Materials design analysis of the prosthetic anterior cruciate ligament

Repair or replacement of the damaged anterior cruciate ligament (ACL) is a significant clinical problem. A design utilizing ultrahigh-molecular-weight polyethylene (UHMWPE) was developed and marketed by an orthopaedic device manufacturer. Mechanical failure rates of greater than 10%/year postoperatively raised the issue of the adequacy of UHMWPE in that design. A study has been made to estimate the forces in the human anterior cruciate ligament for young, middle age, and older patients and to thus derive the minimum materials requirements for a now withdrawn prosthetic anterior cruciate ligament (PACL) design. It is concluded that UHMWPE does not possess adequate yield, creep, or fatigue properties to meet the design. Furthermore, consideration of the varying requirements on the PACL, due to differences in age and activity levels of patients, suggest that a band-type design offers a better possibility of achieving adequate materials performance in the ACL prosthetic replacement.