Tibial component failure mechanisms in total knee arthroplasty.

The purpose of this study was to examine the failure mechanisms and factors associated with failure of a nonmodular metal backed cemented tibial component. Out of 3152 total knee replacements done for osteoarthritis, 41 tibial components had been revised (1.3%). Four distinct failure mechanisms were identified: 20 knees were revised for medial bone collapse, 13 for ligamentous imbalance, 6 for progressive radiolucencies, and 2 for pain. Factors associated with medial bone collapse were varus tibial component alignment more than 3.0 degrees , Body Mass Index higher than 33.7, and overall postoperative varus limb alignment. Ligamentous imbalance was more prevalent in knees with preoperative valgus deformity. There were no knees revised for tibial component polyethylene wear or osteolysis. We conclude that the dominant failure mechanisms for this component design are related to preoperative deformity, technical factors of component alignment, overall limb alignment, and ligamentous imbalance.