Congenital dislocations of the hip cover about 90 per cent. of all cases. They are more usual in females than in males. One or both joints may be in volved. The typical cases are caused by a defective development of the Y-carti lage and acetabulum, which permits the influence of the weight of the body, or the contraction of the muscles, to drag the head of the bone out of the socket on to the dorsum of the ilium.
Pubic and obturator dislocations are very rare. As the child begins to walk the head is pushed farther upward until it is finally arrested and a new joint formed. The head of the bone is small and deformed and the real acetabulum obliterated. Compensatory changes ap pear in the pelvis, which is tilted for ward, and the lumbar spine, which is curved forward. If one hip alone is in volved, there is an additional lateral curvature, and the child limps; if both are involved, there is no limp, but the gait is peculiar. The tilting of the pel vis can be made to disappear by placing the child upon its back and flexing the thighs.
The prognosis as to the utility of the limb is fair. The patient will probably be able to get about, and the deformity will grow no worse.
Treatment. — Inasmuch as operative treatment has a very high mortality and often enough gives but little or no relief, while, on the other hand, some cases— double as well as single—reach adult life, undiagnosed and untreated, with com paratively-slight deformity and no dis ability except a waddling gait, it is proper —Hoffa and Lorenz to the contrary not withstanding—to institute treatment by palliative measures. For unilateral dis locations an elevated. sole to the shoe, and, if necessary, an apparatus to pre vent the head of the femur from riding up any higher on the ilium, fulfill the indications. Or in cases under 5 or 6
years of age—single or double—pro longed traction, for even as long as two years, may produce material and per manent improvement. Mikulicz claims to be able to effect reduction by ma nipulation. An injection of a 10-per cent. solution of zinc chloride above the head of the bone has been advocated for the purpose of strengthening, by new bony formation, the upper rim of the new acetabulum.
Of the operations, that of Lorenz is a type. He makes a vertical antero-ex ternal skin incision, divides the fascia lata transversely, separates the muscles, frees the bone by a cross-cut in the an terior surface of the capsule, gouges out the old acetabulum, making a strong up per rim to it, and replaces the bone by extension, aided by a traction apparatus. Immobilization is replaced by passive motion at the end of four weeks, and the child begins to walk with assistance two weeks later. No further apparatus is used. In difficult cases Lorenz advises a preliminary course of two weeks' ex tension by a thirty-pound weight.
Congenital shoulder dislocations are to be treated according to similar principle.
The anterior knee dislocations are easily reduced, and a good functional re sult may be predicted.
Pathological Dislocations. — Paralytic ("myopathic") dislocations occur usually in the shoulder, where the deltoid and scapular muscles form such important accessories to the joint.
Dislocations by effusion, erosion, or other articular processes occur in the course of the eruptive, continued, or rheumatic fevers. The hip is commonly affected.
Special Dislocations.