Clinical and radiological outcomes of posterolateral fusion alone versus interbody fusion in single-level degenerative spondylolisthesis: A retrospective comparative study

Degenerative spondylolisthesis (DS) involves vertebral translation over a lower vertebra, often linked to degenerative changes. Risk factors include age, gender, body mass index, and sagittal facet orientation. Surgical options like posterolateral and interbody fusion exist, but the benefits of interbody fusion remain debated. This study aims to compare the efficacy of posterolateral fusion (PLF) versus interbody fusion in single-level DS. It evaluates both clinical outcomes, such as pain relief and improvement in radiculopathy symptoms, and radiological outcomes, including fusion success and pseudoarthrosis rates. Eighty-two patients were included: 53 had (PLF) alone, 29 had PLF with interbody fusion. All were adults (≥18) with single-level degenerative lumbar spondylolisthesis (Meyerding Grade I/II) confirmed by radiographs and magnetic resonance imaging, with >12 months follow-up. Outcomes measured with the visual analog scale (VAS) for low back pain and the Oswestry Disability Index (ODI); radiographs assessed fusion (Bridwell Grades I/II) and disc height. SPSS version 28.0 was used to analyze the data; P < .05 was considered significant. The minimal clinically important difference for ODI was defined based on previously published thresholds. The interbody fusion group demonstrated significantly higher fusion success (92% vs 68%, P = .008) and greater disc height restoration (mean difference: 2.6 mm, P < .001), particularly at the L4 to L5 level. Both groups showed comparable improvements in VAS and ODI scores. The interbody fusion group had a longer operative time (mean difference: 70 minutes, P < .001) and a higher complication rate (24.1% vs 7.5%, P = .04). Multivariate analysis confirmed that interbody fusion was associated with higher odds of fusion success and greater restoration of disc height. While interbody fusion offers superior radiographic outcomes, especially at L4 to L5, it does not necessarily translate into better clinical outcomes. It is associated with increased operative time and complication rates compared to PLF alone.