Comparison of survival and cost-effectiveness between unicondylar arthroplasty and total knee arthroplasty in patients with primary osteoarthritis: a follow-up study of 50,493 knee replacements from the Finnish Arthroplasty Register.

Background And Purpose: Both unicondylar arthroplasty (UKA) and total knee arthroplasty (TKA) are commonly used for the treatment of unicompartmental osteoarthritis (OA) of the knee. The long-term survivorship and cost-effectiveness of these two treatments have seldom been compared on a nationwide level, however. We therefore compared the survival of UKA with that of TKA and conducted a cost-benefit analysis comparing UKA with TKA in patients with primary OA.

Patients And Methods: We analyzed 1,886 primary UKAs (3 designs) and 48,607 primary TKAs that had been performed for primary OA and entered in the Finnish Arthroplasty Register between 1980 and 2003 inclusive.

Results: UKAs had a 60% (95% CI: 54-66) survival rate and TKAs an 80% (95% CI: 79-81) survival rate at 15 years with any revision taken as the endpoint. Overall survival of UKAs was worse than that of TKAs (p < 0.001). All 3 UKA designs had poorer overall survival than the corresponding TKA designs. In the theoretical cost-benefit analysis, the cost saved by lower implant prices and shorter hospital stay with UKA did not cover the costs of the extra revisions.

Interpretation: At a nationwide level, UKA had significantly poorer long-term survival than TKA. What is more, UKA did not even have a theoretical cost benefit over TKA in our study. Based on these results, we cannot recommend widespread use of UKA in treatment of unicompartmental OA of the knee.