The effects of patellar thickness on patellofemoral forces after resurfacing.

The purpose of this study was to determine the effect of patellar bone and patellar implant thickness on patellofemoral forces after resurfacing in total knee arthroplasty. Seven cadaver knees were tested using an Oxford Knee Testing Rig. This model gave the specimens 6 degrees freedom while dynamic data were collected. Each knee was tested from full extension to 95 degrees knee flexion. Knees were implanted with Press Fit Condylar femoral, tibial, and patellar implants. The effect of varying patellar thickness on patellofemoral forces was determined by using custom modular oval-domed polyethylene patellar components with progressive thickness increments of 2 mm. Patellofemoral forces were measured by a custom-designed uniaxial patellar load cell. Statistically significant increases in patellofemoral compression forces were found from 70 degrees to 95 degrees flexion with increased patellar bone and patellar implant thickness.