What is spinal fusion?

What fusion does

Spinal fusion is surgery to permanently join two or more vertebrae (the bones of the spine) so there is no movement between them, according to MedlinePlus. Mayo Clinic explains the idea simply: the surgeon places bone or a bonelike material in the space between spinal bones, sometimes with metal plates, screws or rods holding the bones in place, and the bones can then heal as one.

The bone used can come from the person's own body, usually the pelvis (an autograft), or from a bone bank (an allograft). MedlinePlus adds that an artificial bone substitute may be used instead. The American Association of Neurological Surgeons (AANS) says almost all fusion techniques place a bone graft between the vertebrae, and that hardware such as plates, screws and cages may or may not be added. Once the bone has fused, most patients leave the hardware in place, AANS says, rather than have another operation to remove it.

Why it is done, and how

Mayo Clinic lists three broad reasons: the shape of the spine (for example scoliosis, a sideways curve), weakness or instability, where too much motion between two bones makes the spine unstable, and a damaged disc, since fusion may be used to stabilize the spine after a disc is removed. MedlinePlus adds fractures, instability from infections or tumors, spondylolisthesis (one vertebra slipping forward over another) and arthritis of the spine. It says fusion is most often done along with other spinal procedures, such as a decompression or discectomy, which are outlined in what spinal decompression surgery is.

Surgeons can reach the spine from the back, the front or the side, depending on where the bones are and why the fusion is needed, according to Mayo Clinic and MedlinePlus. MedlinePlus says the surgery can take 3 to 4 hours under general anesthesia. AANS notes that fusion can sometimes be done through smaller incisions using minimally invasive techniques, one example being transforaminal lumbar interbody fusion (TLIF), which uses two small incisions and replaces the removed disc with a bone-filled cage.

After surgery and results

Mayo Clinic says a hospital stay of 2 to 3 days is usually needed, while MedlinePlus says up to 3 to 4 days, a reminder that practice varies. Mayo Clinic says it can take several months for the bones to heal and fuse, and a brace may be suggested for a time. Physical therapy can teach how to move, sit, stand and walk so the spine stays in line. For more on timelines, see how long recovery after spine surgery takes.

On results, Mayo Clinic says fusion typically works for fixing broken bones, reshaping the spine or making it more stable. It also says study results are mixed when the cause of back or neck pain is not clear, and that fusion often works no better than nonsurgical treatment for back pain with an unclear cause. MedlinePlus says surgery does not always improve pain, can make it worse in some cases, and that it is hard to predict who will improve, even using scans.

Both sources point out a trade-off. Because the fused section can no longer move, the sections above and below it take more strain and may cause problems later. Mayo Clinic says this can lead to further surgery in the future. The topic is weighed alongside others in what the risks of spine surgery are and in the overview at surgery in outline.

When to get help

Whether fusion is suitable is a matter for a surgeon who has examined the person and reviewed their scans, and practice varies by country and by clinician. Mayo Clinic advises contacting the healthcare team after surgery if there are signs of infection: a change in color around the wound, tenderness or swelling, fluid coming from the wound, chills that cause shaking, or a fever higher than 100.4 degrees Fahrenheit (38 degrees Celsius). MedlinePlus lists nerve damage among the risks of fusion, with weakness, pain, loss of sensation or bowel and bladder problems as possible effects, so these are worth reporting to the surgical team.