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(7) for NS, 2.31 × 10(7) for 2%CHL, and 2.00 × 10(7) 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.