Cancellous bone, demineralised bone matrix, corticocancellous chips, bone putty, etc. So much to choose from. Which, when and why?

An unfavourable wound environment caused by adverse tissue conditions (large gaps within bone), suboptimal surgical technique, or large body mass relative to fixation strength can all lead to delayed healing or nonunion. Under these circumstances, some means of augmenting or accelerating bone regeneration may be necessary. A number of techniques have been used in attempts to achieve this goal, including use of autograft and/or allograft, various organic and inorganic osteoconductive and osteopromotive implants, biomechanical or electromagnetic stimuli, and numerous cellular and humoral factors. The gold standard for augmenting bone healing, however, continues to be the autogenous cancellous bone graft.

There are, nevertheless, a number of drawbacks to bone grafts. For autogenous autografts, these include additional anaesthetic time for graft harvesting and the potential for an insufficient quantity of graft, limited access to donor sites, loss of osteogenic cells, donor site pain or haemorrhage, and failure of the donor bone. Allografts can result in immune-mediated rejection and graft sequestration and disease transmission between donor and host. Bone banks circumvent many of these issues, but they are costly to maintain; in veterinary medicine, there are currently only two bone banks world-wide: Veterinary Transplant Services [VTS; Kent, WA; USA (https://vtsonline.com/)] and Veterinary Tissue Bank [VTB; Chirk, Wrexham, UK (http://vtbank.org/)], both of which have voluntary donor programs to procure tissues. VTS can ship to Europe; however, in the UK there is an import restriction on their products. VTB also is available in Europe and also the UK. In addition, there are other alternative bone augmentation technologies, such as cell and gene therapy, and bone growth and differentiation factors. Cell and gene therapies are not yet refined to the point of clinical orthopedic application; recombinant BMPs also have been used clinically as alternatives or adjuncts to bone graft for treating a few well-defined clinical conditions in humans, and more recently in animals. However, the only approved drug for companion animals, which was approved only to augment bone healing in fracture repair (TruScient®; Pfizer Animal Health; EU only) was withdrawn in 2014/2015. [...]