The effect of total knee design on patellar strain.

Total knee arthroplasty with patellar resurfacing produces an increase in anterior patellar strain up to three times that observed in controls. This increase is independent of surgical capsulotomy and is prominent at flexion angles greater than 30 degrees. Minor alterations in surgical technique do not affect the observed strain. Peak strains were seen at the extremes of flexion in all prostheses. The highest strains were recorded for the Total Condylar prosthesis throughout the range of motion. Although the difference was not statistically significant, the Insall-Burstein knee consistently produced higher strains than did the Robert Brigham knee throughout the functional range of motion (30-90 degrees). For the Robert Brigham knee, sectioning of the posterior cruciate ligament resulted in no significant change in the measured strains.