Spine surgery is perhaps the specialty that is most concerned with bone grafting. Many of the procedures performed by spine surgeons include the fusion of motion segments in the spine. The medical field is constantly involved with research to enhance the chances of bony fusion after the surgical procedures which initiate this process. Much advancement has been made in the filed of bone grafting, however, still the most reliable source of bone graft comes from the patients themselves (also called auto grafts). We are constantly in search of alternatives to auto grafts (placement of bone from one part of body to another) to prevent pain, and complication while achieving reliable fusions in the desired areas.
Fusion procedures can be performed for numerous diagnosis and reasons. Common diagnoses which require fusion are degenerated discs, herniated disc of the neck, deformity of the spine, and motion of the spine. In all of these procedures the intervertebral disc is removed, and structural fillers are placed in that space. In addition to that spacer, or filler, crushed bone is placed to stimulate and enhance the healing of bone and fusions.
We will begin with some common terminology and concepts prior to the discussion of risks and benefits of each option. The most reliable source of bone grafting which provides best chance of fusion is called Auto graft. Auto-graft simply means that the needed bone was harvested from the same patient, and taken from an area with abundant amounts of bone that can be removed without causing dysfunction. Common sources from which we take this graft is the pelvis and the small bone of the leg called the fibula. This bone has the advantage of including living cells which promote bone healing and also has structural integrity which can hold the position of the spine until bony fusion has occurred. Another advantage to Auto grafting is the avoidance of any risk associated with transmitted disease or any other foreign material. Even though the biological properties of Auto grafting are very beneficial, this technique requires another incision on the patient’s body, resulting in more pain and surgical risk.
The term Allo-graft means that the bone for implant was received from another donor which is supplied by a bone bank similar to a blood bank. The bone is obtained from other persons and undergoes many tests to ensure safety and lack of disease. Indeed, the risk of disease transmission is extremely low. Even though physicians usually trust these bones to be disease free the possibility of this issue still exists. Almost any bony configuration can be obtained from a bone bank with almost an unlimited supply. This is important in cases of large deformity correction when large amounts of bone are needed. Other disadvantages are the lack of living cells within these bone grafts. The fusion rates are slightly lower, especially when used to fuse large spinal segments.
Recently, newer materials have been introduced to replace allo-graft as well as auto graft. Examples of these materials include Interpore, and Grafton. These are actually produced from Coral and Calcium. Structurally they only fill cavities but do provide any structural support. In contrast, Allograft and Auto-graft do provide structural support until the body heals and creates a solid bony fusion. When bone is taken from the pelvis as an auto-graft we can place Interpore in the donor area to stimulate bone filling and possibly eliminate the small defect that is created in that area. Even though these materials are used in other orthopedic procedure, in spinal fusion operations we do not use these materials. The reason they are not used often is their lack of ability to introduce cells that promote healing and lack of specific proteins needed for fusion. Specifically, these proteins are called BMP and DBM.
As a supplement to bone graft (Allograft or Auto graft) products exist that have a high concentration of these proteins. DBM (Demineralized Bone Matrix) can be obtained from the American Red Cross and is called Grafton. Grafton is supplied in gel or putty form and can be placed in areas that bony fusions are desirable. Research studies have shown enhanced bony growth in areas that DBM was placed. Many times we mix bone from the bone bank with Grafton to increase the potential of healing in the hope of increasing the potential of bony fusion. Other similar product is DBX supplied by the company named Synthes.
We can use an example of a neck fusion for a herniated disc in that area. Commonly, symptoms consist of arm pain, numbness, or weakness. The neck is approached from the front, the disc is removed and some form of bone graft is placed in that area. Several options exist in choosing bone graft material. One choice is to harvest bone from the pelvis. As mentioned before, this option has the highest chance of healing since it provides an optimal environment for bony fusion. However, associated with harvesting of bone from the pelvis is the extra incision in that area, the risk of infection that is associated with any incision, and the postoperative pain. In contrast the surgeon may choose to get bone from the bone bank. This avoids the need to make an extra incision in the pelvis as well as reduced post operative pain. However, there the potential of healing and bony fusion is slightly decreased. In addition, there is a very slight risk of disease transmission as well as an infection.
In cases that we perform lower back fusion we commonly use bone harvested from the pelvis. The same incision can be used to harvest the bone graft from the back of the pelvis. We utilize newer techniques to harvest bone graft from that area through smaller incisions while maximizing the amount of bone harvested. Accumed, an orthopaedic company, developed instruments to help harvesting of bone graft with small incisions that reduce post-operative pain from the donor site.
When choosing the appropriate procedure for you, discuss these issues with your surgeon to ensure healing and fast recovery with the least chance for possible complications. If you have any concerns and would like more information, contact our office.