Allograft is bone harvested by a tissue bank from a cadaver for use in medical procedures. It can be prepared in a number of different forms (such as chips) for use in a spine fusion.
While allograft bone only provides a calcium scaffolding, does not have any bone-growing cells or bone-growing proteins required to stimulate new bone growth, and thus has a lower chance of fusion as compared to using the patient's bone, it has proven comparable in certain studies to autograft in terms of producing successful fusions.1-3
Uses of Allograft Bone
Allograft bone may be used either on its own or as a supplement to the patient’s own bone.
- Allograft used on its own. In the lumbar spine, allograft bone is restricted for use in ALIF or PLIF procedures in which bone graft is placed in compression between the vertebrae, as the compression fosters a better healing process for the bone. In a posterolateral gutter spine fusion, in which the bone is placed in tension, allograft bone by itself is not likely to result in a solid fusion.
- Allograft as a supplement to the patient’s own bone. Allograft chips may be used to augment the patient’s own bone in a posterolateral gutter fusion. It also may be used if more bone graft is needed in more extensive fusion procedures, such as spinal fusion for adolescent scoliosis.
Allograft Considerations
The main benefit of allograft bone is that there are no surgical risks for the patient associated with harvesting their own bone. However, there are two main drawbacks.
- Lower chance of fusion. Because allograft bone does not contain living bone cells, it is not as effective at stimulating fusion as the patient’s own bone.
- Risk of disease transmission. Despite rules and regulations for tissue banks regarding processing and procedures of human tissue, there is still a small potential risk of disease transmission from using cadaver bone.
The allograft bone used in spine fusion procedures is provided by tissue banks (bone banks). The U.S. Food and Drug Administration (FDA) regulates U.S. tissue banks in an effort to minimize risk of tissue contamination and disease transmission.
One common form of allograft that is used is demineralized bone matrix (DBM). This is the commercialized form of bone morphogenic protein that comes from processing cadaver bone from multiple donors. The amount of actual BMP that is available in each sample varies from manufacturer to manufacturer, but far less is available using synthetic recombinant BMP (Infuse). A more recent form of cadaver-donated tissue is stem cell technology that uses stem cells from one donor to help create bone.
References
- 1.Gibson S, McLeod I, Wardlaw D, et al. Allograft versus autograft in instrumented posterolateral lumbar spinal fusion: a randomized control trial. Spine (Phila Pa 1976). 2002 Aug 1;27(15):1599-603.
- 2.Samartzis D, Shen FH, Goldberg EJ, et al. Is autograft the gold standard in achieving radiographic fusion in one-level anterior cervical discectomy and fusion with rigid anterior plate fixation? Spine (Phila Pa 1976). 2005 Aug 1;30(15):1756-61.
- 3.Samartzis D, Shen FH, Matthews DK, et al. Comparison of allograft to autograft in multilevel anterior cervical discectomy and fusion with rigid plate fixation. Spine J. 2003 Nov-Dec;3(6):451-9.
