Early instability with mobile-bearing total knee arthroplasty: a series of 25 cases.

Between December 1987 and January 2002, 25 cases of clinical instability following mobile-bearing total knee arthroplasty (TKA) with meniscal bearings or rotating platforms presented for evaluation at our institution. These cases were retrospectively identified. All were performed at outside institutions by a variety of surgeons. All clinical examinations were performed by the authors. Nine cases were revised at our institution. All 25 cases had clinical evidence of severe coronal-plane instability and pain. Eight cases had polyethylene dislocation or subluxation that was evident radiographically and clinically. Four cases had extensor-mechanism dysfunction. Eighteen cases had symptoms immediately postoperatively. Twenty-three of the 25 cases had symptoms within 2 years' postoperatively. Any potential long-term benefit of design innovations must be balanced with known problems leading to early failure.