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Hip: B. G. Ochs, U. Schmid, J. Rieth, A. Ateschrang, K. Weise, and U. Ochs Acetabular bone reconstruction in revision arthroplasty: A COMPARISON OF FREEZE-DRIED, IRRADIATED AND CHEMICALLY-TREATED ALLOGRAFT VITALISED WITH AUTOLOGOUS MARROW VERSUS FROZEN NON-IRRADIATED ALLOGRAFT J Bone Joint Surg Br 2008; 90-B: 1164-1171 [Abstract] [Full text] [PDF]

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Bone marrow does not improve osteoinductivity of allografts

Heinz Winkler   (17 October 2008)

Bone marrow does not improve osteoinductivity of allografts 17 October 2008
Heinz Winkler, Consultant Orthopaedic Surgeon Osteitis Center, Privatklinik Doebling, Vienna, Austria Send letter to journal: Re: Bone marrow does not improve osteoinductivity of allografts h-winkler{at}aon.at Heinz Winkler	Sir, We read with interest this paper which concludes that processed and irradiated allografts provide the same clinical results as fresh frozen ones while increasing the safety of the grafts. This is a finding that is well known from literature and is in compliance with our own experience. The authors fear that processing and irradiating the grafts may have compromised their biological and mechanical properties, and claim that “combining autologous marrow, a rich source of autologous osteoinductive cells and growth factors, with sterile allografts” may be the explanation for comparably good clinical performance. However, the comparable efficacy cannot be attributed to the addition of autologous bone marrow. There is no “osteoinductive cell” and there is no growth factor in bone marrow that is able to induce bone formation. Osteoinduction is triggered by proteins that are deposited and stored in the matrix of bone, not in the marrow.1 When set free due to fracture, osteoclastic resorption or demineralisation, these are able to trigger the transformation of mesenchymal stem cells into osteoblasts that consequently build up new bone. These progenitor cells are physiologically recruited by released growth factors through the bloodstream. Iliac crest bone marrow contains only 181 (70 to 401) osteoprogenitor cells among 17 million nucleated cells per cc.2 It cannot be expected that injecting a fractional amount of them into dead bone provides a relevant advantage in comparison with physiological recruitment from the entire body, especially considering that their survival is very unlikely outside a vascularised environment or sophisticated culture media. Simply injecting marrow into an allograft cannot be considered to be creating a “living composite”, as the authors claim, since injected bone marrow cells devoid of blood supply or culture media are doomed to rapid cell death. On the other hand the fear of compromise through processing seems to be overestimated. One reference cited by the authors clearly shows that lipid extracted bone grafts have even better osteoconductive properties than fresh frozen ones and possess comparable mechanical properties, even when irradiated with 25kgy.3 One reason for improved performance is the removal of cell surface antigens eliciting an immune response. Reports of gamma sterilisation compromising mechanical as well as osteoinductive properties of allograft bone have covered exclusively the behaviour of fresh frozen bone, including all allogenic marrow. The authors cite such a reference, where fresh frozen cortical bone has been irradiated.4 However, (as the authors of the reference admit) the differences between irradiated and non irradiated bone are negligible, as long as the bone is dry and free from cells and fatty bone marrow inducing free radicals during irradiation. The processed grafts used in the study group B are supposed to be dry and free of immunogenic cells and lipids and therefore may be estimated to show the described advantages. These should be sufficient to compensate for eventual compromise of osteogenic features occurring during processing. It therefore may be estimated that the processed bone used in the study shows comparable, if not better, biological properties than the unprocessed one, not surprisingly leading to comparable clinical results independent from the addition of autologous bone marrow. An additional invasive procedure for harvesting autologous marrow is therefore unnecessary. H.Winkler, Consultant Orthopaedic Surgeon, Osteitis Center, Privatklinik Doebling, Vienna, Austria. 1. Mizutani H, Urist MR. The nature of bone morphogenetic protein (BMP) fractions derived from bovine bone matrix gelatin. Clin Orthop 1982;171:213-23. 2. McLain RF, Fleming JE, Boehm CA, Muschler GF. Aspiration of osteoprogenitor cells for augmenting spinal fusion: comparison of progenitor cell concentrations from the vertebral body and iliac crest. J Bone Joint Surg [Am] 2005;87-A:2655-61. 3. Thorén K, Aspenberg P, Thorngren KG. Lipid extracted bank bone: bone conductive and mechanical properties. Clin Orthop 1995;311:232-46. 4. Hamer AJ, Stockley I, Elson RA. Changes in allograft bone irradiated at different temperatures. J Bone Joint Surg [Br] 1999;81-B:342-4.