Controversies about Spinal Fusion Surgery: Allografts, Autografts, and Fusion Levels

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.

What Bone Typed Should Be Used with the Fusion?

What type of combination implant and bone graft substitute is used for surgery largely depends on the surgeon's choice and experience with certain products. Cost, risk, availability, safety and postoperative morbidity are all factors that need to be considered.

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 that inhibit bone healing or require medications to do so.

How Many Levels of Fusion?

Another controversy includes how many levels should be fused at the time of surgery. This is especially true in patients who are having an anterior cervical discectomy and fusion in the presence of multiple abnormal discs.

Some surgeons prefer fusing all disc levels that look bad, whereas in most cases only one level will have herniated and be symptomatic. The thought is that if another level is bad, it will probably need to be fused in the future.

The dilemma with fusing increasing numbers of levels is that it places more pressure and strain on the unfused segments. On the other hand, trying to ‘cherry pick’ the one or two bad levels risks inadequately treating the patient’s problem.

Other surgeons feel that fusing only the clearly pathological level(s) (e.g. the one with the herniation that is causing the arm pain) is desirable as it maintains more of the normal motion and biomechanics of the neck.

There is no definitive answer as to which philosophy is better, and each individual patient is a little different. As a patient, the best way to consider this factor is to realize that the number of levels fused is a balancing act. Saving motion segments is desirable but comes at the cost of either under-treating the original problem or possibly needing another level fused in the near future.

The chance that another level will need to be fused in the future is difficult to quantify. Some studies have suggested that the rate of adjacent disc breakdown requiring further surgery is between 10% to 25% over ten years. More data are required before we will be able to definitely answer this controversy.

• Article written By:
• Peter F. Ullrich, Jr., MD

January 8, 2010

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