Rotating platform components for revisions of hinged knee prostheses.

If hinged prostheses are revised with smaller and nonhinged prostheses, do these implants provide adequate fixation, do massive bone grafts in combination with smaller implants reinforce host bone stock, do less constrained prostheses restore ligament tension, and do they avoid problems of the extensor mechanism? To answer these questions, 20 failed hinges were revised to rotating platform revision prostheses with short intramedullary stems in a prospective study. Meticulous soft tissue release techniques and extensive bone grafts were used (tibia, impaction grafting in 16 cases, and structural grafts in four cases; femur, impaction grafting in four cases and structural grafts in 16 cases). The mean followup was 5.3 years (range, 2.3-10.5 years). The Knee Society score improved from a preoperative mean of 21 points (range, 7-49 points) to a mean 81.2 points (range, 59-94 points). One cementless tibial component with extensive impaction grafting became loose. The remaining components (95%) were well-fixed. All cancellous bone grafts showed trabecular remodeling. All structural grafts united to the host bone without resorption. All knees had ligamentous stability after surgery. There were no problems of the extensor mechanism. In this series the rotating platform revision prostheses were used successfully for failed hinged prostheses.