Surgical treatment and clinical outcomes in Lumbar Degenerative Spondylolisthesis

Abstract

Lumbar degenerative spondylolisthesis (DS) is defined as an anterior displacement of one lumbar vertebra relative to the vertebra below due to age-related changes. In clinical practice, DS are most commonly concomitant to a symptomatic lumbar spinal stenosis, i.e., a narrowing of the spinal canal, especially among the older (patient) population. Typical symptoms are low back pain and pain in the buttocks and/or lower limbs. For patients with severe pain and disability, surgery with decompression of nerve structures is the accepted treatment option. In recent decades, the rate of surgery for DS has dramatically increased, and the original method of decompression alone has been more frequently performed with an additional fusion procedure. A fusion can be performed with the use of a bone graft only (non-instrumented fusion), but screws connected to rods are usually utilised (instrumented fusion). Fusion is more invasive, more expensive and seems to have higher complication rates than decompression alone. The evidence for adding fusion to decompression is limited, as well as equivocal, and there is remarkable variation in surgical methods. In some countries, about 50% of procedures involve decompression alone, while in others an instrumented fusion procedure is included in about 90% of cases. This discrepancy in practice indicates a clear need for further high-quality studies. The major objective of this PhD has been to investigate whether decompression alone can be an appropriate choice or if it needs to be supported by a fusion procedure. In paper I, we used registry data to compare all methods of decompression alone to all methods of decompression with fusion. The fusion group experienced somewhat greater pain reduction, but no greater reduction in pain-related disability. In this paper, we were unable to conclude that decompression alone was as good as decompression with fusion. In papers III and IV, we intended to compare the most common operation methods in Norway: micro-decompression alone and micro-decompression with instrumented fusion. We wanted to study the effectiveness of the treatments, i.e., how they work in usual conditions, as well as their efficacy, i.e., how they work in a randomised setting, to gain complementary evidence for the best treatment for this patient group. In paper III, we found that the effectiveness of micro-decompression alone was as good as decompression with instrumentation. In the NORwegian Degenerative spondylolisthesis and spinal STENosis study (NORDSTEN-DS), a multicentre randomised controlled trial (RCT), we have included 267 patients in the period from February 2014 to December 2017. The study protocol of the RCT is included in the thesis, but the data is not yet accessible for analysis and results will not be presented here. An important prerequisite for the comparative clinical studies was to estimate criteria for clinical ‘success’ following surgery. Therefore, in paper II, we searched for criteria for a clinically important outcome assessed by Patient Reported Outcome Measurements (PROMs). Cut-offs for ‘success’ were estimated both for spinal stenosis with spondylolisthesis and for spinal stenosis without spondylolisthesis. We found that the percentage change in a score was able to reflect the perception of being ‘cured’ post-surgery more accurately than the numerical change. The results from paper II were used to determine whether a patient could be classified as a ‘responder’ or not, which is the primary outcome in papers III and IV.