Obesity is Associated with Higher Rates of Revision Following Unicompartmental Knee Arthroplasty

Objectives: To assess if obesity is a risk factor for early revision surgery following unicompartmental knee arthroplasty (UKA). Methods: Data from the Australian Orthopaedic Association National Joint Replacement Registry (AOANJRR) were analysed for the period from 2015 to 2022. All primary UKA procedures performed for any diagnosis were identified and categorized into two patient groups: obese patients (body mass index (BMI) ≥30 kg/m2) and non-obese patients (BMI <30 kg/m2). Rates of revision for all causes, as well as revision for fracture, loosening, progression of disease, and pain were compared. The cumulative percent revision (CPR) was calculated using Kaplan-Meier estimates, and Cox proportional models were used to compare revision rates. Results: There were 26,472 primary UKA procedures included of which 11,901 (45%) procedures were undertaken in obese patients and 14,571 (55%) in non-obese patients. Obese patients had a significantly higher rate of revision compared to non-obese patients (HR 1.15, p = 0.021). Obesity was found to be a risk factor for revision secondary to infection (HR 1.48, p = 0.046), as well as revision secondary to fracture (HR 2.09, p = 0.003). There were no differences in other reasons for revision, including loosening, progression of disease and pain, between obese and non-obese groups. Obese patients had a higher rate of revision compared to non-obese patients when a cemented prosthesis (HR 1.21, p = 0.011), a medial prosthesis (HR 1.16, p = 0.018), or a fixed-bearing prosthesis (HR 1.22, p = 0.009) was used. Conclusion: Based on AOANJRR data, obese patients are at increased risk of higher rate of revision following UKA. Obese patients who undergo UKA with a cemented, medial compartment, or fixed-bearing implant are at particular risk of increased rates of revision.