Femoral component loosening in total knee arthroplasty.

From experience with over 1600 condylar-type total knee arthroplasties performed between 1974 and 1981, the authors identified 15 knees in which the femoral component had loosened and shifted into flexion on the end of the femur. This mode of failure was related to inadequate support of the prosthetic posterior condyle, which resulted from inaccurate surgical cuts, poor cementing technique, or deficient bone stock either primary or secondary to persistent rheumatoid synovitis. Newer prosthetic designs that allow for greater range of motion and maximal function will further test the critical posterior condylar bone interface, as a result of which a higher incidence of femoral component loosening with flexion shift may be seen. Femoral component design changes and surgical techniques that sustain the posterior femoral condyle metal-bone interface may thus be necessary. Femoral components with intramedullary stems may be appropriate for high-risk patients.