There are a variety of bone graft substitutes that are available for use in spine fusion surgery or are being evaluated in various stages of clinical trials. In general, these types of bone graft are a synthetic or a manipulated type of a naturally-occurring product.
There is a lot of interest in developing and refining bone graft substitute options for use in lumbar spinal fusion surgery procedures in order to eliminate the need to harvest the patient’s own bone, thus potentially reducing the risk and pain associated with the procedure and resulting in higher fusion rates.
There are several main types of bone graft substitutes used in spinal fusion surgery, which can be generally categorized into three main areas:
- Demineralized Bone Matrix (DBM)
- Synthetic bone graft extenders
- Bone Morphogenetic Proteins (BMP).
Demineralized Bone Matrix (DBM)
Processing of allograft bone (cadaver bone graft) can be manipulated (demineralized) to extract the proteins that stimulate bone formation. These proteins are processed and available in various forms, such as chips, gel, putty or powder. This type of product is called demineralized bone matrix, and it can be readily used in place of or as an extender to the patient's own bone.
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Although it has successfully fused spines in animal studies, there is no proof that this is a powerful enough stimulus to successfully fuse a human spine; therefore, it is not recommended for use without the addition of the patient's own bone. It is only recommended as a bone graft extender and not as a replacement.
DBM is usually considered a bone graft extender rather than a replacement because its ability to fuse the human spine alone is not proven. As such, DBM can be mixed with regular bone to obtain more graft volume when it is needed for fusion.
Synthetic Bone Graft Extenders
There are several substances such as ceramics, calcium phosphates and other synthetic materials that have similar biomechanical properties and structure similar to that of cadaver bone and may be used as a bone graft substitute. They allow for bone growth on their surface and then they are resorbed by the body, with the patient’s own bone remaining in place.
However, these products do not have all the properties necessary to stimulate a spinal fusion when used alone. They are usually used in combination with the patient’s own bone to augment the amount of bone graft available.
When the patient’s bone marrow cells (bone marrow aspirate) are added to ceramics, clinical studies have demonstrated that these products are effective.
Unlike allograft (cadaver bone), ceramic-based products do not present a risk for disease transfer. However, they may occasionally cause inflammation.
Bone Morphogenetic Proteins (BMP) are another type of bone graft option, as detailed on the following page.