Infections regularly complicate orthopaedic procedures loosing implant stability and impairing bone union. Nevertheless, the question whether infection is caused by pathogens transposed intraoperatively, infiltrating the implant with blood stream or lymph, or dwelling in clinically healthy tissues, remains unanswered. The AIM of our study was to validate the hypothesis that pathogens may residue deep tissue.

Material and Methods: Skin, subcutaneous fat, muscle and fracture gap callus were obtained from 155 adult patients operated on due to closed comminuted fractures of tibia or femur, 75 because of non-alignment of bone axis and 80 due to delayed fracture healing.

Results: Aerobic bacteria were isolated from gap callus of 12% healing and 31% non-healing fractures, but also from deep soft tissues. No anaerobic bacteria were detected. PCR amplifications of 16s rRNA were found positive in 40% of callus specimens proving presence of bacterial DNA even when no isolates were found. The 95% similarity of the genetic pattern of some strains from foot skin and callus, estimated with RAPD technique, suggested their foot skin origin.

Conclusions: The colonizing bacteria and their DNA were detected in fracture callus and deep soft tissues. Contamination was precluded by lack of isolates in disinfected skin and materials used for sampling cultured after surgery. Our results point out that bacterial cells residing clinically non-infected deep tissues may be a source of infection, when activated by mechanical trauma and/or orthopaedic implant insertion.