Intra-Operative Culturing of Donor Allograft Bone: A Lack of Clinical Utility

A common procedure for donor allograft bone includes intraoperative sampling of the allograft for bacterial culture. The goal of this study was assess the clinical effectiveness of intra-operative cultures in identifying microorganisms in donor bone allografts. Retrospective data were collected from 205 patients (230 allografts) to assess the clinical effectiveness of intra-operative cultures in identifying microorganisms in donor bone allografts. Eight of 230 allografts were positive for growth of microorganisms. Seven patients with a positive allograft culture exhibited no signs of surgical site infection during their hospitalization or clinical follow-up. One patient (positive for Staphylococcus similans) developed a clinical postoperative infection which cultured Enterococci. No association between positive intra-operative allograft cultures and the development of postoperative clinical infection was identified. These results fail to support routine intra-operative culturing of commercially supplied sterile allograft bone. Introduction Allograft bone is used frequently to augment bone loss by providing a structural framework for host bone osteoconduction in orthopaedic procedures. There is a risk for disease transmission if the donor bone is contaminated; however, allograft bone used for many orthopedic procedures today undergoes a rigorous evaluation for the presence of microorganisms by the commercial supplier prior to acquisition and use by the hospital. Previously reported contamination rates during the time between harvest and commercial sale can be as high as 2224%, with Staphylococcus epidermidis being the most common organism. However, multiple screening cultures (during processing and packaging) and the use of radiation and peroxide treatment prior to sale and distribution to hospitals are used today to effectively sterilize bone bank allografts. The benefit of utilizing sterile versus aseptic allografts has been observed by a reduction in postoperative infections when using sterile allografts for patients undergoing anterior cruciate ligament reconstructive surgery. However, even with rigorous commercial testing, allograft tissue may still undergo additional intra-operative sampling and culturing by hospital laboratories, the results of which would be unavailable for several days following surgery. This practice was most likely established as an internal check on the sterility of allograft processed within each institution and additional cultures have continued only as a double check to verify sterility. The present study was designed to examine the clinical effectiveness of intra-operative cultures in identifying microorganisms in commercially supplied, sterile allograft bone. Materials and Methods This study was conducted at an affiliated 450-bed community teaching hospital. Patients who underwent an orthopaedic surgical procedure requiring allograft bone use during surgery were Address for Correspondence: D. Gordon Allan, M.D., FRCS(C) Southern Illinois University School of Medicine Division of Orthopaedics and Rehabilitation P.O. Box 19679 Springfield, IL 62794-9679, USA Tel: (217) 545-8865 Fax: (217) 545-7901 e-mail: [email protected] Brett Barnhart is a Resident physicianDivision of Orthopaedics and Rehabilitation, Southern Illinois School of Medicine, Springfield, IL D. Gordon Allan, is an Attending surgeonDivision of Orthopaedics and Rehabilitation, Southern Illinois School of Medicine, Springfield, IL Joseph C. Milbrandt, is Faculty in the Division of Orthopaedics and Rehabilitation, Southern Illinois School of Medicine, Springfield, IL Nancy Khardori, is an Attending surgeonDepartment of Internal Medicine, Southern Illinois School of Medicine, Springfield, IL Adam Hall, is a Medical StudentSouthern Illinois School of Medicine, Springfield Joan Barenfanger, is an Attending surgeonDepartment of Pathology, Memorial Medical Center, Springfield, IL Intra-operative Culturing of Donor Allograft Bone Barnhart et al. University of Pennsylvania Orthopaedic Journal Volume 19 identified from a microbiology database. As per hospital standard, when a commercially acquired allograft was used or placed on the operative field during surgery, a sample was taken and placed in a sterile container. This sample was subsequently sent for (in-house) culture and sensitivity testing. The allograft was used during the operative procedure which always occurred prior to any knowledge of the culture results. In the microbiology laboratory, the allograft specimen was placed in thioglycollate broth only; no initial Gram stain was performed. The broth was examined visually each day for 7 days. If turbidity was not detected, the culture was reported as negative. If turbidity were detected, a Gram stain was performed and subcultures were initiated to identify the specific microorganism(s). Retrospective data were collected from hospital records and included demographic data, type of procedure, surgeon, allograft type, pre-operative wound status, any culture results, and the presence of clinical infection during hospitalization and treatment. The positive culture results were recorded in reference to organism and time of growth postoperatively. Any patient identified as having a positive culture had their outpatient clinical charts reviewed for the presence of post-operative infection and had their identifying hospital number searched for readmissions to this institution within 225 days after surgery. Medical records identified for those readmissions within 225 days were reviewed to assess whether any readmission was due to a postoperative or surgical-site infection. Data were tabulated and basic descriptive statistics performed using Microsoft Excel 2003 (Microsoft Corporation, Redmond, WA).