular grafting technique invented by our predecessors Chen Zhongwei, Yu Zhongjia, Zeng Bingfang, and other orthopedic pioneers had been applied in the restoration of various bone tissues, yet exclusive of the reestablishment of the femoral head. This strategy was implemented by American Dr. Urbannic to treat osteonecrosis of the femoral head and achieved remarkable efficacy in practice. However, it required complicated operative techniques plus the collaboration of two groups of specialized doctors. Therefore, based on this discovery, we embarked on long endless clinical exploration. After the persistent inheritance and practice, we significantly shortened the conventional minimal fibular extraction time from 40 minutes to 10–15 minutes; the novel anterior medial hip operative approach was also devised by us to expose blood vessels and clean femoral head necrosis more completely, realizing the intraoperative possibility of fibular extraction easily. One or two hours by one single group of orthopedic doctors were enough to accomplish the entire operation procedures. With the progress of both diagnosis and treatment of femoral head osteonecrosis, patients suffering from a variety of difficult diseases were followed; one of them was the nonunion of femoral neck fracture. In terms of the nonunion of femoral neck, we established the modified fibular grafting technique with internal fixation. Osteotomy, orthomorphia, and other orthopedic techniques were also performed to treat various femoral head diseases such as femoral head deformity and teenage osteoarthritis, which enlarged the scope of surgical operation effectively. The development of clinic technology was associated with the increased demands of patients. The research about the diagnosis and treatment of femoral head osteonecrosis in recent years enabled me to feel intently that all kinds of diseases were not separated. If patients had felt pain in hip joint, latent possibilities emerged as hip joint disorder, or waist diseases, or even traumatic pain. The greatest benefits could be acquired by patients only after systematic clinic diagnosis and treatment. Meanwhile, we orthopedic doctors should recognize clearly that our objective was to provide a complete and systematic diagnostic and treatment strategy for patients. The reason our book was named as Surgery of the Hip rather than “Surgery of the hip joint” was exactly led by above consideration. We hoped to help our readers grasp systematically what kind of trauma would occur in this hip anatomic area. What kind of disease it would be? Why was there pain and discomfort? We aimed at helping our readers to acquire the relevant surgical techniques from the book, and expected orthopedic specialists to understand

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Preface

the connections between topographic anatomy and the pathophysiology of hip diseases, so as to comprehend the overall diagnosis and treatment of such diseases completely and systematically. Shanghai, China January 2018

Changqing Zhang

Editor’s List

• Editor in chief Changqing Zhang Shanghai Jiao Tong University Affiliated Sixth People’s Hospital, Shanghai, China • Editors Bing Hu Department of Ultrasound in Medicine, Shanghai Jiao Tong University Affliated Sixth People’s Hospital, Shanghai, China Zongyuan Cai Department of Orthopedic Surgery, Shanghai Jiao Tong University Affiliated Sixth People’s Hospital, Shanghai 200233, China Bochang Chen Shanghai Jiao Tong University Affiliated Sixth People’s Hospital, Shanghai, China Jie Chen Shanghai Jiao Tong University Affiliated Sixth People’s Hospital, Shanghai, China Shengbao Chen Shanghai Jiaotong University Affiliated Sixth People’s Hospital, Shanghai, China Shengming Dai Department of Orthopedic SurgeryShanghai Jiao Tong University Affiliated Sixth People’s HospitalShanghai 200233, China Dajiang Du Shanghai Jiao Tong University Affiliated Sixth People’s Hospital, Shanghai, China Bochang Chen Department of Orthopedics, Shanghai Jiao Tong University Affiliated Sixth People’s Hospital, Shanghai, China Youshui Gao Department of Orthopedics, Shanghai Jiao Tong University Affiliated Sixth People’s Hospital, Shanghai, China Junjie Guan Department of Orthopedics, Shanghai Jiao Tong University Affiliated Sixth People’s Hospital, Shanghai, China PeiJun Xu Shanghai Jiao Tong University Affiliated Sixth People’s Hospital, Shanghai, China Hai Hu Department of Orthopedic Surgery, Shanghai Jiao Tong University Affiliated Sixth People’s Hospital, Shanghai 200233, China

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Yigang Huang Department of Orthopaedic Surgery, Shanghai Jiao Tong University Affiliated Sixth People’s Hospital, Shanghai, China Weitao Jia Department of Orthopedics, Shanghai Jiao Tong University Affiliated Sixth People’s Hospital, Shanghai, China Dongxu Jin Department of Orthopedics, Shanghai Jiao Tong University Affiliated Sixth People’s Hospital, Shanghai, China Guangyi Li Department of Orthopedic Surgery, Shanghai Jiao Tong University Affiliated Sixth People’s HospitalShanghai 200233, China Sen Lin Department of Orthopedics, Shanghai Jiao Tong University Affiliated Sixth People’s Hospital, Shanghai, China Jiagen Sheng Department of Orthopedics, Shanghai Jiao Tong University Affiliated Sixth People’s Hospital, Shanghai, China Hui Sun Department of Orthopedic Surgery, Shanghai Jiao Tong University Affiliated Sixth People’s Hospital, Shanghai, China Hao Wu Department of Orthopedics, Qianfoshan Hospital Shandong Provine, China Zongping Xie Department of Orthopedics, Shanghai Jiao Tong University Affiliated Sixth People’s Hospital, Shanghai, China Qingcheng Yang Shanghai Jiao Tong University Affiliated Sixth People’s HospitalShanghai, China Weiwu Yao Department of Orthopedic Surgery, Shanghai Jiao Tong University Affiliated Sixth People’s Hospital, Shanghai, China Jimin Yin Shanghai Jiao Tong University Affiliated Sixth People’s HospitalShanghai, China Yong Feng Shanghai Jiaotong University Affiliated Sixth People’s Hospital, Shanghai, China Ting Yuan Department of Orthopedic Surgery, Shanghai Jiao Tong University Affiliated Sixth People’s Hospital, Shanghai 200233, China Shi Zhan Department of Orthopedic Surgery, Shanghai Jiao Tong University Affiliated Sixth People’s Hospital, Shanghai 200233, China Changqing Zhang Department of Orthopedics, Shanghai Jiao Tong University Affiliated Sixth People’s Hospital, Shanghai, China Wei Zhang Department of Orthopedic SurgeryShanghai Jiao Tong University Affiliated Sixth People’s HospitalShanghai 200233, China Zhichang Zhang Shanghai Jiaotong University Affiliated Sixth People’s Hospital, Shanghai, China

Editor’s List

Editor’s List

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Zhenzhong Zhu Department of Orthopedics, Shanghai Jiao Tong University Affiliated Sixth People’s Hospital, Shanghai, China • Editor’s Secretary Chun Chen Secretary of Department of Orthopedics, Shanghai Jiao Tong University Affiliated Sixth People’s Hospital, Shanghai, China

Acknowledgments

Great appreciation goes to my teachers and mentors, to whom I am deeply grateful. None of these can happen without their support. I want to express my thanks to many of my colleagues and students. We learn from each other and move forward together. Last but not least, I would like to thank my family, my wife and my kids for all the love and support.

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About the Book

Unlike other works on surgery of the hip joint, our work not only describes the disorder within the hip joint, but the related diseases around the hip joint. It is necessary for clinical doctors to consider the existence of hip disorder within hip joint, more importantly, to widen the horizons to peri-hip joint, even the whole body. The way the book is composed contributes to the establishment of integrated thinking method among orthopedic doctors clinically. Several major characteristics are featured here. Firstly, our work systematically demonstrates both adult and pediatric diseases inside and outside hip joint, enabling readers to comprehend the diagnosis and treatment of hip disorders more readily. Secondly, this work summarizes our clinic experience and operative techniques during the diagnosis and treatment of various hip diseases. Thirdly, compared with intraoperative color pictures in our book, line illustrations are shown spatially by our group here, making readers understand and grasp related contents easily. This work that is linked with clinic practice intimately possesses novel theories and abundant knowledge, reflecting the cutting-edge academic advancement and related operative techniques of hip joint surgery. Desirable practical operability is shown here, which could altogether provide potent references for medical students, postgraduates, and clinic orthopedic doctors.

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Contents

1 Surgical Anatomy of the Hip Joint ���������������������������������������������������������������������������   1 Zhenzhong Zhu 2 Biomechanics of Hip Joints ���������������������������������������������������������������������������������������  17 Hai Hu, Shi Zhan, and Zongyuan Cai 3 Assessment of Hip Pain ���������������������������������������������������������������������������������������������  25 Changqing Zhang, Yong Feng, and Shengbao Chen 4 Imaging Examination and Measurement of the Hip Joints �����������������������������������  39 Weiwu Yao and Ting Yuan 5 Application of Ultrasound in the Diagnosis of Hip Diseases�����������������������������������  47 Bin Hu and Jie Chen 6 Pediatric Hip Disorders ���������������������������������������������������������������������������������������������  59 Bochang Chen 7 Osteonecrosis of the Femoral Head���������������������������������������������������������������������������  81 Changqing Zhang, Dongxu Jin, Jiagen Sheng, Weitao Jia, Junjie Guan, Sen Lin, Zhenzhong Zhu, Hao Wu, and Youshui Gao 8 Inflammatory Diseases of the Hip Joint������������������������������������������������������������������� 165 Shengming Dai, Guangyi Li, and Junjie Guan 9 Infectious Diseases in Hip Joint��������������������������������������������������������������������������������� 179 Junjie Guan, Guangyi Li, and Changqing Zhang 10 Hip Bone Tumor��������������������������������������������������������������������������������������������������������� 187 Qingcheng Yang, Ting Yuan, Jimin Yin, and Zhichang Zhang 11 Acetabular Fractures������������������������������������������������������������������������������������������������� 203 Wei Zhang and Hui Sun 12 Fracture of Femoral Head and Femoral Neck��������������������������������������������������������� 213 Wei Zhang and Sen Lin 13 Developmental Dysplasia of the Hip������������������������������������������������������������������������� 237 Changqing Zhang, Dongxu Jin, and Yong Feng 14 Femoroacetabular Impingement (FAI)��������������������������������������������������������������������� 257 Zongping Xie 15 Hip Arthroplasty��������������������������������������������������������������������������������������������������������� 279 Yigang G. Huang 16 Management of Chondral Injuries of the Hip��������������������������������������������������������� 303 Dajiang Du and Peichun Hsu

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About the Editor

Changqing Zhang  Chief physician, doctoral supervisor, second grade professor Vice president of Shanghai Sixth People’s Hospital affiliated to Shanghai Jiaotong University Director of Shanghai Trauma Orthopedic Clinical Medical Center Director of Shanghai Top Priority Clinical Medical Center Dr. Changqing Zhang graduated from Lanzhou Medicine College (now Lanzhou University School of Medicine) in 1986. In 1988, he studied under Prof. Feng Shoucheng and obtained his master’s degree in orthopedic medicine and worked at the Second Affiliated Hospital of Lanzhou University. In 1993, he studied under academician Prof. Gu Yudong; he grasped the specialized knowledge of brachial nerve and hand surgery. In 1996, after learning from Prof. Hou Chunlin, he pioneered the development of partial radiculotomy of brachial nerve C8, tackling the difficulties in spastic cerebral palsy surgery. This novel operative technique was awarded the first prize of excellent thesis among young and middle-aged scholars at the second orthopedic branch of Chinese Medical Association. Having engaged in orthopedic clinical practice and research for over 30 years, he was trained properly in orthopedic hand surgery, trauma surgery, joint, spine surgery, and so forth. Since the year of 2000, Prof. Zhang focused on the treatment of osteonecrosis of the femoral head, femoral neck fracture and nonunion, and other orthopedic complications. Prof. Zhang improved and established novel surgical procedures using free vascularized fibular grafting to treat osteonecrosis of the femoral head. Over 4000 cases of afflicted patients have been treated for the past 17 years. The overall clinical cure rate exceeded 80%, reaching the advanced and leading level internationally. Prof. Zhang innovatively combined modified free vascularized fibular grafting technique with open reduction and internal fixation to treat femoral neck fracture nonunion, which became the best operation strategy to treat the nonunion of fracture of femoral neck. Prof. Zhang established and developed autologous platelet-rich plasma (PRP) extracting kit, which realized commercial industrialization. He firstly unraveled that PRP could not only restore tissue damage but exert decent anti-infection ability. Meanwhile, PRP facilitated the repair of cartilage, tendon, and bone. In 2014, Prof. Zhang firstly proposed the theory of fast track fracture in the elderly, emphasizing the significance of operative treatment in the first 48 hours. Also, Prof. Zhang formulated the related surgical operative procedures in detail, which enabled the dramatic breakthrough and increase in the treatment of fracture among the elderly. Prof. Zhang was awarded the “outstanding contribution prize” of centennial development of Shanghai medicine in 2017, the “benevolent doctor· Shanghai outstanding specialist award” in 2015, the second “top ten doctors” of Shanghai in 2012, and the “top ten pacesetters in the professional ethics construction of Shanghai employees” in 2012. Prof. Zhang was awarded the “7th young and middle-aged expert with distinguished contribution in national health and family planning” in 2015, the “national star of customer satisfaction service” in 2015, the “national advanced worker” in 2014, and the “national advanced worker in health system” in 2012.

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Prof. Zhang was honored with the “top 100 trans-century excellent academic leaders of Shanghai Health System” in 2009, the “Shanghai leading talents ” in 2008, the “Shanghai outstanding subject leader” in 2007, and other academic awards. Prof. Zhang’s academic achievements were awarded the first prize of Chinese medical science progress prize (2016), the first prize of science and technology progress of the Ministry of Education (2012), the first prize of Shanghai science and technology progress award (2013), and other 12 provincial and ministerial awards. In academic service, Prof. Zhang is the committee member of World Reconstructive Microsurgery Union, the chairman of Asia Pacific Society of Reconstructive Microsurgery, the chairman of microsurgery branch of the Chinese Medical Association, the committee member of orthopedic branch of the Chinese Medical Association, the vice president of orthopedic division of the Chinese Physicians Association, the president of orthopedic branch of Shanghai Physicians Association, the designated chairman of orthopedic branch of Shanghai Medical Association, and many other academic positions. Meanwhile, he serves as the editor-in-chief, deputy editor, and editorial board member of several domestic and foreign academic magazines, including the editor-in-chief of the International Journal of Orthopedics.

About the Editor

1

Surgical Anatomy of the Hip Joint Zhenzhong Zhu

1.1

Overview

The hip joint is the largest ball-and-socket joint in the human body. It consists of the femoral head and the acetabulum. Connecting the pelvis and the lower limb, the hip joint is the pivot of the transmission of body weight from the trunk to the lower limbs; it also has very important roles in retaining balance, supporting the weight of the upper body and walking. The cuplike acetabulum forms at the union of three pelvic bones—the ilium, pubis, and ischium, with the prominent rim augmented by the ring-shaped fibrocartilaginous lip, the acetabular labrum, which extends the joint beyond the equator and makes the joint stable as well as flexible at the same time. The joint capsule is tough and tight, with multiple ligaments around it. Iliofemoral ligament, the strongest one among these ligaments, lies in front of the joint capsule, also known as the Y ligament or Bigelow ligament. This ligament can limit hyperextension of the hip joint, strengthen the joint capsule, and help to maintain the upright posture. There is a 1.2-cm-long V-shaped ligament between the deep acetabulum and the femoral head. It is called the femoral head ligament, which contains vessels to nourish femoral head. The femoral head is hemispherical, and the femoral head is oriented medially and anteriorly. In the center of the femoral head, there is a fossa, where the femoral head ligament attaches, and the rest is the articular surface, covered by a lubricated layer called hyaline cartilage. The cup-shaped acetabulum and the spherical femoral head make the joint congruent. The hip movements have three mutually perpendicular main axes, all of which pass through the center of the femoral head, resulting in three degrees of freedom and three pair of principal directions: flexion and extension; lateral rotation and medial rotation; and abduction and adduction (Fig. 1.1).

Z. Zhu (*) Shanghai Jiaotong University Affiliated Sixth People’s Hospital, Shanghai, China

1.1.1 Acetabulum The acetabulum is located at the midpoint of the line connecting the anteroinferior iliac spine and the ischial tuberosity. It is a deep hemispherical recess with an average diameter of 4.5 cm; it is oriented laterally and distally. The acetabulum consists of three parts: ilium, ischium, and pubis. Contributing two-fifths of the structure is the ischium, which provides lower and side boundaries to the acetabulum (posterior wall). The ilium forms the dome, providing a little less than two-­ fifths of the structure of the acetabulum. The rest (anterior wall) is formed by the pubis, near the midline. It is bounded by a prominent uneven rim. At the lower part of the acetabulum is the acetabular notch, on which the transverse acetabular ligament attaches. There is a small hole between the deep part of the acetabulum and the notch, called the acetabular hole, through which the blood vessels that nourish the acetabulum pass. The acetabulum grasps almost half the femoral ball, a grip augmented by a ring-shaped fibrocartilaginous lip, the acetabular labrum, which extends the joint beyond the equator. This will make the hip joint more stable.

1.1.2 Proximal Femur Proximal femur includes femoral head, femoral neck, the greater trochanter, and the lesser trochanter. It is supported by the femoral neck, and its diameter ranges from 4.5 to 5.5 cm. The surface of the femoral head is coated by articular cartilage and fits the acetabulum. The articular surface of the femoral head is larger than that of the acetabulum, which increases the range of motion of the femoral head. Usually, the anterior, upper-lateral, and posterior edges of the femoral head are not covered by the acetabulum. These parts of the cartilage surface around the femoral head contact with the articular cartilage surface of the acetabulum only when the hip joint is extremely flexed or extended. The articular cartilage surface can be divided into three areas: The area on the stress axis that projects to the femo-

© Springer Nature Singapore Pte Ltd. and Shanghai Scientific and Technical Publishers 2021 C. Zhang (ed.), Hip Surgery, https://doi.org/10.1007/978-981-15-9331-4_1

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Z. Zhu

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b Anterior superior iliac spine Anterior superior iliac spine

Hip bone

Anterior inferior iliac spine Femoral head

Femoral neck

Femoral shaft

Anterior inferior iliac spine Femoral head Femoral neck Superior pubic ramus

Femoral shaft

Collodiaphysial angle Ischium

Posterior superior iliac spine

Spine of ischium

Anteversion angle

Fig. 1.1  Osseous composition of hip joint. (a) Anterior view; (b) Lateral view

ral head is the pressure-bearing area, the inner side and the outer edge of the femoral head are the non-pressure-bearing areas. The fovea capitis is a small, concave, depression within the head of the femur that serves as an attachment point for the ligament tears, a conduit of a small artery to the head of the femur, that is, the foveal artery. This artery is not present in everyone but can become the only blood supply to the bone in the head of the femur when the neck of the femur is fractured or disrupted by injury in childhood.

1.1.3 Femoral Neck The flattened pyramidal process of bone between the femoral head and the femoral shaft is called the femoral neck. The angle between the longitudinal axes of the femoral neck and shaft is called the neck-shaft angle (NSA). Through NSA, the weight of the upper body can transmit from the narrow hip weight-bearing area to the wide base of the femoral neck. This angle also increases the range of motion of the lower limbs. The NSA of an adult is about 127 ° (male 132 °, female 127 °). The NSA in children is larger, about 160 °, and will decrease with age. If the NSA is less than 110 °, it is called coxa vara, and if it is more than 140 °, it is called coxa valga (Fig. 1.1a). On the coronal section, the angle formed between the long axis projection line of the neck and the line connecting femoral condyles is called the femoral anteversion or torsion. The adult anteversion is 10 °~15 ° (male 12.2 °, female 13.2 °, Fig. 1.1b). Hip external rotators are much stronger than internal rotators. This fact is considered to be the cause of the formation of anteversion. The anteversion is a measurement of the angle between the long axis of the neck and the coronal axis of the femoral condyles, the knee, and the ankle.

1.2

 nterior Surgical Approach to the Hip A and the Anatomical Characteristics

The groin separates the anterior part of the hip and the abdomen. The inguinal ligament, which lies in the deep, is an important structure in this area. The ligament runs from the pubic tubercle to the anterior superior iliac spine. The iliopectinal arch forms a septum which subdivides the space deep to the inguinal ligament into a lateral muscular lacuna and a medial vascular lacuna. They are important passages between the abdomen/pelvic cavity and anteromedial thigh region. The sartorius muscle originates from the anterior superior iliac spine, runs obliquely across the upper and anterior part of the thigh in an inferomedial direction, inserts into the superomedial surface of the tibia. The anterior hip region is divided into two triangular areas by sartorius. The medial one includes the femoral nerve and the femoral artery and vein. It is an important structure to be protected cautiously during hip surgery. The anterolateral area is mostly covered by muscles, with less important blood vessels and nerves. Therefore, it is a common area for various surgical approaches (Fig. 1.2).

1.2.1 A  natomy of the Anterolateral Hip Region and Common Approaches 1.2.1.1 Anatomical Landmarks 1.2.1.1.1 Anterior Superior Iliac Spine Located at the anterior extremity of the iliac crest of the pelvis, it provides attachment for the inguinal ligament, sartorius muscle, and tensor fasciae latae muscle. It can also be used as a landmark when measuring the length of the lower

1  Surgical Anatomy of the Hip Joint

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Medial triangle

Musculus glutaeus medius

Tensor fasciae latae muscle

Sartorius muscle

Lateral triangle

Fig. 1.3  Common inter-muscle space via anterior approach

go through the following structures: the fascia lata, the sartorius muscle, and the tensor fasciae latae muscle (Fig. 1.3). Fig. 1.2  Divisions of hip anterior triangulation

limbs. Because the lateral femoral cutaneous nerve runs near it, the anterior superior iliac spine is seldom used as a bone donor site. 1.2.1.1.2 The Greater Trochanter of the Femur It is a large, irregular, quadrilateral eminence on lateral proximal femur, and it is directed lateral and medially and slightly posterior. The greater trochanter of femur serves for the insertion of the tendons of many hip abductors and external rotators. Its superior border is difficult to be felt because of the attachment of the fascia lata between the iliac crest and the tip of the greater trochanter. However, if the thigh is abducted and the fascia lata is relaxed, the greater trochanter is easy to be touched. 1.2.1.1.3 Median Point of Inguinal Ligament Press hard below the midpoint of the inguinal ligament and rotate the lower limb. Then feel the femoral head rotating under the fingers.

1.2.1.2 Anatomy of Superficial Structures The anterior approach of the hip joint usually enters between the sartorius muscle and the tensor fasciae latae muscle, and the lateral approach enters between the tensor fasciae latae muscle and the gluteus medius. These two approaches will

1.2.1.2.1 Sartorius Muscle It is the longest muscle in the human body, located on the medial side of the anterior (lateral) approach, originating from the anterior superior iliac spine and part of the notch between the anterior superior iliac spine and the anterior inferior iliac spine. It runs obliquely across the upper and anterior part of the thigh in an inferomedial direction. The lateral femoral cutaneous nerve is often passing through in the superficial layer of the origin of the muscle. The nerve should be protected during the operation. The upper part of the sartorius muscle receives the blood supplies from the branch of the profound femoral artery and the lateral circumflex artery. Both arteries are about 10-cm below the anterior superior iliac spine and enter the muscle at its medial edge. The muscular branches of the femoral nerve that innervate the sartorius muscle are accompanied by the blood vessels (forming the vascular bundle) into the muscle. Therefore, through this approach, the muscle is transected below the anterior superior iliac spine and is pulled to the medial side, which will protect the vessels and nerves. 1.2.1.2.2 Tensor Fascia Latae Muscle It locates between the sartorius and gluteus medius and in front of the lateral approach to the hip joint. The muscle is triangular, sharing the same origin, the anterior part of the iliac crest, with the sartorius muscle. After running down with Sartorius, Tensor fascia latae muscle is inserted between

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the two layers of the iliotibial band of the fascia lata about the junction of the middle and upper thirds of the thigh. Rectus femoris runs between the two muscles. The tensor fasciae latae muscle is 16-cm long, 3-cm wide, and 1.3-cm thick. Tensor fasciae latae mainly receives blood supply from the ascending branch of the lateral femoral circumflex artery and is innervated by the superior gluteal nerve. Because of the overlap between the posterior margin of tensor fascia lata and the anterior margin of gluteus medius, it is difficult to locate the gap between the two muscles through the lateral approach.

1.2.1.3 Deep Anatomy The muscles located deeply in the anterior lateral hip region, from medial to lateral side, include the rectus femoris, the iliopsoas, gluteus medius, and gluteus minimus. 1.2.1.3.1 Rectus Femoris The rectus femoris muscle is one of the four quadriceps muscles. It is fusiform in shape, with an anterior straight tendon rising from the anterior inferior iliac spine, a flat and thin reflected tendon rising from a groove above the rim of the acetabulum and the capsule. The two unite at an acute angle and spread into an aponeurosis which is prolonged downward on the anterior surface of the muscle, and from this, the muscular fibers arise. Its superficial fibers are arranged in a bipenniform manner, the deep fibers running straight down to the deep aponeurosis. The muscle ends in a broad and thick aponeurosis and, gradually becoming narrowed into a flattened tendon, is inserted into the base of the patella together with the vastus medialis and the vastus lateralis. The rectus femoris muscle receives blood supplies from multiple vessels, mainly the descending branch of the lateral femoral circumflex artery; it is innervated by the femoral nerve. Two bundles of vessels and nerves enter the muscle from the upper and middle part of the medial margin. During the dissection of deep structures through the anterior (lateral) approach, it is safe to go through the gap lateral to the muscle. It can protect the vessels and nerves mentioned above. Cut off the origin of the rectus femoris or retract it medially. The vastus intermedius, covered by fascia, lies deep to the rectus femoris. Under the fascia runs lateral femoral circumflex artery that is divided into ascending, descending, and transverse branches: the ascending branch supplies the tensor fascia lata muscle and sartorius muscle, etc.; the descending branch supplies the lower part of the quadriceps and the knee joint; the transverse branch passes lateralward over the vastus intermedius, pierces the vastus lateralis, and winds around the femur, just below the greater trochanter, anastomosing on the back of the thigh with the medial femoral circumflex artery, the inferior gluteal artery, and the perforating arteries of the profunda femoris artery. The branch

Z. Zhu Sartorius muscle Musculus rectus femoris

Ascending branch of lateral femoral circumflex artery

Tensor fasciae latae muscle

Fig. 1.4  Interface and anatomy of ascending branch of lateral femoral circumflex artery

of the lateral femoral circumflex artery that extends to the anterior part of the femoral neck and travels in front of the iliopsoas muscle through the lateral margin to the deeper layer. The branches supply the base of the femoral neck along the intertrochanteric line, the joint capsule, and the femoral neck in the capsule. The artery supplies the neck in the joint capsule is large, and it is located along the femoral neck under the synovial membrane. The reticular artery near the medial femoral circumflex artery is one of the blood supplies of the femoral head, traveling to the upper part of the femoral neck. During the operation, the ascending branch of the lateral femoral circumflex artery should be cut and ligated to reveal the origin of the vastus intermedius and the anterior joint capsule (Fig. 1.4). 1.2.1.3.2 Iliopsoas The iliopsoas refers to the joined psoas, and the iliacus muscles and the psoas major unites with the iliacus at the level of the inguinal ligament and crosses the hip joint to insert on the lesser trochanter of the femur and some fibers insert on the joint capsule. The muscle is covered by the upper part of the sartorius muscle and the rectus femoris from the front, adjacent to the femoral nerve and blood vessels. The posterior (deep) surface is attached to the anterior medial side of the joint capsule with a bursa between them. The bursa communicates with the joint cavity; it disappears with the degenerative change of the joint, resulting in adhesion of iliopsoas tendon to the anteromedial wall of the capsule. During the dissection of deep structures through the anterior (lateral) approach, the fibers inserting on the joint capsule must be carefully peeled off and then be retracted medially to enlarge the surgical field.

1  Surgical Anatomy of the Hip Joint

1.2.1.3.3 A  nterior Capsule, Ligaments, and Blood Supplies The capsule of the hip joint is cylindrical, thick, and tough, which is divided into the outer fibrous layer and the inner synovial layer. The fibrous layer originates from the acetabular rim, the transverse ligament of the acetabulum, and the outside of the acetabular labrum. In the distal part, the anterior part attaches to the intertrochanteric line. The posterior part attaches to the intertrochanteric crest 1.25  cm to the lesser trochanter (i.e., the lateral 1/3 of the femoral neck). The anterior part of the femoral neck is completely encapsulated in the capsule. The fibrous membrane is composed of superficial longitudinal fibers and deep transverse fibers; some fibers are spiral, oblique, and arcuate. The anterior wall and the upper wall are very thick. The medial and inferior medial wall is very thin even after the enhancement of the iliofemoral ligament. Under the iliopsoas tendon, the fibrous layer is absent, forming the weak part of the articular capsule. Therefore, medial inferior and inferior posterior dislocations are more common after a great amount of force being applied to the hip joint. The synovial layer of the articular capsule is thin, soft, and lubricated, which is composed of thin layers of loose connective tissue, lined with a single layer of squamous epithelium—mesothelium. The edge connects with articular cartilage. The synovial epithelium secretes synovial fluid, which is slightly alkaline. In addition to lubrication effect, it is also a medium for material metabolism for structures within the joint, for example, articular cartilage. The surface of the femoral neck is covered by synovium. The proximal margin of the synovium originates from the acetabular rim and covers the acetabular labrum and adipose tissue. Ligamentum teres is also covered by the synovium. At the distal end, the synovial membrane folds upward at the attachment of the fibrous membrane, covering the femoral neck and reaching the rim of the joint surface of the femoral head. Under the femoral neck, the synovial membrane forms several folds under which run blood vessels that nourish the head and the neck. Therefore, if the synovium and the blood vessels running under it remain undamaged after femoral neck fracture, the healing of the fracture will be more easily to be achieved. The synovial cavity sometimes communicates with the bursae iliopectinea. The lateral and medial femoral circumflex arteries form an arterial ring at the base of the femoral neck outside the capsule. Then, four vascular bundles branch off superior medially from the ring to the anterior, posterior, superoposterior, and inferoposterior part of the femoral neck, which is generally arranged in groups and rarely dispersive. They are called the anterior retinacular arteries, posterior retinacular arteries, superoposterior retinacular arteries, and inferoposterior retinacular arteries. The combination of posterior and

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superoposterior retinacular arteries is referred to as the superoposterior retinacular arteries. These vascular bundles pierce the joint capsule at its attachment on the femoral neck, running between the fibrous layer and synovial layer of the articular capsule over the surface of the femoral neck until the inferior sulcus of the head. They anastomose with each other under the synovium of the articular cartilage margin to form an intracapsular artery ring. These intraarticular arteries are thin and often incomplete. The superior and inferior arteries are often reticular; the anterior and posterior ones are often absent. The reticular arteries give off the physeal arteries and metaphyseal arteries. After the physis disappears, the metaphyseal and physeal arteries anastomose, widely, and nourish the femoral head and neck together. Some reticular arteries that enter the femoral neck anastomose nutrient artery of the femur. After the blood vessels enter the femoral head, they anastomose with the nutrient arteries and artery to the ligament of head of the femur. Retinacular arteries are tenuous and attach to the surface of the femoral neck. Focal hematoma, edema, or fracture displacement can damage the arteries, resulting in avascular necrosis of the femoral head.

1.2.2 A  nterior Medial Anatomy of the Hip Region Unlike the anterior lateral triangle, the medial triangle is bounded superiorly by the inguinal ligament, medially by the medial border of the adductor longus muscle and laterally by the medial border of the sartorius muscle. Its floor is formed by the pectineus and iliopsoas muscle as well as their fascia. The two muscles form a triangular fossa, fossae iliopectinea, whose tip is the projection of the lesser trochanter; the femoral vessels pass through the fossa. Generally, this area remains undisturbed during the operations; it mainly includes adductors, femoral vessels, and femoral nerve.

1.2.2.1 Femoral Artery It enters the femoral sheath, within the femoral triangle, from behind the midpoint of inguinal ligament as the common femoral artery, a continuation of the external iliac artery. Then, it runs into the adductor canal, and becomes the popliteal artery as it passes through an opening in adductor Magnus near the junction of the middle and distal thirds of the thigh. In addition to the superficial epigastric artery, the superficial circumflex iliac artery, and the superficial ­external pudendal artery, the femoral artery gives off the profunda femoris artery that arises from the posterior side of the femoral artery about 3–4 cm below the inguinal ligament. At its origin, the profunda femoris artery gives off the medial and lateral femoral circumflex arteries, and during its course, it gives off three or four perforating arteries. The femoral artery

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is superficial in the upper part of the femoral triangle, which is more likely to be injured, leading to an aneurysm or pseudoaneurysm. The artery is adjacent to the femoral vein, which can cause arteriovenous fistula more easily.

1.2.2.2 Femoral Vein Accompany with femoral artery, Femoral vein descends from medial toward posterior to artery at the lower tip levels of femoral triangle mentioned above. There are several deep veins of the thigh that drain into the femoral vein. About 8  cm below the inguinal ligament, deep veins of the thigh drain into the femoral vein. About 2.5 cm below the inguinal ligament, the great saphenous vein drains into the femoral vein through the cribriform fascia of the saphenous hiatus. The lateral femoral cutaneous nerve and genitofemoral nerve are located in this area. The genitofemoral nerve runs in the groove between the iliacus and the psoas, over the surface of the Iliacus, through the gap between muscles to the thigh, lateral to the femoral artery. The femoral nerve gives off anterior and posterior divisions 3–4 cm below the inguinal ligament. The two divisions give off several cutaneous branches (anterior cutaneous branch, saphenous nerve) and muscle branches with the superficial circumflex iliac artery running through them.

1.3

 ateral Surgical Approach to the Hip L and the Anatomical Characteristics

The greater trochanter of the femur is an important structure on the lateral side of the hip joint. It is the mechanical fulcrum of hip abduction and external rotation. It is also an important structure for controlling the movement of the pelvis and lower limbs. As the midpoint of the lateral and posterior approach, it lies superficially and is covered by the fascia lata. The lateral hip region can be divided into the upper and the lower part by the great trochanter. The gluteus medius and the gluteus minimus connect the upper lateral portion of

the great trochanter and the pelvis. Vastus lateralis connects the lower portion and distal femur (Fig. 1.5).

1.3.1 Anatomical Landmarks 1.3.1.1 Anterior Superior Iliac Spine It is easy to palpate the anterior superior iliac spine at the anterior part of the iliac crest by moving the fingers from distal to proximal. 1.3.1.2 The Greater Trochanter On the upper thigh, it can be palpated at the lateral hip region with the leg moving in the sagittal plane (Fig. 1.6).

Musculus glutaeus maximus

Greater trochanter

Vastus lateralis muscle

Musculus glutaeus medius

Fasciae latae Musculus vastus intermedius

Musculus rectus femoris

Fig. 1.5  The muscle junctions of femoral greater trochanter

Fig. 1.6  Surface signs commonly used in lateral hip approach

Anterior superior iliac spine

Greater trochanter of femur

1  Surgical Anatomy of the Hip Joint

1.3.2 Superficial Anatomy 1.3.2.1 Fascia Lata It is the deep fascia of the thigh, firm and tenacious, enclosing the thigh muscles. It originates from the inguinal ligament and iliac crest; the deep fascia of the leg is continuous above with the fascia lata; posterior continuation becomes the gluteal muscle fascia. The upper part of the fascia lata covers the sartorius muscle and the gluteus medius with a single layer and encloses the tensor fasciae latae and gluteus maximus with two layers. The fascia lata and the upper part of the tensor fascia lata are tightly connected; the fascia lata is thickened at its lateral side where it forms the iliotibial tract. 1.3.2.2 Gluteus Medius It is situated on the outer surface of the pelvis; the superior anterior part of the muscle is beneath the skin; the posterior lower part is covered by the gluteus maximus; the anterior part is adjacent to tensor fascia lata and is partially covered by it. The piriformis locates posterior to the gluteus medius and the gluteus maximus beneath it. The whole muscle is broad, thick, and radiating. It originates on the outer surface of the ilium, and the fibers of the muscle converge into a strongly flattened tendon that inserts on the lateral surface of the greater trochanter. There is 1 ~ 2 bursa(s) separates the tendon of the muscle from the surface of the trochanter over which it glides. The paralysis of this muscle can lead to gluteus medius gait and positive Trendelenburg sign. Deep branches of superior gluteal vessels and superior gluteal nerves run between the gluteus medius and the gluteus minimus; the two muscles are nourished and innervated by these vessels and nerve. The lower part of the gluteus medius

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locates on the lateral side of the upper part of the rectus femoris, and the two muscles are innervated by different nerves, and through the gap between them, the joint capsule can be exposed safely.

1.3.2.3 Gluteus Minimus It is situated immediately beneath the gluteus medius, and the anterior fibers join the latter. The shape, origin, insertion, function, blood supply, and innervation of the gluteus minimus are the same as the gluteus medius. Therefore, it can be regarded as a part of the gluteus medius. The greater trochanter is often cut off and turned upward together with the insertion of these two muscles to fully expose the joint capsule through a lateral approach. 1.3.2.4 Vastus Lateralis Vastus Lateralis locates lateral to rectus femoris and midfemoris muscle. It originates from the lateral femoral muscle crest at the base of the greater trochanter, surrounds the upper femur from the posterolateral side. When the greater trochanter needs to be exposed through lateral approach, the origin of this muscle needs to be cut and pulled distally (Fig. 1.7). 1.3.2.5 Vessels and Nerves to Be Protected Through the Lateral Approach Important vessels and nerves are the deep branch of superior gluteal vessels and superior gluteal nerves. The deep branch of the superior gluteal artery lies under the gluteus medius and immediately subdivides into the superior and inferior divisions: the superior division, running forward, nourishes the gluteus medius, minimus, and ilium, anastomosing with the deep iliac circumflex artery and the deep branch of the medial femoral circumflex artery; the inferior division, run-

Tensor fasciae latae muscle

Musculus rectus femoris Fasciae latae Musculus glutaeus medius Vastus lateralis muscle

Musculus glutaeus maximus

Fig. 1.7  Deep anatomy of lateral hip joint

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ning distally, nourishes the gluteus medius, minimus and the hip joint, and the arteries to the trochanteric fossa anastomose with the inferior gluteal artery and the deep branch of medial femoral circumflex artery. The superior gluteal nerve innervates the gluteus medius, minimus, and tensor fascia lata. Below the tensor fascia lata, there are ascending branches, transverse branches, and descending branches of the lateral femoral circumflex artery. The superior gluteal nerve gives off superior and inferior branches: the superior branch runs along the upper margin of the gluteus minimus; the inferior branch runs between the gluteus medius and minimus, innervating the gluteus medius, minimus, and tensor fascia lata. The superior gluteal artery leaves the pelvis through the greater sciatic foramen above the piriformis, accompanied by the superior gluteal nerve and the superior gluteal vein, where its average diameter is 3.1 mm. Then, the artery gives off two branches: the superficial and the deep. The former nourishes the gluteus maximus. The latter runs deep to the gluteus medius and gives off into the superior and inferior branches. The superior branch advances along the superior margin of the gluteus minimus, anastomosing with the deep iliac circumflex artery and the ascending branch of the lateral femoral circumflex artery around the anterior superior iliac spine. The inferior branch advances laterally between the gluteus medius and the gluteus minimus, nourishing the two muscles, and giving off vessels piercing the gluteus minimus to nourish the hip joint. The branch to the trochanteric fossa anastomoses with the inferior gluteal artery and the deep branch of the medial femoral circumflex artery. When performing surgery around the sacroiliac joint, the surgeon should be careful not to damage the superior gluteal artery. Because when it is severed, the artery tends to retract into the pelvic cavity. If necessary, an emergent laparotomy should be performed to ligate the internal iliac artery. Otherwise, massive internal bleeding could happen.

maximus (innervated by the inferior gluteal nerve) and the gluteus medius (innervated by the superior gluteal nerve). Because of the neural interface, the approach accords with the requirements of anatomy. Moore and Osborne advocate the approach should pass through the fibers of the gluteus maximus. Although the latter does not utilize the neural interface, it was more commonly used in clinic because the hip joint can be fully exposed without causing obvious denervation.

1.4.1 Anatomical Landmarks 1.4.1.1 The Great Trochanter The great trochanter of the femur is a large, irregular, and quadrilateral eminence. It locates on the junction of the neck and the shaft; it is directed lateral and medially and slightly posterior. It is about the width of the palm below the iliac crest, which locates on the midpoint of the line connecting the anterior superior iliac spine and the ischial tuberosity. The skin incision through the posterior approach is usually centered on it. 1.4.1.2 Posterior Superior Iliac Spine Protuberance at the posterior end of iliac crest. 1.4.1.3 Ischial Tuberosity It is a large swelling posteriorly on the superior ramus of the ischium. It can be easily palpated at the lower edge of the gluteus maximus when the hip joint is flexed (Fig. 1.8). 1.4.1.4 Body Surface Projection 1. Piriformis: The surface projection of the upper margin of the piriformis draws from the posterior superior iliac spine and the great trochanter; the surface projection of Greater trochanter of femur

1.4

 osterior Surgical Approach P to the Hip and the Anatomical Characteristics

The posterior part of the hip joint is covered by two layers of muscles: the gluteus maximus and the external rotators (including the piriformis, obturator internus, superior and inferior gemellus, and quadratus femoris). The sciatic nerve descends vertically through the two layers of muscle and passes the surgical field of the posterior approach area. According to the positional relationship between the approach and the gluteus maximus, there are currently two different opinions on this approach. Marcy-Fletcher advocates that the posterior approach passes through the anterior margin of the gluteus maximus, i.e., between the gluteus

Fig. 1.8  Hip joint posterior approach and surface signs

1  Surgical Anatomy of the Hip Joint

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the lower edge of the piriformis is a line connecting the midpoint between the posterior superior iliac spine and the tip of the coccyx and the greater trochanter. 2. It descends from the upper thirds of the line connecting the posterior superior iliac spine and the ischial tuberosity to the midpoint of the line connecting the ischial tuberosity and the great trochanter. 3. Superior gluteal vessels and nerve: It is situated at the upper thirds of the line connecting the superior anterior iliac spine and the tip of great trochanter. 4. Inferior gluteal vessels and nerve: It locates on the midpoint of the line connecting the posterior superior iliac spine and the ischial tuberosity.

passes out of the pelvis above the upper border of the piriformis muscle; the inferior gluteal artery, nourishing the lower part of gluteus maximus passes out of pelvis below the lower border of the piriformis muscle. The branches anastomose with each other; they have rich blood flow. The gluteus maximus is innervated by the inferior gluteal nerve. The nerve enters the deep surface of the medial part of gluteus maximus (near the origin of the muscle) below the lower border of the piriformis and innervates the whole muscle. Therefore, the gluteus maximus fibers should be separated in the lateral part and the insertion through the fibers in order to protect the nerve; even if it is separated at the medial part, the nerve trunk will not be damaged.

1.4.2 Superficial Anatomy

1.4.3 Deep Anatomy

The gluteus maximus is the superficial muscle in the posterior hip region, which is approximately square. It arises from the posterior gluteal line of the inner upper ilium and the posterior surface of the lower part of the sacrum, the base of the spine. The fibers are directed obliquely downward and lateralward. The gluteus maximus has two insertions: the iliotibial band of the fascia lata and the gluteal. The deep fascia connects the fascia lata, which together surround the gluteus maximus and tensor fascia lata in the posterior part of the hip as well as the gluteus medius. The gluteus maximus, the fascia lata (over the surface of the gluteus medius) and the tensor fascia lata form a muscular sheath in this region, called the pelvic “deltoid muscle” (Fig. 1.9). The gluteus maximus receives blood supplies mainly from the superior and inferior gluteal arteries. The superior gluteal artery, nourishing the upper part of gluteus maximus,

The deep muscles behind the hip joint are piriformis, gemellus superior, obturator internus, gemellus inferior, and quadratus femoris from top to bottom. They are adjacent to the deep surface of the gluteus maximus. Between the two layers of muscles are there some loosening connective tissue, making it easy to separate the layers; the joint capsule is anterior to these hip external rotators, some of which, therefore, should be severed to expose the capsule through a posterior approach. It is vital to be familiar with the anatomy of these muscles as well as the vessels and nerves passing out of the pelvis, especially the piriformis and structures superior and inferior to it. It is the key to perform a safe operation in this area (Fig. 1.10).

Fasciae latae Vastus lateralis muscle Musculus glutaeus maximus

Fig. 1.9  Superficial anatomy of posterior approach in hip joint

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Musculus glutaeus medius tendon

Vastus lateralis muscle Musculus quadratus femoris

Musculus glutaeus maximus

Fasciae latae Musculus piriformis Musculus obturator externus

Musculus obturator internus tendon and gemellus muscle

Fig. 1.10  The main muscle groups in posterior approach of hip joint

1.4.3.1 Piriformis The piriformis is a flat muscle, pyramidal in shape. It originates from the anterior (front) part of the sacrum, exits the pelvis through the greater sciatic foramen, runs posteriorly to the hip joint, and inserts on the greater trochanter of the femur. The piriformis divides the greater sciatic foramen into an inferior and superior part. The nerve and vessels that emerge superior to the piriformis are the superior gluteal nerve and superior gluteal vessels (lateral to medial). Inferiorly, it is the same, and the sciatic nerve, the posterior femoral cutaneous nerve, and the internal pudendal vessels also travel inferiorly to the piriformis. The nerve of the obturator internus and the quadratus femoris pass out of the pelvis through the inferior part and enter the muscles. In addition, the relationship between the sciatic nerve and the piriformis is various. And the nutrient branch of the inferior gluteal artery often runs along with the sciatic nerve. 1.4.3.2 Obturator Internus It locates below the piriformis. It is one of the few muscles in the human body whose fibers bend at a right angle. It goes around the lesser sciatic notch and shares the same insertion, the trochanteric fossa, with the gemellus muscles. 1.4.3.3 Quadratus Femoris It is situated below the obturator internus and the inferior gemellus. Its fibers pass laterally from the ischial tuberosity to the greater trochanter. The quadratus femoris is a flat, quadrilateral skeletal muscle. At the lower edge of the insertion, a cross anastomosis is formed by the ascending branch of the first perforating artery, the descending branch of the inferior gluteal artery, and the transverse branch of

the medial and lateral circumflex femoral artery. Because its blood supplies are very rich, the quadratus femoris should be protected carefully during the surgeries to avoid unmanageable bleeding.

1.4.4 V  essels and Nerves to Be Protected Through the Posterior Approach The sciatic nerve and the superior and inferior gluteal artery are easily damaged through the posterior approach to the hip joint.

1.4.4.1 Sciatic Nerve The nerve passes beneath piriformis and through the greater sciatic foramen, exiting the pelvis, then traveling between the superficial and deep layers of muscles. It is usually surrounded by adipose tissue and not easy to notice. Paying attention to its location can avoid iatrogenic injury. If the retractor is improperly placed and the muscles are pulled excessively, or if the artificial femoral head is reduced in the acetabulum without protecting the nerve, damages can be caused to the sciatic nerve, resulting in flaccid paralysis of the muscle below the knee joint. The severed external rotators of the hip joint should be retracted medially together with the sciatic nerve. Then place the retractor in the incision. This technique can protect the nerve from iatrogenic injuries. 1.4.4.2 Superior and Inferior Gluteal Artery The position of these arteries entering the hip region is in the medial part of the piriformis. Surgical approaches usually avoid passing through this area. However, since the two arteries leave the pelvic via the upper and lower borders of

1  Surgical Anatomy of the Hip Joint

the piriformis, they give off many branches to enter and nourish the gluteus maximus. When the gluteus maximus is bluntly dissected, these arterial branches are easily injured, causing much bleeding. Given this anatomical feature, these branches should be recognized and ligated before dissection to prevent the small blood vessels from retracting into the muscle, which can cause uncontrollable bleeding. As the pelvic fracture happens, the superior or inferior gluteal artery can be pierced by the fracture ends of the greater sciatic notch. After being severed, the vessels can retract into the pelvis. Under this circumstance, the extraperitoneal approach is required to enter the pelvis. The proximal internal iliac artery is then ligated to control the bleeding.

1.5

Blood Supplies of the Hip Joint

The blood supplies of the adult hip joint can be mainly divided into vessels nourishing the acetabulum and ones nourishing the proximal femur. Four arteries nourish the proximal femur: medial and lateral circumflex femoral artery, obturator artery, and femoral nutrient artery. With the growth and development of the human body, the main blood supply of femoral head is continually changing, and there are numerous individual variations. The main blood supply to the acetabulum is the superior and inferior gluteal artery. In addition, arteries such as the first perforating branch of the profound femoral artery and obturator artery form much collateral circulation around the hip joint. The study of these blood supplies is important for the understanding of the growth and development of the hip joint as well as the pathophysiology of various diseases and trauma.

1.5.1 Blood Supplies Around the Hip Joint 1.5.1.1 Medial Femoral Circumflex Artery The medial femoral circumflex artery originates from the femoral artery and the profound femoral artery, and winds around the posterior side of femur proximal to the less trochanter, moving toward the greater trochanter. Occasionally, the medial femoral circumflex artery may arise directly from the femoral artery, the origin of the lateral femoral circumflex artery. After passing through the pectineus and iliopsoas, the perforating branch of the medial femoral circumflex artery anastomoses with the lateral femoral artery, the first perforating artery, and the inferior gluteal artery near the lower edge of the obturator muscle. In addition, an acetabular branch is sent out, along with the articular branch of obturator artery, traveling below the transverse acetabular ligament, then, entering the acetabulum. This branch anastomoses with the articular branch of the obturator artery. The

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medial circumflex femoral artery gives off posterior inferior retinacular artery between the medial capsule and the obturator muscle, and gives off posterior retinacular artery at the intertrochanteric crest (posterolateral to the capsule). It also gives off branch anastomosing with the superior gluteal artery. The artery continues to travels to the lateral side, and the terminal branch becomes the posterior superior retinacular artery that is running obliquely behind the hip capsule and passing over the intertrochanteric fossa. The posterior superior retinacular artery, vital blood supply of the hip joint, nourishes the femoral head, the neck, and the greater trochanter. The medial and lateral femoral circumflex arteries communicate with each other and form an extraarticular artery ring. When the medial femoral circumflex artery ascends from the trochanteric fossa, it gives off many small branches entering the bone through the nutrient foramen to nourish the base of the femoral neck. There are 3–4 branches here going through the lateral attachment of the capsule, advancing proximally beneath the thickened synovium of the femoral neck. It eventually reaches the junction of the femoral head and neck. And enters the femoral head via 4–5 large vascular foramina at the edge of the articular cartilage whose number is relatively constant.

1.5.1.2 Lateral Femoral Circumflex Artery The lateral femoral circumflex artery originates directly from the femoral artery or the profound femoral artery in the femoral triangle and is generally larger than the medial femoral circumflex artery. The two arteries form an extraarticular ring that encircles the base of the femoral neck. The lateral femoral circumflex artery forms the anterior portion of the ring, and the medial femoral circumflex artery forms the medial, posterior, and lateral portions. However, only 10% of the rings are complete. Behind the sartorius and rectus femoris, the lateral femoral artery and divides into ascending, transverse, and descending branches. The ascending branch nourishes the tensor fascia lata, sartorius muscle; The descending branch runs downward, entering the lower part of the quadriceps and the muscle as far as the knee; the transverse branch pierces the vastus lateralis, and winds around the femur, just below the greater trochanter, anastomosing on the back of the thigh with the medial femoral circumflex artery, the inferior gluteal artery, and the perforating arteries of the profunda femoris artery. The branch of the lateral femoral circumflex artery that extends to the anterior part of the femoral neck travels along the lateral margin to deep layers in front of the iliopsoas muscle. It supplies the base of the femoral neck along the intertrochanteric line, the neck where the joint capsule attaches, and the femoral neck within the capsule. The artery entering the neck within the capsule is large. It travels along the femoral neck beneath the synovial membrane. Near the retinacular artery of the medial femoral

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circumflex artery, it gives off divisions to the femoral head that ends at the upper part of the femoral neck.

1.5.1.3 Obturator Artery The obturator artery usually originates from the anterior trunk of the internal iliac artery and passes anterodistally beneath the parietal peritoneum in the pelvis. The obturator artery exits the pelvis through the obturator canal and divides into the anterior and posterior terminal branches. The anterior branch walks along the anterior edge of the obturator and is nourish the obturator externus and anastomoses with the posterior branch and the branch of the medial femoral circumflex artery. The posterior branch walks along the posterior edge of the obturator, and nourishes the adjacent muscle. An acetabular division enters the acetabulum through the acetabular notch to the soft tissue in the joint. One of them reaches the femoral head concave through the ligamentum teres and enters the inferomedial femoral head. This artery is called artery to the ligament of the femoral head, which is the only blood supply of the femoral head that does not pass through the femoral neck. It is the main source of blood supply to the femoral head before the physis closes. The obturator artery gives off a branch to pubis in the superomedial pelvis, which ascends behind the pubis and anastomoses with the inferior epigastric artery and collateral branch of the obturator artery. The obturator artery forms a vascular ring at the attachment of the obturator externus. There are many branches in the acetabulum’s fat and synovium. Artery to the ligament of the femoral head is only a division of the acetabular branch. At the posterior aspect of the acetabulum, the branch from the inferior gluteal artery anastomoses with the obturator artery ring, and it enters into the posterior part of the acetabulum. 1.5.1.4 Superior Gluteal Artery The superior gluteal artery is the continuation of the posterior trunk of the internal iliac artery. It passes through between the lumbosacral trunk and the first sacral nerve; it exits the pelvis above the superior margin of the piriformis muscle. The branch supplies the gluteal muscle, the superior portion of the acetabulum, the upper part of the joint capsule, the great trochanter, and so on. When the superior gluteal artery travels out from the ischiatic notch, it immediately gives off a descending branch to the posterior edge of the acetabulum and the posterior portion of the joint capsule; the other branch runs transversely along the ilium under the gluteus minimus, and the branch supplies the muscle. 1.5.1.5 Inferior Gluteal Artery The inferior gluteal artery is the continuation of the anterior trunk of the internal iliac artery. It descends behind the internal pudendal artery and travels between the second and the third sacral nerves. It escapes from the pelvis below the piri-

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formis to the deep side of the gluteus maximus. The branches of it nourish the gluteus maximus, joint capsule, sciatic nerve, buttocks, and the skin of back thigh. The communicating branch arises from the inferior gluteal artery, traveling downward to form the cruciate anastomosis with the first perforating branch of the profound femoral artery and the medial and lateral femoral circumflex arteries. In addition, to give off a large number of branches to supply the gluteus maximus, the inferior gluteal artery sends out two main branches to supply the deep structures of the hip joint. The transverse branch crosses and nourishes the sciatic nerve, and gives off a branch traveling downward that is called posterior acetabular artery, which supplies the lower, posterior margin of the acetabulum, and adjacent fibrous joint capsules. The trunk continues to travel through the obturator externus, the gemellus superior, the gemellus inferior, and the piriformis. There are many small branches entering these muscles and the superoposterior edge of the greater trochanter. Medial to the sciatic nerve, a branch travels downward between the nerve and the posterior part of the acetabulum, going around the ischium, and anastomoses with the obturator artery at the lower part of the acetabulum, the notch of the ischial tuberosity, and outside the obturator to supply the lower part of the acetabulum.

1.5.1.6 Femoral Profound Artery The first perforating branch of the profound femoral artery originates from the femoral artery at the level of the adductor Magnus and passes through the upper part of the adductor Magnus. Below the attachment of the gluteus maximus, it gives off branches to supply the gluteus maximus and the adductor Magnus. A large branch ascending along the femur and gives off two divisions: one to inferoposterior part of the less trochanter below the quadratus femoris; the other one to inferoposterior part of the great trochanter anastomoses with the inferior gluteal artery and the medial and lateral femoral circumflex artery. The area is nourished by these vessels (Fig. 1.11).

1.5.2 B  lood Supply to the Head and Neck of the Femur 1.5.2.1 Retinacular Arteries It is also called sub-synovium arteries, cervical ascending or artery capsular arteries, and metaphyseal artery. Retinacular arteries enter the femoral neck near the physis; it is the main blood supply to the femoral head. The lateral and medial femoral arteries form an arterial ring at the base of the femoral neck outside the capsule between the trochanters. The arterial ring gives off four vascular bundles to the medial superior part of the neck. They are called anterior, posterior, superoposterior, and inferoposterior retinacular arteries. The

1  Surgical Anatomy of the Hip Joint

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Fig. 1.11  Blood supply around hip joint Arteriae iliolumbalis

Internal iliac artery

External iliac artery

Superior gluteal artery

Inferior gluteal artery Obturator artery

Lateral femoral circumflex artery

Medial femoral circumflex artery

Profunda femorisartery

Femoral artery

a

Ligamentum capitis femoral artery

b

Posterior superior retinaculum artery

Anterior retinaculum artery

Medial femoral circumflex artery Lateral femoral circumflex artery Profunda femorisartery

Fig. 1.12  Blood supply for femoral head. (a) Anterior view; (b) Posterior view

Femoral nutrient artery

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posterior and the superoposterior retinacular arteries are often called the superoposterior retinacular arteries. These vascular bundles pass through the attachment of the joint capsule at the femoral neck, and travel between the fibrous and the synovial layer of the joint capsule. An intraarticular arterial ring is formed eventually, under the synovial membrane, when the bundles reach the margin of the articular cartilage on femoral head (Fig. 1.12a). This arterial ring is tenuous and often incomplete. The upper and lower parts are often reticulated, and the anterior and posterior parts are often absent. The retinacular arteries give off branches to epiphysis and metaphysis. After the physis closes, these vessels anastomose with each other to nourish the femoral head and neck. Branches that enters the femoral neck anastomose with the nutrient arteries of the femur; those enter the femoral head anastomose with the nutrient arteries and the artery to the ligament of the femoral head. Retinacular arteries are tenuous and run over the surface of the femoral neck. Therefore, focal hematoma, edema, or displaced fracture ends can injure the vessels. Torsion of the vessels can lead to ischemia or avascular necrosis of the femoral head. Of the blood supply to the femoral head, 70% comes from the retinacular arteries, 25% from the nutrient artery, and only 5% from the artery to the ligament of the femoral head (Fig. 1.12b). The femoral head has less blood supply than the femoral neck does. The higher the site of the femoral neck fracture is, the less blood supply will remain at the upper end of the fracture. The degree of displacement determines the severity of the vascular injury. The amount of remain vessels determines whether the femoral head can survive. After the fracture, the nutrient arteries in the femoral neck are all broken. When the displacement is massive, the superoposterior retinacular arteries are most likely to be damaged. Superoposterior displacement, accompanied by external rotation of the lower extremity, can also damage the inferoposterior retinacular arteries, causing the ischemia of the femoral head. The degree of vascular injury is proportional to the degree of displacement of the fracture. Therefore, it is not advisable to use large-weight traction to reduce the fracture in the early stage. Early weight-bearing is not the main cause of avascular necrosis of the femoral head, but the direct cause of the collapse of the necrotic femoral head that fails to complete the creeping substitution. After a femoral neck fracture, the artery to the ligament of the femoral head becomes the blood supply compensation, especially for the partially necrotic femoral head that can regain partial blood supply from the artery. When the fracture is significantly displaced, most of the proximal blood supply is lost, and it is often difficult for the bone tissue to survive unless receiving the blood supply from the distal end. Poor realignment, imperfect fixation, and early weight-­ bearing can cause malunion or nonunion.

Z. Zhu

Correct reduction and strong fixation can restore the blood supply to the head and neck of the femur after fracture, make the fracture heal and restore the height of the collapsed head through the creeping substitution. The size of the necrotic head depends on the extent of damage to the artery. Maintaining the artery to the ligament of the femoral head is important for the survival of the femoral head. From the perspective of surgical intervention, the diameter and location of the implants, as well as surgical techniques, have a great impact on the blood supply. Thick screws make the risk of avascular necrosis much higher than three pins. The former may damage the nutrient artery, artery to the ligament of the head and blood supply to the anterior femoral head. Pins have less effect on blood supplies, but superoposterior 1/4 region of the femoral head should be undisturbed to protect important vessels. The closer the needle runs in the central area of the head and neck, the less likely to damage the blood supply. In the medial third of the femoral head, because there is an anastomosis of the lateral epiphyseal artery and artery to the ligament of the head, this is the safe area for insertion of the pins. If the fracture line passes through the superolateral junction of head and neck and the displacement is significant, the injury of the lateral epiphyseal artery is the main cause of avascular necrosis of the femoral head.

1.5.2.2 Artery to the Ligament of the Femoral Head Most of this artery originates from the branch of the obturator artery, which has many variations in different people and age. Some scholars believe that the artery provides about 1/3 of the blood supply to the femoral head, while others believe that it has less contribution, and the probability of hardening and occlusion of this artery increases with age. With a few exceptions, artery to the ligament of the femoral head is not as important as the superior and inferior retinacular arteries. 1.5.2.3 Nutrient Artery of the Femur It originates from the perforating artery of the profound femoral artery. It enters the medullary cavity through nourishing canals in the middle of the femoral shaft, and gives off two branches to the two ends of the femur. When traveling, it winds the central sinus. The superior branch runs proximally within the medullary canal, through the femoral neck to the femoral head. On the one hand, the nutrient arteries give off parallel branches to reach the ends, and at the same time, the branches form the endosteum vascular network that gives off branches piercing the cortical bone to the periosteum where the endosteum and periosteal vascular network anastomose with each other. Adult nutrient arteries nourish the femoral head and neck, and in children, the artery is blocked by the physis.

1  Surgical Anatomy of the Hip Joint

However, some scholars believe that some small arteries can pierce the physis to the femoral head.

1.5.3 Blood Supplies to the Acetabulum The blood supplies to the acetabulum also come from nearby arteries. The medial and lateral femoral circumflex artery, the obturator artery, the superior gluteal artery, and the inferior gluteal artery form an arterial ring around the acetabulum. The ring gives off a branch to nourish the capsule. The

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superior gluteal artery mainly nourishes the superior part; the inferior gluteal artery supplies the posterior acetabulum and the nearby joint capsule. The acetabular branch of the obturator or the medial femoral circumflex artery enters the acetabulum and becomes the artery to the ligament of the femoral head. Furthermore, it also nourishes the soft tissue in the acetabulum and nearby hip bone. These branches anastomose with a vascular ring at the base of the neck, and the acetabular branch anastomoses with the nutrient artery of the internal iliac artery.

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Biomechanics of Hip Joints Hai Hu, Shi Zhan, and Zongyuan Cai

2.1

Overview

Although the musculoskeletal system is complex, it follows the basic laws of mechanics. Biomechanics may be defined as studies of mechanics that act on biological organisms, to be specific in this context, human beings. It is an interdisciplinary discipline that includes biology, engineering, sports science, and medicine. Generally, classical laws of mechanics in biological models are used to describe the characteristics and functions of organisms in biomechanics. It focuses on the forces, moments, and movements or deformations of tissues such as bone, cartilage, ligaments, synovial fluid, and tendons. Despite its role of theoretical support for clinics, it is very important for the development and design of devices commonly used in clinical joint replacement and fracture fixation. Biomechanics of the hip joints includes solid biomechanics, kinematics, and kinetics. Solid mechanics describes the mechanical properties of living organisms, including the transmission of forces and tribology between joint surfaces. Kinematics mainly describes the movement, coordination, and control of the musculoskeletal system. Kinetics mainly describes the process of living organisms and their situation of force, in order to understand the joint stability, coordination, fracture healing, gait, and other changes. As hip joint is an important component of the human motor system, comprehending the physiological and pathological biomechanical characteristics of the hip joint helps us with understanding the pathogenesis of hip joint diseases, guiding the effective treatment and rehabilitation of hip joint diseases, and improving the design qualities of surgical method and implants (e.g., joint prosthesis).

2.2

Hip Solid Mechanics

2.2.1 Hip Mechanical Properties The hip joints are ball-and-socket joints, which exhibits both stability and mobility. The congruence of the articular surfaces, depth of the acetabular cavity as well as surrounding muscles and ligaments provide a wide range of motion for the hip joint as well as enough stability. In detail, hip joints have the following characteristics: (1) Accurate ball-andsocket joints; (2) Thick and tight joint capsules; (3) Strong ligaments; and (4) Well-developed muscles around joints. The first three are statically stable structures, while the last is a dynamic stability structure [1] (Fig. 2.1).

2.2.2 Bony Stable Structure The ball-and-socket configuration of the hip joints is the main guarantee for its inherent stability. In daily activities, hip joints are influenced by compressive stress, tensile stress, shear stress, moment, and friction. When loading, the force on the sacrum transmits through the hip joint to the femoral neck and then to the lower limb. Due to the neckshaft angle, the direction of resultant force on femoral neck is not in line with femoral neck axis, causes, the compressive stress is always greater than the tensile stress. The maximum compressive and tensile stress locates at the medial edge of the femoral neck. The closer to the neutral axis of the femoral neck, the smaller the compressive stress and the tensile stress is. And the stresses get to zero at the neutral axis of the femoral neck. Because the resultant force is oblique to the femoral neck, a shear stress is generated. The magnitude of shear stress depends on the inclination angle between the direction of resultant force and axis of the femoral neck.

H. Hu (*) · S. Zhan · Z. Cai Department of Orthopedic Surgery, Shanghai Jiao Tong University Affiliated Sixth People’s Hospital, Shanghai, China © Springer Nature Singapore Pte Ltd. and Shanghai Scientific and Technical Publishers 2021 C. Zhang (ed.), Hip Surgery, https://doi.org/10.1007/978-981-15-9331-4_2

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H. Hu et al. Anterior view (Looking from the back) Musculus glutaeus medius Tensor fasciae latae muscle Sartorius muscle

Musculus glutaeus maximus Musculus piriformis

Musculus glutaeus minimus Musculus pectineus

Quadratus femoris muscle

Musculus adductor longus Musculus adductor brevis Musculus gracilis Adductor magnus (front) Adductor magnus (back) Biceps femoris muscle Sagittal view (Looking laterally) Musculus glutaeus medius (back)

Tensor fasciae latae muscle Musculus glutaeus minimus (front)

Musculus glutaeus maximus

Sartorius muscle Musculus rectus femoris Iliopsoas muscle

Semimembranosus muscle

Musculus pectineus

Biceps femoris muscle and semitendinosus muscle

Musculus adductor longus Musculus adductor brevis

Adductor magnus (back)

Musculus adductor longus Musculus pectineus Musculi adductor brevis Musculus obturator externus

Horizontal view (Looking down) Musculus glutaeus minimus (front) Musculus glutaeus medius (front)

Musculus glutaeus medius (back) Quadratus femoris muscle Superior gemellus muscle Musculus piriformis Musculus glutaeus minimus (back) Inferior gemellus muscle Musculus obturator internus

Musculus glutaeus maximus

Fig. 2.1  The direction of contraction of the muscles around the hip

2  Biomechanics of Hip Joints

19 PR

R

M

G a

QR

Q1

b

P1 R1

Fig. 2.3  Stress of hip joint in patients with acetabular dysplasia Fig. 2.2  A schematic diagram of the resultant force produced by the abductor muscles

Bony structural defects of the hip can lead to decreased containment between femoral head and acetabulum. For instance, acetabular dysplasia causes passive hip instability and then asks for more stresses of soft tissues surrounding acetabular (especially the anterior articular capsule labial structure). Over time, the increased stress may lead to labral injury and subsequent cartilage degeneration [2]. As shown in Fig.  2.2, under normal circumstances, the abductor’s muscles produce a resultant force M, and the human body can maintain balance only when M × a = G × b (G is gravity). According to the formula: M  =  G  ×  b/a, with the load surface tilting, the femoral head also moves outwards, thus b increases and a decreases. As the arm changes, body can maintain balance only when M increase continuously. In order to maintain pelvic balance, abductor muscles, such as the gluteus medius and other muscles, have to contract more. The long-term muscle tension and contracture are also the causes of the weakness of the gluteus medius and hip pain in the clinical practice. As M increases, the resultant force R of M and G will increase. The R can be decomposed into a downward force PR, pushing the pelvis downwards, and a

outward force QR, pushing the femoral head outwards (Fig.  2.3). Although these two forces do not change along with the load surface tilting, the resultant force R increases when the femoral head shifts outwards, then PR and QR tend to increase consequently. Figure 2.3 shows a schematic diagram of pathological hip biomechanics of hip dysplasia. QR tends to push the femoral head to the lateral side and cause subluxation or dislocation of the femoral head. In this case, R1 = R, that is, the resultant force R1 on the acetabular load surface changes, and it can be decomposed into two components: the pressure P1, perpendicular to the load surface, and shear Q1, parallel to the load surface. These two components keep changing until P1 = R1, and then gradually decreases to its original value. During this process, the pressure on the acetabulum is greater than the normal one. According to the Poisson’s effect, the cartilage is squeezed, then expands horizontally, which results in the generation of large shear stress at the tide line. Little by little, a rupture occurs at a deep layer of cartilage, that is, at the boundary between calcified cartilage and noncalcified cartilage. On the other hand, the tensile stress and strain were generated by the lateral expansion of cartilage. If they are large enough, they will damage the collagen fibers and network structure on the joint surface. When the acetabular load surface tilts more severely, the pressure P1 of the acetabulum

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load-bearing surface tends to decrease, while the shear stress QR of the acetabular load surface increases. QR acts on the load-bearing cartilage surface directly, causing more damage on cartilage surface. The greater the degree of acetabular tilt, the greater the damage would be [3]. In addition, changes in the geometry of the proximal femur will affect the hip arm, altering the hip loading situation. When the hip is in varus, the resting muscle tension of the abductor muscle increases, the joint contact force reduced accordingly. Meanwhile, as the femoral head penetrated the acetabulum, the stability of the joint increased. However, the hip arm increased, and the proximal femoral shear increased. When the hip is in valgus, the arm becomes short, the resting muscle tension of the abductor muscle and the joint contact force increased, while the femoral head was away from the acetabulum and the stability of the joint reduced. Therefore, for total hip arthroplasty, neutral or eversion can reduce the shear force, which helps to reduce PMMA wear of the prosthesis.

2.2.3 S  tatic Stability Function of the Joint Capsule, Ligament, and Labrum The hip joint capsule itself is thicker and can prevent the dislocation of the hip joint during extreme activity. The three different ligaments on the capsule form a complex ligament system together to maintain hip stability: (1) iliofemoral ligaments, the anterior ligament restricts hip hyperextension and internal rotation; (2) pubofemoral ligament, the anterior medial ligament, restricts the hip abduction and external rotation; (3) ischiofemoral ligament, the posterior ligament limits the internal rotation and adduction when the hip flexes. The strength of the posterior ligament is significantly lower than that of the anterior ligament, so the rate of posterior hip dislocation is significantly higher than that of the anterior dislocation. The labrum is a horseshoe-shaped fibrocartilage tissue attached to the acetabular rim that not only deepens the acetabulum but also increases the coverage of the femoral head, making hip joint much more stable. Moreover, the labrum has important biomechanical effects [4–7], such as to synovial fluid flow regulation, joint suction, and sealing maintain and load sharing. A clinical study showed that the cases of acetabular labrum resection or pathological labrum lesion are prone to suffer from early hip arthritis or joint-related diseases [8]. A labral tear weakens the stability of the hip and causes an abnormal sliding of the hip surface, accelerating the wear of the articular cartilage [8]. In addition, there is a character of “creep” for the joint capsule and ligament tissues [9]. A fixed posture lasting for a long period after hip trauma, hip arthritis, or hip surgery, often causes contracture on one side and relaxation on the other side, resulting in joint stiffness and dysfunction. To understand

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the biomechanical properties of joint capsules and ligaments can help rehabilitation exercises for these diseases.

2.2.4 Hip Dynamic Stability Structure Compared to statical stability structures, the muscles around the hip provide hip joint dynamic stability. Under the control of the nervous system, the coordination and antagonism of multiple muscles play an important role in maintaining hip stability during standing or exercising [10]. There is still little research on the dynamic stability of hip joints. It is unclear how many muscles are involved, how muscles coordinate or antagonize, and how the muscle function changes under pathological conditions. In theory, there are two sets of muscle systems in the human body: local and global. Local muscles are considered important joint stability structures. Because they cling to the joints, they can act directly on the axis of the joints and produce major joint tightening forces (not torsional forces), such as the gluteus minimus. Simultaneously, these muscles constantly receive feedback from the nervous system to regulate joint tension. In contrast, the global muscles are relatively superficial, tend to have a larger physical cross-sectional area, such as the gluteus maximus. Due to their larger arms, they can produce a larger twisting force on the joints. The following section describes some of the deep muscles that play a major role in the dynamic stability of the hip. Deep external rotation muscles (quadratus femoris, obturator internus, obturator externus, superior gemellus, and inferior gemellus) are important stability muscles of the hip joint. Together with gluteal muscle, they are called “Hip Joints Rotating Sleeves.” Ward and his colleagues speculated that these muscles can control hip stability and fine joint movement [11]. Patients who underwent prosthetic replacement via a posterior approach with retained or repaired externally rotated muscles had a significantly lower rate of dislocation [12]. These studies show indirect confirmation of the stability function of these externally rotating muscles. However, the piriformis, the other external rotation muscle, with a horizontal force direction when contraction, shows no joint compression. Whether this muscle contribute to the dynamic stability of the hip joints needs further study. The iliocapsularis originates from the inferior border of the anterior lower iliac spine and the anteromedial joint capsule and terminates in the lesser trochanter. When contracting, it can tense the anterior joint capsule, enhancing the stability of the joint accordingly. The fibers of gluteus maximus are parallel to the femoral neck and attached to the upper side of the joint capsule. This anatomical feature again demonstrates that it is an important hip stability muscle.

2  Biomechanics of Hip Joints

The gluteus medius is the main hip abductor muscle and an important stability muscle of the hip and pelvis, especially when walking during single-leg standing phase, which prevents pelvic tilt and maintains straightness. Its fibers were divided into three groups: anterior, intermediate, and posterior fibers. Each fiber group has its innervation and fiber direction. During walking, the posterior fibers firmly lock the femoral head in the acetabulum, while the intermediate fibers initiate hip abduction activity and the anterior fibers initiate pelvic rotation [13]. A study about falling risk for the elderly people found that the weakened abductor function seriously affected the gait control, elderly people with whom are likely to fall [14]. The iliopsoas contains two parts, psoas and iliacus. Both have their innervation and actively contracting during hip flexion. In the late standing phase of the gait cycle, the iliacus plays an important role in stabilizing the hip joint.

2.2.5 Hip Biotribology Hip wear is a cause of hip osteoarthritis and other related diseases. Therefore, the understanding of hip biotribology is helpful for the diagnosis and treatment of these diseases. There is a layer of compressed lubricating fluid between the articular surfaces of the hip joints, forming fluid-film lubrication with a lubricating effect. Studies have shown that hip size and shape have a certain influence on contact force [15]. Hip joint motion is a rotational sliding motion. When it does flexion, extension, abduction, adduction, and rotation, the soft tissue filled in the acetabular socket could be squeezed in or out with the pressure on the joint decreases or increases. When the contact between the femoral head and acetabulum slides and/or rotates relatively, friction will be generated. It contains two types, static friction, and dynamic friction. The dynamic friction coefficient depends on the slip velocity between the two surfaces and is usually smaller than the static friction coefficient. Therefore, to start the motion between the two surfaces, a force of high energy is often required. And once it is started, the force to maintain the motion is reduced. The intact acetabular labrum prevents joint fluid from spilling and keeps the hip joint in a low-friction environment. Once the labrum is broken, the fluid in the joint flows out, and so-called fluid–membrane lubrication loses, then the friction between the joints increases. This may damage articular cartilage and cause osteoarthritis [16].

2.3

Hip Kinematics and Dynamics

The hip joints, the rigid ball-and-socket joints, can carry out multiaxial movement centered around the femoral head. For the sake of analysis, only three axes perpendicular to each

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other are selected generally. The line connecting the centers of the bilateral femoral heads is horizontal axis, the motion around whom is the flexion and extension; the line through the anterior–posterior direction of the femoral head is sagittal axis, the motion around whom is adduction and abduction. The line connecting the centers of the hip and knee joints is the mechanical axis, or rotation axis, the motion around whom is an internal and external rotation. In daily life, most activities are a combination of motions around these three axes. The maximum motion of the normal hip joint is on the sagittal axis, with 0–140 ° flexion and 0–15 ° extension. The other ranges of motion are 0–45 ° abduction and 0–30 ° adduction, 0–45 ° external rotation, and 0–50 ° internal rotation when the hip flexes. These activities are limited by joint capsules and bony structures. The normal hip joints can fully extend, but if the anteversion angle of a proximal femur is too large, the trochanter and pelvis will impinge posteriorly when the joint extends, and the external rotation will also decrease. If the anteversion angle of the proximal femur is too small, the joint impinges anteriorly, and the internal rotation is reduced. A healthy person needs about 100 ° hip flexion and extension, 20 ° internal and external rotation, and 20 ° adduction and abduction in daily life. In different postures (decubitus, sitting, standing, and eccentric position), the characteristics of hip movements are different. Each position has a more detailed division: for instance, standing position, subdivided standing (bipedal standing, one-leg standing), walking (different speed level, upstairs, and downstairs), running, and so on. Meanwhile, the hip joint movement needs the coordinated movement of the surrounding segments (such as the waist, pelvis, etc.) to complete the functional requirements of the hip joint. Given an example, the abnormal movement of the knee joint could affect the hip joint movement characteristics [17]. Walking, the most frequent activity in the hip joint, is a kind of periodical movement, which is often taken for biomechanical studies. It is divided into the stand phase and swing phase. In the late swing phase, the lower limb moves forward with the heel, and hip flexion is the greatest. At the beginning of the stand phase, the body moves forward, the hip joint is extensive and reaches the maximum when the heel is off the ground. The kinetics of hip joints are quite complex, and their stress conditions are not a single load but a combination of multiple loads. It changes with body movements, coupled with the irregular shape of the skeletal section. The calculation is more complicated. As measurements in  vitro are affected by muscles, ligaments, and other factors, the inner mechanical parameters of the joint cannot be obtained directly. Before the emergence of implantable sensors, researchers used various mathematical models to calculate the hip joint force, of which finite element analysis is an important tool. The CT/MRI scanning images of the hip

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joints were modeled by modeling software and imported into the finite element analysis software. After adding appropriate boundary conditions, the mechanical properties of hip joints under different stress situations can be simulated. In a few cases, the inner stress of the hip joint can be measured by placing a strain sensor in the prosthesis. As Bergmann [18] confirmed, under normal gait, the hip stress was 2.1–4.3 times of body weight, and it reached 2.3–5.5 times of body weight when going upstairs. When the patient collapsed emergently, the stress reached 8 times of body weight. Abnormal hip kinematics and kinetics often lead to hip joint injury and other related diseases. The most typical example is the femoral acetabular impingement (FAI). In FAI, cam deformity at the femoral head–neck junction and/or pincer deformity make the original concentric circular motion of the femoral head in the acetabulum inconsistent, resulting in damage to the labrum and cartilage, even complaint of pain and limited activity [19]. The acetabular pincer deformity can be excessive growth anterior acetabular or more general deformities such as coxa profunda or Otto’s disease. When the hip flexes, the femoral neck impinges to the rim of the acetabulum, compressing the anterior labrum. With repeated hip flexion, the labrum keeps undergoing microdamage, and gradually separates from the acetabular cartilage and eventually exfoliates. As the disease progresses, the continuous pressure between the inferior posterior rim of the acetabulum and the posteromedial side of the femoral head causes acetabular cartilage damage, as so-called “flushing injury.” The cam deformity on the femoral side causes the femoral head to lose its normal spherical structure, and the femoral head and neck offsets decrease as well. In the hip flexion situation, the deformed femoral head and neck rotate past the anterior upper acetabular rim, which results in shear stress and squeezing stress. The contact region between femoral head and acetabulum is between acetabular cartilage and labrum. Therefore, unlike the pincer type, the acetabular cartilage is damaged firstly in cam FAI [19]. In recent years, biomechanical scientists have been trying to evaluate FAI’s complex 3D geometry and hip function accurately, and describe the exact site of impact during hip motion, as FAI has a feature of repeated dynamic impingement of the hip joints, whereas conventional X-ray, CT, and MRI can only obtain its static morphology. Puls et al. used the isometric method combined with a dynamic hip center detection for FAI, got significantly improved accuracy. It has been applied for aiding diagnosis and preoperative planning [20]. It is very important to define the hip center in hip dynamic range simulations. Studies found that concentric activity does not occur around a fixed joint center point in

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hip joint activity. However, there is a certain degree of displacement [21], similar to the conchoid movement [22]. So previous methods for studying kinematics and kinetics of hip joints based on fixed concentric circles will be biased inevitably, and then led to inaccurate results for FAI. Puls and his colleagues [20] compared the method rotating around the dynamic hip center with the method rotating around a fixed center, the rotation error of the latter reached 5.0–5.6 °. Therefore, accurate kinematic measurement and simulation can help to determine the degree and range of FAI clinically. However, questions still need to be answered in the future. Such as, how to measure quickly and accurately in clinical practice, like the application of dual-fluoroscopic measurement, and how to get the three-dimensional kinetics of soft tissue (such as the acetabular labrum) in FAI.

References 1. Neumann DA. Kinesiology of the hip: a focus on muscular actions. J Orthop Sports Phys Ther. 2010;40(2):82–94. 2. Nepple JJ, Carlisle JC, Nunley RM, et al. Clinical and radiographic predictors of intra-articular hip disease in arthroscopy. Am J Sports Med. 2011;39:296–303. 3. Maquet P.  Biomechanics of hip dysplasia. Acta Orthop Belg. 1999;65(3):302–14. 4. Adeeb S, Sayed Ahmed E, Matyas J, Hart A, Frank B, Shrive N.  Congruency effects on load bearing in diarthrodial joints. Comput Methods Biomech Biomed Eng. 2004;7:147–57. 5. Ferguson SJ, Bryant JT, Ganz R, Ito K. The acetabular labrum seal: a poroelastic finite element model. Clin Biomech (Bristol, Avon). 2000;15:463–8. 6. Ferguson SJ, Bryant JT, Ganz R, Ito K. The influence of the acetabular labrum on hip joint cartilage consolidation: a po-roelastic finite element model. J Biomech. 2000;33:953–60. 7. Ferguson SJ, Bryant JT, Ito K. The material properties of the bovine acetabular labrum. J Orthop Res. 2001;19:887–96. 8. Ferguson SJ, Bryant JT, Ganz R, et  al. An in  vitro investigation of the acetabular labral seal in hip joint mechanics. J Biomech. 2003;36:171–8. 9. Hewitt J, Guilak F, Glisson R, et  al. Regional material properties of the human hip joint capsule ligaments. J Orthop Res. 2001;19(3):359–64. 10. Retchford TH, Crossley KM, Grimaldi A, et  al. Can local muscles augment stability in the hip? A narrative literature review. J Musculoskelet Neuronal Interact. 2013;13(1):1–12. 11. Ward SR, Winters TM, Blemker SS. The architectural design of the gluteal muscle group: implications for movement and rehabilitation. J Orthop Sports Phys Ther. 2010;40(2):95–102. 12. Khan RJ, Yao F, Li M, et  al. Capsular-enhanced repair of the short external rotators after total hip arthroplasty. J Arthroplast. 2007;22(6):840–3. 13. Gottschalk F, Kourosh S, Leveau B.  The functional anatomy of tensor fasciae latae and gluteus medius and minimus. J Anat. 1989;166:179–89. 14. Arvin M, Hoozemans MJ, Burger BJ, et al. Effects of hip abductor muscle fatigue on gait control and hip position sense in healthy older adults. Gait Posture. 2015;42(4):545–9. 15. Afoke NY, Byers PD, Hutton WC. Contact pressures in the human hip joint. J Bone Joint Surg Br. 1987;69(4):536–41.

2  Biomechanics of Hip Joints 16. Song Y, Ito H, Kourtis L, Safran MR, Carter DR, Giori NJ.  Articular cartilage friction increases in hip joints after the removal of acetabular labrum. J Biomech. 2012;45(3):524–30. 17. Powers CM.  The influence of abnormal hip mechanics on knee injury: a biomechanical perspective. J Orthop Sports Phys Ther. 2010;40(2):42–51. 18. Bergmann G, Deuretzbacher G, Heller M, et  al. Hip contact forces and gait patterns from routine activities. J Biomech. 2001;34(7):859–71. 19. Kuhns BD, Weber AE, Levy DM, Wuerz TH. The natural history of femoroacetabular impingement. Front Surg. 2015;2:58.

23 20. Puls M, Ecker TM, Tannast M, Steppacher SD, Siebenrock KA, Kowal JH. The equidistant method – a novel hip joint simulation algorithm for detection of femoroacetabular impingement. Comput Aided Surg. 2010;15(4–6):75–82. 21. Gilles B, Christophe FK, Magnenat-Thalmann N, Becker CD, Duc SR, Menetrey J, Hoffmeyer P. MRI-based assessment of hip joint translations. J Biomech. 2009;42(9):1201–5. 22. Menschik F.  The hip joint as a conchoid shape. J Biomech. 1997;30(9):971–3.

3

Assessment of Hip Pain Changqing Zhang, Yong Feng, and Shengbao Chen

3.1

Overview

Pain is one of the most common clinical symptoms of hip diseases. The symptoms of hip pain are complex, and the pain site may occur in the groin, upper trochanter, proximal femur, or buttocks. The cause is also complex. It may come from the hip joint cavity, around the hip joint, or from the pelvis, lumbar spine, sacroiliac joint, or retroperitoneal space. Because of the rich soft tissue of the hip and pelvis and the complex anatomy, it is difficult to define the cause of pain by routine examination. Therefore, the diagnoses of the cause of hip pain and the purposeful treatment are important for restoring the physical and mental health of patients. The source of hip pain can be divided into inside the hip, around the hip, and outside the hip. The sources of outside the hip pain include the waist, abdomen, pelvic cavity, and knee (Table 3.1). Usually, according to the detailed medical history, the nature of pain, physical examination, auxiliary examination, diagnostic injection treatment, etc., a correct diagnosis can be made for most patients; for those who cannot make a definite diagnosis, they should be closely observed changes in pain and outcomes.

3.2

Clinical Features

3.2.1 Medical History A detailed medical history should be carried out. It is important to record the location, frequency, duration, and mitigation factors of pain. The radioactivity of pain contributes to

Table 3.1  Classification of common diseases causing hip pain Hip joint diseases Osteonecrosis of femoral head Developmental dysplasia of the hip Femoro acetabular impingement Labral injury or tear Hip dislocation or subluxation Traumatic acetabular, femoral head, and femoral neck fracture Hip infection Hip instability Cartilage damage or degeneration Bone marrow edema syndrome Synovial chondromatosis Tumors of the acetabulum and femoral head

Diseases Around the hip Iliotibial tract syndrome Iliopsoas tendonitis Greater trochanteric bursitis Muscle-tendon strain Piriformis syndrome Myositis ossificans Hamstring syndrome Intertrochanteric fracture

Diseases outside the hip Sacroiliac joint disease Ankylosing spondylitis Sports hernia Lumbar disorders Abdominal disorders Pubic ostitis Pelvic diseases Knee problems Pelvic fractures

the diagnosis; the onset and duration of pain are essential for differential diagnosis. In addition, the following characteristics of pain should be asked: Is the pain relieved or aggravated, or maintain the state? Does it cause the patient to wake up at night? What factors can relieve symptoms (position or medicine)? What factors make the symptoms worse? Whether there is a certain action or posture can aggravate symptoms? Previous medical history includes childhood hip disease, trauma, surgery history; increasing activity level for possible stress fractures; risk factors for ischemic necrosis, including

C. Zhang (*) · Y. Feng · S. Chen Department of Orthopedics, Shanghai Jiaotong University Affiliated Sixth People’s Hospital, Shanghai, China e-mail: [email protected] © Springer Nature Singapore Pte Ltd. and Shanghai Scientific and Technical Publishers 2021 C. Zhang (ed.), Hip Surgery, https://doi.org/10.1007/978-981-15-9331-4_3

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glucocorticoid use, alcohol abuse; and medical history of other systemic or local diseases, etc. All previous treatments and responses to treatment should also be documented, including the use of drugs, local block injection, physiotherapy, adjustments to work and daily activities, and the use of ancillary equipment such as walking sticks, crutches, walkers, wheelchairs, etc.

Table 3.3  Sensory nerve assessment

3.2.2 Physical Examination

140 °; extension 10 °; abduction 30 °~45 °; adduction (when the hip is in the slightly flexed position) 20 °~30 °. In the supine position, the internal rotation is 30 °~45 °; the external rotation is 40 °~50 °. In the prone position, the internal rotation is 40 °~50 °; the external rotation is 30 °~40 °. When examining the abduction and external rotation, the pelvis should be kept stable, that is, the iliac crest is at the same level, and the lateral curvature of the lumbar vertebrae is eliminated to compensate for the activity of the hip joint. Provocative tests: These tests are helpful to distinguish different disorders that may have similar presentations. Keep in mind that none of these tests are 100% reliable in every circumstance.

3.2.2.1 Observation Pay attention to the patient’s standing posture and gait, from standing to sitting position, the ability to stand up from the seat and to go to the examination bed, the mobility of the spine, and whether there is a C sign (Patients with intra-articular hip pathology often localize the area of pain by cupping the thumb and index finger in the shape of the letter C above the affected area.). The bilateral hip joints should be fully exposed, compared with each side of the hip, whether there are deformities, swelling, scars, rashes, ulcers, the length of limbs or muscle atrophy. Observe the height of the greater trochanter of the femur, and whether there is an abnormality in the position of the buttocks, knees, and feet. When there is a hip disease, it usually makes hip flexion, mild abduction, and external rotation. In this case, the intra-articular pressure is relatively small.

Nerve root L1 L2 L3 L4 L5 S1

Dominant area Anterior inguinal region and pubis The front of the thigh The lower part of the front of the thigh and the knee Medial calf Lateral calf Plantar

1. Trendelenburg test: Lifting the unaffected leg off of the ground, with normal abductor strength, the patient should be able to maintain a level pelvis. If the abductors are weak, pelvis drops toward the unaffected side with the

3.2.2.2 Palpation Check and record the most obvious tender points, whether there are swelling and muscle spasm, especially the adductor muscle which is an early manifestation of the hip disease. The bony markers include the anterior superior iliac spine, iliac crest, posterior superior iliac spine, sciatic tubercle, and greater trochanter, etc. Evaluate whether the pelvic is tilt. Check muscle strength (Table 3.2). Check the nervous system, especially the sensory nerve (Table 3.3). Check the arterial pulsation such as the femoral artery, posterior tibial artery, dorsal artery. Check tendon reflexes. 3.2.2.3 Movement The active and passive range of motion (ROM) of the hip joint was assessed: the lower extremity was straightened, and the patella was in the neutral position, 0 °. Flexion 130 °~ Table 3.2  Grading of muscle strength Grade 5 4 3 2 1 0

Ability to move Movement against gravity with full resistance Movement against gravity with some resistance Movement with gravity alone Movement without gravity No movement but slight visible/palpable muscle contraction is present No movement, no contraction

Fig. 3.1  Trendelenburg test

3  Assessment of Hip Pain

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Fig. 3.3  Posterior femoroacetabular impingement test Fig. 3.2  Anterior femoroacetabular impingement test

raised leg (Fig.  3.1). In addition, abductor dysfunction can also be caused by pain or neurogenic problems. 2. Anterior femoroacetabular impingement test: The patient is supine with the hip dynamically brought into flexion, adduction, and internal rotation; the test is positive if the patient has reproducible groin pain with this movement, and typically signifies the presence of intra-articular pathology especially in the presence of anterior bone abnormalities and associated with labral injury (Fig. 3.2). 3. Posterior femoroacetabular impingement test: This test is performed with the patient’s buttock at the end of the examination table with both legs suspended. With the patient’s hip extended, the examiner externally rotates the hip, and the test is positive if this maneuver reproduces pain. The test is helpful to detect the presence of associated posterior lesions in the joint (Fig. 3.3). 4. Logroll test: The patient is supine with the leg extended. The leg is passively rolled into full internal rotation and external rotation. It is a sensitive test for intra-articular hip pathology. 5. Thomas test: In the supine position, the patient grasps one knee with both hands and flexes it to the chest as the hip of the contralateral leg is allowed to completely extend. The test result is positive for a hip flexion contracture if the leg is unable to completely extend (Fig. 3.4). 6. Patrick test: The patient is supine with hip flexion, abduction, and lateral rotation. And the ipsilateral foot is placed in a 4-shaped position on the opposite knee. The examiner

Fig. 3.4  Thomas test

holds the pelvis with one hand and pushes down the bending knee joint with the other hand. If the pain is similar to the patient’s clinical symptoms, which means positive. It indicates abnormal sacroiliac joint or spasm of Iliopsoas muscle (Fig. 3.5). 7. Lasegue test (Straight leg raise test): The examiner grasps the ankle of the leg and place the other hand on the front of the thigh to maintain the knee in full extension. Slowly raise the leg until the patient complains of pain or maximal flexion has been achieved. The positive test result is induce/reproduce the patients pain down the leg, which is often indicative of lumbar spine pathology with radiculopathy (Fig. 3.6).

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knee while performing the same maneuver evaluates for tensor fascia latae contracture (modified Ober test). 10. Leg-clamping test: The patient is supine with knee flexion at 90 ° initiative, do active adduction by leg-­clamping to resist to the examiner. If the patient feels pain accompanied by or without loss of strength, suggesting adductor-­related disorders.

Fig. 3.5  Patrick test

3.2.2.4 Measurement The measurement of the length of the lower limbs and the circumference is the main method for checking the asymmetry. It should be performed in the patient’s standing position or the supine position. And it is important to distinguish between the true and the false length of the lower limb. The lower limbs must be placed in a symmetrical position, the pelvis should be placed at the same level, and the iliac crest on both sides should be on one lateral surface to measure the relative length and true length of the lower limbs. If there is a deformity on one side, the healthy side should be placed in the same state, and the measured length comparison is reliable. Symmetrical circumference measurements can be used to understand the degree of muscle atrophy. 1. Apparent lower limb length: The patient is supine, and the distance from the umbilicus to each side of the medial malleolus is measured. Values are affected by developmental arrest, obesity, or lower extremity asymmetry; suggesting abductor or adductor tendons, or pelvic tilt due to scoliosis. 2. True lower limb length: The patient is supine, the feet are separated by 15 ~ 20 cm, and the distance from the anterior superior iliac spine to the ipsilateral medial malleolus is measured. Even if the length of the apparent lower extremity is different, the length of the true lower extremity may be equal. Mild unequal lengths within 1 cm may be considered normal, but may cause symptoms in some patients. Progressive unequal length of the lower limbs suggests a sinking of the prosthesis.

Fig. 3.6  Lasegue test

8. Anterior compression test of iliopsoas tendon: The patient is supine, the examiner’s finger pressed against the anterior capsule of the hip to prevent the hip from snapping. It is often used to inspect the medial snapping hip caused by the iliopsoas muscle. 9. Ober test: The patient is in the lateral decubitus position with the affected side up. The examiner stands behind the patient and, with the patient’s knee in 90° of flexion, abducts and extends the hip as far as is comfortable. The leg is then allowed to slowly adduct. The test is positive for iliotibial band contracture when the knee does not reach the midline (Classic Ober test). Extending the

3.3

Laboratory Tests and Imaging Examination

Laboratory tests based on medical history and physical examination, including blood routine, erythrocyte sedimentation rate, C-reactive protein, procalcitonin, gout, rheumatism, and rheumatoid immune disease-related tests, are helpful for the diagnosis of hip diseases. Imaging studies of hip pain include X-ray, Computed Tomography (CT), Magnetic Resonance Imaging (MRI), Magnetic Resonance Arthrography (MRA), Electromyography (EMG), hip ultrasound, and Positron Emission Tomography-Computed Tomography (PET-CT).

3  Assessment of Hip Pain

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3.3.1 X-Ray 3.3.1.1 Anteroposterior View It can help understand whether the whole structure of pelvis and hip joint is abnormal. By measuring some parameters, we can know the development of hip joint, fracture, osteonecrosis of femoral head, and so on (Fig. 3.7). 1. CE Angle: The angle between the line from the center of the femoral head to the lateral edge of the acetabulum and the vertical line through the center point of the femoral head. The normal CE angle is 25° or more. Values of 20-25° are considered borderline DDH. Values of less than 20° are diagnosed as DDH. 2. Tonnis angle: The inclination angle of the weight-­bearing area of the acetabulum. The angle should be 30 min 16–30 min 5–15 min Around the house only Not at all Yes, easily With little difficulty With moderate difficulty With extreme difficulty No, impossible Yes, easily With little difficulty With moderate difficulty With extreme difficulty No, impossible Rarely/never Sometimes or just at first Often, not just at first Most of the time All of the time (continued)

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Table 3.5 (continued) Item X. Have you had any sudden, severe pain—‘shooting’, ‘stabbing’ or ‘spasms’  – from the affected hip?

XI. How much has pain from your hip interfered with your usual work (including housework)?

XII. Have you been troubled by pain from your hip in bed at night?

Scores 1 2 3 4 5 1 2 3 4 5 1 2 3 4 5

Categories No days Only 1 or 2 days Some days Most days Every day Not at all A little bit Moderately Greatly Totally No nights Only 1 or 2 nights Some nights Most nights Every night

Table 3.6  WOMAC osteoarthritis index

Index I. Pain 1. Walking 2. Stair climbing 3. Rest 4. Weight bearing II. Stiffness 1. Morning stiffness 2. Stiffness occurring later in the day III. Physical function 1. Descending stairs 2. Ascending stairs 3. Rising from sitting 4. Standing 5. Bending to floor 6. Walking on flat 7. Getting in/out car 8. Going shopping 9. Putting on socks 10. Rising from bed 11. Taking off socks 12. Lying in bed 13. Getting in/out bath 14. Sitting 15. Getting on/off toilet 16. Heavy domestic duties 17. Light domestic duties

Scores rating No 0

3.5.2.4 Disadvantages The shortcomings are mainly from patients’ subjective judgment, the degree or frequency of the rating items lacks specific description, and there are certainly individual variation. 3.5.2.5 Applicable Population The scale is applied to assess outcome after total hip replacement by measuring patients’ perceptions in adjunction to surgery.

Slight 1

Moderate 2

Severe 3

Extreme 4

3.5.3 WOMAC Osteoarthritis Index The scoring system was designed a disease-specific instrument for osteoarthritis in the hip and knee and for evaluating clinical outcomes after total hip replacement, and it is self-administered instrument with three subscales: pain, stiffness, and physical function (Table 3.6).

3  Assessment of Hip Pain

3.5.3.1 History In 1988, it was proposed by Bellamy et  al., patients with symptomatology of hip or knee osteoarthritis were evaluated with 17 items on 5 dimensions. They can also be used to monitor disease progression and determine the efficacy of antirheumatic drugs. 3.5.3.2 Grading Standard the higher the score is, the more serious the patient condition is. 3.5.3.3 Advantages 1. Internationally recognized osteoarthritis evaluation criteria. 2. The self-assessment of patients is relatively simple. 3.5.3.4 Disadvantages 1. The scope of application is relatively narrow. 2. There is likely to have ceiling effects when used in a young and active population. 3.5.3.5 Applicable Population It is appropriated to use in outcome measure for older patients with osteoarthritis or rheumatoid arthritis in the hip and knee.

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3.5.4 S  hanghai Sixth Hospital Hip Function Scoring System Based on a comprehensive analysis of their pros and cons of used frequently hip rating scales, a new hip functional score was proposed. The scoring system is completely self-assessed by the patient, highlighting the importance of pain in hip diseases. The scoring system consists of I  ~  V parts, including I pain (45 points), II daily living ability (25 points), III walked activities (21 points), IV labor ability (9 points), and V self-rating on the hip health score (100 points). Among of them, the V part is the VAS score (on 100-point scale, 0 point is the worst, 100 points is the best), and the patient would give himself/ herself a general rating based on the health status of the involved hip joint on day of evaluation, and then presented a score in the form of scale of 20 centimeters, which is a necessary and appropriate compensation for rating the relative healthy hip when bilateral involved. The final total weight score is the total score of the I  ~  IV part × 85% + V part score × 15%, and the total weight full score is 100 points (Table 3.7).

3.5.4.1 History In 2018, the team of Professor Changqing Zhang from Shanghai Sixth People’s Hospital designed and proposed a

Table 3.7  Shanghai sixth people’s hospital (SSPH) hip score Item I. Pain (45 points)     • None     • Mild: Occasional pain or awareness of pain of low grade, no compromise of activities     • Moderate: No effect or a little compromise on average activities, rarely may have marked pain following unusual activities, may take aspirin occasionally     • Marked: Walking or daily activities can elicit pain; pain is tolerable but affect or limitation of ordinary activities, require pain medicine stronger than aspirin occasionally     • Severe: Spontaneous pain, ambulatory or daily activities are likely to exacerbate pain; takes pain medicine stronger than aspirin usually or frequently     • Extreme: Lasting spontaneous pain and unable to tolerable, reject any activity and need taking strong pain relief medicine frequently II. Daily activities (25 points) A. Socks or ties shoes with knee-crossing “4” posture (7 points)     • With ease     • Mild restriction: Can complete but have a little discomfort when put pressure on the knee     • With difficulty     • Unable B. Sitting (5 points)     • Comfortable in any chair for one hour     • Uncomfortable on a medium height chair (such as a sofa) for one-half hour     • Uncomfortable on a high chair for one-half hour     • Unable to sit comfortably in any chair less than one-half hour C. From sitting to standing (4 points)     • With ease     • With difficulty, standing-up on support by upper limbs or other aids     • Unable to stand by oneself D. Squat or hip flexion (5 points)     • Normal, with easy to squat or hip flexion over 120°

Points 45 40 30 20 10 0

7 5 2 0 5 3 2 0 4 2 0 5 (continued)

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Table 3.7 (continued) Item     • With slight restriction to squat or hip flexion more than 90° with aids     • Moderate restriction, it is somewhat difficult to squat, or hip flexion less than 90° with aids     • Severe restriction, it is marked difficult to squat, or hip flexion less than 60° with aids     • Unable to squat, stiff joints, or hip flexion less than 30° E. Stairs (4 points)     • Normal, without use of banister     • Foot over foot using banister     • Stairs in any manner (aids)     • Unable to do stairs III. Walked Activities (21 points) A. Distance walked (9 points)     • Unlimited or continuously walked more than 1500 meters     • Continuously walked for 45 minutes or walked less than 1500 meters     • Continuously walked for 30 minutes or walked less than 1000 meters     • Continuously walked for 15 minutes or walked less than 500 meters     • Only indoor activities, or walked for less than 50 meters     • Unable to walk B. Support required to walk (7 points)     • None     • Single cane for long walks     • Single cane most of the time     • One crutch or two canes     • Use a walker or two crutches     • Not able to walk at all C. Gait (caused by the hip) (5 points)     • Normal, no limp     • Slight or mild limp     • Moderate limp     • Severe limp or waddling gait     • Unable to go IV. Labor ability (9 points)     • Unlimited physical labors     • Tolerated moderate-intensity physical labor / activities     • Tolerated light-intensity physical labor (such as usual housework, shopping, standing operation instruments, control equipment, and assembly work)     • Only partial light-intensity physical labor / activities under non-weight-bearing conditions (such as work by hands under sitting position or light activities in the legs such as typing and sewing)     • Unable to do any intensity physical labor/activities     ■ Total scores of I–IV parts (100 points) V. Self-rating on the hip health status (100 points;0 point is the worst, 100 points is the best):     Patients’ self-rating for hip health status (with scale of 10 cm) as following:

0

20

40

60

80

Points 4 3 1 0 4 3 1 0

9 8 6 4 2 0 7 6 4 3 2 0 5 4 3 2 0 9 7 5 3 0

100

    ■ Final total hip weight scores (100 points): Total scores of I–IV parts *85% + VAS self-rating scores of V*15% Remarks: (1) when patients with bilateral involvements, pain, part of daily activities (including socks or ties shoes, sitting, Squat or hip flexion) and self-rating of hip health status would be scored separately; and another part of daily activities (such as from sitting to standing, stairs), walked activities, and labor ability cannot be scored separately (avoid interference and measurement bias); (2) Scores on self-rating for hip health status was considered to be 15% weight proportion at final total hip weight scores

new hip rating scale. which was based on analyzing the advantages and disadvantages of other used frequently hip score scales, and combined with the clinical features on diseases involvement of bilateral hips. After a potential questionnaire of hip rating assessment and its revised versions were sent to two rounds of Delphi consultations to dozens of experts in orthopaedics and epidemiology, the final measurement item of

this scale was determined. According to distinction of its importance, the weight of each item and their scores were calculated.

3.5.4.2 Grading Standard The lower the score is, the more serious the patient symptom is.

3  Assessment of Hip Pain

3.5.4.3 Advantages 1. The completeness and consistency of measured item presented in the scale was evaluated and proved to be relatively good and acceptable. 2. The scale is self-administered by patients, and it is simple, practical and can be used not only for on-site evaluation, but also suitable for off-site evaluation or in the remote follow-up. 3. Either unilateral or bilateral hips can be evaluated, which solves the defect of measurement bias when both hips are simultaneously involved. 4. Patient’s self-rating on the hip health status is a new additional item, and controlled its weight proportion to 15%, which is contributed to the balance and reliability of the total score, especially for diseases with involvements of bilateral hips. 3.5.4.4 Disadvantages The validity and reliability on the new hip scale is still subject to more clinical studies to test and verify its value. 3.5.4.5 Applicable Population It is suitable for adult (except for the elderly) with hip diseases (such as osteonecrosis of the femoral head necrosis, osteoarthritis, hip dysplasia, hip fracture etc.), whether unilateral or bilateral involvements; it may be a little doubtable to the elderly for its value.

Bibliography 1. Bellamy N, Buchanan WW, Goldsmith CH, et al. Validation study of WOMAC: a health status instrument for measuring clinically important patient relevant outcomes to antirheumatic drug therapy in patients with osteoarthritis of the hip or knee. J Rheumatol. 1988;15(12):1833–40. 2. Brown MD, Gomez-Marin O, Brookfield KF, et  al. Differential diagnosis of hip disease versus spine disease. Clin Orthop Relat Res. 2004;419:280–4. 3. Buckland AJ, Miyamoto R, Patel RD, et  al. Differentiating hip pathology from lumbar spine pathology: key points of evaluation and management. J Am Acad Orthop Surg. 2017;25:e23–34. 4. Byrd JW, Jones KS.  Diagnostic accuracy of clinical assessment, magnetic resonance imaging, magnetic resonance arthrography, and intra-articular injection in hip arthroscopy patients. Am J Sports Med. 2004;32:1668–74. 5. Byrd JWT, Potts EA, Allison RK, et  al. Ultrasound-guided hip injections: a comparative study with fluoroscopy-guided injections. Arthroscopy. 2014;30(1):42–6. 6. Chan YS, Lien LC, Hsu HL, et al. Evaluating hip labral tears using magnetic resonance arthrography: a prospective study comparing hip arthroscopy and magnetic resonance arthrography diagnosis. Arthroscopy. 2005;21:1250. 7. Dawson J, Fitzpatrick R, Carr A, et al. Questionnaire on the perceptions of patients about total hip replacement. J Bone Joint Surg Br. 1996;78:185–90.

37 8. Defroda SF, Daniels AH, Deren ME.  Differentiating radiculopathy from lower extremity Arthropathy. Am J Med. 2016;129(10):e1121–7. 9. Dreyfuss P, Dreyer SJ, Cole A, et  al. Sacroiliac joint pain. J Am Acad Orthop Surg. 2004;12:255–65. 10. Feinberg JH. Hip pain: differential diagnosis. J Back Musculoskelet Rehabil. 1994;4:154–73. 11. Frank RM, Slabaugh MA, Grumet RC, et al. Posterior hip pain in an athletic population: differential diagnosis and treatment options. Sports Health. 2010;2(3):191–6. 12. Grumet RC, Frank RM, Slabaugh MA, et  al. Lateral hip pain in an athletic population: differential diagnosis and treatment options. Sports Health. 2010;2(3):191–6. 13. Harris WH.  Traumatic arthritis of the hip after dislocation and acetabular fractures: treatment by mold arthroplasty. An end-result study using a new method of result evaluation. J Bone Joint Surg Am. 1969;51:737–55. 14. Hasan BA.  The presenting symptoms, differential diagnosis, and physical examination of patients presenting with hip pain. Dis Mon. 2012;58(9):477–91. 15. Hung C Y, Chang K V, Ozcakar L.  Snapping hip due to gluteus medius tendinopathy: ultrasound imaging in the diagnosis and guidance for prolotherapy. Pain Med. 2015;16(10):2040–1. 16. Iagnocco A, Filippucci E, Meenagh G, et al. Ultrasound imaging for the rheumatologist III.  Ultrasonography of the hip. Clin Exp Rheumatol. 2006;24:229–32. 17. Keeney JA, Peelle MW, Jackson J, et  al. Magnetic resonance arthrography versus arthroscopy in the evaluation of articular hip pathology. Clin Orthop Relat Res. 2004;(439):163–9. 18. Kubicki SL, Richardson ML, Martin T, et al. The acetabular fossa hot spot on 18F-FDG PET/CT: epidemiology, natural history, and proposed etiology. Skelet Radiol. 2015;44:107–14. 19. Magee T. Comparison of 3.0-T MR vs 3.0-T MR arthrography of the hip for detection of acetabular labral tears and chondral defects in the same patient population. Br J Radiol. 2015;88(1053):20140817. 20. Magerkurth O, Jacobson JA, Morag Y, et al. Capsular laxity of the hip: findings at magnetic resonance arthrography. Arthroscopy. 2013;29(10):1615–22. 21. Minardi JJ, Lander OM. Septic hip arthritis: diagnosis and arthrocentesis using bedside ultrasound. J Emerg Med. 2012;43(2):316–8. 22. Ostrom E, Joseph A. The use of musculoskeletal ultrasound for the diagnosis of groin and hip pain in athletes. Curr Sports Med Rep. 2016;15(2):86–90. 23. Peng PW.  Ultrasound-guided interventional procedures in pain medicine: a review of anatomy, sonoanatomy, and procedures. Part IV:hip. Reg Anesth Pain Med. 2013;38(4):264–73. 24. Plante M, Wallace R, Busconi BD. Clinical diagnosis of hip pain. Clin Sports Med. 2011;30(2):225–38. 25. Rho M, Mautner K, Nichols JT, et al. Image-guided diagnostic injections with anesthetic versus magnetic resonance arthrograms for the diagnosis of suspected hip pain. Pm & R. 2013;5(9):795–800. 26. Rowbotham EL, Grainger AJ.  Ultrasound-guided intervention around the hip joint. Am J Roentgenol. 2012;198(1):W122–7. 27. Schon L, Zuckerman JD.  Hip pain in the elderly: evaluation and diagnosis. Geriatrics. 1988;43:48–62. 28. Tibor LM, Sekiya JK. Differential diagnosis of pain around the hip joint. Arthroscopy. 2008;24:1407–21. 29. Wahl CJ, Warren RF, Adler RS, et al. Internal coxa saltans (snapping hip) as a result of overtraining: a report of 3 cases in professional athletes with a review of causes and the role of ultrasound in early diagnosis and management. Am J Sports Med. 2004;32:1302–9. 30. Yue B, Tang T.  The use of nuclear imaging for the diagnosis of periprosthetic infection after knee and hip arthroplasties. Nucl Med Commun. 2015;36:305–11. 31. Harris WH. Traumatic arthritis of the hip after dislocation and acetabular fractures: treatment by mold arthroplasty. An end-result

38 study using a new method of result evaluation. J Bone Joint Surg Am, 1969;51(4):737–55. 32. Dawson J, Fitzpatrick R, Carr A, et al. Questionnaire on the perceptions of patients about total hip replacement. J Bone Joint Surg Br, 1996;78(2):185–190. 33. Bellamy N, Buchanan WW, Goldsmith CH, et al. Validation study of WOMAC: a health status instrument for measuring clinically

C. Zhang et al. important patient relevant outcomes to antirheumatic drug therapy in patients with osteoarthritis of the hip or knee. J Rheumatol, 1988;15(12):1833–40. 34. Chen SB, Xu F, Feng Y, et al. Development on a hip functional score of adults based on patient-reported outcomes. Chinese Journal of Orthopaedics, 2018;38(21):1314-21. [Article in Chinese].

4

Imaging Examination and Measurement of the Hip Joints Weiwu Yao and Ting Yuan

4.1

Imaging Examination of the Hip Joint

Ever since the German physicist W.C. Roentgen discovered the X-ray in November 8, 1895, and used it in the clinic, the diagnosis of bone the joint diseases has been greatly improved. An imaging examination of the hip joint plays an important role in the diagnosis and differential diagnosis of hip joint diseases. The most commonly used types of imaging examinations of the hip joint include X-ray, CT, and MRI.

4.1.1 X-Ray Examination of the Hip Joint An X-ray imaging of the hip joint is simple and cheap, also it can indicate joint space, articular surface, and the whole image of the hip joint. The most common forms of X-ray imaging are anteroposterior films, lateral films, frog films, posteroanterior oblique films, oblique obturator films, and ilium oblique films. X-ray radiography has succeeded in digital imaging technology; it is divided into two categories, one of them directly translates the X-ray signal into a digital radiography (DR) system, the other indirectly translates the X-ray signal into a digital signal computed radiography (CR) system. The advantages of DR and CR are: First, the resolution of images is improved. Second, multiple functions can be processed, and better storage management becomes convenient in the later stages, Third, images post-processing can be carried out according to the diagnostic needs, and can show bone tissue, articular soft tissue, and so on, so the disease detection rate is increased.

4.1.1.1 Anteroposterior Films of the Hip Joint With the patient in the supine position, straighten the legs, 2 feet keep internal rotation 15 degrees and draw toes together, the tube center aims at the femoral head and is perpendicular W. Yao (*) · T. Yuan Department of Orthopedic Surgery, Shanghai Jiao Tong University Affiliated Sixth People’s Hospital, Shanghai, China

to the inguinal plane. This position can indicate the frontal images of the hip joint, the femoral head, neck of the femur, greater trochanter and lesser trochanter, upper femur. In order to compare the diseased side with the healthy side, anteroposterior images of the hip joint are often replaced by anteroposterior images of the pelvis or anteroposterior images of the bilateral hip.

4.1.1.2 Lateral Films of the Hip Joint With the patient in the supine position, raise the diseased hip up to the same height as the midline of the detection line, straighten the diseased leg, keep abduction and internal rotation, keep contralateral hip and knee flexion, the patient holds the legs with hands so that the thigh is perpendicular to the ground. The tube center horizontal line aims at the neck of femur and is perpendicular to the cassette. This position can indicate the lateral images of the femoral head, neck of the femur, greater trochanter, and lesser trochanter. 4.1.1.3 Frog Films of the Hip Joint Do not take frog films for a suspected hip fracture or hip joint dislocation. When taking frog films, with the patient in the supine position, keep bilateral hip and knee flexion, draw feet together, and keep two thighs at maximum abduction. The tubing center aims at the midpoint of the femoral head on both sides. This position can indicate the frontal images of two acetabulum and the lateral images of the bilateral neck of the femur. 4.1.1.4 Posteroanterior Oblique Films of the Hip Joint The posteroanterior oblique films of the hip joint are of great value in detecting the posterior dislocation of the femoral head. Patients with prone position, contralateral hip raise 35–40 degrees, knees and elbows are bent to support the body. The hip that is detected aims at the middle line of the cassette, and greater trochanter aims at the film center. The shoot is perpendicular to the cassette. This position can i­ndicate the oblique images of the hip joint, ilium, and upper femur.

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4.1.1.5 Obturator Oblique Films of the Hip Joint The patient is in the oblique supine position. Namely, the coronal plane of the patient’s body keep 45 degrees with bed, the detected hip is above. The contralateral hip and knee are supported by cotton pads on the back. Horizontal shoot, namely, the tube centerline which is coming in from the midpoint of the connection between the superior ramus of the pubis and the inferior ramus of the ischium aims at the hip joint. Obturator oblique films of the hip joint are mainly used to indicate obturator, iliopectineal line, anterior hip column, and posterior acetabular margin. 4.1.1.6 Ilium Oblique Films of the Hip Joint The patient is in oblique supine position, the detected hip is below, the coronal plane of patient body keeps 45 degrees with bed, place the cassette horizontally and directly face the hip joint, the tube centerline which is coming in from the anterior internal hip joint is perpendicular to cassette, aiming at the hip joint shooting. Ilium oblique films of the hip joint can indicate the whole ilium wing crista iliaca, posterior hip column, and anterior acetabular margin.

4.1.2 CT Examination of the Hip Joint The CT plain scan and contrast enhancement are often used for hip joint CT.  All CT examination is plain scan first. Some complex diseases need CT contrast enhancement, like a tumor or vascular disorders. Computed tomography (CT) shows the sectional anatomical image, no structural overlap, the density resolution is significantly higher than that of the X-ray plain. The multi-slice CT (MSCT) further improvers the temporal and spatial resolution, which greatly improves the detecting rate and diagnostic accuracy of osteoarthropathy [1], it can carry out post-processing techniques such as multi-plane reconstruction, surface

Fig. 4.1  Axial and coronal CT

W. Yao and T. Yuan

overlay display and volume display at the same time, and we can know the location, border, and relationships with surrounding organizations from multi-sections. The structure of a hip joint is complex, the plain X-ray has limited ability to diagnose acetabular fractures or hip joint lesions due to overlapping. CT can significantly improve the diagnostic accuracy (Fig. 4.1). Spiral three-dimensional CT reconstructs bone structure, which can display the three-dimensional structure of the hip joint and the lesions involved area. For example, threedimensional CT reconstruction can observe the head of the femur and acetabula, respectively, which can display the relationship of the acetabula and head of the femur; otherwise, hip joint three-dimensional CT can provide data for three-dimensional printing implants [2]. It is of great significance to the diagnosis of disease and the design of preoperative surgery (Fig. 4.2). During the CT examination, the patient should take the supine position and try to maintain the left and right symmetry. Fig. 4.2 shows the boundary of the tumor on the medial side of the left acetabular, the damage to the bone cortex and the relationship with the surrounding tissue can be observed.

4.1.3 MRI Examination of the Hip Joint Magnetic resonance imaging (MRI) is an examination technique that relies on the mission of hydrogen protons, with no radiation damage. Different tissues of bone and muses system have different hydrogen protons, and relaxation time, different signal intensities are generated, and images are formed by forming different gray scales after computer processing. The advantage of MRI is the high resolution of soft tissue, multiparameter imaging, multi-directional imaging, such as cross

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Fig. 4.4  Cross section of the femoral lesser trochanter

Fig. 4.2  Three-dimensional reconstructive CT

Fig. 4.5  Cross section of the femoral head

Fig. 4.6  Cross section of the upper acetabulum Fig. 4.3  CT and MRI of right acetabular tumor

section, coronal plane, sagittal plane, or any angle, MRI can sensitively detect changes in water content in tissue components and lesions earlier than X-ray and CT (Fig. 4.3). Compared with CT, MRI can clearly show the condition of the surrounding tissue reaction zone of the tumor and the relationship between tumor and surrounding muscle, blood vessels, nerve, and other soft tissue structures. During the hip joint MRI examination, the patient’s position is the same as that of CT examination, supine position and toes contact are adopted to keep the body as symmetrical as possible.

MRI has good soft-tissue resolution and the advantage of multiple sequence imaging, it not only can display that the articular cartilage, ligaments inside and outside joints, intervertebral disc, and bone marrow, it can also reflect some of the pathological changes that CT cannot, such as edema of soft tissue and bone marrow cavity, bone contusion, muscle tear, the change of the bone marrow, and the injury and degenerations of tendons, ligaments and cartilage, and so on. MRI is the preferred examination method for joint lesions and an effective method for preoperative staging and efficacy observation of bone tumors (Figs. 4.4, 4.5 and 4.6). Fig. 4.5 show that the right acetabular medial tumor can be seen, and the signal is uneven.

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Fig. 4.6 shows that the tumor destroys the iliac bone and bulges into the pelvis.

4.2

II. X-Ray Measurement and Parameters of the Hip Joint

4.2.1 Hip Parameters

Skinner line

4.2.1.1 Shenton Line (Menard Line) A continuous arc between the medial margin of the femur neck and the upper margin of the ipsilateral obturator foramen. The integrity of this line disappears with hip subluxation and dislocation. It can also be used to evaluate the position of the prosthesis (Fig. 4.7). 4.2.1.2 Calve Line (Iliac Neckline) The arc of the outer margin of the ilium and the outer margin of the femur neck, it can reflect the relationship between the femoral head and the acetabulum, and the integrity of the upper margin of the acetabulum (Fig. 4.7). 4.2.1.3 Skinner Line Anteroposterior films of the hip joint in adults, the line between the upper margin of the greater trochanter and the crypt which round ligament of the head of the femur attach, the angle with femoral stem central axis is 90 degrees in adults. The Dislocation fractures of the neck of femur or greater trochanter will lead to Skinner line exceed the round ligament fossa (Fig. 4.8). Skinner line goes through the apex of the femoral greater trochanter and the acetabular round ligament fossa, and is perpendicular to the axis of the femoral shaft.

Fig. 4.8  Skinner line

4.2.2 Proximal Femur Parameters 4.2.2.1 Neck-Shaft Angle On the AP films of the hip joint, draw the femoral shaft axis and the femoral neck axis, respectively, the Angle between the two lines intersecting on the medial side is the neck-shaft Angle (NSA). The normal range is 110–140 degrees (Fig. 4.9), more than 140 degrees is coxa valga, and less than 110 degrees is coxa vara. 4.2.2.2 Femoral Neck Anteversion The angle between the neck of the femur axis and the human coronal plane. Femoral neck anteversion (FNA) is 12–15 degrees in adults (Fig. 4.10).

Fig. 4.7  Shenton line (red line) and Calve line (blue line)

4.2.2.3 Femoral Offset It is the vertical distance between the center of the femoral head and the axis of the femoral shaft, which is an important reference index for the reconstruction of hip joint biomechanics. The recovery of femoral offset by hip replacement is very important to balance the tension of the soft tissue of the hip joint (Fig. 4.11). Normal value is 110 ° ~ 140 °. Femoral neck anteversion is 12–15 degrees for adults. Femoral offset is the vertical distance between the center of the femoral head and the axis of the femoral shaft.

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4.2.3 Acetabular Parameters 4.2.3.1 Center Edge Angle (CEA) On the AP films of the pelvis, it is an angle formed by the line which is between the center of the femoral head and the external superior margin of the acetabulum with the vertical line at the center of the femoral head. The normal range is 22 degrees for 2 years old, 28 degrees for 4 years old, 30 degrees for 6 years old, and 35 degrees for 15 years old (Fig. 4.12). This angle reflects the relationship of the acetabulum and the femoral head; it is an important index to determine the stability of femoral head in acetabular fossa. When acetabular dysplasia, dislocation of the hip joint, shape change of femoral head, and external movement of the femoral head, this Angle decreases.

Fig. 4.9  Neck-shaft angle

Fig. 4.10  Femoral neck anteversion

Fig. 4.11  Femoral offset

4.2.3.2 Acetabular Index It is a method to determine the depth and inclination of the acetabulum, that is, the Angle formed between the central line of bilateral y-shaped cartilage and the line which is between the upper margin and the lower margin of the acetabulum. The normal range is 30 degrees for newborn, 20 degrees for 2 years old, 10 degrees for adults (Fig. 4.13). To some extent, the acetabular index reflects the inclination of the acetabular stress surface. The higher the index, the more likely the dislocation of the hip joint will occur. Acetabular index plays an important role in the treatment and prognosis of developmental dysplasia of the hip (DDH). 4.2.3.3 Sharp Angle On the AP films of the pelvis, the angle between the line of the lower margin of the bilateral tear drops and the line from the lower margin of the tear drop to the upper margin of the acetabulum. Normal angle is 33–38 degrees. When the angle

Fig. 4.12  Acetabular center edge angle

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Fig. 4.13  Acetabular index

Fig. 4.15  Kohler line

Fig. 4.14  Sharp angle

Fig. 4.16  HE angle

is greater than 40 degrees, it can be diagnosed with acetabulum dysplasia (Fig. 4.14).

4.2.3.5 HE Angle The angle between the line of the bilateral acetabulum and the extension line of the epiphyseal plate of the femoral head, normal range is about 25 degrees, HE angle is greater than 25 degrees when coxa vara. Continuous measurement of HE Angle can be used to understand the progression of coxa vara (Fig. 4.16).

4.2.3.4 Kohler Line (Nelaton) The double tangential line between the inner margin of the ischium and the inner margin of the ilium, which represents the medial border of the acetabulum, Acetabular invagination or hip joint replacement when the bone mill file is too deep the acetabulum comes down to the medial side of the line, it is used for the evaluation of prosthesis depth in hip arthroplasty (Fig. 4.15).

4.2.3.6 Perkin Grid The P-line is made from the outer upper margin of the acetabulum and is perpendicular to the Y-line which is the line

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of the bilateral acetabulum. The P-line and Y-line divide the acetabular area into four quadrants. The normal epiphyseal center of the femoral head is located in the inner and lower quadrant, if the center of ossification moves out-and-­ downward or out-and-upward of the quadrant represents the dislocation of the hip joint (Fig. 4.17).

References 1. Conway WF, Totty WG, Mcenery KW. CT and MR imaging of the hip. Radiology. 1996;198(2):297–307. 2. Rengier F, Mehndiratta A, Tenggkobligk HV, et  al. 3D printing based on imaging data: review of medical applications. Int J Comput Assist Radiol Surg. 2010;5(4):335.

Fig. 4.17  Perkin grid

5

Application of Ultrasound in the Diagnosis of Hip Diseases Bin Hu and Jie Chen

Ultrasound is an important part of modern imaging, and it plays an important role in the diagnosis of abdominal, cardiovascular, thyroid, and breast diseases. With the improvement of the performance of ultrasonic equipment and the advancement of inspection techniques, the application of ultrasound in the musculoskeletal system including the hip joint has become more and more mature. It has excellent performance on soft tissue structures such as muscles, tendons, blood vessels, and nerves. Ultrasound has the characteristics of high resolution, portability, and noninvasiveness. Realtime ultrasound can dynamically observe the movement of muscles and tendons, and provide important information that other images cannot obtain.

5.1

 ormal Adult Hip Ultrasound N Detection

Adult hip joints are relatively deep. Depending on the size of the subject and the depth of the structure being observed, a combination of a 5  ~  7  MHz low-frequency probe and a 7  ~  12  MHz high-frequency probe can be used for detection. The Ultrasound examination of an adult hip joint includes four parts: the anterior, the medial, the lateral, and the posterior. Mastering several important bony landmarks of the hip, such as the anterior superior iliac spine, the anterior inferior iliac spine, the femoral head, the greater trochanter of the femur, and the ischial tuberosity can help to clarify the anatomy in the sonogram.

B. Hu (*) · J. Chen Shanghai Jiao Tong University Affiliated Sixth People’s Hospital, Shanghai, China

5.1.1 Anterior Part The patient is examined in the supine position. In this area, we mainly observe the joint cavity, acetabular labrum, anterior muscle group, vascular nerve bundle, etc. 1. Hip joint: The probe is parallel to the femoral neck. The curved, strong echo of the femoral neck and the thin layer joint capsule can be clearly shown on the oblique sagittal position scan. There is a potential cavity between the joint capsule and the femoral neck, which is the anterior crypt of the joint. It is formed by the joint capsule covering the anterior of the hip joint folding back at the intertrochanteric line. Most people’s anterior recess is a homogeneous hypoechoic layer on the sonogram. Only a few people have a two-layer structure (Fig. 5.1). Under normal circumstances, there is only a small amount of synovial fluid in the anterior crypt, which acts as a lubricant. The fluid often accumulates in the hip joint effusion first, and is also a common site of synovial hyperplasia of the hip joint. 2. Acetabular labrum: Moving the probe slightly toward the head, we can see the strong echo of the acetabulum and the femoral head. The superior anterior part of the labrum can be seen between the two, which has a triangular hyperechoic structure and acetabular labrum tear often occurs here (Fig. 5.2). A thin layer of hypoechoic articular cartilage is visible on the surface of the femoral head. 3. Anterior muscle group: The iliopsoas muscle consists of the iliacus and the psoas muscle. It ends at the lesser trochanter of the femur through the anterior aspect of the hip joint. At the level of the front of the hip joint, the muscle bundle and the tendon component coexist. In the sonogram, the iliopsoas muscle is located in the anterior medial aspect of the hip joint. The muscle bundle is located in the shallow part showing as a band-like hypoechoic area, and the thin layer of a hyperechoic area of the tendon is located in the deep part (Fig. 5.3). There

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Fig. 5.1  Longitudinal section of the front crypt. The anterior crypt is a thin layer of hypoechoic structure (the scale shows the thickness of the anterior crypt), and the deep curved strong echo is the femoral neck

Fig. 5.2  Sonogram of the anterior labrum of the joint. The acetabular labrum is a triangular slightly hyperechoic structure. The thin layer of cartilage is visible on the surface of the femoral head, showing hypoecho

is a potential cavity between the iliopsoas tendon and the joint capsule, which is the iliac crest sac. Ultrasound can detect bursitis or effusion. Two anterior thigh muscles, the sartorius muscle and the rectus femoris, are displayed in the longitudinal section of the anterior superior iliac spine and the anterior inferior iliac spine, respectively (Fig. 5.4). 4. Vascular nerve bundle: The probe is placed under the middle of the inguinal ligament, showing the femoral artery and femoral vein. The blood flow signal is detected by color Doppler ultrasound. The femoral nerve can be explored on the lateral side of the femoral artery. The transverse section is a mesh-like structure and in the deep part of the nerve is the iliacus (Fig. 5.5).

the inside. The deeper side of the first two is the short adductor muscle and the deeper adductor Magnus. All of the muscle-tendon talked above are from the pubic bone (Fig. 5.6).

5.1.2 Medial Part The patient is in the supine position, and the hip is slightly abducted and extorted for examination. The medial transverse section of the vascular nerve bundle is scanned. The pubic muscle, the long adductor muscle, and the gracilis muscle are displayed from the outside to

5.1.3 Lateral Part The patient is placed in lateral position with the lower extremities straightened. This area mainly observes the greater trochanter, gluteal muscles and tendons, and bursa. The greater trochanter of the femur has a strong echo structure with a slightly uneven surface. The tendons of the gluteus medius and gluteus minimus are attached here (Fig. 5.7). The former is attached to the lateral posterior superior part of the greater trochanter, while the latter is attached to the anterior part of the greater trochanter. The bursa is present next to the tendon, and when the pathological changes occur and the effusion increases, ultrasound can be used to detect. The gluteus maximus fibers are visible in the shallow part of the lateral area, and the lower deep muscle fibers end in the gluteal tuberosity. The lower superficial layer and the upper muscle fibers end at the iliotibial band. The iliotibial bundle is

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located in front of the greater trochanter and is the tendon part of the tensor fascia.

5.1.4 Posterior Part The patient is in a prone position with the lower extremities straightened. The gluteal muscle, the hamstring muscle, and the sciatic nerve are mainly observed in this area. The ischial tuberosity is an important anatomical landmark. In the transverse or longitudinal section of the buttock, the ultrasound image mainly shows the gluteus maximus muscle. The probe is gradually moved down to observe the hamstring muscles, including the long head of the biceps femoris, the semitendinosus, and the semimembranosus. All three are from the ischial tuberosity (Fig. 5.8). The sciatic nerve ascends on the lateral side of the ischial tuberosity running deep in the gluteus maximus, and has an elliptical mesh-like structure in the cross-section.

5.2

Fig. 5.3  Long axis section of the iliopsoas tendon. The arrow shows the iliopsoas tendon in front of the femoral head, which showing striplike hyperecho, and the anterior part is the muscular part of the iliopsoas muscle

Fig. 5.4  Longitudinal section of the sartorius muscle and rectus femoris. (a) The longitudinal section of the sartorius muscle, the proximal end of which is from the anterior superior iliac spine; (b) The longitu-

 ltrasound Diagnosis of Adult Hip U Disease

5.2.1 Joint Effusion Joint effusion is commonly detected by ultrasound in cases of hip pain, and is usually located in the anterior crypt.

dinal section of the rectus femoris muscle, the proximal end of which is from the anterior inferior iliac spine and the shallow part is the sartorius muscle

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Fig. 5.7  Cross section of the hip. It shows that the gluteal muscle tendon (arrow) is attached to the greater trochanter of the femur, and the surface of the trochanter is smooth Fig. 5.5  Cross section of vascular nerve bundle in the inguinal region. Transversely below the middle of the inguinal ligament, showing the femoral vein (V), femoral artery (A), femoral nerve (arrow) from the inside to the outside

Fig. 5.8  Longitudinal section of the buttocks. Showing the hamstring tendon (scale) attached to the ischial tuberosity (arrow)

Fig. 5.6  Hip inner cross section. Transversely below the medial aspect of the inguinal ligament, showing femoral artery (A), femoral vein (V), and pubic muscle (arrow)

Simple effusions are anechoic, compressible, and devoid of Doppler flow [1]. In the oblique sagittal image of the femoral neck in front of the hip, the anterior crypt of the hip is thickened with anechoic inside. When the probe is pressurized,

the thickness of the anechoic is significantly thinner (Fig.  5.9). When the liquid is cloudy, it may also be hypoechoic. Sometimes a floating flocculated echo may be seen, representing old bleeding or debris after inflammation. There is no uniform standard for the normal thickness of the anterior crypt. It is generally considered to be meaningful when the value is greater than 8 mm or the difference between the two sides is greater than 2  mm. When the effusion increases, the range of the liquid zone increases, exceeding the anterior crypt to the front of the femoral head or even around the joint.

5  Application of Ultrasound in the Diagnosis of Hip Diseases

Fig. 5.9  Hip effusion. A longitudinal section of the hip joint, seeing a large amount of effusion in the anterior crypt, poor sound transmission, flocculent echo floating, is considered to be pus formation

5.2.2 Hip Synovitis Acute or chronic joint damage, osteoarthritis, infection, joint replacement surgery, systemic diseases (such as rheumatism and gout) can cause hip synovial hyperplasia and synovitis. The best position to observe the synovial membrane is the anterior joint crypt, which is probed in the oblique sagittal position in front of the femoral neck. On the sonogram, the anterior crypt is thickened and hypoechoic (Fig. 5.10). According to the state activity of the disease, it can be divided into active synovitis and quiescent synovitis. The former blood flow signals in the synovium can be detected by color Doppler ultrasound. Changes in synovial thickness and blood flow signals help to determine the therapeutic effect.

5.2.3 Peri-Hip-Joint Mass Compared with CT and MRI, ultrasound is the simplest and most convenient imaging method for examining tumors around the hip joint. The main roles of ultrasound examination are: (1) To determine whether there is a tumor and to determine the size, level of the tumor, and the relationship with the surrounding tissue. (2) To determine whether the tumor is cystic or solid. Ultrasound has higher accuracy in this judgment, which can be identified by the type of echo and the presence or absence of blood flow signals. (3) For cystic lesions, most of the diagnosis can be based on the history and the anatomical relationship of the lesion and adjacent tissue, rather than the sonographic appearance of the cystic contents. (4) The ultrasound findings of solid tumors are mostly non-specific and require ultrasound-guided histological biopsy for diagnosis.

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Fig. 5.10  Anterior crypt synovial hyperplasia. The arrow shows that the synovial of the front crypt is thickened, and the thickness of the synovial is unchanged by the probe with compression

5.2.3.1 Cystic Mass Common cystic peri-hip-joint mass includes synovial cysts, acetabular labral cysts, bursal cysts, hematomas, and abscesses. The gray scale ultrasound findings of the femoral pseudoaneurysm are similar to cysts. Color flow signal of the tumor can be detected by color Doppler ultrasound. 1. Hip synovial cyst: It can be derived from the joint capsule, muscular layer, etc. Ultrasound can find well-defined anechoic masses at the corresponding sites, and the shape is mostly round or elliptical. Due to the high tension, the mass will not deform under the pressure of the probe (Fig. 5.11). 2. Acetabular labral cyst: Mostly after the labrum is damaged, the joint fluid is formed. The labrum damage is caused by trauma or degeneration, and the upper part is where the damage more likely to occur. The typical clinical manifestation is hip pain, which occurs mostly in the groin. The pain can be severely or progressively aggravated and can be accompanied by a squeaky feeling. A symptom of joint locking can occur when the damaged labrum is embedded into the joint cavity. The activity of the hip joint is limited to varying degrees, and the pain symptoms worsen when the hip joint is adducted and rotated. Due to the limitation of the acoustic window, ultrasound can only observe the anterior labrum of the joint. When the lesion occurs, an oval anechoic cyst can be seen beside the hyperechoic labrum, with clear boundary is clear, and there is no blood flow signal inside. 3. Hematoma: Hematomas in soft tissue often have a clear history of trauma. A small number of patients who use anticoagulant therapy can develop spontaneous bleeding without any cause. There are significant differences in the

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sonographic appearance of hematoma at different stages. In the early stage of bleeding, there is an uneven echo mass, and the echo intensity is unevenly distributed from low to high. The shape of the hematoma can be elliptical or irregular. The edges are unclear and there is no blood flow signal inside. As time progresses, the echo of the hematoma gradually decreases. After 4–5 days of hemorrhage, the hematoma is liquefied, showing anecho, and the boundary is clear. This is the best time for pumping (Fig.  5.12). The unabsorbed hematoma gradually organized in the periphery and inside after 2 months, showing a low echo, irregular shape, unclear boundary. There is a strong echo when calcification occurrs. 4. Abscess: An Abscess can be caused by hip trauma, foreign body, osteomyelitis, and joint replacement. The abscess is

Fig. 5.11  In the anterior oblique sagittal section of the joint, there is an oval anechoic cyst with clear boundary

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located in the joint cavity or surrounding soft tissue. Patients with hyperglycemia, abnormal renal function, and low immune function are more likely to have abscesses. The clinical manifestations are local swelling and pain, and fluctuating feeling on palpation. When the abscess is small in a deep position with a thick wall of cavity, the sense of fluctuation is not obvious. In severe cases, systemic symptoms may occur. Ultrasound shows that the lesions are mainly hypoechoic; the blood flow signal in the peripheral inflammatory reaction area increases with no blood flow signal in the internal liquefaction area. When the probe is pressurized, and the liquefaction part shows a floating feeling (Fig. 5.13). For patients with sinus formation, ultrasound can observe the course and distribution of the sinus, and the positional relationship with the abscess, which is helpful for the formulation of the surgical plan. 5. Bursal effusion and bursitis: The bursa is a closed sac containing a small amount of synovial fluid inside. The inner wall covers the endothelial cells, usually located near the joint between the bony prominence and the tendon or between muscle and skin. Its main function is to promote sliding and reduce friction and compression between soft tissue and bone. A few of them are connected to the joints. The hip bursa has the ischial tuberosity sac, the iliopsoas sac, the gluteus medius bursa, and the gluteal minimus bursa, etc., which cannot be displayed under ultrasound under normal conditions. The ischial tuberosity sac and the iliopsoas sac are common places lesions occur. The cause of bursa effusion is hip degeneration and bursitis caused by various causes, including traumatic, infectious, and inflammatory (rheumatoid arthritis). The clinical features of acute bursitis are local pain, swelling, activity disorders, and tenderness in palpation. High-frequency ultrasound can observe the synovial hyperplasia of the sac, the thickening of the bursa wall, the accumulation of fluid, and the deposition of calcium. Color Doppler ultrasound shows a good cor-

Fig. 5.12  Hip soft tissue hematoma. Female patient, 1 month after hip trauma, the local lateral bulge of the joint, no pain. Ultrasound detects a huge hematoma in subcutaneous tissue

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tomical structure. Color Doppler ultrasound can evaluate the blood supply of the tumor (Fig. 5.15). For those who have doubts about the judgment of benign and malignant, it is feasible to perform an ultrasound-guided biopsy.

5.2.4 Muscle Tear Improper force, excessive muscle fatigue, or overload often lead to muscle fiber damage. According to the severity of the tear, it can be categorized into four different grades. The sonograms of the different degrees of damage are also varied.

Fig. 5.13  Hip abscess. Transverse scanning at the front of the hip joint, a large abscess formation around the femoral head, mainly hypoechoic, and scattered dotted echoes inside

5.2.4.1 Grade 0 Damage The damaged muscle fibers are reversible. The connective tissue is not involved. There is no abnormal change in ultrasonography. 5.2.4.2 Grade 1 Damage The muscle stretch is within the elastic limit. The patient has pain, the muscle function is normal, and the muscle damage is less than 5%. Gross pathological examination reveals a small range of broken muscle fibers, often near the junction of the muscle belly and tendon. Ultrasound examination shows that the local muscle fiber texture is unclear and hypoechoic, which may be accompanied by a small amount of bleeding. After a few weeks, the sonogram shows that the muscle fiber structure returned to normal.

Fig. 5.14  Hip ischial tuberosity bursa. At the posterior longitudinal section of the hip, effusion can be seen in the superficial bursa of the ischial tuberosity (arrow). The liquid permeability is slightly poor, and a rich blood flow signal is visible on the wall of the bursa, suggesting bursitis accompanied by effusion

relation between the richness of the synovial blood flow signal and the severity of the inflammatory (Fig.  5.14). Ultrasound can also guide the puncture suction of the fluid in the bursa.

5.2.3.2 Solid Tumors Common solid tumors around the hip joint, including lipoma, hemangioma, schwannomas, synovial-derived tumors, and tumor-like lesions. The tumor tissue derived from the mesenchymal tissue has a variety of pathological types, most of which have no specific ultrasound findings. The main purpose of the ultrasound examination is to determine the position and the size of the tumor, and the relationship with the surrounding and the relationship with the surrounding ana-

5.2.4.3 Grade 2 Damage The muscle stretch exceeds the elastic limit. The range of muscle fiber damage is further expanded but does not exceed half of the whole in the cross-section. The patient sometimes feels the tearing of the muscles. The muscle function is lost, and the local swelling is obviously visible. An ecchymosis occurs under the skin. The weakened area of the muscles can be found by palpation. The sonogram shows a continuity interruption in a large number of muscle fibers, or the interruption at the junction between the muscle fibers and the epimysium. A hematoma is formed at the interrupted site, with low echo or no echo. When the probe is pressurized, the muscle ends are floating in the hematoma area. In the later stage of the disease, the hematoma is organized, and the surrounding hyperplasia and scar of granulation tissue are formed, gradually replacing the muscle fiber tissue. 5.2.4.4 Grade 3 Damage The muscle breaks completely and loses its function. The local soft tissue is more swollen, and the local muscle layer can have an emptiness feeling when palpated. Ultrasound examination shows a complete interruption of muscle continuity, retraction of both ends, thickening, irregular edge morphology, hema-

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Fig. 5.16  Gluteus maximus tear. The patient is a 35-year-old male. Three days after the car accident, the gluteus maximus is completely broken, the broken end is separated, and the hematoma forms

Fig. 5.15  A solid mass in soft tissue in front of the hip joint. The patient is a 45-year-old male. A huge hypoechoic mass is seen in the anterior muscle layer of the hip. The shape is irregular, lobulated, the border is clear. Surgical pathology indicates chondrosarcoma

toma filling between the ends, and increased distance of the end of the limb during passive stretching (Fig. 5.16).

5.2.5 Tendinopathy Repetitive hip movements cause minor damage to the surrounding tendon, which is the main cause of tendinopathy, and it is common in the elderly or professional athletes. Rheumatism, autoimmune diseases, and other reasons can also lead to inflammatory changes in the hip tendon, and more common in the tendon attachment, also known as attachment inflammation. Hip tendon lesions occur in the gluteus medius tendon and the gluteus maximus tendon attached to the greater trochanter of the femur. Ultrasound shows thickening of the tendon and reduction of echo intensity. When the inflammation is active, the color flow signal can be seen in the tendon. Most of the hip tendonitis is calcified inflammation, and the calcification is mostly punctate, plaque-like echo, with or without sound shadow. Inflammation can cause localized bone erosion (Fig. 5.17).

Fig. 5.17  Gluteus minimus tendinitis with bone erosion. Lateral transverse section of the hip, thickening of the gluteus minor tendon, reduced echo intensity, uneven distribution, and the surface of the cortical bone of the greater trochanter is not smooth, showing a worm-like change

5.2.6 Snapping Hip Syndrome

internal or external. An external snapping occurs when there is a friction between the iliotibial band or the gluteus maximus tendon and the greater trochanter of the femur. An internal snapping mostly happens with the friction created between the iliopsoas tendon and the pubic trochanter. It can also be seen in the joint mouse and labrum tearing. Ultrasound is the only imaging examination that can be performed under motion. It plays an important role in the diagnosis of the hip, especially for the snapping caused by the tendon.

During the active extension or flexion of the hip joint, the patient hears or feels the hips snapping when the hip joint moves to a certain position. According to the cause and location of the snapping, a snapping syndrome is divided into

5.2.6.1 Iliotibial Band Snapping Syndrome The patient is placed in the contralateral position, and the probe is transected at the greater trochanter level. During the flexion of the hip joint, the tendon bundle strikes across the

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ditions. Ultrasound diagnosis of DDH (Graf method) is the earliest method for the diagnosis of DDH based on the coronal plane of the hip joint. It can comprehensively observe the osseous acetabulum and cartilage acetabulum and judge the spatial relationship of the femoral head and acetabulum. It is currently the most widely used method in the world.

5.3.1 Ultrasonic Examination Method

Fig. 5.18  Iliotibial band Snapping Syndrome. The affected side’s Iliotibial band is obviously thickened, the echo intensity is reduced, and the arrow refers to the deep greater trochanter. Under the moving condition, the iliotibial band slides across its surface and makes a sound

greater trochanter of the femur in an instant. We also can see the iliotibial band snaps when it crosses the greater trochanter of the femur. Due to long-term friction, the iliotibial band is thicker than normal (Fig. 5.18).

5.2.6.2 Iliopsoas Tendon Snapping Syndrome Dynamic ultrasonographic examination during provocative maneuvers is the diagnostic test of choice for symptomatic snapping iliopsoas tendons at the level of the pelvic brim or femoral head [2, 3]. The patient is in a supine position, and the lower extremity is extended. The probe is transected at the iliopsoas tendon in front of the hip joint, and the iliopubic tuberosity is shown. The hip joint continuously performs flexion, abduction, extorsion, and extension. At the same time as the sounding, the iliac crest muscle tendon laterally passes over the iliopubic tuberosity and slides inward. In the quiescent state, ultrasound often finds tendon thickening and echo reduction of the iliopsoas tendon.

5.3

Ultrasound Diagnosis of Developmental Dislocation of the Hip

Developmental dislocation of the hip (DDH) is the most common developmental disease in pediatric orthopedics. The currently accepted principles of DDH treatment are early detection and early treatment. The earlier the treatment, the simpler the treatment, and it is easier to get a normal or near-normal hip joint. Since the baby’s femoral head is mainly cartilage, it cannot be developed on the X-ray. The DDH diagnosis and treatment guidelines developed by the Chinese Medical Association in 2017 indicate that for infants younger than 6 months, ultrasonography is an important auxiliary examination method for DDH, and it is recommended to use ultrasound screening in areas with better medical con-

Select a 7 ~ 12 MHz linear array probe according to the age of the child. In the lateral position, the hip joint is slightly rotated and close to the straight position. A special examination bed can be selected to facilitate the fixation. In the contralateral decubitus position, the hip joint is slightly pronated and close to the straight position. A special examination bed can be selected to facilitate the fixation. The probe should be scanned at the lateral side of the hip joint to prevent the sound beam from tilting forward or backward. Generally, check the left side first, and then the right side.

5.3.2 The Normal Sonogram The sonogram of the normal hip joint clearly shows the morphology and their spatial relationship of the acetabulum and femoral head. The development of osseous acetabulum is good, the top edge of the bone is sharp or slightly blunt, the cartilage acetabulum completely covers the femoral head, and the spatial relationship of the femoral head and acetabulum is normal, and the two are in close contact. The Graf method uses the coronal section of the acetabular center as a standard image for measurement and diagnostic typing, i.e., the image shows the lowest point of the ilium ossification, the flat iliac rim, and the labrum. The standard image also shows the structure of the femoral head, osteochondral interface, bony rim, perichondrium, bone top, cartilage top, joint capsule, and synovial fold (Fig. 5.19).

5.3.3 Ultrasound Measurement Measurements are taken on standard images through the center of the acetabulum. Taking the apex of the perichondrium as the starting point, the tangential line to the iliac margin is called the baseline; the tangential line to the top of the iliac ossification is called the bony roof line; the line connecting the bony rim to the midpoint of the hip labrum is called the cartilage roof line. The baseline and the bony roof line form the bone angle (α), which reflects the development of the osseous acetabulum. The larger the angle of α, the more mature the acetabular development. The baseline and cartilage roof line constitute the cartilage angle (β), reflect-

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ing the development of acetabular cartilage, especially the lateral margin of the cartilage. The smaller the β angle, the better the acetabular coverage of the femoral head (Fig. 5.20).

According to the measured values of α and β, the Graf method divides the hip joint into type I  ~  IV (Table  5.1), which is essential on the difference in the shape of the ace-

tabulum and the positional relationship with the femoral head. Type I is a normal hip joint, and type II contains a series of conditions from mild hip dysplasia to dislocation of the femoral head. Type III and IV are dislocated joints, and the femoral head is displaced posterosuperiorly. Therefore, it is often impossible to display the acetabulum and femoral head simultaneously on a coronal plane. Figures  5.21, 5.22, and 5.23 show the sonogram of the II ~ IV hip joint. Overall, ultrasound has great diagnostic value for adult hip soft tissue diseases, and has a high sensitivity to hip joint fluid and synovial hyperplasia. The

Fig. 5.19  Normal baby hip joint section. (1) Bone cartilage interface of the femoral head; (2) Femoral head; (3) Cartilage acetabular apex; (4) The lowest point of ilium ossification; (5) Synovial reentry; (6) Joint capsule; (7) Labrum; (8) Perichondrium; (9) The outer edge of the ilium; (10) bony rim

Fig. 5.20  Hip ultrasound measurement

5.3.4 Ultrasound Classification

Table 5.1  Graf hip classification Graf classification Type I

Type II a/b

Type II c Type III Type IV

Bone roof/bone roofine angle (α) Shape and alignment of femoral head and acetabulum is good α ≥ 60 ° Slightly poor morphology, no dislocation α = 50 °~59 °

Bone edge Sharp or slightly blunt Round or curved

Cartilage roof/cartilage roofine angle (β) Complete coverage of the femoral head I a: β ≤ 55 ° I b: β > 55 ° Complete coverage of the femoral head β = 55 °~77 °

Poor morphology, no dislocation α = 43 °~49 ° Poor morphology, femoral head dislocated α 90). The contour of femoral head returned to normal, the osteogenesis at the end of the grafted fibula was good, cystic changes disappeared and bone mineral density was increased.

7.10.9 Case 9 7.10.9.1 Medical History A 41-year-old male patient with nephrotic syndrome was admitted due to left hip pain for 1 month after glucocorticoid administration. Radiographs (Fig.  7.159) showed a normal contour of bilateral femoral heads, large areas of density unevenness in both femoral heads, cystic changes obviously in the left side, sclerosis around the necrotic lesions in both sides, and normal joint space in both sides. MRI (Fig. 7.160) showed an uneven low signal area in the cross-section of the T1-weighted phase of bilateral femoral heads. Coronal

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T2-weighted fat-saturated image of the right femoral head showed slightly high signal changes in the medial part of the femoral head and a small amount of effusion in the joint. Coronal T2-weighted fat-saturated image of the left femoral head showed bands of uneven signal intensity in the weight-­ bearing area, extensive edema in the head and neck, and obvious joint effusion. The Harris score: excellent (≥90) on the right side and poor (50 years Hip pain Hip internal rotation ≥15° Pain with hip internal rotation Morning stiffness of the hip ≤ 60 min

Clinical Set B Age >50 years Hip pain Hip internal rotation 10 joints (at least 1 small joint) (B) Serology    Negative RF and negative ACPA    Low-positive RF or low-positive ACPA    High-positive RF or high-positive ACPA (C) Acute-phase reactants    Normal CRP and normal ESR    Abnormal CRP or abnormal ESR (D) Duration of symptoms