Once a correct diagnosis has been made and the patient has decided to proceed with spinal fusion surgery, then obtaining a solid fusion is the next focus. Pseudoarthrosis, which means lack of a solid fusion, is becoming a less common outcome of spinal fusion surgery thanks to modern instruments and surgical techniques. However, there are a number of fusion risks that can adversely create this outcome, including the patient's own health and personal habits (host factors) and the technique of the spine surgeon.
Host Factors that Affect Spinal Fusion
There are a number of factors that negatively impact on obtaining a solid fusion following spinal fusion surgery, including:
- Smoking (nicotine)
- Chronic steroid use
- Diabetes Mellitus or other chronic illnesses
- Prior back surgery or attempted fusion
- Post-surgery activities
Of all these factors, the one that most negatively impacts the fusion rate and is under the control of the patient is smoking. Nicotine has been shown to be a bone toxin and it inhibits the ability of the bone growing cells in the body (osteoblasts) to grow bone. A fusion is basically a race between the bone growing cells and the bone eating cells (osteoclasts). Continuing to smoke after a spine fusion surgery, especially immediately after surgery, favors the bone eating cells and significantly undermines the body's ability to grow the bone need to create a fusion.
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Since having a spinal fusion surgery for low back pain is almost always the patient's decision, it only makes sense for patients to make a concerted effort to allow the body its best chance possible of allowing the bone to heal by not smoking. While quitting smoking is difficult, it is definitely worth it when considering a lumbar fusion surgery.
In addition to not smoking, most surgeons will restrict a patient's activity level for several months following the surgery. Typically, mild activity such as walking is encouraged as it promotes healthy circulation and aids in the healing process. However, activities such as repetitive bending, lifting, and twisting, are usually not permitted. Once the bone fuses, the patient is encouraged to gradually resume normal activities as bone is a living tissue and will become stronger when appropriate stress is applied to it over a period of time.
Another factor that may contribute to obtaining a solid spine fusion is the type of bone that is used. Typically, bone graft is taken from the patient's hip. Several types of bone graft substitutes and supportive materials are currently either in use or in various stages of development, and researchers are hopeful that new materials will help improve the success rate of obtaining a solid fusion, especially for patients who are at high risk for non-fusion.
Spine Surgeon Technique
Technically, there is a wide variety of surgical procedures that can be done to fuse the spine. The spine fusion surgery can be done with the following approaches:
- From the front (anterior lumbar interbody fusion/ALIF) ( figure 1, figure 2)
- From the back (posterior lumbar interbody fusion/PLIF or posterolateral gutter) ( figure 3, figure 4)
- From both front and back (anterior/posterior)
With any type of spine surgery, the specific technique used is largely dependent on the spine surgeon's experience and his or her comfort level with the approach.
There has been a recent trend in spine surgery toward trying to do more minimally invasive types of procedures. Anterior fusions - approached from the front - are done through a laproscope or a mini-open incision and carry less morbidity (unwanted aftereffects) than spine fusion surgery done through a posterior incision. However, there are a number of considerations with anterior spine fusion, including:
- Some types of pathology do not lend themselves well to an anterior fusion alone
- Not all spine surgeons are comfortable with the approach or do not believe it is the best approach
- There are some unique risks associated with approaching the spine fusion surgery from the front
No matter how the spine fusion surgery is done, the goal is to obtain a solid fusion and stop the motion at the level fused. For in-depth descriptions of the types of lumbar fusion, please see Lumbar Spinal Fusion Surgery.