Bone grafting is typically a part of spinal fusion surgery for symptomatic degenerative disc disease. The fusion is accomplished when the graft material placed between the two bones of a motion segment induces bony incorporation on both sides, and heals them together as one bone. This eliminates motion but also hopefully reduces the pain from that segment of the spine.
There are a number of different types of bone grafts that can be used for spinal fusion:
Synthetic bone graft substitutes (man made)
Allograft (cadaver bone from a bone bank)
Autograft (bone graft taken from the patient’s own body).
Bone graft material can be morselized into small pieces or used as larger pieces for structural purposes to help achieve a spinal fusion.
More Spinal Fusion Info:
Graft site morbidity refers to any consequences that result from the harvesting of the patient’s own bone (an autograft). Undesirable side effects and complications that can result from the bone graft harvesting procedure include early post-operative pain, chronic pain, scarring, bleeding, infection, and more.
In spinal fusion surgery the most common site for obtaining autograft bone is from the portion of the pelvis called the iliac crest – the boney prominence around the belt-line of the hip. The bone graft can be harvested from the front (anterior iliac crest) or from the back (posterior iliac crest) of the pelvis. The ilium is also a source for harvesting bone marrow aspirate, which contains cells that serve to stimulate bone formation.
The incidence of donor site pain, or pain related to bone graft harvesting for spinal fusion, varies greatly and has been reported to persist for over 3 months in 2.8 to 39% of patients. Pain lasting for up to 2 years has been reported in 15 to 39% of patients.
Harvesting bone from the back of the pelvis can often be done through the same incision used for the spinal fusion by dissecting between the tissue planes, or through a separate skin incision.
The sensory nerves that exit in this region (cluneal nerves) may be cut, bruised, or stretched. Injury to these nerves can result in persistent pain. When harvesting bone from the front of the pelvis the nerve at risk is the lateral femoral cutaneous nerve, which supplies sensation to the anterior thigh. Injury to this nerve can also result in significant pain (meralgia paristhetica).
Blood vessel injury can cause significant blood loss and hematoma formation.
Violation of the sacroiliac joint (where the pelvis attaches to the spine) can occur during posterior iliac crest harvest (when bone graft is taken from the back).
Fractures of the front most portion of the ilium (ASIS - anterior superior iliac spine) can result if the graft is taken too close to the anterior iliac spine.
There are specific, genetically engineered bone growth proteins (BMPs - bone morphogenic proteins) which stimulate fusion.
There are also preparations of bone growth factors harvested from donated bone (demineralized bone matrices [DBM’s])).
Another option is to harvest the patient’s bone marrow and apply it to a synthetic scaffold as a way to deliver the cells that make bone to the fusion site.
Every method of bone grafting has its own advantages and disadvantages (pain, scarring, infection, cost, etc), but there are many viable options and patients are well-served to be educated about their choices regarding this aspect of a spinal fusion, and proactively work together with their surgeon to select the option that is right for them.
Ebraheim NA, Elgafy H, Xu R. Bone-Graft Harvesting From Iliac and Fibular Donor Sites: Techniques and Complications. 2001 JAAOS 9(3):210-18.
