Advancing Evidence-Based Spine Surgery
In an ongoing quest to advance evidence-based spine surgery, the authors of this study evaluated a nationally-representative sample of patients undergoing posterior lumbar fusion (PLF). They analyzed the data on over 66,000 patients who had spinal fusion for acquired spondylolisthesis. Complication rates while in the hospital were reported and described. The goal of this research is to help surgeons select the most appropriate patients for this procedure in order to have the best outcomes possible.

Acquired spondylolisthesis is usually a condition seen in older adults (though it can be seen in younger individuals). Acquired means it's something that happens to the person, rather than being a condition he or she was born with. When spondylolisthesis occurs in childhood, it is usually as a result of an injury. In older adults, degeneration of the disc and facet (spinal) joints can lead to spondylolisthesis. This type of acquired spondylolisthesis is sometimes referred to as degenerative spondylolisthesis.

Spondylolisthesis describes a condition of the spine in which one of the vertebral bones in the lumbar spine (low back) slips forward over the one below it. As the bones shift, the spinal canal opening (where the spinal cord is located) narrows. The result can be pressure on the spinal cord or peripheral nerves leaving the spinal cord in the lumbar region. Back, buttock, and leg pain are the main symptoms of this condition. Over time, leg weakness may also develop.

Studies show that surgery to fuse the spine is very effective. But when surgery and hospitalization are involved, there is always the risk of complications that can negatively impact the final outcomes. Studying these problems and the patients who develop them may help surgeons identify a subgroup of individuals who are the most (and least) likely to experience complications.

Surgeons from the Department of Neurosurgery at Stanford University in California conducted this study. They used data from the Nationwide Inpatient Sample (NIS) -- data collected from patient records while in the hospital. And in particular, information about patients having a posterior lumbar fusion procedure for acquired spondylolisthesis. Because it's a nationwide database, the results will reflect national (not regional or local) trends.

As it turns out, they found that the death rate following posterior lumbar fusion for acquired spondylolisthesis was fairly low (0.15 per cent). That's much less than one per cent. But the overall complication rate was 11 per cent and that's fairly high. Hematomas (pocket of blood at the surgical site) were the main problem. These are usually fairly minor.

More serious complications included blood clots, heart attacks, kidney infections or kidney failure, and less often, neurologic problems. Patients 65 years old and older were much more likely to develop complications. Anyone with more than one medical problem was also at increased risk of post-operative complications.

The authors examined the data collected with several other thoughts in mind. For example, did the complication rates differ based on hospital size (small or large), location (rural or urban), or patient characteristics such as gender or race? No, there was no difference in complication rates based on these factors.

But they did find that the risk of death went up when complications developed. And, of course, the number of days in the hospital increased with most minor and all major complications. Any complication increased the cost of hospitalization by thousands of dollars.

The results of this study will help surgeons develop treatment recommendations and national policy decisions to improve safety for patients having a posterior lumbar fusion for acquired (degenerative) spondylolisthesis. Knowing that patient age and the presence of other illness, diseases, or conditions will complicate the results of surgery are important findings.

Spinal fusion is still a safe and effective procedure for this condition. But now, surgeons can screen their patients more carefully before suggesting spinal fusion. And patients can be given more accurate information about what to expect, what could happen, and how likely it is that they might develop complications while in the hospital. This information will help both surgeons and patients weigh the pros and cons, risks and benefits of spinal fusion for this condition.

The authors make suggestions for additional studies to follow up on what they were able to report. For instance, they did not figure out how many people left the hospital but were later readmitted for one or more complications. They did not evaluate how or why the complications occurred -- did the type of fusion that was done make a difference? How about number of levels fused or type of instrumentation used in the surgery (e.g., plates, screws, pins, wires)? There is plenty of room for additional study on this topic and in finding specific ways to reduce in-hospital complication rates.
Paul S. Kalanithi, MD, et al. National Complication Rates and Disposition After Posterior Lumbar Fusion for Acquired Spondylolisthesis. In Spine. August 15, 2009. Vol. 34. No. 18. Pp. 1963-1969.