Long-term survivorship after medial unicompartmental knee arthroplasty: the influence of medical comorbidities and previous knee surgery.

PURPOSE: To evaluate long-term implant survivorship after medial unicompartmental knee arthroplasty (UKA) and determine whether medical comorbidities or previous ipsilateral knee surgery were associated with revision, complications, or clinical outcomes. METHODS: This retrospective cohort included 168 medial UKAs with a mean follow-up of 119.7 ± 29.3 months in the survivorship analysis. Revision of any prosthetic component was the endpoint for Kaplan-Meier analysis. A nested cohort of 76 knees underwent outpatient clinical evaluation; analyses of comorbidities, previous surgery, complications, and clinical outcomes were restricted to this cohort. RESULTS: Eighteen revisions occurred. Implant survivorship was 100% at five years, 96% at seven years, 86% at ten years, and 78% at 15 years. In the 76-knee clinical cohort, 92.1% had at least one comorbidity and 54.0% had multimorbidity; no evaluated comorbidity category was significantly associated with revision or long-term clinical outcomes. Previous ipsilateral knee surgery was associated with a lower Knee Society clinical score (73.6 ± 14.1 vs 80.7 ± 12.5; p = 0.036) and a non-significantly higher rate of complication or revision (28.6% vs 8.1%; odds ratio 4.56; p = 0.054). CONCLUSION: Medial UKA provided satisfactory long-term survivorship in a real-world cohort. No clear association was identified between the evaluated comorbidity categories and long-term outcomes, although small subgroups and the absence of severity measures preclude definitive conclusions. Previous ipsilateral knee surgery was associated with a lower objective clinical score and may identify knees requiring more cautious pre-operative counselling.