gms | German Medical Science

Objectives: To quantitatively evaluate the level and rate of bacterial contamination of ACL autograft during harvesting and to compare it to the rate of contamination from accidently dropping the graft onto an operating room floor.

Methods: Fresh ACL specimens were sterilely recovered from 27 primary total knee arthroplasties (TKAs). Total of 162 specimens from 27 TKAs. Eighty one specimens were used as the controls while the others 81 specimens were dropped onto the operative room floor adjacent to the operating table. Each retrieved specimen was immediately transported to the microbiology laboratory for tissue culture. Each tissue sample was incubated in 5% CO2 for 72 hours for aerobic growth and for 7 days for fastidious and anaerobic bacteria growth. The colony-forming units (CFU) per gram were calculated from the total number of CFUs per plate using colonies counter (Schuett Biotec.de Count D-37079, Gottingen, Germany).

Results and Conclusion: Contamination rates (positive cultures) for the control and dropped groups were 17.3% (n=14/81) and 27.2% (n=22/81), respectively. The difference in the contamination rate between the groups was not statistically significant (p = 0.131). The most common organisms identified were Staphylococcus epidermidis (35.7%) and Staphylococcus aureus (21.4%) in the control group and Staphylococcus epidermidis (31.8%), Bacillus species (13.6%) in the dropped group. The contamination level (CFU/g) for both groups was low. The mean rank of the CFU for those dropped and control specimens with positive cultures were 24.25 and 9.46, respectively. ACL autograft specimens with positive cultures in the dropped group were significant higher CFU than that of the control group (p = 0.000).

A relatively high rate of ACL autografts contamination can be expected during harvesting and preparation (17.3%) or after accidentally dropping a specimen (27.2%). Although the types of organisms isolated differed between specimens contaminated during harvesting and preparation and dropped specimens, quantification of autograft contamination level revealed a very low CFU/g in either case.

Clinical relevance:

Intraoperative autograft contamination carries a very low risk of infection because their level of contamination (in CFU) is low. Therefore, saving and reimplantation of grafts with a known contamination incident after proper decontamination is highly recommended over discarding them or using an allograft. Routine decontamination of all autografts before implantation and optimizing the operating room environment will further minimize the risk of surgical site infection.