Clinicals

Clinicals on Femur 1◊◊The upper end of the femur is a common site for fracture in the elderly. The neck may break immediately beneath the head (subcapital), near its midpoint (cervical) or adjacent to the trochanters (basal), or the fracture line may pass between, along or just below the trochanters. Fractures of the femoral neck will interrupt completely the blood supply from the diaphysis and, should the retinacula also be torn, avascular necrosis of the head will be inevitable. The nearer the fracture to the femoral head, the more tenuous the retinacular blood supply and the more likely it is to be disrupted. Avascular necrosis of the femoral head in children is seen in Perthe’s disease and in severe slipped femoral epiphysis; both resulting from thrombosis of the artery of the ligamentum teres. In contrast, pertrochanteric fractures, being outside the joint capsule, leave the retinacula undisturbed; avascular necrosis, therefore, never follows such injuries (Fig. 162). There is a curious age pattern of hip injuries; children may sustain greenstick fractures of the femoral neck, schoolboys may displace the epiphysis of the femoral head, in adult life the hip dislocates and, in old age, fracture of the neck of the femur again becomes the usual lesion. 2◊◊Fractures of the femoral shaft are accompanied by considerable shortening due to the longitudinal contraction of the extremely strong surrounding muscles. The proximal segment is flexed by iliacus and psoas and abducted by gluteus medius and minimus, whereas the distal segment is pulled medially by the adductor muscles. Reduction requires powerful traction, to overcome the shortening, and then manipulation of the distal fragment into line with the proximal segment; the limb must therefore be abducted and also pushed forwards by using a large pad behind the knee. Fractures of the lower end of the shaft, immediately above the condyles, are relatively rare; fortunately so, because they may be extremely difficult to treat since the small distal fragment is tilted backwards by gastrocnemius, the only muscle which is attached to it. The sharp proximal edge of this distal fragment may also tear the popliteal artery, which lies directly behind it (Fig. 163). 3◊◊The angle subtended by the femoral neck to the shaft may be decreased, producing a coxa vara deformity. This may result from adduction fractures, slipped the femoral epiphysis or bone-softening diseases. Coxa valga, where the angle is increased, is much rarer but occurs in impacted abduction fractures. Note, however, that in children the normal angle between the neck and shaft is about 160°. Clinical features 1◊◊Lateral dislocation of the patella is resisted by the prominent articular surface of the lateral femoral condyle and by the medial pull of the lowermost fibres of vastus medialis which insert almost horizontally along the medial margin of the patella. If the lateral condyle of the femur is underdeveloped, or if there is a considerable genu valgum (knock-knee deformity), recurrent dislocations of the patella may occur. 2◊◊Adirect blow on the patella may split or shatter it but the fragments are not avulsed because the quadriceps expansion remains intact. The patella may also be fractured transversely by violent contraction of the quadriceps — for example, in trying to stop a backward fall. In this case, the tear extends outwards into the quadriceps expansion, allowing the upper bone fragment to be pulled proximally; there may be a gap of over 2 in (5 cm) between the bone ends. Reduction is impossible by closed manipulation and operative repair of the extensor expansion is imperative. Occasionally this same mechanism of sudden forcible quadriceps contraction tears the quadriceps expansion above the patella, ruptures the ligamentum patellae or avulses the tibial tubercle. It is interesting that following complete excision of the patella for a comminuted fracture, knee function and movement may return to 100% efficiency; it is difficult, then, to ascribe any particular function to this bone other than protection of the soft tissues of the knee joint anteriorly.

Clinical features on patella 1◊◊The upper end of the tibial shaft is one of the most common sites for acute osteomyelitis. Fortunately, the capsule of the knee joint is attached closely around the articular surfaces so that the upper extremity of the tibial diaphysis is extracapsular; involvement of the knee joint therefore only occurs in the late and neglected case.

2◊◊The shaft of the tibia is subcutaneous and unprotected anteromedially throughout its course and is particularly slender in its lower third. It is not surprising that the tibia is the commonest long bone to be fractured and to suffer compound injury. 3◊◊The extensive subcutaneous surface of the tibia makes it a delightfully accessible donor site for bonegrafts.

Clinical features on hip joint Trendelenburg’s test The stability of the hip in the standing position depends on two factors, the strength of the surrounding muscles and the integrity of the lever system of the femoral neck and head within the intact hip joint. When standing on one leg, the abductors of the hip on this side (gluteus medius and minimus and tensor fasciae latae) come into powerful action to maintain fixation at the hip joint, so much so that the pelvis actually rises slightly on the opposite side. If, however, there is any defect in these muscles or lever mechanism of the hip joint, the weight of the body in these circumstances forces the pelvis to tilt downwards on the opposite side. This positive Trendelenburg test is seen if the hip abductors are paralysed (e.g. poliomyelitis), if there is an old unreduced or congenital dislocation of the hip, if the head of the femur has been destroyed by disease or removed operatively (pseudarthrosis), if there is an un-united fracture of the femoral neck or if there is a very severe degree of coxa vara. The test may be said to indicate ‘a defect in the osseo-muscular stability of the hip joint’. A patient with any of the conditions enumerated above walks with a characteristic ‘dipping gait’.

Dislocation of the hip The hip is usually dislocated backwards and this is produced by a force applied along the femoral shaft with the hip in the flexed position (e.g. the knee striking against the opposite seat when a train runs into the buffers). If the hip is also in the adducted position, the head of the femur is unsupported posteriorly by the acetabulum and dislocation can occur without an associated acetabular fracture. If the hip is abducted, dislocation must be accompanied by a fracture of the posterior acetabular lip. The sciatic nerve, a close posterior relation of the hip, is in danger of damage in these injuries, as will be appreciated by a glance at Fig. 156. Reduction of a dislocated hip is quite simple providing that a deep anaesthetic is used to relax the surrounding muscles; the hip is flexed, rotated into the neutral position and lifted back into the acetabulum. Occasionally, forcible abduction of the hip will dislocate the hip forwards. Violent force along the shaft (e.g. a fall from a height) may thrust the femoral head through the floor of the acetabulum, producing a central dislocation of the hip.