MECHANICAL ANALYSIS AND OPTIMIZATION OF A CUP ARTHROPLASTY

The surgeon performing cup arthroplasty is free to relocate the acetabulum and the greater trochanter within certain limits. A method was developed so that optimum relocation can be accomplished based on a mechanical analysis of the hip. Clinical observations indicated that acetabular pressure and abductor muscle force should be minimized. A force and pressure analysis was written based on information that can be obtained from an X-ray. The problem was then formulated as a constrained optimization problem from which optimum geometry can be obtained which minimizes either acetabular pressure or abductor force. A computer program was written using the sequential unconstrained minimization technique, and extensive numerical results were obtained. The results show that minimum abductor force is the best optimization criterion, that the acetabulum should be moved medially and inferiorly, and that the tip of the greater trochanter should be moved laterally to obtain the minimum abductor force. An example is given which shows that these modifications can lead to significant reductions in abductor force and acetabular pressure. © 1969.