Page 243 - Clinical Anatomy

ECA4 7/18/06 6:47 PM Page 228

228 The lower limb

and subsequently wired back in place), and an excellent view of the hip
joint is thus obtained.

Nerve supply

Hilton’s law states that the nerves crossing a joint supply the muscles acting
on it, the skin over the joint and the joint itself. The hip is no exception and
receives fibres from the femoral, sciatic and obturator nerves. It is impor-
tant to note that these nerves also supply the knee joint and, for this reason,
it is not uncommon for a patient, particularly a child, to complain bitterly of
pain in the knee and for the cause of the mischief, the diseased hip, to be
overlooked.

Clinical features

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 oppo-
site side. If, however, there is any defect in these muscles or lever mecha-
nism 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 paral-
ysed (e.g. poliomyelitis), if there is an old unreduced or congenital disloca-
tion 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 (Fig. 168)

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 unsup-
ported 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.