Revision Unicompartmental Knee Arthroplasty: Worse than a Primary, but Better than a Revision Total Knee Arthroplasty

Background: Revision of a unicompartmental to a total knee arthroplasty (TKA) is often compared to primary TKA with regard to its technical difficulty and complication rates. We sought to compare medical and surgical complications following revision unicompartmental knee arthroplasty (UKA) to those following primary TKA and aseptic revision TKA.

Methods: A national administrative claims database was queried for patients undergoing revision UKA between 2010 and 2019. Patients undergoing revision of a UKA were matched to patients undergoing primary TKA and aseptic revision TKA based on age, sex, Elixhauser Comorbidity Index, payer status, and a history of obesity, osteoporosis, tobacco use, and alcohol use disorder. Revision-free survivorship as well as 2-year and 90-day complication rates were compared. Multivariable logistic regression analysis was performed to determine the independent risk of medical and surgical complications.

Results: A total of 3,924 matched primary TKAs, revision of a failed UKA, and aseptic revision TKA patients were included. Overall survivorship was 96.9% (95% confidence interval [CI] 95.9 to 97.8) for primary TKA, 93.4% (95% CI 92.1 to 94.8) for revision UKA, and 89.8% (95% CI 88.2 to 91.5) for aseptic revision TKA at 2-year follow-up (P < 0.001). At two years, revision UKA patients had higher rates of aseptic loosening (2.2 versus 0.8%, P = 0.004), instability (2.4 versus 0.8%, P = 0.002), and mechanical failures (3.0 versus 1.5%, P = 0.012) than primary TKA patients. The 90-day complication rates were comparable between primary TKA and revision UKA patients (all P > 0.05); the risk of reoperation, acute kidney injury, wound dehiscence, hematoma, and transfusion were all higher in the revision TKA than in the revision UKA cohort (all P < 0.05).

Conclusions: Revision-free survivorship and arthroplasty-related complications at two years following revision UKA are lower than that for primary TKA, but higher than that for aseptic revision TKA, whereas medical complications are similar to those following primary TKA.