I'm doing some research on-line for my brother who is going to have a spinal fusion. He has a condition called degenerative spondylolisthesis. They are talking about extending the fusion from L4-L5 to L5-S1. From my reading, I'm not sure there's any real advantage to doing that? Am I understanding this correctly?
You have certainly distilled down the information that has been published on this topic. Though there have been studies with conflicting results, a recent study from the UCLA Comprehensive Spine Center at the University of California (Los Angeles) provides some clarity on the subject.
By following 107 patients for five years or more, they found that the extended fusion did NOT improve clinical results. They concluded there is no need to fuse the L5-S1 segment as a preventive measure against developing adjacent segment disease. However, the authors did suggest that lumbosacral fusion should be used for patients with instability at the L5-S1 level (not just for disc degeneration).
Clinical results (improved pain and function) and patient satisfaction were good-to-excellent in 82 per cent of the patients. The incidence of adjacent segment disease (ASD) was actually less in this group (the lumbar floating fusion group) compared with the (extended) lumbosacral fusion (LSF) group.
The higher rate of adjacent segment disease in the lumbosacral fusion (LSF) group may be the direct result of a longer fused rigid segment. With a longer area fused, there is an increased load and stress on the normal segments above. Some researchers have concluded from their studies that increasing age is a risk factor for ASD but age was not statistically significant in this study.
The UCLA surgeons involved in the study concluded that extending spinal fusion to include the sacrum for patients with degenerative spondylolisthesis is not helpful. In fact, the extended fusion increases the risk of adjacent segment disease above the start of the fusion. Without this extension, the surgery is shorter and with less blood loss. There is also the advantage of less bone graft and a lower risk of pseudoarthrosis (failed fusion with spine motion still present).
Given this information, it would still be good to find out the surgeon's rationale for recommending extended fusion. There may be issues of instability or other mechanical problems to consider that you or your brother are not aware of.