Not all previous surgeries are the same: Procedure‐specific infection risk in total knee arthroplasty patients with a history of previous knee surgery

PURPOSE: While patient-level factors for prosthetic joint infections (PJIs) following total knee arthroplasty (TKA) are well-established, prior ipsilateral knee procedures are typically treated as a uniform risk factor despite likely variation in risk profile across procedure types. This study aimed to evaluate the procedure-specific risk of revision for infection in patients undergoing primary TKA with a history of one or more prior ipsilateral knee surgeries. METHODS: A retrospective nationwide cohort study using data from the Swiss Implant Registry analysed all primary TKAs performed between 2015 and December 2022. The primary outcome was revision for infection, whereas secondary outcomes included all-cause revision and all-cause mortality at 2 years. Multivariable logistic regression adjusted for age, sex, body mass index and American Society of Anesthesiologists classification, with individual prior procedures entered in a second block. Cumulative surgical burden was analysed as a categorical variable. RESULTS: Among 121,692 TKAs, 40,535 (33.3%) had a history of at least one ipsilateral knee intervention. All-cause revision occurred in 4232 patients (3.5%) and revision for PJI in 803 (0.7%). Any prior surgery was independently associated with higher rates of all-cause revision (odds ratio [OR] 1.33, 95% confidence interval [CI] 1.25-1.42; p < 0.001) and revision for PJI (OR 1.22, 95% CI 1.06-1.42; p = 0.005). On procedure-specific analysis, prior surgery for knee infection was associated with the highest risk of PJI revision (OR 3.30, 95% CI 1.56-6.96; p = 0.002), followed by tibial osteotomy (OR 2.12, 95% CI 1.60-2.82), synovectomy (OR 2.18, 95% CI 1.27-3.73), tibial osteosynthesis (OR 1.71, 95% CI 1.10-2.68) and anterior cruciate ligament reconstruction (OR 1.44, 95% CI 1.10-1.90; all p < 0.05). Infection risk was significantly elevated only in patients with more than two prior procedures (OR 2.01, 95% CI 1.51-2.68, p < 0.001). CONCLUSION: Prior ipsilateral knee surgery is associated with procedure-specific and cumulative risk of revision for infection after TKA, supporting the integration of prior surgical history into preoperative risk stratification protocols. LEVEL OF EVIDENCE: Level III.