A congenital predisposition to dislocation is the chief cause of this condition. The head of the femur takes a position near the acetabulum, more often in front or above it (Lange) but occasionally behind (lloffa). The increasing weight forces the head gradually further upward and backward so that in the older dislocations we generally find a luxatio iliaca (Spitzy).
Differential Diagnosis.-1. The Waddling Gait in Rickets.—Curva tures of the neck (coca vara) and of the shaft produce an elevated. tro chanter. This will cause a limp and a marked lordosis and also the Trendelenburg symptom. The gait, however, is much more steady than in dislocation. The displacement of the head is lacking and it is palpable beneath the femoral artery. The Röntgen ray will establish the diagnosis.
2. Coxitis.—In this disease the head is firm either in part or in toto. Passive motion is painful. The leg becomes rigid and is dragged on account of the effort to avoid movements in the hip. The steps are unequal. The Trendelenburg symptom is absent and the head is pal pable beneath the artery. The surrounding tissues are swollen and painful on pressure, owing to exudation in the joint.
In cases where severe destructive processes have forced the head out of the acetabulum (pathological dislocation) the history and a careful examination will prevent mistakes.
3. Paralytic Dislocations. — Separation of the articulating bodies takes place in paralysis of the gluteal and pelvic muscles. The stronger muscles press the head against the acetabulum (see Paralysis of the deltoid).
4. The Similar Gait in Spinal Muscular Atrophy, Muscular Dystro phies, and Spastic Para plegias.—Careful examination reveals a normal condition of the articulating bodies provided it is not combined with rigidity due to a spastic state of the muscles (Gaugele).
The prognosis in a ease of congenital dislocation of the hip is unfa vorable, since a spontaneous cure never occurs. It is not possible to out grow the deformity, but Drehmann has reported cases where recovery took place in slight subluxations. The increasing weight of the child tends to push the bead further away from the acetabulum. Shortening increases the adductor contraction and tends to twist the femur inwards. In bilateral deformities this is apt to lead to severe functional disturb ances. Compensatory scoliosis is generally not of the fixed type, on ac
count of the constant counterpoise of the body when walking or sitting.
An erosion of the ileum may occur above the old acetabulum to such an extent that the head finds a new support and a false joint is produced.
The dislocation in the newborn is not very pronounced, but treat ment is imperative as soon as it has been correctly diagnosticated. The author succeeded in four eases of unilateral dislocation of the hip (sub luxation) in preventing a complete dislocation (luxation) by the use of constant extension, using weights up to one kilogram (2.2 pounds) and preventing the child from bearing the weight of its body for two years.
Most of the eases coming under observation are over two years of age, since the peculiarities of gait become apparent about that age.
The ideal form of treatment is the bloodless method of reduction introduced by Lorenz. Pravaz and Paci had previously attempted to reduce the dislocated joint, but reluxation occurred owing to insufficient fixation. Lorenz placed the bloodless method on a sound basis. His method has undergone modification and changes at the hands of different surgeons, but they do not change the important features of his operation, namely, reposition and retention.
Reposition.—The child is placed in deep narcosis on the edge of the operating table, the dislocated hip on the outside. An assistant fixes the leg, preferably by strong flexion of the sound leg. The head is then pulled downward by traction on the femur. there is marked shortening, extension weights gradually increasing up to 20 kilograms (14 pounds) are applied for one or two days before the operation.
Resistance from shortening of the muscles and fascia must be over come in pulling the head downward. Lever-like motions are necessary to overcome this resistance. Flexion and abduction tighten the shortened muscles while forced adduction and massage relax them. Reduction may now be accomplished, especially in cases of subluxation forward and upward, by means of forced extension, light pressure on the troehanter, and inward rotation (reduction across the upper_ border of the acetab ulum).