[Biomechanical explanation of ethiopathogenesis of bone apposition on femoral neck by coxarthrosis]

The radiological appearance of appositional new bone on the medial part of the neck of the femur in coxarthrosis

The X-rays of 448 hip joints with coxarthrosis (representing 304 patients) were examined. The majority (87.5%) showed appositional new bone formation on the medial part of the femoral neck in antero-posterior X-rays. Further studies showed that the extent of new bone formation on the posterior surface of the femoral neck was usually much greater than that found on the medial margin. Well trabeculated cancellous bone lay between the new bone cortex and the persisting cortex of the femoral neck. The new bone formation is considered to be a response to abnormal forces caused by limping. The radiological appearance was clearly defined into four major groups and it is suggested that the pattern observed may be related to the type of limp, the presence of a flexion deformity or anteversion of the femoral neck.

A photoelastic study of a model of the proximal femur. A biomechanical study of unstable trochanteric fractures I

In attempt to standardize an experimental model for biomechanical studies of unstable trochanteric fractures, acrylic models of the proximal femur were investigated by the photoelastic technique. By matching the stress distribution in the acrylic models to those calculated by Pauwels, it was found that the optimal femoral shaft and resultant hip joint force angles were 5 degrees and 6 degrees to the vertical, respectively. The abductor muscle pull was determined to be 55 per cent of the resultant hip joint force at 15 degrees medial inclination to the vertical.