When two or more bones of the spine are fused, one or more discs are removed. This means that the remaining discs, and particularly those directly above and below the fused site, need to absorb more shock.
For patients with severe disc degeneration, facet joint problems or other painful conditions causing spinal instability, fusion may seem like the best option. Research is available to help health professionals and patients understand risk factors for ASD after fusion. This information can help patients make the best treatment decisions.
Risk Factors for ASD
A systematic review of five studies found the yearly incidence of ASD post-lumbar fusion to be between 0.6% and 3.9%. Several risk factors were identified in the review:
— Age over 60
— Pre-existing degeneration of the facet joints around fused site
— Pre-existing degeneration of discs around fused site
— Having a multilevel fusion
— Fusions around, but not including, the L5-S1 level
The location of fusion, the condition of the spine surrounding the fused site and the age of the patient are, then, important factors to consider when deciding whether or not fusion is the best treatment option. See more on this systematic review at www.ncbi.nlm.nih.gov.
Another study sought to assess the re-operation rate due to adjacent segment degeneration over more than two years post-fusion. The patients in this study all received fusion at the L4-L5 level. Presenting with severe pain, neurological problems and spinal instability, 6.4% of those studied required reoperation.
This study also found age to be a risk factor, but identified two other factors not covered in the above systematic review:
— BMI (body mass index)
— Pre-existing stenosis (narrowing of the spinal canal) in adjacent spinal segment
Being overweight or obese adds extra stress to spinal discs, increasing the likelihood, particularly after fusion, of degeneration. The spinal canal must be considered along with the condition of joints and discs around the site of fusion, although the cause of stenosis in the participants of this study may have been disc or joint related.
See more on this study at www.ncbi.nlm.nih.gov.
If you’re over 60 and have signs of wear throughout the spine, be wary of spinal fusion. Make sure you’ve considered less invasive surgical options and other spinal fusion alternatives, such as artificial disc replacement. Get second and third opinions if your surgeon is not open to considering other options besides fusion.