There are risks with any surgery and those associated with spinal fusion have special considerations. The success of this surgery relies on the body's ability to form bone. It also relies simultaneously on its ability to tolerate metallic hardware in order to keep the vertebral bones in place. Consequently, the most significant risks are associated with the bone fusion process or the fixation hardware itself.
Statistics
The risks associated with spinal fusion surgery are not insignificant. A 2002 study published in "The Spine Journal" stated that major complications associated with fusion surgery can be as high as 29 percent. While most to the time the results of fusion are favorable, total or complete elimination of pain and other symptoms in the back and legs is rare.
Risk Factors
The primary objective in fusion surgery is to bring two vertebrae together so that in time they will grow into a single, bony unit. This inhibits movement between the bones and therefore the spinal nerve roots will no longer be irritated. Successful spinal fusion depends on the patient's ability to create new bone material to fill the intervertebral space, as well the ability to heal in general. According to a July 2009 article in the journal "Applied Radiology," surgical risks increase in older patients and patients who smoke cigarettes. As reported by Ortho-Preferred, other risk factors include whether the patient had a previous surgery and the number of spinal fusion levels required.
Fusion Failure Risk
Fusion is encouraged when the surgeon grafts bone into the intervertebral space. The bones are stabilized with hardware to allow them to grow together. However, as reported in "Applied Radiology" in July 2009, failure to fuse is the major complication of the procedure. The resulting pseudarthrosis or incomplete fusion can cause a return of symptoms or additional pain.
Adjacent Vertebrae Pathology
When the vertebrae are fused the bones above and below the fused segments must move more to compensate for the immobility in between them. This produces more mechanical strain, which can result in pathology. Consequently, arthritis and disk pathology in the intervertebral segments above and below the fusion occurs in about 10 percent of patients.
Hardware Issues
The hardware required to immobilize the vertebrae can fail due to metal fatigue. The July 2009 issue of "Applied Radiology" states this breakage can cause a pseudarthrosis that may require another surgery to replace the hardware. The metallic screws, plates and rods also can irritate tissues causing cavity formation, pressure sores and pain. In addition, the bone surrounding screws can erode and weaken resulting in vertebral fracture. One of the most severe issues with hardware fixation is the possibility of neurological damage. When a piece of hardware breaks or slips off it can penetrate neural tissues and produce weakness, paralysis, pain, and bowel or genitourinary problems.
General Surgical Considerations
The National Institutes of Health states that another problem with this surgery is infection. Infection can be either in the vertebral bones or in the tissues around the bones or hardware. In addition, deep vein thrombosis, systemic infections, blood clots, bleeding and pulmonary emboli may occur.
References
- MedlinePlus: Spinal Fusion
- Spinal Fusion: American Academy of Orthopaedic Surgeons
- "Applied Radiology"; Diagnostic imaging of spinal fusion and complications; M. Hayeri and J. Tehranzadeh; July 2009
- The Spine Journal: Complications of spinal fusion in treatment of adult spinal deformity
- Ortho-Preferred: Fusion of the Spine
