BMI is a key risk factor for early periprosthetic joint infection following total hip and knee arthroplasty.

AIM: To identify patient and surgical risk factors that are associated with periprosthetic joint infection (PJI), especially whether obesity is a risk factor following total hip arthroplasty (THA) and total knee arthroplasty (TKA). METHODS: New Zealand Surgical Site Infection Improvement Programme data was analysed using deep infection within 90 days of the index procedure as the outcome. This was tested against surgical and patient factors for statistical associations in a multivariate model. RESULTS: A total of 10,690 primary THAs and 9,481 primary TKAs were recorded by the NZSSIIP between 2013 and 2015. Multivariate analysis showed statistically significant associations with deep infections for BMI (BMI >40kg/m2 OR 5.62, 95% CI 2.25-14.0), male gender (OR 1.7, 95% CI 1.05-2.74) and age greater than 75 for THAs (age 40kg/m2 OR 1.94, 95% CI: 0.63-5.70) and male gender (OR 2.96, 95% CI 1.51-5.80). CONCLUSIONS: These findings show that obesity is one of the most important modifiable patient factors in predicting PJI following THA and TKA.