Obesity is associated with higher rates of revision following medial unicompartmental knee arthroplasty.

BACKGROUND

Obesity has been suggested to be a potential risk factor for revision surgery following unicompartmental knee arthroplasty (UKA), however the orthopaedic literature is currently inconclusive.

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 (BMI ≥ 30 kg/m2) and non-obese patients (BMI < 30 kg/m2). 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. Rates of revision for all causes were compared. The cumulative percent revision (CPR) was calculated using Kaplan-Meier estimates, and Cox proportional models were used to compare revision rates.

RESULTS

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). 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

Obese patients are at increased risk of revision following UKA particularly in relation to fracture and infection. In obese patients cement usage, medial UKA and fixed-bearing implants are associated with increased rates of revision.