Excellent early outcomes following lateral robotic-assisted unicompartmental knee arthroplasty

Lateral unicompartmental knee arthroplasty (UKA) has historically shown mixed results and there is limited contemporary literature on lateral robotic-assisted UKA (RA-UKA) outcomes. This study aimed to evaluate the short-term survivorship, clinical, and radiographic outcomes of lateral RA-UKA.

A retrospective review identified 138 lateral RA-UKAs performed from 2016 to 2022 at a single institution, with a study population of 58% women, a mean BMI of 27 kg/m², and a mean age of 62 years. The mean follow-up was two years. Kaplan-Meier analysis assessed survivorship free from all-cause reoperation and revision. A radiographic review evaluated component positioning, aseptic loosening, and osteoarthritis progression.

The one- and two-year survivorship free from all-cause revision was 100% (95% confidence interval [CI]: 100 to 100%). The one- and two-year survivorship free from all-cause reoperation was 97% (95% CI: 91 to 99%) and 96% (95% CI: 90 to 98%), respectively. There were six (4%) reoperations, most commonly for arthroscopic lysis/removal of scar tissue, synovitis, and osteophyte. The mean anatomic tibiofemoral angle decreased from 9.7° to 5.9° valgus. At the latest follow-up, 11 (8%) knees showed radiographic osteoarthritis progression. From preoperatively to two years postoperatively, the mean Knee Injury and Osteoarthritis Outcome Score for Joint Replacement increased from 56 to 82 (P < 0.0001), and the mean visual analog scale for pain decreased from 53 to 18 (P = 0.001).

Short-term follow-up of contemporary lateral RA-UKA demonstrated high survivorship free from all-cause reoperation (96%) and revision (100%). Patients had significant improvements in PROMs, and a minority had osteoarthritis progression.