Unicompartmental knee arthroplasty implant survival in patients with borderline indications

Introduction: In the literature, 80%-92% of patients are satisfied with their medial femorotibial unicompartmental knee arthroplasties (UKAs). These results are associated with a 10-year implant survival rates ranging from 94% to 98% in various studies. Such outcomes are generally reported after excluding patients with obesity, chronic anterior instability, frontal deformities, or preoperative knee flexion deformities exceeding 10( degrees). These contraindications remain controversial in the literature. The primary objective of this study was to compare the survival rates of implants used for medial femorotibial UKA performed under borderline indications with those of procedures performed under conventional indications and to identify the prognostic factors for revision surgery. Hypothesis: We hypothesized that the survival of medial femorotibial UKAs is not impacted by these contraindications. Materials and methods: This was a retrospective, single-center, observational, epidemiological study. All consenting patients who underwent medial femorotibial UKA between 2009 and 2015 were included. Patients who underwent other types of arthroplasties concurrently were excluded. The primary evaluation criterion was implant survival, which was characterized by no need for revision surgery. The borderline indications were defined as follows: obesity (Body Mass index BMI > 30), anterior cruciate ligament (ACL) deficiency, preoperative lower limb frontal deviation >10 (degrees), or preoperative flexion deformity >10 (degrees). Results: A total of 468 patients were included, and the average follow-up duration was 8.5 years [7.1; 10.3]. Among them, 270 (57.7%) underwent UKA under at least one borderline indication, whereas 198 (42.3%) underwent UKA under conventional indications. Forty revision surgeries were recorded, and the average time to revision surgery was 26 months. No statistically significant difference in survival was observed between patients with borderline indications and those with conventional indications. Multivariate analysis revealed that obesity (HR = 3.0 [1.5-5.7]) and ACL deficiency (HR = 3.5 [1.4-8.8]) significantly increased the risk of revision surgery. Discussion: This study revealed no significant difference in survival between UKAs performed under borderline versus conventional indications. Larger studies are needed to confirm these findings.