CHAPTER VI.

DISLOCATIONS OF THE HIP.

TRAUMATIC dislocation of the hip usually occurs in healthy adult males as the result of severe violence applied to the lower extremity while the hip-joint is flexed and abducted; similar violence applied to the fully extended limb is more likely to give rise to a fracture of the neck of the femur than to a dislocation. The spontaneous and congenital forms of dislocation are dealt with elsewhere in connection with diseases of joints and deformities respectively.

VARIETIES. The traumatic dislocations are divided into (1) the regular dislocations of the hip, which comprise the posterior and the anterior dislocations; and (2) the irregular dislocations, in which there is coexisting injury to structures which remain intact in the regular forms.

The points that have to be remembered in connection with these dislocations are: that the acetabulum is shallowest at its lower part— where it is also somewhat defective-and that a very strong ligament, called from its shape the Y-ligament, extends from the region of the anterior inferior spine of the ilium downwards across the front of the joint and ends in two bands, one of which passes vertically downwards to the base of the lesser trochanter, whilst the other runs horizontally outwards to be inserted into the outer and upper end of the anterior inter-trochanteric line. This ligament is very strong, and great violence is required to rupture it. The Y-ligament is the principal factor that determines the particular form of the displacement; in the regular dislocations it is always intact. It is, moreover, one of the chief agents in aiding reduction.

Another structure that plays an important part in dislocations of the hip is the tendon of the obturator internus muscle. This muscle arises from the inner surface of the obturator foramen and the fascia covering it, passes out of the pelvis through the lesser sacro-sciatic notch, where it is joined by the two gemelli, and with them is inserted into the digital fossa at the back of the femur. The tendon acts as a powerful reinforcement

to the posterior part of the capsule of the joint, and determines the particular form of dislocation when the head of the bone is dislocated backwards; when the head of the bone lies below the tendon, the displacement is known as a sciatic dislocation, and when it lies above it, as a dorsal dislocation.

The regular dislocations are all primarily sub-cotyloid, as the head of the bone always escapes from the acetabulum at its lower part, the inferior portion of the capsule being torn. The sub-cotyloid position is, however, one of unstable equilibrium, and a further displacement invariably occurs, the head always passing either backwards or forwards, the direction that it takes being mainly determined by the direction of the force producing the injury, and the position of the limb at the time of the accident.

The Regular Dislocations. The regular dislocations of the hipnamely, those in which the Y-ligament and the margin of the acetabulum remain intact—are divided into four groups, in two of which the head of the bone passes backwards, while in the remaining two it is found in front of the acetabulum. These dislocations are classified as follows:

I. The most common are the backward dislocations, and of these the true dorsal dislocation is the more frequent. The head of the bone, after leaving the acetabulum, passes backwards and upwards around its posterior margin, and finally rests upon the dorsum ilii, above the tendon. of the obturator internus.

2. Instead of passing above the obturator tendon, the head of the bone may rest below it, and is thereby guided backwards until it reaches the sciatic notch; this is termed the sciatic dislocation.

3. After leaving the acetabulum, the head of the bone may pass obliquely inwards and forwards until it rests over the obturator foramen— the thyroid dislocation.

4. In other cases, the head of the bone does not remain over the thyroid foramen, but travels upwards and inwards, and is then found in the neighbourhood of the spine of the pubes-the pubic dislocation.

Two other regular forms of dislocation are described, namely, the supra-spinous, in which the head of the bone lies above the anterior inferior iliac spine; and the everted dorsal form, in which the head of the bone lies upon the dorsum ilii, but is directed forwards instead of backwards. In both of these rare dislocations the outer limb of the Y-ligament is torn. The Irregular Dislocations.--These are always accompanied by rupture of the Y-ligament or fracture of the acetabulum; hence the head of the bone, instead of passing out through the lower part of the capsule and then travelling either forwards or backwards, may leave the acetabulum anywhere, and generally passes upwards. Many of the signs characteristic of the regular dislocations are therefore absent.

TREATMENT OF THE REGULAR FORMS OF DISLOCATION.

In all the regular dislocations, manipulations designed to cause the head of the femur to pass back into position along the path that it followed as it escaped from the joint should be tried. Reduction may be effected in this way, without the necessity for pulling on the exceedingly powerful muscles which surround the joint. A general anaesthetic should always be employed, although the bone may sometimes be replaced without one.

FIG. 28.-REDUCTION OF A DORSAL DISLOCATION OF THE HIP BY BIGELOW'S METHOD. First Stage. The assistant steadies the pelvis and the surgeon flexes the affected limb to its utmost limit, and at the same time slightly adducts it and rotates it inwards so as to disengage the head of the bone.

OF DISLOCATIONS BACKWARDS.-(a) Dislocation upon the Dorsum ilii.-When possible, the method of reduction by manipulation called after Bigelow, who introduced it should be attempted.

Bigelow's Method. The patient is laid flat on his back upon the floor or a low couch, and the surgeon, standing on the affected side, raises the thigh, and flexes it fully upon the abdomen, whilst an assistant fixes the pelvis (see Fig. 28). The knee should also be flexed to a right angle, and is useful in the later stages as a lever for rotating the

limb. As the full flexion of the thigh is carried out, the femur should be rotated somewhat inwards and slightly adducted; by doing this the Y-ligament is relaxed, and the head of the bone is disentangled. When flexion has been carried to its fullest limit, downward pressure should be made upon the knee, so as to depress the head of the bone, and at the same time the limb should be strongly rotated outwards. Abduction is next carried out to its fullest limit (see Fig. 29), the result being that the head of the bone passes downwards behind the acetabulum, and then forwards to a point opposite the rent in the capsule. The limb is finally

FIG. 29.-REDUCTION OF A DORSAL DISLOCATION OF THE HIP BY BIGELOW'S METHOD. Second Stage. The fully flexed limb is now abducted and rotated outwards to its utmost limit.

circumducted outwards, and brought down parallel to its fellow (see Fig. 30); the head of the bone is thus made to enter the rent and slip into the acetabulum. The success of these manœuvres depends upon the integrity of the Y-ligament, which forms a fixed point around which the head of the bone rotates.

Reduction by Traction.-Should reduction by manipulation fail, either because the opening in the capsule is too small, or because the Y-ligament has been injured, attempts should be made to reduce the dislocation by traction. The patient should be anæsthetised and laid upon his back, while an assistant fixes the pelvis. The surgeon flexes the hip

FIG. 30.-REDUCTION OF A DORSAL DISLOCATION OF THE HIP BY BIGELOW'S METHOD. Final Stage. The limb is circumducted outwards and brought down to the middle line parallel with its fellow.

FIG. 31.-REDUCTION OF A DORSAL DISLOCATION OF THE HIP BY TRACTION. The pelvis is steadied by an assistant and the surgeon makes traction at right angles to the pelvis by grasping the limb as shown above.