What are the Risk Factors for Infection after Operative Treatment of Subtalar Fracture Dislocations?

Category: Ankle; Trauma Introduction/Purpose: Subtalar fracture dislocations are a rare hindfoot injury with relatively little evidence to inform surgeons about outcomes and risk factors for complications. Some previously documented poor prognostic factors include lateral and complicated dislocations, total talar extrusions, and concomitant fractures. The mechanism of injury often results from high energy trauma and has been reported as severe inversion (medial dislocation) or eversion (lateral dislocation) of the foot. The purpose of this study was to assess the risk factors associated with deep infection after operative treatment of subtalar fracture dislocations. Methods: A retrospective cohort study at a single level 1 trauma center was performed to identify patients who had operative treatment of a subtalar fracture dislocation over an 11 year period (2008-2019). Patients were identified by review of the electronic health record and data collected included patient demographics, injury characteristics, and treatment choices. Deep infection was defined as return to the operating room for debridement. Minimum follow-up for inclusion was 3 months. Descriptive analyses (means, medians, standard deviations, ranges, frequency distributions) were used to assess and describe the group. Chi-square tests of association and independent-sample t tests were used to assess differences between the infected group and those without infection. Results: A total of 154 met criteria for this study. The most common associated fractures were talus (47%) and calcaneus (33%). Approximately every 1 in 8 patients (12.3%) patients developed a deep infection. The infected group was older (47.2 vs 39.5 years, p=0.03). Tobacco users were found to have a significantly higher rate of postoperative deep infection (74 vs 34%, aOR=7.4, 95% CI, 2.3-24.1, p=0.001). There was a significantly higher proportion of infection in patients with Gustilo-Anderson type 3 open fractures (32 vs 12%, aOR=5.7, 95% CI, 1.6-20.3, p=0.007). The infected group had a higher proportion of below the knee amputation (47 vs 1%, p<0.001). Conclusion: Infection after operative management of subtalar fracture dislocations can be devastating, with 47% of infected patients requiring amputation. Risk factors for infection after subtalar fracture dislocation include older age, smoking, type 3 open fracture, and freshwater contamination. Ultimately demographic and injury characteristics seem to drive the risk of infection in subtalar fracture dislocations.