Patellofemoral replacement polymer stress during daily activities: a finite element study.

Isolated, symptomatic patellofemoral arthritis, although uncommon, has been reported to affect 8% of women and 2% of men over the age of fifty-five years1. Both conservative and surgical nonarthroplasty interventions have been advocated; however, reports on such interventions have suggested limited success2. Patellofemoral joint replacement designs as an alternative solution are beginning to reemerge largely through an appreciation of design requirements and the importance of component placement, which have been major factors in earlier clinical disappointments3-6. This study describes the influence that three different patellofemoral implant design geometries have on stresses that are associated with polymer abrasion and delamination and suggests their efficacy in clinical use. The designs included the LCS PFJ (low-contact stress patellofemoral joint; DePuy, a Johnson and Johnson Company, Warsaw, Indiana), Vanguard (Biomet, Warsaw, Indiana), and Scout (Waldemar Link, Hamburg, Germany). The former two designs are available for clinical use in the United States. Geometries for a three-dimensional, finite element model of each patellofemoral design were created by measuring the articular surfaces of implantable quality parts with use of a point laser profilometer. Surgical procedure was followed when positioning the components into a virtual left knee (Fig. 1). The results of a kinematic analysis of a generic total …