Contamination of primary total hip replacements in standard and ultra-clean operating theaters detected by the polymerase chain reaction.

Background: Many organisms that are responsible for low-grade infection after total hip replacement (THR) are not recognized by routine culture.

Patients and methods: We examined wound contamination during primary total hip replacement performed in standard and ultra-clean operating theaters. 20 THRs were performed in each type of theater. Paired tissue specimens taken at the beginning and end of surgery were analyzed by bacterial culture and for the presence of bacterial DNA by the polymerase chain reaction (PCR). In total, 160 specimens (80 for culture, 80 for PCR) from 40 THRs were tested.

Results: In standard theaters, none of the 20 specimens taken at the start of surgery were positive by culture, but 3 were positive by PCR (15%). Of the 20 specimens taken at the end of surgery, 2 were positive by enriched culture and 9 were positive by PCR. All specimens positive by culture were also positive by PCR. In ultra-clean theaters, none of the 20 specimens taken at the start of surgery were positive by culture, but 2 were positive by PCR. Of the 20 specimens taken at the end of surgery, none were positive by culture, but 6 were positive by PCR. All specimens that were positive by culture were positive by PCR.

Interpretation: Wound contamination of primary THR occurs frequently in both standard and ultra-clean operating theaters and contamination is greater at the end of surgery than at the beginning (p=0.04). In this small series, we found no differences in wound contamination between standard and ultra-clean theaters (p=0.1).