Outcomes and Implant Survival in Lateral Unicompartmental Knee Arthroplasty: The Path Less Traveled.

Abstract

Unicompartmental knee arthroplasty (UKA) is an effective treatment for isolated lateral compartment osteoarthritis (OA). Surgeons have been reticent to adopt this procedure due to the difficulty of exposure and historically higher rates of revision when compared to total knee arthroplasty (TKA). The purpose of this study was to evaluate our series of lateral UKAs. We retrospectively reviewed 548 fixed-bearing, cemented lateral UKAs performed at a single institution between January 2001 and May 2023. The diagnosis was OA in 98.5% of cases, and 71% of patients were women. The average age and body mass index (BMI) at the time of surgery were 67 years (range, 28 to 93) and 27.8 (range, 18.0 to 49.5), respectively. The primary outcomes included implant survivorship and revision rate with associated causes. The secondary outcomes included complication rates and analysis of pre- and postoperative tibio-femoral angle (TFA). The 10-year survivorship was 95.7%. There were 19 cases (3.5%) that required revision after a mean time in situ of 6.5 years, most commonly due to progression of OA (n = 14), followed by aseptic loosening (n = three), periprosthetic fracture (n = one), and infection (n = one). An additional 11 cases (2.0%) required reoperation without revision. The early (≤ 90 days) complication rate was 2.2%. Postoperative limb alignment did not differ significantly between revised and non-revised cases. In non-revised patients, mean pre- and postoperative TFA was 9.8 and 5.3° valgus, respectively. Patients revised for OA progression had similar alignment (preoperative 11.6°, P = 0.15; postoperative 5.3°, P = 0.94). Lateral UKA demonstrated excellent 10-year survivorship and a low complication rate. Most revisions were due to the progression of arthritis, which occurred independently of postoperative alignment. These findings support lateral UKA as a durable, joint-preserving option for appropriately selected patients.