Spinal Fusion (Arthrodesis)
When a slipped vertebra leads to the enlargement of adjacent facet joints, surgical treatment generally involves both laminectomy (as described above) and spinal fusion. In spinal fusion, two or more vertebrae are joined together using bone grafts, screws, and rods to stop slippage of the affected vertebrae. Bone used for grafting comes from another area of the body, usually the hip or pelvis. In some cases, donor bone is used.
Although the surgery is generally successful, either type of graft has its drawbacks. Using your own bone means surgery at a second site on your body. With donor bone, there is a slight risk of disease transmission or rejection. In recent years, a new development has eliminated those risks for some people undergoing spinal fusion: proteins called bone morphogenic proteins are being used to stimulate bone generation, eliminating the need for grafts. The proteins are placed in the affected area of the spine, often in collagen putty or sponges. Regardless of how spinal fusion is performed, the fused area of the spine becomes immobilized.
Spinal fusion is major surgery, usually lasting several hours. There are different methods of spinal fusion:
- Bone is taken from the pelvic bone or from a bone bank. The bone is used to make a bridge between vertebrae that are next to each other. This bone graft helps new bone grow.
- Metal implants are used to hold the vertebrae together until new bone grows between them.
What to Expect After Surgery
- You will need to be watched in the hospital for a few days after surgery.
- Bed rest is not usually needed while you recover at home.
- Your doctor may recommend that you wear a back brace while you recover.
- Rehabilitation can take a long time. It includes walking, riding a stationary bike, swimming, and similar activities.
Why It Is Done
- Spinal fusion may be done by itself or along with surgery to remove bone and tissue that are narrowing the spinal canal and squeezing the spinal cord.
- It may be done as a follow-up after surgery that was done to treat problems such as spinal stenosis, herniated discs, injuries, infection, and tumours.
- Spinal fusion was first used to treat fractures or other problems. It is now also used to treat age-related spinal problems and spinal stenosis.
How Well It Works
Spinal fusion is often needed to keep the spine stable after injury, infection, or a tumour. There is not a lot of research about how well it works for other spinal problems. One study showed no clear difference between spinal fusion and intense rehabilitation for treating chronic low back pain. As you decide about having spinal fusion, talk with your doctor about the benefits and risks.
The surgery costs a lot and has serious risks. Although this type of surgery is common, there is no guarantee it will work to relieve your pain.
The risks of this surgery depend on your age and overall health, what you're having the surgery for, and the type of procedure you have.
- Pain at the bone graft site.
- Failure of the fusion, breakage of metal implants, or both.
- Blood clots that may also lead to pulmonary embolism.
- Nerve injury.
- Graft rejection.
What to Think About
Because there are so many things to consider when spinal fusion is recommended, seek a second opinion before making a decision. Operating on spinal instability involves surgically joining the loose upper vertebra to the lower one by inserting two large titanium screws through both facet joints and then packing out the evacuated disc space with bone chips taken from the pelvic bone. This is called a spinal fusion. It is usually done after first removing the flaccid disc (and sometimes part of the facet joint) in order to relieve the pressure on the spinal nerve root. These procedures are called discectomy and partial facetectomy.
More recently, a whole slew of less invasive operative techniques have come into vogue to provide sorts of quasi-fusions. They involve using plastic or metal struts to join together either the transverse or spinous processes of two segments to limit excessive movement (and compression) rather than obliterate movement altogether, as the older fusions did. Though their rationale may be straightforward in controlling segmental participation, certain doubts exist about their efficacy, mainly because their alignment in situ has difficulty in forward shear.
Furthermore, limiting segmental movement in this way brings almost to a halt any possibility of regenerating disc health by conservative means (because disc nutrition requires as much ‘good’ segmental movement as possible) so patients have to be sure that the slower route of regenerating disc health has been fully tried and tested before being discarded for the quick fix. And indeed, if surgery is to be contemplated, patients need actual figures of a surgeon’s experience in using the device or procedure and the outcomes, without feeling difficult or demanding.
As you might imagine, surgical technique is of the essence with any spinal operation (similarly to using a hammer and chisel on a Stradivarius violin) because the spine is never quite the same afterwards; it is hard to ‘go back’ and conservative treatment is never quite as effective.
Apart from disturbing the delicately poised spinal mechanics, prolific scar formation causes many problems. If the scarring becomes invasive, it can be just as space-occupying and obtrusive as the structure deemed worthy of removal. In particular, the nerve root can be slowly strangled by the growth of adhesions, eventually causing the same symptoms of pressure on the nerve, and the old pain starts up again. Post-operative adhesions are similar to the post inflammatory condition called ‘root sleeve fibrosis’.
The other complication of spinal fusion is the strain translated to the next working level up (L4 if L5 has been fused, or L3 if L4 and L5 have been fused). Both are almost flimsy compared to the robust L5–S1 junction and are ill-equipped to act as the seat of spinal movement. They are not bedded deeply in the pelvis like L5, nor do they have the august ilio-lumbar ligament to lash them down. Thus they are progressively over-taxed by routine movement. The problem usually takes several years to manifest and affects L3 more seriously than L4. Intrinsic spinal strengthening is therefore a critical part of a post-fusion regimen.”
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