Applied anatomy of the hip and buttock CHAPTER CONTENTS The cup-shaped acetabulum is a little below the middle The hip joint e239 third of the inguinal ligament. The acetabular articular surface is an incomplete cartilaginous ring, thickest and broadest above, Capsule and ligaments e239 where the pressure of body weight falls in the erect posture, Muscles e240 narrowest in the pubic region. The rough lower part of the cup, Flexor muscles . e240 the acetabular notch, is not covered by cartilage. The centre of the cup, the acetabular fossa, is also devoid of cartilage but Extensor muscles . e242 contains fibroelastic fat. The acetabular labrum, a fibrocarti- Abductor muscles . e244 laginous ring attached to the acetabular rim, deepens the Adductor muscles . e244 cup and enlarges the contact area with the femoral head (see Lateral rotator muscles . e244 Standring, Fig. 81.5). The part of the labrum that bridges the Medial rotator muscles . e245 acetabular notch does not have cartilage cells and is called the transverse acetabular ligament. If forms a foramen through Bursae e245 which vessels and nerves may enter the joint. The acetabular Nerves e246 labrum is triangular in section. The base is attached to the Blood vessels e246 acetabular rim and the apex is free. The femoral head is ovoid or spheroid but not completely Topographical anatomy e246 congruent with the reciprocal acetabulum. It is covered by Anterior side . e246 articular cartilage except for a rough pit for the ligamentum Lateral side . e247 teres, a flattened fibrous band, embedded in adipose tissue Posterior side . e247 and lined by the synovial membrane (Figs 2, 3). The ligament connects the central part of the femoral head with the aceta- Joint movements e247 bular notch and its transverse acetabular ligament. The liga- ment is extra-articular and contains a tiny branch of the obturator artery partly responsible for the vascular supply of The hip joint the femoral head. The femoral head and neck also receive arterial supply from the capsular vessels, arising from the medial and lateral circum- The hip joint is a ball-and-socket joint, formed by the femoral flex arteries (see Fig. 3). head and the acetabulum (Fig. 1, see Standring, Fig. 80.15). The articular surfaces are spherical with a marked congruity; this limits the range of movement but contributes to the con- siderable stability of the joint. In the anatomical position, the Capsule and ligaments anterior/superior part of the femoral head is not covered by the acetabulum. This is because the axes of the femoral head The capsule is a cylindrical sleeve, running from the acetabular and of the acetabulum are not in line with each other. The axis rim to the base of the femoral neck. It is supported by power- of the femoral head points superiorly, medially and anteriorly, ful ligaments. while the axis of the acetabulum is directed inferiorly, laterally Anteriorly these are two ligaments: the fan-shaped ilio- and anteriorly. femoral ligament of Bertin situated craniolaterally; and the © Copyright 2013 Elsevier, Ltd. All rights reserved. The Hip and Buttock 1 4 7 1 6 2 6 3 4 3 5 Fig 3 • Coronal section through the hip: 1, ilium; 2, ligamentum 2 5 teres; 3, branch of obturator artery; 4, branch of medial circumflex artery; 5, femur; 6, branch of lateral circumflex artery; 7, joint capsule strengthened by the iliofemoral ligament (lateral part). Fig 1 • The hip joint: 1, ilium; 2, femur; 3, ligamentum teres; 4, labrum acetabulare; 5, transverse acetabular ligament; 6, joint capsule. 2 1 1 2 3 4 5 3 Fig 2 • The acetabulum: 1, articular cartilage; 2, acetabular Fig 4 • Anterior ligaments: 1, iliofemoral, lateral part; 2, iliofemoral, fossa; 3, ligamentum teres; 4, labrum acetabulare; 5, transverse medial part; 3, pubofemoral. acetabular ligament. pubofemoral ligament, in a more caudomedial orientation. Muscles Together they resemble the letter Z (Fig. 4). Posteriorly the capsule is strengthened by the ischiofemoral ligament (see The hip joint is surrounded by a large number of muscles. Standring, Fig. 81.3). These three ligaments are coiled round According to their function these are divided into six groups: the femoral neck. Extension ‘winds up’ and tautens the liga- (1) flexors, (2) extensors, (3) abductors, (4) adductors, (5) ments, thus stabilizing the joint passively (Fig. 5a); flexion lateral rotators, (6) medial rotators. In this chapter the ana- slackens them (Fig. 5b). Lateral rotation tightens the iliofemo- tomical and kinesiological aspects of particular importance in ral ligament and also the pubofemoral ligament. Medial rota- orthopaedic medicine are discussed. tion tightens the ischiofemoral ligament. Abduction tightens the pubofemoral and the ischiofemoral ligaments. Adduction tightens the lateral part of the iliofemoral ligament. Flexor muscles The ligamentum teres plays only a minor role in the control of hip movements. Adduction from a semi-flexed position is The flexor muscles of the hip joint (Table 1) are anterior to the only movement where this ligament is under tension. the axis of flexion and extension. © Copyright 2013 Elsevier, Ltd. All rights reserved. e240 Applied anatomy of the hip and buttock Fig 5 • Lateral view of the ligaments in (a) (b) extension (a) and flexion (b): 1, iliofemoral, lateral part; 2, iliofemoral, medial part; 3, pubofemoral. 2 1 3 Table 1 Flexor muscles Muscle Innervation Peripheral nerve Spinal Iliopsoas* Femoral and lumbar plexus L2, L3 Sartorius* Femoral L2, L3 1 Rectus femoris* Femoral L3 5 Tensor fasciae latae Superior gluteal L5 Pectineus Femoral and obturator L2, L3 4 Adductor longus* Obturator L2, L3 3 Adductor brevis Obturator L2, L3 Adductor magnus Obturator and sciatic L3, L4 2 Gluteus medius Superior gluteal L5 Gluteus minimus Superior gluteal L5 *Clinically important muscles. Fig 6 • The iliopsoas and associated structures: 1, psoas; 2, pectineus; 3, iliopsoas tendon; 4, inguinal ligament; 5, iliacus. The iliopsoas is the most powerful of the flexors (Fig. 6). It the muscle acts on two joints, with the accessory function of originates at the lumbar vertebrae and the corresponding lateral rotation and abduction of the hip as well as flexion and intervertebral discs of the last thoracic and all the lumbar medial rotation of the knee. At the surface, the muscle divides vertebrae, the superior two-thirds of the bony iliac fossa and the anterior aspect of the thigh into a medial and a lateral the iliolumbar and ventral sacroiliac ligaments. The insertion is femoral triangle. During active flexion, abduction and lateral to the lesser trochanter. Although its main function is flexion, rotation at the hip and 90° flexion at the knee, the muscle it is also a weak adductor and lateral rotator. The distal part of becomes prominent and is easily palpable. the muscle is palpable just deep to the inguinal ligament, where The rectus femoris combines movements of flexion at the it lies bordered by the sartorius muscle laterally and the femoral hip and extension at the knee. Its origin is at the anterior artery medially (Fig. 7). inferior iliac spine, a groove above the acetabulum and the The sartorius is mainly a flexor of the hip, originating at the fibrous capsule of the hip joint and inserts into the common anterior superior iliac spine and inserting at the proximal part quadriceps tendon at the proximal border of the patella (see of the medial surface of the tibia (see Fig. 7). Consequently Fig. 7). The origin can be palpated only in a sitting position © Copyright 2013 Elsevier, Ltd. All rights reserved. e241 The Hip and Buttock Quadratus lumborum 3 Psoas minor 1 Psoas major Iliacus Anterior superior iliac spine 2 Inguinal ligament Piriformis Coccygeus Levator ani Pubic tubercle Tensor fasciae latae Pectineus Adductor longus Gracilis Sartorius Adductor magnus Fig 8 • Lateral view of the hip muscles: 1, gluteus maximus; 2, iliotibial tract; 3, tensor fasciae latae. Rectus femoris Iliotibial tract because of tension in the overlying structures. The tendon and muscle belly are bordered medially by the sartorius muscle, and laterally by the tensor fasciae latae and the vastus lateralis, Vastus lateralis the largest part of the quadriceps. The tensor fasciae latae (see Fig. 7) originates at the outer Vastus medialis surface of the anterior superior iliac spine, and inserts into the proximal part of the iliotibial tract – a strong band which thickens the fascia lata at its lateral aspect. Thus the course of the tensor is dorsal and distal. Acting through the iliotibial tract the muscle extends and rotates the knee laterally. It may also assist in flexion, abduction and medial rotation of the hip. In the erect posture, it helps to steady the pelvis on the head of the femur (Fig. 8). The muscle can be palpated easily during resisted flexion and abduction of the hip with the knee extended. A number of other muscles are also active during flexion of the hip joint but only via their accessory function. These are the pectineus, adductor longus and brevis, and the most ante- rior fibres of the adductor magnus and the glutei (medius and minimus). Fig 7 • Anterior view of the hip muscles. From Standring, Gray’s Anatomy, 40th edn. Churchill Livingstone/Elsevier, Philadelphia, 2009 with Extensor muscles permission. These (Table 2) are posterior to the axis of flexion and exten- sion of the hip. © Copyright 2013 Elsevier, Ltd. All rights reserved. e242 Applied anatomy of the hip and buttock Table 2 Extensor muscles Muscle Innervation Peripheral nerve Spinal Gluteus maximus* Inferior gluteal Mainly S1 Semimembranosus Sciatic S1, S2 Semitendinosus Sciatic S1, S2 Biceps femoris Sciatic S1, S2 *Clinically important muscle. 1 3 1 2 2 3 Fig 10 • Extensors of the hip (hamstrings): 1, semitendinosus; 2, semimembranosus; 3, biceps femoris. Fig 9 • 1, Posterior superior iliac spine; 2, gluteus medius; The semimembranosus inserts at the posterior aspect of 3, gluteus maximus.