Sagittal alignment in operative degenerative lumbar spondylolisthesis: a scoping review

BACKGROUND: The benefit of surgical intervention over conservative treatment for degenerative lumbar spondylolisthesis (DLS) patients with neurologic symptoms is well-established. However, it is currently unclear what breadth of available evidence exists on regional and global sagittal alignment in DLS surgery. As such, the purpose of the current study is to conduct a scoping review to map and synthesize the DLS literature regarding the current radiographic assessment of sagittal spinal alignment in DLS surgery. METHODS: A comprehensive search of the MEDLINE, EMBASE and Cochrane databases from January 1971 to January 2023 was performed for all DLS studies examining sagittal spinal alignment parameters with DLS surgery according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses extension for Scoping Review (PRISMA-ScR) protocol. RESULTS: From 2,222 studies, a total of 109 studies were included, representing 10,730 patients with an average age of 63.0 years old and average follow-up of 35.1 months postoperatively. Among included studies, 93 (85%), were largely published in the last decade and predominantly represented retrospective cohorts 70 (64%) or case series 22 (20%). A common theme among the reporting of radiographic parameters in the included investigations was the assessment of the magnitude and/or maintenance of a radiographic change postoperatively, with 92 (84%) studies reporting these findings. The majority of studies focused on index DLS level [33 (30%) studies] or lumbar spine radiographic imaging [33 (30%) studies] only. Thirty-seven (34%) studies reported spinopelvic parameters, with only 13 (12%) of included studies assessing 36-inch standing lateral radiographs and overall alignment. CONCLUSIONS: There is increasing prevalence of investigations assessing sagittal spinal alignment parameters in DLS surgery. Although, there is an increasing prevalence of studies investigating sagittal spinal alignment parameters in DLS surgery the quality of the currently available literature on this topic is of overall low evidence and largely retrospective in nature. Additionally, there is limited analysis of global sagittal spinal alignment in DLS suggesting that future investigational emphasis should prioritize longitudinally followed large prospective cohorts or multi-centre randomized controlled trials. Attempts at standardizing the radiographic and functional outcome reporting techniques across multi-centre investigations and prospective cohorts will allow for more robust, reproducible analyses of significance to be conducted on DLS patients.