Investigation of postoperative allograft-associated infections in patients who underwent musculoskeletal allograft implantation

Background. The rate at which allografts are used in surgical procedures has doubled in the United States during the past decade. In 2002, one outpatient surgical center (SC-X) identified a cluster of surgical site infections (SSIs) after anterior cruciate ligament reconstructive surgery (ACLRS). Therefore, we conducted an investigation to determine the extent of the outbreak and to identify risk factors. Methods. Our investigation included retrospective cohort and observational studies. A case patient was defined as any patient who acquired a SSI after undergoing ACLRS at SC-X between February 2000 and June 2002 ( the study period). Data collected included demographic characteristics, clinical information, and graft details, such as processing method (i.e., aseptic or sterile). Results. Of 331 patients who underwent ACLRS during the study period, 11 (3.3%) met the case definition. All infections occurred at the tibial fixation site of the graft and involved 8 different microorganisms; the median time to a positive culture result was 55 days after ACLRS. The infection rate for patients who received aseptically processed allografts was 4.4% ( 11 of 250 patients), compared with 0% ( 0 of 81) for patients who received autografts or sterile allografts (P = .07). Use of a supplementary staple for tibial fixation, compared with other fixation methods that did not involve such staples, increased the risk of infection 10-fold in univariate analysis (relative risk [RR], 10.0; 95% confidence interval [CI], 3.0 - 32.9) and 9-fold when controlling for tissue processing method (RR, 9.0; 95% CI, 2.8 - 28.8). Conclusions. The use of sterile allograft tissue appears to be associated with a significant reduction in the risk of postoperative infection, particularly in the presence of adjunctive fixation. Larger clinical studies are necessary to confirm this observation.