Utility of Sonication for Fracture-Related Infection

Abstract

Objectives: To determine the utility of sonication compared to traditional tissue culture in the setting of fracture-related infections (FRIs).

Methods: Design: Retrospective cohort.

Setting: One Level 1 Trauma Center.

Patient selection criteria: Patients with prior fracture fixation that required a reoperation for suspected infection, nonunion, or hardware failure with available sonication data between 2018 and 2023 were included.

Outcome measures and comparisons: The primary outcome was positivity of sonication compared to traditional tissue culture. FRI was diagnosed based on clinical FRI diagnosis by the treating team in collaboration with infectious disease specialists. Secondary aims were to identify specificity and sensitivity of sonication and tissue culture and patient-specific factors associated with positive sonication in the setting of negative tissue culture.

Results: Of 79 patients identified, 67 met inclusion criteria. Mean age was 57 years (IQR: 43-72), and 50% were female. Most fractures were in the lower extremity (85%), and 73% were treated with plate fixation. Eighteen patients had positive tissue cultures, of which 15 were positive on sonication. Forty-nine patients had negative tissue cultures. Twenty-seven patients (40%) had positive sonication. Thirty cases were classified as FRI. Patients with positive sonication with negative tissue cultures were more likely male (66.6% vs. 32.4%, p=0.048), older (65.5 vs. 55.7 years, p=0.045), and had higher reoperation rates for suspected infection (50% vs. 13.5%, p=0.0093) compared to negative sonication. Sonication demonstrated a higher sensitivity (80% vs. 56%) and lower specificity (92% vs. 97%) than tissue culture for FRI detection. The total sonication cost was $229 per patient compared to $122 for standard tissue cultures.

Conclusion: Sonication demonstrated higher sensitivity for FRI detection compared to traditional tissue culture. Given its minimal additional cost and higher sensitivity, sonication is recommended as an adjunct diagnostic tool in reoperations for suspected orthopedic infections, hardware failure, and nonunion of unclear etiology.

Level of evidence: Diagnostic Level IV.

Keywords: Sonication; fracture-related infections; microbiology; sensitivity; specificity.