Spinal fusion surgery or arthrodesis is a surgical procedure that connects two or more spinal vertebrae together.
In the beginning it was thought that the best and most durable fusions occur when the vertebrae grow together and form one large piece of bone. Many different hardware configurations have been developed but nothing seems to work as well as growing a solid bony fusion. But, even then people would often develop problems one or two years after surgery.
Your spine normally has a small amount of controlled motion between each pair of vertebrae. This motion is controlled by the intervertebral disc and the facet joints. This small amount of motion at each level is what allows us to bend and twist. Excessive or uncontrolled motion between the vertebrae may cause back pain or pinched nerves.
Pressure on nerves may cause pain or other problems depending on which nerve is being squeezed. You may experience pain or weakness radiating into one or more of your arms and legs; if the nerves that go to your bowels and bladder are affected you may have difficulty controlling your urine and bowel movements.
If the nerves that go into your legs and feet are involved you may have difficulty feeling the floor or picking your feet up. You may notice that you are tripping or falling more than you have in the past. Exactly which symptoms you may have will depend on precisely which nerves are being squeezed, and how much they are being squeezed.
Spinal fusion surgery is used to prevent abnormal motion and correct congenital deformities such as scoliosis. Abnormal or excessive motion in your spine may also develop because of infections, injuries, or tumors.
Spinal fusion surgery may also be combined with Spinal Stenosis Surgery. This surgery involves removing some of the bone in your spine that is pressing on nerves. If your surgeon thinks that there is a risk of developing instability or abnormal motion, he may talk to you about fusing the vertebrae together.
Advances in Spinal Fusion Surgery
Earliest fusions were big risky surgeries requiring several hours of surgery and months of rehabilitation afterwards. The surgeries had a high rate of complications both during and after surgery, and a high rate of failure of the fusion.
When doctors began using rods and screws to stabilize the spine, failure rates improved. However, the goal was still to grow bone between the vertebrae, because eventually the screws and rods would break and the fusion would fail.
The next generation of technology began using hardware placed into the disc space that would both stabilize the spine, and hold the bone graft in place.
The most recent development in spinal fusion is not really a fusion at all. Doctors are now using artificial disc replacements to prevent abnormal motion but still allow a small amount of controlled motion.
The First Fusion Surgeries
The goal of any spinal fusion surgery is to stop abnormal motion between the vertebrae. The earliest spine surgeons did this by harvesting bone from your pelvis or ribs and placing it between the vertebrae. You would then be placed into a whole body cast or brace, for several weeks or several months, until the fusion could heal.
The surgeries would often take several hours and be complicated by large amounts of blood loss. These fusions would often fail because the bone graft would shift out of place or failed to grow into solid union between the vertebrae.
Weeks or months in a body cast or brace often caused many secondary complications such as pressure sores, skin infections, and muscle atrophy. Too much time out of the brace, or too much activity, risked causing migration or failure of the bone graft.
Combining Hardware With Bone Graft
The earliest use of hardware was lag screws screwed into the vertebra and connected together by steel rods. Surgeons hoped that by fastening the bones together with screws and rods they could allow more activity and prevent many of the postoperative complications.
This did work well, but there were still problems. Bone graft would move out of position or refuse to grow, screws would eventually loosen, or metal rods would fatigue and break and the fusion would fall apart. If the boney fusion between the vertebrae could not be achieved, the hardware would eventually fail.
Eventually hardware was developed that could be placed into the disc space and held in place by compression. These small cylindrical cages could be packed with bone graft that could grow to form the boney connection between the vertebrae.
The introduction of this technique reduced failure rates due to graft migration and hardware failure. People were able to mobilize sooner, return to normal activities faster, and success rates improved.
One Major Problem Remained
In many cases when a solid fusion was achieved people would develop problems at the level above or below the levels that were fused. This would happen because immobilizing one area of the spine always puts additional stress and strain on the levels above and the levels below the area that is fused.
People would often develop abnormal motion at these adjacent levels and require a second surgery within a few years. To solve this problem, the doctors needed a system that would allow a small amount of controlled motion between the vertebrae, similar to a natural disc.
Artificial Disc Replacement
The most recent development in controlling abnormal motion uses a small mechanical device that is placed into the disc space. These instruments are attached to the vertebra above, and the vertebra below. They allow controlled motion and prevent abnormal motion.
This latest evolution in controlling spinal motion has many advantages, including reducing the stress on adjacent disc levels. When combined with modern surgical techniques, blood loss and the time under general anesthesia are limited. People can be mobilized the next day with physical therapy minimizing problems with pressure sores, braces, and blood clots.
Is Spinal Fusion Surgery For You?
If your doctor has x-rays or other studies that demonstrate abnormal motion at one or more levels in your spine you may need to at least consider the spinal fusion.
The first thing to consider is the severity of your symptoms. If your only symptom is pain, you should do everything possible to control it, before considering surgery. If you can use medications, activity modification, Back Pain Injections and other Back Pain Treatments to manage your pain and avoid surgery, that may be a better choice even if your pain is not completely relieved.
Unlikely To Emerge Pain Free
Even with modern techniques and devices you are unlikely to go through the spinal fusion surgery and emerge pain free. There will likely be a certain level of back pain that you will need to live with. All of these surgeries are much less effective when they are done to relieve back pain. They are more effective when they are performed to relieve upper or lower extremity pain, or other symptoms.
If the symptoms you're having are more severe such as Cauda Equina Syndrome which may cause muscle weakness or difficulty controlling your bowels and bladder your options may be limited. If your symptoms are causing severe limitation, and cannot be controlled any other way, spinal fusion surgery may be the best option you have.
You should always discuss the risks and benefits of any surgery with your doctor. You should understand what those risks and benefits are, and you should be the one to decide if surgery is the best thing for you, because you are the one that will have to live with the results of that surgery.