[A roentogenographical study on the alignment of the lower extremities in secondary coxarthrosis]

Alignment of the lower extremities in secondary coxarthrosis (273 lower extremities) and controls (240 normal lower extremities) were studied using roentogenograms of whole lower extremities including the pelvis taken in the standing position with both legs. Secondary coxarthrosis, which is caused by congenital dislocation of the hip joint, was classified into four groups: unreduced dislocation, high dislocation, incomplete dislocation, and dysplasia of the acetabulum. Comparative studies were conducted using statistical data on measured items, obtained from secondary coxarthrosis cases and controls. In controls, the femoro-tibial angle (FTA) was 175.5 +/- 2.08 degrees and the mechanical axis passed through the medial side to the middle of the knee. It has been noted that a tendency for bow-legs was seen after the age of 50. In coxarthrosis with high dislocation, the most marked knock-knees were observed (FTA of 172.5 +/- 3.88 degrees), while in coxarthrosis with incomplete dislocation and dysplasia of the acetabulum, there was a tendency to coxa valga but no tendency toward knock-knees was evident. Cases of total hip replacement revealed that it is possible to improve knock-knees by installing a socket in the primary acetabulum as much as possible, correcting the difference between the length of the legs and elimating adduction contracture. It was also possible to study factors contributing to bow-legs and knock-knees by means of multivariate analysis.