Contamination of banked femoral head allograft: Incidence, bacteriology and donor follow up

Background: Allograft donations are not uncommonly found to be contaminated . The issue of contaminated donations from live donors at the time of surge ry, and the significance of this to the patient in terms of subsequent seps is of the arthroplasty, were examined. Methods: The donations of femoral heads to the Queensland Bone Bank over a 9-year period were reviewed, and the incidence and bacteriology of contamin ation were detailed. Clinical outcomes were determined for donors who herd positive cultures at the time of retrieval and they were compared with thos e of culture-negative donors. Results: Between March 1987 and February 1996, 232 femoral heads were donat ed to the Queensland Bone Bank. Four specimens a err sent for culture with each femoral head (surface swab of femoral head, acetabular swab, bone biop sy and capsule). In 51 cases, one or more positive cultures were obtained ( 22% contamination rate). The majority of organisms cultured were Staphyloco ccus epidermidis. One hundred and seventy donations came from surgery perfo rmed at the Princess Alexandra Hospital, and 40 femoral heads were consider ed contaminated. Deep infection was recorded in one of the 40 cases with co ntaminated donations and three out of 130 non-contaminated donations had su bsequent septic episodes. Conclusion: The contamination rate detailed in the present report is higher than in most series. This may be due to the fact that four bacteriological specimens are taken to assess contamination. Two of these specimens are ti ssue samples which yielded more positive results than did the two swabs. Al l other series take no more than two bacteriological specimens, which are u sually bone swabs. These are shown to have a poor yield of positive culture s. Therefore there is a significant underestimation of contamination rates by other bone banks. This has implications for the recipients of bone from those banks, particularly when the allograft material is not secondarily st erilized. This is important given increasing allograft usage, and the incre asing numbers of revision joint arthroplasty and impaction grafting procedu res bring performed. Sterilization of all bone by irradiation to 25 kGy is recommended.