Are Cadaver Bone Grafts Safe?

June 5, 2007
by: Peter

Not too long ago there were numerous articles concerning the illegal harvesting of non-donated cadaveric bone graft. Normally, patients need to be screened before being harvested and conditions such as infection or bone tumors need to excluded from the donor pool. There is a relative shortage of donor bodies, and this has led to a black market of bone harvesters. Basically, once a family gives a loved one over to a cremation or burial service, they do not know if anyone is harvesting and selling tissue from the deceased. X-rays have even shown bodies that have had their long bones harvested and then replaced with PVC piping prior to burial.

The biggest scandal to date involved Biomedical Testing Services (BTS) which had harvested hundreds, perhaps thousands, of cadaver bones that had not met FDA tissue donor eligibility requirements. Although the FDA felt the risk of transmission was low, they encouraged companies that had purchased bone tissue from BTS to offer patients implanted with the tissue free communicable disease testing. Specifically, patients were offered tests for hepatitis, syphilis and HIV (the virus that causes AIDS). The tissue from BTS had been processed in the normal manner, but the FDA still felt there might be some (although little) risk of subsequent disease transmission.

Stealing tissue is a gruesome business, but for the patients that had been implanted with stolen bone, this was an especially unwelcome turn of events, to say the least. To my knowledge there have not been any proven infections because of the stolen bone, and the overall risk to receiving an infection from cadaver bones has always been and remains very low. There are, however, good synthetic alternatives for bone graft, and recent advancements in spinal fusion technology have largely obviated the need for using cadaveric bone for spinal fusion.

Bone graft often provides two components to a fusion, the first being structural support, and the second is as a scaffolding and signal for the body to start the fusion process. Structural support can be provided by other materials such as PEEK (a type of plastic), carbon fiber, or titanium. All of these compounds are inert and the body really does not care if they are implanted. They are not a biological graft such as allograft (cadaver bone) but in some ways this is good. The first reaction to a structural allograft implanted in the intervertebral disc space is that the host bone goes through osteolysis, or resorption of bone around the graft. So the fusion construct initially gets weaker before it gets stronger. Inert materials do not cause this reaction. The other problem with a biological allograft used for structural support is that the host body has to very slowly cut new bone channels into the graft (Haversian canals) and then lay down new bone (enchondral ossification). This is an extremely slow process, and it takes many years for most implanted allograft structures to be fully incorporated by the host bone.

Stealing tissue is a gruesome business, but for the patients that had been implanted with stolen bone, this was an especially unwelcome turn of events, to say the least.

As far as the scaffolding and signal to fuse process goes, allograft bone is very poor at actually creating bone. It lacks the cells and proteins to initiate the fusion process. The gold standard for spinal fusion material is still cancellous bone harvested from the patient’s own iliac crest, but harvesting a patient’s own bone can be painful and has a fairly high incidence of postoperative complications. Fortunately, there are now numerous synthetic bone graft substitutes and extenders that can be used instead of a patient’s own bone. The most popular one at this point is bone morphogenic protein, or BMP, (Infuse-Medtronic) which is a protein produced by recombinant DNA technology that carries a strong signal for the body to grow bone. Since its release in 2003, it has been used to successfully grow bone in fusion surgery in thousands of patients.I have had extensive experience using bone marrow aspirated with a needle from the patient’s iliac crest and combining it with a very porous B-tricalcium phosphate (Vitoss- Orthovita) . This combination has been very reliable in growing bone in the intervertebral disc space, and has the advantage of not only being much less expensive than BMP, but also does not carry the theoretical risk of inserting a recombinant protein into a patient. BMP has been inserted into thousands of patients and the risk of inserting pharmacological doses of one protein does not seem to be great. However, just as with allograft bone, we do not know the true safety of these compounds and may not for years.

Bottom line, although allograft has traditionally been felt to be safe for human use, where there is a viable synthetic alternative, grafting of material from one human to another should be avoided. In some situations of spine surgery, such as long anterior strut grafts, allograft bone still may be preferable, but for short anterior interbody constructs, there are numerous synthetic alternatives.

By: Dr. Ullrich

More reading:

• Spinal Fusion
• Bone Graft for Spine Fusion