Autograft bone for spinal fusion
Autograft bone (patient’s own bone) is harvested from the iliac crest (hip). This technique has been the gold standard since the 1950’s. Autograft bone usually achieves a fusion in 90%-95% of patients.

The principal disadvantage with using autograft bone is that another incision needs to be made over the hip to harvest the bone graft. Possible complications associated with taking out bone graft include:

Graft site chronic pain (which happens 10% to 25% of the time)

Infection

Bleeding

Damage to the lateral femoral cutaneous nerve (a sensory nerve that supplies sensation to the front of the thigh)

Pelvis bone fracture

The chances of a complication increase with the size of the bone graft and patient obesity. For those who opt to use an autograft, many patients find the bone graft harvest site to be more painful than the cervical surgery site itself.



2. Allograft bone for cervical spinal fusion
Allograft bone (a.k.a. ‘bank’ bone or donor bone from a cadaver) eliminates the need to harvest the patient’s own bone. Basically, the donor graft acts as a bone scaffolding onto which the patient’s own bone grows and eventually replaces over years. There are no living cells in the bone graft, so there is little chance of a graft ‘rejection’ like with an organ transplant. However, bone graft healing remains an issue, as there is a somewhat greater likelihood of bone graft failure with allograft compared to autograft.

With allografts, the speed of healing may be slower than an autograft bone fusion. In addition:

In one-level spinal fusions, it yields nearly equivalent fusion rates as autograft bone.

Anterior cervical instrumentation (plates & screws) are commonly employed with allografts to increase fusion rates.

With increasing numbers of levels to be grafted/fused, the differences in fusion rates between allograft and autograft become more significant.

There is a theoretical risk of transmission of an infection from a donor. The risk of contracting a disease such as HIV or hepatitis from an allograft has been estimated to be between 1 in 200,000 to 1 in 1 million. However, with modern procurement and sterilization methods for bone tissue, the risk is essentially moot.

Potential risks and complications of a spinal fusion surgery include:

The principal risk from a spine fusion is that the graft does not heal. In general, allograft bone does not heal quite as well as autograft bone, but both yield good results when used in the anterior cervical spine.

If a graft is used without instrumentation, there is a small chance (1% to 2%) of a graft dislodgment or extrusion. If this happens, another operation is necessary to reinsert the bone graft, and instrumentation (plates) can then be used to hold it in place.

Controversies about spine fusion surgery
While physicians agree on many things about spine fusion surgery, there are some areas that lack consensus. Two such areas are the type of bone used (autograft vs. allograft) and how many levels should be fused.

Type of bone used with fusion surgery
Whether an autograft or allograft is used is based mostly on a combination of the surgeon’s and patient’s preference. Some surgeons still feel most comfortable with autograft as it yields the best fusion rates. Other surgeons have had good results with allograft bone and wish to avoid the postoperative pain and possible complications associated with harvesting a bone graft.

In some instances, it may be more compelling to use a patient’s own bone. There are some situations where it is more difficult to get a solid fusion and using a better bone graft is reasonable. Factors that may make obtaining a solid fusion difficult include:

Revision surgery (previously failed grafts)

Smokers/smokeless tobacco product users

Multiple level fusions

Disease states which inhibit bone healing or which require medications that do so
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Bone graft for spinal lumbar fusion

Bone graft for spinal fusion surgeries may either be harvested from the patient (autologous bone) or from a cadaver (allograft bone).

Autologous bone is harvested from the patient's pelvic bone (iliac crest) and provides the spinal fusion with a calcium scaffolding for the new bone to grow on (conduction). In addition, autologous bone also contains bone-growing cells (osteoblasts) and bone-growing proteins (bone morphogenic proteins).

Allograft bone simply provides a calcium scaffolding and does not have any bone-growing cells or bone-growing proteins. In the lumbar spine, allograft bone is restricted for use in ALIF or PLIF procedures in which bone graft is placed in compression (the compression aids the healing process for the bone). In a posterolateral gutter spine fusion, in which the bone is placed in tension, allograft bone by itself will not heal well (although allograft chips combined with autograft may be used to extend the harvested bone graft).

Autologous bone, in which the bone is harvested from the patient’s body during spine surgery, has the obvious disadvantage of higher post-operative pain. Most of the pain associated with bone graft harvesting is either from too much muscle stripping or from cutting the small sensory nerves (cluneals) that lie in the fat layer over the pelvis (iliac crest). With careful surgical technique, both of these pitfalls may be avoided.

In posterolateral gutter spine fusion and PLIF procedures, a single incision can be used for the spinal fusion surgery and to harvest the bone from the pelvis (iliac crest). The pelvis can be approached through a plane that has no nerves or blood vessels, and only the top portion of the crest needs to be stripped of its muscles (gluteal muscles). Use of this surgical technique minimizes the blood loss and post-operative pain associated with bone graft harvesting.

Bone harvested for ALIF procedures is done through a separate incision (one inch to two inches long) over the iliac crest. Again, only the very top portion of the iliac crest needs to be removed and the soft cancellous (spongy) bone from in between the cortical (hard) layers of bone is scooped out.

Scooping the bone out of the pelvic bone does not result in a lot of pain because there are no nerve fibers inside the bone. However, care must be taken to avoid the sensory nerve in this region (lateral femoral cutaneous nerve) as damage to this nerve can produce pain and numbness in the front of the thigh (meralgia parasthetica). In general, this approach should be associated with minimal post-operative pain or discomfort because limited soft tissue stripping is needed.

There are currently several products on the market and in development that act either as a bone graft extender or substitute. Demineralized bone matrix (bone that has had the calcium removed) has been available for the past several years. It carries some of the bone morphogenic proteins that the body uses to induce bone formation. There are also calcium hydroxyappetite products or coral, both of which have structures similar to bone and act as scaffolding for new bone.

There has been a lot of excitement among spine surgeons awaiting the new bone morphogenic protein products that are expected to be strong inducers of bone growth (osteoinductive). These new products will be relatively expensive, but will probably be able to grow bone even better than the patient’s own bone and bone graft harvesting may no longer be necessary.




3) My OSS was assisted by a laparascopic surgeon who did the abdominal part. How does that differ from today's minimally invasive approaches??

I am not certain I know how to answer this question, but maybe someone else does and will come along and answer it for you....