Radiographic features of neonatal congenital dislocation of the hip.

Over the 10-year period 1969 to 1978, 271 consecutive cases of congenital dislocation of the hip were diagnosed at birth. Standard anteroposterior radiographs of the pelvis were obtained routinely and were analysed retrospectively. The medial gap, a measure of the separation between the proximal femur and the pelvic wall, was found to be significantly increased in cases with unilateral or bilateral dislocation when compared to normal. A medial greater than five millimetres is indicative of femoral head displacement and is of value where the clinical diagnosis is uncertain. The rate of missed dislocation at birth was 0.6 cases per thousand. Treatment with the Malmo splint was the normal routine. The Pavlik harness was applied if splintage was poorly tolerated by the infant, or in the rare instance of limited hip abduction. Failure to maintain reduction by splintage occurred in 3.3 per cent. The incidence of pressure deformities of the femoral head was 2.95 per cent and there was a residual deformity in later childhood of 1.1 per cent. It is presumed that this lesion can be attributed to the effect of splintage and it was notably avoided in the later period of the review when greater mobility of the abducted hips was encouraged.