1 LECTURE 07 HIP JOINT + MUSCLES OF HIP UPPER PART OF FEMUR Note the head, which forms about 2/3 of a sphere covered with articular cartilage. The head is directed upwards, medially and slightly forwards. Note also the neck, the greater and lesser trochanter. Note the trochanteric fossa (obturator externus). Posteriorly the intertrochanteric crest with the quadrate tubercle in the middle, and the linea aspera to which the majority of the thigh muscles attach. Note also the gluteal ridge or tuberosity from the linea aspera towards the quadrate tubercle (gluteus maximus), the pectineal line from linea aspera to lesser trochanter (pectineus), and the spiral line (vastus medialis) branching anteriorly to join the intertrochanteric line. SLIDE OR SKETCH of upper part of femur (Williams and Warwick 1980) Fig 3.182 post aspect ACETABULUM The term acetabulum is derived from L. 'vinegar cup' (Arnold's glossary) and was used to describe the cup and ball with which clowns entertained people long ago. The ball was connected to the cup with a piece of string. In just the same way, the head of the femur is connected to the acetabulum by the ligamentum teres. This is not so much a ligament as a mesentery, which carries an artery to the head of the femur (a branch of the obturator artery). This blood supply is important before the epiphysis of the head fuses with the neck (Joseph 1982) p441 about the age of 20 (Grant and Basmajian 1980) (p298). sketch acetabulum 2 HEAD OF FEMUR The head of the femur is not well supplied with blood: until the age of 18-20, the epiphysis forming the distal half of the head remains unfused, and is separated by the epiphyseal plate from proximal half of the head and the neck of the femur. The neck and proximal head receive their blood supply from the lateral and medial circumflex arteries, (branches off profunda femoris) via the joint capsule; while the head receives its supply from a small branch of the obturator artery via ligamentum teres (Gardner et al. 1986) p217; (Adams 1978) p208. After fusion, the circumflex supply becomes more important (particularly medial circumflex, (Williams and Warwick 1980) 391b, and the supply from the ligamentum teres is minor. As a result, fractures of the head or neck of the femur in the adult may interrupt the blood supply to parts of the head of the femur, resulting in slow healing or avascular necrosis. (This also happens in the scaphoid and the talus). SKETCH blood supply to head of femur (Gardner et al. 1986) p217 ARTICULAR SURFACES The bony acetabular socket only forms about 1/2 of a sphere, but this is extended by the cartilaginous acetabular lip or labrum, which helps to retain the head of the femur in the socket. The acetabulum is not completely lined with articular cartilage: there is a C-shaped band of cartilage around the rim: the gap is called the acetabular notch, nearest the obturator foramen. This is bridged by the transverse ligament (which forms part of the attachment for the ligamentum teres). CLOSE PACKING As with all joints, the articular surfaces are not completely congruent, although there is one position of the joint where the surfaces fit together best, i.e. the position of close-packing, in which the ligaments surrounding the joint are taut. In the hip, this position is in full extension (and medial rotation? ) LOADING It appears that under light loads, only a part of the acetabular surface is in contact with the femoral head; these are the anterior and posterior thirds, or the extremes of the C; the middle of the horseshoe is not in contact 3 (Greenwald and O'Connor 1971), Fig. 4 but under loads corresponding to walking, the whole area is contacted throughout the step cycle. sketch CAPSULE AND LIGAMENTS The capsule is strong, and is thickened by three ligaments, one from each component of the hip bone: 1 Iliofemoral - this is like an upside down 'Y', running across the front of the hip joint from the AIIS down to the intertrochanteric line. It resists hyperextension and medial rotation (Hollinshead and Rosse 1985). 2 Pubofemoral - This is also on the anterior aspect, running from the pubis under the medial branch of the iliofemoral to blend with the capsule. It resists abduction (Hollinshead and Rosse 1985). 3 Ischiofemoral - This is on the posterior aspect. Like the other ligg., it is taut in full extension, i.e. close packing. SLIDE ligaments Cunningham fig 222 FB1 2-1, 2-2 Gray’s 35 4.64 MOVEMENTS AT THE HIP flexion to c 120°, extension to c 30° abduction (40° for slow abduction, 70-80° if kicked out (Joseph 1982) p444 adduction internal rotation, external rotation 4 FASCIA The deep fascia of the thigh is the fascia lata, thickest proximally and laterally. It is attached above to the iliac crest and inguinal ligament, and below to condyles of the femur and tibia and to the head of the fibula. Iliotibial tract. On the lateral surface it is thickened to form a strong band, the iliotibial tract, found only in man (Kaplan, 1958). This seems to serve as a tie from the iliac crest to the knee, which reduces the stress in the femur (Pauwels). When the knee is extended, it passes in front of the instant centre of rotation; when the knee is flexed, it passes behind it. This means that (a) it stabilises the knee in extension but not in flexion and (b) it rubs past the lateral epicondyle during running or cycling, and may result in bursitis, the iliotibial tract syndrome (Kulund 1988) p462. MUSCLES Flexors of the hip joint: Iliacus and psoas. Psoas major we referred to before as the prevertebral muscle of the lumbar region, whose tendon runs between the anterior of the hip joint and behind the inguinal ligament, to insert on the lesser trochanter. Proximal attachment L1-L5, including TP's, discs and margins of bodies. Lumbar plexus located within psoas major, innervated by L1-2. Note also psoas minor may be present on front of psoas major. Iliacus: The tendon of psoas is joined by the fibres of iliacus, a fan shaped muscle with its origin in the iliac fossa. Together they are often known as the iliopsoas---they have a common action in flexing the thigh on the pelvis, but of course it is only the psoas which has the additional action of flexing the lumbar vertebral column on the pelvis. Sketch TS GM10 Fig 20-16 5 Extensors of the hip joint: Gluteus maximus. This is a large, strong, coarse muscle lying superficially in the buttock. Its fibres run down and laterally, from their origin on the posterior part of the ilium, just lateral to the PSIS, from the sacrum and coccyx, and from the sacrotuberous ligament to the insertion. This is 1/4 on the gluteal ridge (deeper fibres of lower part of muscle), but the main part (3/4) joins with the fascia lata to form the iliotibial tract. This runs down to the lateral condyle of the knee, in front of its axis of rotation, so that gluteus max. also helps to maintain the knee in extension (GM10 p257). Abductors of the femur: Gluteus medius and minimus, tensor fasciae latae. The first two are associated with gluteus maximus and lie deep to it; they run from the lateral or posterior surface of the blade of the ilium down to the greater trochanter. Tensor fasciae latae has its bony insertion into the iliac crest between the tubercle and ASIS, and is about the size of a bar of soap. It is present in all mammals (Kaplan 1958) even though they do not possess an iliotibial tract. SLIDE FB1 2-5, 1-6 note line of action (In primates such as the chimpanzee, gluteus medius acts primarily as an extensor, since the iliac blades are in the coronal plane, and face posteriorly. Only in man do gluteus medius and minimus act significantly in lateral balance control--Robinson et al. J. Hum. Evol. (1972) 361-369). Medial rotators of the femur There are no specific medial rotators of the hip, but the muscles which carry out this function are the anterior fibres of gluteus medius, gluteus minimus and tensor fasciae latae (all innervated by the superior gluteal nerve). T.f.l. is active during medial rotation (confirmed by palpation, electromyography, and electrical stimulation; Kaplan 58). If T.f.l. is paralysed, medial rotation, flexion and abduction are slightly weakened (Müller-Vahl, 1985). 6 Lateral rotators of the femur Deep again to the glutei are six muscles which pass around the back of the hip joint to insert on the greater trochanter---and so act to laterally rotate the thigh. The muscles fan out from their insertions on the greater trochanter to their origins as follows: Muscle Origin Piriformis anterior of sacrum gemellus sup. lesser sciatic foramen, upper margin Obturator internus (tend.) obt. membrane (inner surface) gemellus inf. lesser sciatic foramen, lower margin Obturator externus obt. membrane (outer surface) Quadratus femoris ischial tuberosity 7 sketch e.g. G&S Fig. 7.06 posterior aspect SLIDE FD1 1-4 All of these muscles are in the gluteal region, which you realise is outside the pelvis, on its posterolateral aspect. The main gateway from the inside of the pelvis out to the gluteal region is the greater sciatic foramen. Through it passes the piriformis muscle, from the anterior aspect of the sacrum (inside the pelvis) through the gluteal region to the greater trochanter. The muscle is most important not for its action, but as the key landmark of the gluteal region. Thus the sciatic nerve also emerges from the pelvis through the greater sciatic foramen, and appears below the lower border of piriformis, with the posterior femoral cutaneous nerve, inferior gluteal nerve, and the pudendal nerve. Note that the peroneal component may split piriformis (cf McMinn & Hutchings), while the tibial component emerges below it. It is said that spasm of the piriformis may impinge on the sciatic leading to so called "piriformis syndrome" Kulund 2 422. Note also that injections into the buttock should be into the upper lateral quadrant of the buttock to avoid the sciatic and gluteal nerves (Platzer p246; Snell 2 842). Superior gluteal nerve and vessels emerge above the muscle Inferior gluteal nerve and vessels emerge below the muscle (Internal iliac -> superior + inferior gluteal aa. + nn. Superior gluteal n. -> gluteus medius, minimus + T.f.l. inferior gluteal n. -> gluteus maximus etc. 8 CLINICAL ASPECTS OF HIP JOINT FRACTURES Fracture of the neck of the femur (Snell 2 p586) may be subcapital (elderly) or intertrochanteric (young or middle-aged). Subcapital occurs in the elderly. The thigh muscles pull the distal fragment upward, so that the limb is shortened; the lateral rotators act to put the thigh into external rotation (Slide FH1 1-5). Complicated by avascular necrosis, (see above) so the best thing is to replace hip rather than to hope for it to heal. PROSTHESES Various kinds, most common are stainless steel ball and high density polythene socket (Charnley believed it was necessary to have the two bearing surfaces of different hardnesses (Gruebel Lee and Hirsh 1983) p229a. Alternative are available in ceramic. Interestingly, the ceramic one is aspheric, which is said to have advantages in increasing contact surface and lubrication (Grell 81/82). Apparently a case where technology has been forced to mimic nature. Teflon doesn't work - it wears quickly in spite of its low coefficient of friction, and produces fragments which cause and inflammatory reaction (Gruebel Lee and Hirsh 1983). SLIDES CONGENITAL DISLOCATION OF THE HIP is one of the commonest congenital deformations. It is of particular interest for two reasons: (1) it is completely curable by conservative treatment provided it is diagnoses very early, ideally on the day of birth, and (2) it suggests that mechanical factors may help to mould the joint, rather as mechanical factors contribute to the remodelling of bone. C.D.H. is a spontaneous dislocation of the hip occurring before, during or shortly after birth. In Western races, it is one of the commonest congenital deformities. If diagnosed at birth, it can be treated effectively by splinting: if undiagnosed or poorly treated, the patient may be crippled for life. Etiology of CDH It is 6 times as common among girls: commoner in the left hip than in the right (presumably because of the way the fetus lies in the uterus ?): and commoner in people whose ancestors come from parts of Eastern Europe. 9 Causes 1) Genetically determined joint laxity. This is basically looseness of the capsule, and probably resolves spontaneously. 2) Hormonal joint laxity. In female babies, a ligament-relaxing hormone may be secreted by the fetal uterus, in response to oestrone and progesterone reaching the fetal circulation. This may also cause temporary instability. 3) Genetically determined dysplasia of the hip. This involves defective development of the acetabulum and the femoral head: the roof of the acetabulum slopes steeply, and the head of the femur is usually small, so that dislocation is likely. SLIDE 1 FH1 1-4 Diagnosis If tested at birth, a click or thump can be heard or felt as the hips are abducted (in the flexed position). This is due to the head of the femur snapping back into place in the acetabulum. Treatment If diagnosed early, the treatment is to keep the baby's hips partially abducted with double nappies, for up to 3 months. After this time X-rays are easier to diagnose, and most cases, such as those due to laxity of the joint capsule, will have resolved by this time. Those involving congenital dysplasia of the hip are likely to require further treatment by splinting for up to 6 months. If done properly, the head of the femur is held into the acetabulum, which then starts to develop normally: presumably the result of mechanical factors which determine the configuration of the bony socket. The splinting seems to worry the parents much more than the baby: the baby manages very well with her hips permanently abducted, and some babies even learn to walk like this. Prognosis The surprising point is that with this treatment, the hip then becomes quite indistinguishable from normal. But if left longer than the first year, the condition becomes progressively more difficult to treat. Redislocation is common, and osteoarthrosis and pain result. After 18 months of age without treatment, surgery is necessary (Adams Outline of Orthopaedics). 10 PERTHES’ DISEASE This is a form of avascular necrosis, occurring most often in boys from 4-8 years old; often the cause appears to be trauma. If the joint becomes inflamed, the increased pressure may occlude the lateral epiphyseal vessels running in the retinaculum, which provide the main blood supply to the head. Apley & Solomon p258. References Adams JC. Outline of fractures, including joint injuries, Churchill Livingstone, Edinburgh ; New York, 1978, ix, 320 pp. Gardner ED, O'Rahilly R, Müller F and Gray DJ. Anatomy : a regional study of human structure, Saunders, Philadelphia, 1986, ix, 809 pp. Grant JCB and Basmajian JV. Grant's Method of anatomy : by regions, descriptive and deductive, Williams & Wilkins, Baltimore, 1980, xvii, 625 pp. Greenwald AS and O'Connor JJ. The transmission of load through the human hip joint. J Biomech 1971;4:507-28. Gruebel Lee DM and Hirsh DM. Disorders of the hip, Lippincott, Philadelphia, 1983, xiii, 282 pp. Hollinshead WH and Rosse C. Textbook of anatomy, Harper & Row, Philadelphia, 1985, xii, 1041 pp. Joseph J. A textbook of regional anatomy, University Park Press, Baltimore, 1982, xxii, 519 pp. Kulund DN. The Injured athlete, Lippincott, Philadelphia, 1988, xviii, 603 pp. Williams PL and Warwick R. Gray's Anatomy, Churchill Livingstone, Edinburgh, 1980.