The natural history of unicompartmental arthroplasty. An eight-year follow-up study with survivorship analysis.

From 1983 to 1987, 82 unicondylar arthroplasties were performed for primary unicompartmental osteoarthrosis. Seven knees had lateral compartment arthroplasties and 75 had medial unicompartmental knee arthroplasties (UKA). At a minimum follow-up period of four years, eight patients had been revised, one patient was scheduled for revision, and one patient had died with a failed UKA, for a total failure rate of 12%. Reasons for failure were progression of tricompartmental arthritis in two patients (2.4%), polyethylene wear in two (2.3%), component failure in two (2.3%), component loosening in three (3.5%), and technical error in one (1.6%). Furthermore, 14 (17%) patients showed roentgenographic evidence of impending failure and an additional 12 (15%) patients showed a gradual decline in Hospital for Special Surgery knee scores. Unicondylar knee arthroplasty does not appear to provide as reliable pain relief as total knee arthroplasty. Progression to tricompartmental arthritis, polyethylene wear, and component loosening were seen to limit the usefulness of this arthroplasty. Unlike total knee arthroplasty, factors affecting the success or failure of UKA cannot be predictably controlled by the surgeon.