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BMJ No 7107 Volume 315 Editorial Saturday 30 August 1997
The trouble with bone allograftWe need a safe, abundant alternativeAllogeneic bone is the most commonly grafted tissue.(1) Its applications are expanding in all aspects of orthopaedic surgery, notably in the restoration of bone stock in patients undergoing revision hip replacement or surgical treatment for bone tumours. This expansion has occurred despite concerns about the supply and safety of allogeneic bone grafts and the complications of the procedure.(1-6) In the absence of an alternative, however, demand has begun to outstrip supply. Bone tissue for allograft is obtained mainly through the donation of femoral heads from primary hip replacement. Guidelines have been developed which stipulate strict criteria for donation.(3)(7) As a result, up to 50% of potential donors are excluded. The remainder are tested for antibodies to HIV-1, HIV-2, and hepatitis B and C viruses. Tests for HIV and hepatitis C virus should be repeated 180 days after the harvest, and grafts are discarded if they test positive or if test procedures are not satisfactory. In addition, about 18% of harvested femoral heads are contaminated with bacteria or fungi.(4) For revision hip surgery, each acetabular reconstruction requires two to four femoral heads, and most bone banks in England are reporting difficulties meeting demand. In Scotland the supply of femoral heads has been virtually exhausted (Lumley SP, Galea G, British Association of Tissue Banks meeting, Lancaster 1996). Some centres are therefore using cadaveric donation, formerly a source of large grafts reserved for specialist centres. This source is unpredictable and places extra demands on staff and the next of kin. Adequate standards of asepsis are often not achievable at the time of harvesting, and bacterial contamination rates are higher than for live donation.(4) Similarly, cadaveric donors cannot provide repeat tests for viral antibodies, yet about 1 in 1000 British heterosexual men outside London carries HIV.(8) Unlike blood donors, cadaveric donors are not self selected. Screening histories have to be obtained from relatives. They may be incomplete, and the risk of viral infection remains unknown.(5) The main complications after bone allograft are infection, fracture, and non-union. In a recent review of 718 large allografts the complication rate was 46%.(2) Rates increase with the size of the graft and the complexity of the procedure. They also reflect the success of graft incorporation. This depends on the intrinsic bone forming properties of the graft, the bone forming potential of the host, the graft's mechanical stability, and the surface area of the host-graft contact. Despite an understanding of the function of many isolated proteins in the bone matrix, the bone forming properties of bone allograft are poorly understood. In most femoral heads such properties are probably minimal, and mechanical failure is an increasing problem.(9) Large grafts in general incorporate poorly, and fracture, non-union, and infection can be expected in 19%, 17%, and 11% of procedures respectively.(3) Morsellised allograft offers better results,(10) but applications are limited to those in which it can be adequately impacted to form a stable construction. Graft incorporation may in part depend on the patient's immune response, and antigenic disparity between donor and recipient has been cited as a disadvantage.(6) The immune response is directed mainly against cellular debris in the graft, but the bone matrix itself is also antigenic. It stimulates resorption of the graft, which can lead to rapid dissolution of the graft.(11) However, the relation between the patient's immune response and graft incorporation is not clear, and outcome remains largely unpredictable. Bone allograft, particularly in its morsellised form, has proved valuable to countless patients for restoration of bone stock. However, it is not without its problems, and the shortage created by its widespread use is testimony not so much to its success as to the lack of a safe, abundant alternative. Fabian H Norman-Taylor Specialist registrar
Department of Trauma and Orthopaedics, Nicola Santori
Clinical research fellow
Cambridge Hip and Knee Unit, References 1 Warwick R M, Eastland T, Fehily D. Role of blood transfusion service in tissue banking. Vox Sanguinis 1996;71:71-7. 2 Mankin H J, Gebhardt M C, Jennings L C, Springfield D S, Tomford W W. Long-term results of allograft replacement in the management of bone tumours. Clin Orthop 1996;324:86-97. 3 British Orthopaedic Association. The collection and storage of bone allografts. London: British Orthopaedic Association, 1992. 4 Chapman P G, Villar R N. The bacteriology of bone allografts. J Bone Joint Surg (Br) 1992;74:398-9. 5 Tomford W W. Transmission of disease through transplantation of musculoskeletal allografts. J Bone Joint Surg (Am) 1995;77:1742-54. 6 Stevenson S, Shaffer J W, Goldberg V M. The humoral response to vascular and nonvascular allografts of bone. Clin Orthop 1996;323:86-95. 7 Kearney J N. Technical manual for musculoskeletal tissues. Wakefield: British Association of Tissue Banks, 1996. 8 Unlinked Anonymous HIV Serosurveys Steering Group. Unlinked anonymous HIV seroprevalence monitoring programme in England and Wales. London: Department of Health, 1995. 9 Harris W H. Management of the deficient acetabulum using cementless fixation without bone grafting. Orthop Clin North America 1993;24:663-5. 10 Sloof T J, Buma P, Schreurs B W, Schimmel J W, Huiskes R, Gardeniers J. Acetabular and femoral reconstruction with impacted graft and cement. Clin Orthop 1996;323:108-15. 11 Berry B H, Lord C F, Gebhardt M C, Mankin H J. Fractures of allografts. J Bone Joint Surg (Am) 1990;72:825-33.
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