The Disappearing Unicompartmental Knee Prostheses

The disappearance of unicompartmental knee prostheses is linked to poor clinical results, lack of financial profitability, technological innovation, laboratory consolidation or restructuring, and the takeover bids and counter-takeovers of the world giants producing orthopaedic equipment. SULZER MEDICA created CENTERPULSE to manage its Orthopaedic branch, and ZIMMER bought out BIOMET to create ZIMMER BIOMET. Smith & Nephew still produces unicompartmental implants in Europe, such as the Goeland, Genesis, Accuris Uni, and Journey Uni. Gonometric, Preservation, Miller-Galante II, and PCA were all cemented prostheses with femoral condyles, tibial bases, and polyethylene thicknesses ranging from 8 to 12 mm. Miller-Galante II had poor results, but Berger et al. showed 98% survival at 10 years. The PCA prosthesis had a 9.5% revision rate due to femoral loosening and premature wear of the polyethylene. The Marmor Modular Knee had a survival rate of 93% at 12 years’ follow-up, with excellent results in 57% of cases. Dr. Leonard Marmor was the father of the modern CUP, which was replaced by the MOD3 in 1984. The MOD3 had an early failure rate of 6%, but a 95% survival rate at 8 years. The Genesis replaced the MOD3 with a proportional increase between the width and length of the implant and a tapered component appearance. The discontinuation of the marketing of unicompartmental prosthesis is due to a combination of factors related to the implant, its components, type of sterilization, thickness of the polyethylene, characteristics of certain components, evolution in time, survival, mechanical loosening, premature wear of polyethylene, human factors, functional results, revision rate, economic factors, and impoverishment of design companies. Orthopaedic surgeons need to consider strong actions to reverse a potentially disastrous trend of American-led conglomerates dominating the world market for orthopaedic implants.