Risk Factors and Infection Presentation of Gram-Negative Fracture Related Infections.

Abstract

Objective: To assess factors associated with gram-negative (GN) fracture related infections (FRIs) and the impact of GN infections in treatment and outcomes in FRIs.

Methods: Design: Retrospective cohort.

Setting: Single Level I Trauma Center.

Patient selection criteria: All patients with extremity FRIs between 2013-2020.

Outcome measures and comparisons: A univariate analysis of FRI bacteriology was conducted in two manners. Two group analysis compared Any GN (AGN) to Gram-positive (GP) only (GPO) FRIs . Three group analysis compared Gram-negative only (GNO) vs. GPO vs. Polymicrobial GN including GP (PGN) FRIs.

Results: 299 patients met inclusion criteria. The mean age was 45.59 (18-92), and 187 (62.5%) were male. 76 (25%) patients had a GN microbe on intraoperative culture. In the AGN vs. GPO comparison, there were more male GN FRI patients (AGN=74% vs. GPO=59%, p=0.02). Cardiovascular disease was less common in AGN FRI patients (AGN=17% vs. GPO=30%, p=0.028). Multisystem trauma (AGN=67% vs. GPO=50%, p=0.014), external fixation (AGN=50%, vs. GPO=33%, p=0.014), skin grafting (AGN=27% vs. GPO=15%, p=0.045) and flap coverage (AGN=32% vs. GPO=16%, p=0.011) were more common in the AGN FRI. AGN FRI patients had more sinus tracts on presentation (AGN=42% vs. GPO=27%, p=0.013) and higher rates of amputation (AGN=15% vs. GPO=6%, p=0.021. Nonunion rates did not differ between the groups (AGN=20% vs. GPO=22%, p=0.731). Total number of reoperations needed for infection clearance was similar between AGN (3.5 +/-2.7) and GPO (2.9 +/-2.5) FRIs (p=0.068). The 3-group comparison was performed between the following groups (GNO, GPO, PGN). Post-hoc analysis of the 3-group analysis demonstrated PGN infections had no significant differences from GNO FRI in regard to injury characteristics (lower extremity, polytrauma), surgical characteristics (external fixation, flap coverage) and sinus tract formation.

Conclusion: Male sex, multi-system trauma, external fixation, and need for flap coverage or skin graft were associated with gram negative FRIs. Nonunion rates were similar between Gram-negative vs. Gram-positive only or Gram-negative vs. polymicrobial including Gram-negative FRIs. In comparison to patients with Gram-positive only FRI, any Gram-negative FRI led to a higher rate of amputation.

Level of evidence: III.