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Lumbar Spinal Fusion Surgery

Considering spinal fusion surgery as treatment for a spinal condition like degenerative disc disease? Call the specialists at United Spine & Joint. Contact us to determine what option is best for you, what your insurance will cover and any additional surgery costs.

What is Lumbar Spine Fusion?

A lumbar spine fusion is a type of back surgery designed to treat low back pain from degenerative disc disease. It is called a ďspine fusionĒ because the surgery involves placing small morsels of bone either in the front of the spine (in the disc space) and/or along the back of the spine (in the posterolateral gutter) so that the bone grows together and fuses that section of the spine.

The fusion is designed to eliminate motion in that fused segment of the spine, thereby decreasing or eliminating the back pain created by the motion.

The spine is not actually fused at the time of the surgery. Instead, the surgery creates the conditions for the spine to be able to fuse and the fusion is a process that will set up over a 3 to 6 month (and up to 18 month) period of time following the spinal fusion surgery (see figure 1).

Lumbar spinal fusion surgery for low back pain caused by degenerative disc disease is usually considered an option for patients who:

  • Have not found sufficient pain relief from extensiveóusually at least six monthsóof non-surgical treatment (such as physical therapy, medications, and other treatments)
     
  • Have ongoing low back pain that limits their ability to function in their daily activities at work and/or at home
     
  • Have received a diagnosis that a specific disc space is the pain generator and other possible causes of the patientís low back pain have been considered and ruled out

It is important to stress that the decision to undergo a fusion procedure for low back pain is entirely the patientís decision and he or she needs to carefully weigh the risks and possible complications along with the potential benefits of surgery, as well as consider the full range of alternatives to a spine fusion surgery.

It is often a good idea for patients to get a second (or third) opinion from other surgeons and/or other types of spine specialists prior to deciding whether or not to have spinal fusion.

The decision to have a spine fusion procedure to treat low back pain from degenerative disc disease is a very personal one. Degenerative disc disease is for the most part a non-crippling, non-progressive type of back condition, although in a minority of cases it can cause severe back pain and can significantly impact on an individualís ability to function.

History of Spinal Fusion Surgery

Fusion surgery for the treatment of lower back pain has been done since the early 1900ís. At that time, spine fusion procedures were done to limit the deformity created by tuberculosis infections, and it was found that not only did the fusion procedure limit the deformity, it also reduced the patientís low back pain as well.

Since then, spine fusion procedures have had variable popularity for the treatment of pain from lumbar degenerative disc disease and remain somewhat controversial in the medical community. Surgeons and researchers span the spectrum in terms of their beliefs as to how useful spine fusion surgery is and when and how it should be performed.

  • Some spine surgeons do not believe fusion surgery is at all useful and is never indicated for the treatment of low back pain from lumbar degenerative disc disease.
     
  • Some spine surgeons are very willing to offer patients a fusion procedure, and some are even willing to do multiple level fusion surgery.

As with most things in medicine, the truth lies somewhere in between the two far ends of the spectrum of beliefs about spine fusion surgery as a treatment for low back pain from degenerative disc disease. In general, when done by a skilled surgeon for a patient with the right indications, spinal fusion surgery is usually an effective treatment that brings significant relief from severe, ongoing low back pain caused by degenerative disc disease.

Each patient has to weigh the risks of a major surgical procedure and a long healing process with the potential benefits. The spine fusion surgery works best for treating one level of the spine, although two levels can be fused if the patient has severe low back pain. As the number of levels fused increases, the risks of the procedure increase (e.g. a nonunion) and the potential benefits decrease. Only rarely and in extreme cases would most spine surgeons recommend or even offer a three or four-level spine fusion surgery.

Who is a good candidate for Spinal Fusion Surgery?

The biggest risk for spine fusion procedure is continued pain, meaning that the surgery did not substantially reduce or eliminate the patientís pain. The number one reason this occurs is that the fused disc was improperly identified as the cause of the patientís pain, so fusing the disc was unnecessary and irrelevant. This is why getting an accurate diagnosis is critical.

One of the most difficult and crucial parts of any type of low back surgery is selecting the patients who will do well with a certain procedure. It is especially critical to select the right patients for a lumbar spine fusion surgery for two reasons:

  • Lumbar spine fusion is an extensive surgery and the healing process takes a long time (about 3 to 6 months, and up to 18 months)
  • The spine fusion forever changes the biomechanics of the back and is thought to increase the stress placed on the other (non-fused) joints in the lower spine and possibly lead to degeneration of the adjacent levels of the spine.

Lumbar spine fusion surgery is generally not recommended until a patient has tried 6 to 12 months of adequate non-surgical care. Spinal fusion is best for treating low back pain caused by severe degenerative disc changes and is best for treating one, or maybe two, levels of the lower spine (typically the L4-L5 level and/or L5-S1 level).

Prior to recommending or offering spine surgery, a surgeon must also consider other causes of low back pain that can closely mimic the symptoms of degenerative disc disease. These conditions include:

If a patientís low back pain and other symptoms do not improve with extensive conservative (nonsurgical) treatment and other causes of low back pain have been ruled out, then he or she may be considered for a spine fusion surgery. Importantly, while failing conservative treatment is a necessary prerequisite for spine fusion surgery, it is not sufficient. Prior to recommending spine fusion surgery, a spine surgeon has to be confident that he or she is fusing the segment of the spine that is generating the patientís pain (the ďpain generatorĒ). Obviously, fusing a structure that does not cause pain will not reduce the patientís low back pain or lead to a successful outcome.

MRI scans have greatly increased the spine surgeonís ability to diagnose degenerative disc disease. Unfortunately, a lot of the changes that are seen on MRI scans are more related to normal aging than to a pathologic and painful disc. Differentiating a painful disc from an aging disc is often difficult but there are some clues that help. In general, a painful disc will be severely degenerated whereas the rest of the discs will be well preserved. Other characteristics of a painful disc on an MRI scan include:

  • Disc space collapse, which means that the disc has gotten shorter/flatter
     
  • Endplate erosion, which is erosion of the top and bottom outer material of the disc
     
  • Edematous changes in the vertebral body (Modic changes), which is when the MRI shows irritation of the bone marrow, may be an indicator of a painful disc. There is a characteristic bright signal on the MRI scan when this occurs.

If a spine surgeon is uncertain as to whether or not a disc is painful, a CT-discogram may be ordered. A discogram is a direct pain provocation test that is designed to try to elicit the patientís pain by injecting a dye into the disc space. If the test creates the patientís normal pain, it can be assumed that the test is positive and the disc is generating the patientís pain. Some major drawbacks of the procedure are:

  • It involves an injection into the spine, which has several risks (albeit rare)
     
  • It is usually painful
     
  • It is a subjective test, and both false positives and false negatives can occur
     
  • Accuracy of the test is largely dependent on the skill of the discographer

Discograms are used by some surgeons before every spine fusion, and it is certainly warranted to gather as much information as possible before undergoing a fusion procedure. However, discograms are probably not necessary on a routine basis, and the test itself is somewhat controversial. The test should only be used if the results are going to change the surgeonís recommendations (e.g. if negative, spine surgery will not be recommended). If the results are ignored and the surgical choice is made off of the MRI findings, then a discogram does not serve any useful purpose.

Increasing Success of Spine Fusion Surgery

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 patientís own health and personal habits (host factors) and the technique of the spine surgeon.

Factors that Affect Spinal Fusion

There are a number of factors that negatively impact on obtaining a solid fusion following spinal fusion surgery, including:

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 bodyís ability to grow the bone need to create a fusion.

Since having a spinal fusion surgery for low back pain is almost always the patientís 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 patientís 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 patientís 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.

Spinal Fusion Approaches

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:

With any type of spine surgery, the specific technique used is largely dependent on the spine surgeonís 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 fusionsóapproached from the frontóare 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.

Spine Fusion Alternatives

There are a couple of alternatives to spine fusion surgery that may be considered for patients with low back pain from lumbar degenerative disc disease. Currently, the main fusion alternatives include:

  1. IDET, or Intradiscal electrothermal coagulation (or annuloplasty). This procedure involves inserting a needle into the lumbar disc space, passing a catheter through the needle, and heating up the annulus (the outer core of the disc space). The exact mechanism by which the procedure relieves pain has not been clearly established, but it is theorized that the heat contracts and thickens collagen fibers in the disc wall, which in turn seals up painful tears and cracks and reduces pain. The procedure also cauterizes nerve endings which is thought to make them less sensitive. Not all patients benefit from IDET, and the treatment is more likely to help people with less severe degenerative disc disease than people with significant disc degeneration. IDET is minimally invasive and usually done on an outpatient basis (no overnight hospital stay) under mild sedation and a local anesthetic. Although the procedure is minimally invasive it has largely fallen out of favor in the spine world as it has marginal clinical efficacy. Most insurance companies no longer cover the procedure.
  1. Artificial discs. Disc replacement surgery involves replacing the painful disc in the spine with an artificial disc. As of August 2006, two brands of lumbar artificial disc are available for use in patients in the U.S.: the Charite lumbar artificial disc and the PRODISC-L lumbar artificial disc. A number of other artificial disc brands are in the clinical trial testing phase. The goal of artificial disc replacement surgery is to preserve the normal motion of the spine (unlike fusion, which eliminates motion at the painful spinal segment). Artificial disc surgery has two primary theoretical advantages over spinal fusion; 1) it is thought that preserving spinal motion reduces the risk that other segments of the lumbar spine will wear down prematurely; 2) it is believed that artificial disc surgery may achieve better pain reduction than fusion. However, these potential benefits come at the expense of greater risk with the surgery. Any motion preservation device can fail by extrusion or wearing out with time. Revision surgeries are expensive and extremely dangerous. The risk/benefit ratio of artificial disc versus fusion is still largely unknown, and currently many insurance companies are not covering the procedure.
     
  2. Posterior dynamic stabilization. This treatment is different from fusion in that posterior dynamic stabilization seeks to preserve motion in the spine while also taking pressure off the diseased vertebral disc. The theory is that removing pressure from the painful disc will create a favorable healing environment and reduce pain. The devices used in the surgery are designed to unload pressure from the vertebral disc in the same way a dynamic (moveable) brace unloads pressure from an injured knee or ankle to allow it to heal. Various forms of posterior dynamic stabilization devices are still in the investigative or testing phase or early in use, and their efficacy and potential risks and complications have not yet stood the test of time.
     
  3. Disc regeneration. Researchers in cellular and molecular biology are exploring ways to use gene therapy to stimulate regeneration of the vertebral disc and/or to slow or prevent degeneration of the disc. The hope is that this therapy could prevent the need for surgery. For example, in animal studies, the BMP-12 gene (bone morphogenetic protein) has dramatically increased the generation of cells in both the nucleus and the annulus of the vertebral disc. BMP-12 is a molecule that, among other duties, promotes formation of embryonic joints. Research is also being performed on gene therapy that could inhibit the degeneration process. Gene therapy for treatment of the intervertebral disc is still in the early stages of research.

Patient's Decision: Spinal Fusion

The decision to have a spine fusion procedure done to treat low back pain is a very personal one, and it is entirely the patientís decision. Degenerative disc disease is for the most part a non-crippling, non-progressive type of back condition and does not lead to neurological deficits or result in a progressive crippling condition.

The natural history is for the low back pain to improve with time (although it may take many years) as the natural aging process leads the disc space to have less motion. With continued degeneration, bony growth around the disc will try to capture the excess motion. Therefore, continuing non-surgical treatments (such as medication, exercise) to manage the painful symptoms and living with the discomfort is always an option.

Unlike many other types of surgery, with spinal fusion surgery only the patient can decide if the pain and inability to complete oneís normal daily activities is bad enough to warrant spinal fusion (or any other) type of surgery. And the best way for a patient to make an informed decision about whether or not to have spinal fusion is to fully understand the trade-offs between spinal fusion and other non-surgical and surgical treatment options.

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