Time-dependent effects of chlorhexidine soaks on grossly contaminated bone

OBJECTIVE: The purpose of this study was to quantify the reduction in the bacterial burden of grossly contaminated bone segments using different chlorhexidine (CHL) solutions. We hypothesized that 4% CHL would be the most efficient decontaminate. METHODS: Fifty-four bone segments were harvested from fresh-frozen porcine legs. Each specimen was dropped onto a Mueller-Hinton medium that was inoculated with Staphylococcus aureus (lux). These genetically engineered bacteria emit photons in proportion to their number, allowing for quantification. The segments were retrieved after 5 seconds of exposure. Baseline imaging provided the initial bacterial load. An equal number of specimens were soaked in normal saline (NS), 2%CHL, or 4%CHL. Specimen reimaging was completed at the 5-, 10-, 20-, 30-, and 60-minute marks. RESULTS: The average bacterial count on the bone segments were 2.18 × 10 for NS, 2.31 × 10 for 2%CHL, and 2.00 × 10 for 4%CHL. The percent reduction in bacterial counts at the 5-, 10-, 20-, 30-, and 60-minute marks were NS: 0%, 0%, 0%, 29.84%, 72.23%; 2%CHL: 93.09%, 98.16%, 99.21%, 99.63%, 99.81%; 4%CHL: 94.32%, 97.60%, 99.25%, 99.63%, 99.82%. At all time intervals, there was a significant difference between the 2%CHL and 4%CHL groups compared with the NS group (P < 0.0001) and no difference between the 2%CHL and 4%CHL groups. CONCLUSIONS: This study provides new data supporting the use of CHL to decontaminate grossly soiled bone segments. To maximize efficiency and decrease potential untoward effects, the authors recommend 20-minute soaks using 2% CHL for contaminated bone segments.