Surgical site infection (SSI) following hardware placement in patients with unstable malleolar fractures is a serious complication. SSI may require prolonged exposure to antimicrobials, removal of hardware, and can even lead to amputation. Identifying factors that place patients at greater risk for SSI may help target interventions to prevent these infections and reduce their occurrence and incidence.
This study was a retrospective analysis of patients in the National Surgical Quality Improvement Program (NSQIP). Current Procedural Terminology (CPT) codes were used to identify adult patients who underwent operative management for closed malleolar fracture from 2006-2013. NSQIP collects information on surgical variables and 30-day post-operative morbidity and mortality outcomes. Using univariate analysis, characteristics between patients with and without SSI were compared. Logistic regression was used to perform a multivariable analysis of risk factors for SSI while controlling for covariates. Length of stay was modeled using linear regression.
The analysis sample included 7,054, patients, of whom 116 developed a SSI. Patients with SSI were similar to those without in terms of sex, race and smoking status. But patients with SSI were significantly older, more likely to have diabetes, and had higher anesthesia class. Multivariable analysis identified several significant risk factors for SSI, including diabetes (odds ratio [OR] 2.6, 95% CI: 1.5-4.5, p<0.0001), ASA class 3+ (OR 2.3; 95% CI: 1.03-5.0, p=0.04), unclean surgery (OR 2.4, 95% CI: 1.3-4.2, p<0.0001) and inpatient location (OR 1.7, 1.1-2.7, p=0.01). After controlling for other factors, SSI increased LOS by 1.3 days (95% CI: -5.4-7.9, p=0.71) but this effect was not statistically significant.
SSI are serious complications following operative treatment for ankle fracture. In the first 30 days postop, SSIs occur with increased frequency in a few distinct groups. Because of the presence of prosthetic material, additional studies to follow patients for a full year after surgery are needed to see whether other risk factors emerge.