Similar Functional Results in Patients Outside the Classical Criteria for Medial Unicompartmental Knee Arthroplasty

Background: The indications for unicompartmental knee arthroplasty (UKA) are restricted by multiple criteria. The aim of this study was to explore the functional results of UKA in a population of patients outside the classical criteria. Methods: This study included a population of 197 patients who underwent UKA for medial osteoarthritis between 2017 and 2020. Two groups of patients were compared: those meeting the classical criteria and those presenting with ≥1 contraindication (e.g., age of ≥75 years, body mass index [BMI] of ≥30 kg/m 2 , or coronal limb deformity of >8°). The implant that was used was a modern fixed-bearing primary medial UKA component. The minimal follow-up was 3 years. The primary outcome was the functional results, including the Knee Society Score (KSS), and the secondary outcomes were the complication and revision rates. Results: There were 100 patients in the indication group and 97 in the off-indication group. No significant differences were observed between the 2 groups for height, sex ratio, operated side, or osteoarthritis stage (p > 0.05). There was no significant difference in the KSS between the 2 groups (p = 0.96). At 3 years of follow-up, the survival rate without revision was 100% in the indication group and 95.38% in the off-indication group (p = 0.57). The rate of complications was 12.9% in the indication group and 8.96% in the off-indication group (p = 0.47). Conclusions: UKA for medial osteoarthritis yielded the same functional results for patients presenting with ≥1 theoretical contraindication, including a BMI of ≥30 kg/m 2 , age of ≥75 years, and coronal limb deformity of >8°, without altering the complication or revision rates at 3 years of follow-up. Level of Evidence: Therapeutic Level III . See Instructions for Authors for a complete description of levels of evidence.