Lavage of contaminated surfaces: an in vitro evaluation of the effectiveness of different systems

Lavage is an effective, additive therapeutic procedure with a broad application in surgery. In addition to irrigation with the conventional syringe, the pulsed jet lavage system is used. The effectiveness of bacterial reduction depends on, among other things, the irrigation pressure. Complications of high-irrigation pressure in bone and joint surgery are intramedullary seeding of bacteria, visible damage of the bone, or delayed healing of the fracture by lavage of the fracture zone. The purpose of this in vitro study was to evaluate the effectiveness of mechanical irrigation on several surfaces using different systems of irrigation.

Four different test surfaces (nonbiological surfaces: sterilized bone cement and titanium osteosynthesis plates; biological surfaces: gamma-irradiated bovine muscle and cancellous bone) were contaminated with a defined suspension of different bacterial species (Staphylococcus aureus, Enterococcus faecalis, Pseudomonas aeruginosa). The samples were irrigated with three different systems (conventional 50-ml plastic syringe, manual pump irrigator, jet lavage) in a standardized, randomized experimental setup. After irrigation of the sample the amount of residual bacteria (colony-forming units) was determined.

An effective bacterial reduction was achieved with the use of irrigation regardless of the system that was used and surface that was cleaned. On average P. aeruginosa was reduced around log 1.907, E. faecalis around log 1.666 and S. aureus around log 1.506. On biological surfaces, a reduction around log 0.801 for muscle and around log 1.738 for bone samples was achieved independent of the system that was used for irrigation. For the titanium surface a reduction of log 1.652 compared with log 2.580 for the bone cement surface was demonstrated. Statistical analysis showed that mechanical lavage resulted in a significant reduction of all tested bacterial species on the surfaces. The best bacterial reduction was achieved with the manual pump irrigator (P = 0.06). The results demonstrate that the manual pump irrigator achieved significantly better bacterial reduction (P = 0.039) on "biological surfaces" (bone and muscle) compared with nonbiological surfaces (titanium and cement).

The results show that irrigation is an effective technique for bacterial reduction on contaminated surfaces. A remarkable finding was the limited bacterial reduction of Staphylococcus aureus from gamma-sterilized muscle. The use of a continuous manual pump irrigator showed a greater reduction of bacteria contamination compared with the other means of irrigation investigated. In conclusion, the manual continuous irrigation system proved to be practical, economical and effective in reducing the bacterial load on various surfaces.