The Minns meniscal knee prosthesis: biomechanical aspects of the surgical procedure and a review of the first 165 cases.

The Minns knee prosthesis has been designed so that the ligaments, soft tissues and musculature about the knee can return to their full functioning during the movement and loading that occur in usage. By utilising a third component made of polyethylene that slides back and forth in a straight line between the metallic femoral and tibial components, the knee is able to roll and slide at the plastic/metal junctions without creating high forces and loosening moments on the tibial component. The tibial tray has a central cut-out to allow the functioning of both cruciate ligaments, and the femoral component is of the total condylar design. Experimental and theoretical studies on the functioning and clinical performance of this design and the biomechanical implications of the technique of surgical implantation are described. The results of the first 165 cases, followed up for a maximum of 5 years, were ranked according to pain, mobility, and restoration of function; 75% were rated as excellent, both subjectively and objectively, 13% as good, and 9% as fair. The average range of motion measured at least 6 months postoperatively was 103 degrees. Eight knees dislocated laterally because of instability and were successfully revised using the sliding plateau without being necessary to remove the metallic components. Minimal wear has been seen on the removed menisci up to 4.5 years' use.