Spinal fusion generally refers to instrumented posterior spinal fusion performed for adolescent scoliosis and kyphosis deformities. Spinal fusion performed in adults carries similar traits, but different issues occur. For detailed information about adolescent instrumented posterior spinal fusion, click here.
When is fusion necessary?
There are numerous potential reasons why a surgeon may consider fusion. Some are:
- Canal stenosis
- Cervical disk herniation
- Recurrent lumbar disk herniation
- Spondylolisthesis (forward slippage)
- Instability
- Adult spinal deformity
- Vertebral fractures
- Vertebral tumors
The mainstay treatment of /en/adults/adult-spinal-disorders/treatment-of-lombar-spinal-stenosis.34.aspx/en/adults/adult-spinal-disorders/treatment-of-lombar-spinal-stenosis.34.aspx is decompression to increase the canal diameter. However, wide decompression may lead to instability in the posterior part of the spine that may cause local kyphosis, which may require surgical correction. Therefore, your surgeon may suggest performing decompression with instrumented fusion.
In cervical (neck) disc herniations that require surgical treatment, fusion is often necessary after removal of the herniated disc. In this operation, the disc is removed frequently through a skin incision on the front of the neck, and graft bone or a titanium cage is implanted instead of the disc. Although cervical discectomy is generally accompanied by fusion, the same is not true for lumbar disc surgery.
A standard lumbar disc surgery is done with a minimal invasive technique using a microscope. Recurrence rates are reported to be up to 20 percent. The surgery for the recurrence can again be done in a minimally invasive fashion or single-level fusion may be preferred. This decision is based on symptoms as well as X-ray and MRI findings.
Forward slippages (spondylolisthesis) are typically treated with single-level fusion.
Another condition that can be treated with fusion surgery is instability, which is abnormal movement between two vertebrae (one vertebral segment). Instability may cause back or neck pain, and also may damage the neighboring nerves. Therefore, fusion is preferred, especially if instability involves more than one segment.
If adolescent onset deformities such as scoliosis or kyphosis is not in treated in adolescence, they progress into adulthood. Deformities can also start and progress in adulthood due to degeneration, which is called de novo scoliosis. Both of these conditions are referred to as adult scoliosis. Spinal fusion can be necessary for neglected severe curves or smaller curves that tend to progress.
Vertebral fractures and tumors do not always necessitate fusion. Fusion may be necessary in some cases, especially those associated with spinal cord or nerve injury.
In some cases, fusion may be considered as a pain treatment in the absence of obvious instability. One of the greatest obstacles in the successful management of pain through fusion is the difficulty in determining the source of pain. Theoretically, the source of pain is painful movement, and fusing the vertebra together will eliminate the pain. Unfortunately, using the available techniques, it is not always possible to understand which of the complicated structures in the lower back or neck is the source of pain. Due to the difficulty in identifying the source of pain, spinal fusion surgery as a pain management technique is controversial. In these cases, fusion is often considered as the last resort and suggested only after other conservative (non-surgical) precautions failed.
How fusion is achieved?
There are various surgical approaches and methods to fuse the spine—all include the addition of a bone graft between the vertebras. The approach to the spine for grafting can be done from the front (anterior approach), from the back (posterior approach), or a combination of both. While an anterior approach is used more commonly in the neck, fusion in the thoracic and lumbar spine are performed generally through the posterior approach.
The goal of fusion is to construct a stable union between two or more vertebrae. Instrumentation such as rods, screws and cage, may or may not be used in fusion. Instrumentation may sometimes be used to correct a deformity; however, it is mostly used as an internal splint to keep the vertebra together while bone grafts heal.
Independent from the insertion of instrumentation, the use of bone or bone substitutes are necessary to achieve bony fusion. The bone graft may be harvested from the patient him/herself (autograft) or from bone bank (allograft). Autografts are currently accepted as the gold standard for fusion. Allograft (cadaver bone) may be used as an alternative. Although bone healing and fusion is not as high as an autograft, allograft does not require bone harvest using another incision and therefore results in less pain.
Smoking, medications, or your general health status may affect the rate of healing and fusion.
Ongoing research is concentrating on synthetic bone and bone morphogenic proteins, and several other bone substitutes that can be used instead of auto or allografts.
New "minimal invasive" surgical techniques enable fusion through smaller surgical incisions. enable fusion through smaller surgical incisions. The indications for surgery in minimally invasive surgery are similar to the traditional large incision. However, it is important to understand that a small incision does not mean a smaller risk.
What is the recovery duration after spinal fusion?
Pain and discomfort after spinal fusion is generally more severe than after other spinal operations. However, pain can be managed with oral or intravenous painkillers and pain pumps (PCA, patient controlled analgesia). PCA is a device that releases a predetermined amount of narcotic painkiller to the blood stream when the patient presses a button.
Likewise, recovery after fusion surgery is generally longer compared to other spinal surgery operations. Bone and graft healing after fusion is similar to that of healing of the broken bones. Your surgeon will want to see early proofs of fusion in X-rays, which appears around six weeks post-operation. Activities should be limited during this period, and returning to normal life activities should be gradual. Although bone healing starts earlier, it takes around six months when the newly formed tissue is strong enough.
The period of sick leave depends on the length of the fusion, and also on your occupation. Generally, it’s between 6-12 weeks.
What should I expect long-term after spinal fusion surgery?
A rehabilitation program may be advised after surgery, including muscle and cardiovascular training. Brace use may be beneficial in the early post-operative period.
Although fusion is a proven effective surgery, it is important to know that it does not return your spine to "normal". In a normal spinal column, there is a certain amount of motion between the vertebrae. Appling fusion eliminates the movement between vertebrae. This changes the loading dynamics of the upper and lower segments of a fusion.
Fusion not occurring for a specific time after surgery is known as non-union or pseudarthrosis. If the bone does not fuse to share loads, the implants will eventually loosen and break. This necessitates a revision surgery. The rates of non-union range from 5 percent to 35-40 percent in different series depending on the type of the surgery and grafts used. Smoking significantly increases the risk of non-union.
A solid fusion can increase the loads applying to adjacent segments, especially at the upper adjacent segment, and may accelerate the normal degenerative processes. This risk ranges among individuals.