Previous bariatric surgery was not associated with an increased risk of reintervention within 2 years after knee arthroplasty: A nationwide register-based study from Denmark

PURPOSE: Obesity is a major risk factor for knee osteoarthritis (KOA). Bariatric surgery (BAS) effectively induces weight loss, but some of these patients subsequently require knee arthroplasty (KA) despite substantial weight reduction. However, the impact of prior BAS on the risk of reintervention, antibiotic use and mortality following KA remains unclear. The objective was to evaluate the impact of prior BAS on the risk of reintervention and mortality after KA in patients with KOA, compared with patients undergoing KA without prior BAS and to examine whether body mass index (BMI) at the time of KA modifies these effects.

METHODS: We conducted a nationwide, register-based cohort study analysing patients undergoing primary KA. KOA patients with prior BAS were propensity score-matched to a control group based on BMI (non-obese: BMI < 30 kg/m 2, obese: BMI 30-39 kg/m 2, morbidly obese: BMI ≥ 40 kg/m 2) and the type of KA (i.e., total knee arthroplasty [TKA] or unicondylar knee arthroplasty [UKA]) and other health and socioeconomic data. Using Cox regression models, we compared hazard ratios (HRs) for outcomes, including: (1) reintervention rates (within 90 days and 2 years) and (2) mortality (within 2 years).

RESULTS: Among 99,965 patients having KA, 1448 had prior BAS and 98,517 did not. After matching, 1427 BAS KOA patients were compared with 6194 KOA controls. Patients exposed to earlier BAS showed no statistical difference in 90-day reintervention rates (9 [0.6%] vs. 52 [0.8%], HR: 0.75, 95% confidence interval [CI]: 0.37-1.52) or 2-year reintervention rates (43 [3.0%] vs. 195 [3.2%], HR: 0.95, 95% CI: 0.69-1.33). Revision due to infection and mortality did not differ between groups.

CONCLUSIONS: No differences were observed in the risk of reintervention within 2 years or mortality between patients with and without prior BAS before KA.

LEVEL OF EVIDENCE: Level II, prognostic studies-investigating natural history and evaluating the effect of a patient characteristic.