Analysis of optimal range of socket orientations in total hip arthroplasty with use of computer-aided design simulation.

A three-dimensional computer-aided design model of a total hip replacement was used to study the effects of anteversion and abduction of the acetabular component and anteversion and varus-valgus angulation of the femoral component on the range of hip flexion and extension that could be obtained without component impingement. Impingement of the component was defined as impingement between the neck of the femoral component and the edge of the acetabular component. To achieve an angle of hip flexion greater than 90 degrees and an extension angle greater than 30 degrees without component impingement, the optimal angulations were found to be between 1 and 30 degrees of anteversion and 30 and 50 degrees of abduction of the acetabular component, as well as 10 degrees of anteversion of the femoral component. When the valgus angulation of the femoral component was reduced from 7 to 0 degrees, the allowable range of flexion without impingement increased under the same conditions of acetabular-component orientation and femoral-component anteversion. Significant inverse correlations were found between the anteversion angle of the acetabular component and both the lumbar lordosis angle and the sacrohorizontal angle.