Unusual mechanical complications of unicompartmental low contact stress mobile bearing patellofemoral arthroplasty: a cause for concern?

Abstract

The Low Contact Stress Patellofemoral Arthroplasty (LCS PFA) is a newer design belonging to the second generation of inlay type implants, addressing the problems encountered in the first generation models (Lubinus & Richard's). The cemented mobile bearing metal backed patellar component in this system is "modular"; allowing interchangeable usage with either the trochlear component in a PFA or the femoral component of a total knee arthroplasty, thus obviating the need for patellar revision during conversion of PFA to TKA. The younger active patient with a PFA may exert extreme joint reaction forces on their patellar implant, rendering early loosening of the patellar implant. The endurance of this implant with repeated flexion beyond 90 degrees is also a concern. We describe a series of three unusual mechanical failures associated with this particular design of metal backed patellar component of the unicompartmental LCS patellofemoral arthroplasty.