The fate of the joint space in Legg-Calvé-Perthes' disease

This study was undertaken to identify variations in the hip joint space in patients with healed Legg-Calvé-Perthes' disease (LCPD) and to correlate these changes with the radiological outcome of treatment.

The width of the joint space was measured on radiographs of 121 skeletally mature individuals with healed LCPD. The joint space width at the stage of healing in 79 patients was compared with the joint space at skeletal maturity. The hips were graded by the Stulberg classification and the femoral head radius was measured. Associations between the joint space width, the Stulberg class and the femoral head radius were tested. The reproducibility of measurement was tested by measuring 30 radiographs twice and computing the intra-class correlation coefficient (ICC). The joint space width was measured on radiographs of 25 patients taken both while recumbent and standing, to determine if the joint space alters on weight-bearing.

The reproducibility of measurements was satisfactory; no difference was noted in the joint space in recumbent and weight-bearing films. Increased joint space was noted both at healing of the disease and at skeletal maturity; the width was minimally increased in Stulberg Class I hips and considerably increased in Class III, IV and V hips. There was a significant correlation between the increase in joint space and enlargement of the femoral head.

An increase in joint space width occurs quite frequently following LCPD; the increase is most evident in hips with a poor outcome. The implications of this observation need to be elucidated.