Outcomes of Aseptic, Septic, and Occult Infected Index Nonunion Repair: A Retrospective Comparative Study

OBJECTIVES: To compare nonunion surgery effectiveness for occult infected, aseptic, and septic nonunions in patients identified using the FRI criteria. METHODS: Design: Retrospective Review. SETTING: Single Level I Tertiary Academic Center. PATIENTS SELECTION CRITERIA: All skeletally mature patients over a 10-year period with nonunions and inflammatory labs at the time of index surgery were evaluated. Patients were classified using fracture-related infection (FRI) criteria as septic (SP) or aseptic. Aseptic patients were further stratified by intraoperative cultures into aseptic (AP, culture-negative) and occult infected (OP, culture-positive) groups. Exclusion criteria were pathologic fractures. OUTCOME MEASURE AND COMPARISONS: Primary outcome measured was successful union after index nonunion surgery without need for additional surgical interventions. RESULTS: A total of 208 patients with nonunion fractures were included (OP: 29; AP: 125; SP: 54). Mean age was similar between groups (OP: 47.6 ± 21.2 years, range 19.9-79.9 years; AP: 54.5 ± 25.6 years, range 15.4-93.4; SP: 54.9 ± 23.5 years, range 16.5-81.3, p=0.854). Male sex distribution in occult infected patients, aseptic patients, and septic patients was 65.5%, 66.4%, and 46.3%, respectively (p=0.035). Occult infected patients had the highest rate of successful union after index surgery without need for additional operative intervention (79.3%), followed by aseptic patients (72.8%) and septic patients (50.0%) (p=0.004). Postoperative infections following index nonunion surgery were significantly lower in aseptic patients (16.0%) and occult infected patients (10.3%) compared to septic patients (35.2%) (p=0.005). CONCLUSIONS: Index nonunion surgery in septic patients, as defined by FRI criteria, was associated with worse outcomes compared to aseptic and occult infected patients. The success of surgery in occult infected nonunion is comparable to aseptic cases, suggesting that subclinical fracture related infection does not significantly compromise outcomes. LEVEL OF EVIDENCE: Prognostic Level III.