Purpose: A retrospective review was done to evaluate survival of unicondylar arthroplasty and identify factors that increased the odds of revision. Our hypothesis was that younger age, increased weight, use of a thinner tibial component, polyethylene shelf aging.

Methods: 411 medial compartment unicondylar arthroplasties encompassing 12 designs were performed at one institution from 1984 to 1998. Patient age and weight averaged 67 ± 8 years and 83 ± 15 kg, respectively. Eighty-seven percent of the tibial components were metal-backed. Initial tibial component thickness averaged 8.5 ±1mm. Polyethylene shelf age averaged 1.3 ± 1.2 years.

Results: Four factors made revision more likely (p < 0.05, Cox proportional hazards regression): younger patient age, thinner tibial component, longer polyethylene shelf age. Gender and weight did not influence survival. With an endpoint of any component revision, Kaplan-Meier survival at nine postoperative years was 80% (95% confidence interval: 75% to 84%). In knees in which tibial component initial thickness was greater than 7mm and polyethylene shelf age was under 1 year, nine-year survival was 94% (95% confidence interval: 91% to 99%).

Conclusions: A 94% likelihood of survival at nine postoperative years may be a reasonable expectation when the procedure is performed with appropriate materials and designs..

Funding : Commerical funding

Funding Parties : Inova Health Care Services