The c/b ratio in the radiological monitoring of the hip joint in congenital dislocation of the hip.

We report a method of monitoring hip joint development for congenital dislocation of the hip in children. The c/b ratio was measured on serial radiographs of 41 hips in 38 patients. The measurement was compared to c/b ratio obtained from normal hips. It was used to detect concentric reduction or its loss by migration of the femoral head during growth. The age at diagnosis ranged from 8 months to 10 years 6 months. The normal c/b ratio was found to change little with age. Deviation of the c/b ratio from normal in congenital dislocation of the hip resulted in a poor outcome and identified cases requiring further surgical intervention. This measurement of c/b ratio is simple and accurate, using easily determined points. The graphic display promotes critical analysis of situation and allows selection of cases at risk for treatment.