Effect of posterolateral fusion versus posterior lumbar interbody fusion on sagittal radiographic parameters in adult patients with low-grade isthmic spondylolisthesis: a randomized controlled trial

Abstract

Abstract Background: This randomized controlled study aims to specifically investigate and compare the effects of posterolateral fusion (PLF) and posterior lumbar interbody fusion (PLIF) on sagittal radiographic parameters, and to evaluate the correlation between the changes in these parameters and the clinical outcome. Methods: A total of 42 patients with single level low-grade isthmic spondylolisthesis were included in the study. The patients were randomly allocated into 2 groups: PLF group (21 patients) and PLIF (group 21 patients). The mean age was 40.23 ± 10.25 years in the PLF group and 35.81 ± 10.58 in the PLIF group. Of the 42 patients, 13 cases were male and 29 cases were female. All patients had a follow-up period of at least 24 months. Radiographic outcomes included pelvic incidence (PI), pelvic tilt (PT), sacral slope (SS), lumbar lordosis (LL), sagittal vertical axis (SVA), T1 pelvic angle (TPA), slip angle (SA), slip degree (SD) and disc height (DH). Clinical outcomes were assessed by Oswestry Disability Index (ODI) and visual analogue scale (VAS). Results: Upon comparing postoperative measurements of both groups, only SA, SD and DH were significantly better in PLIF group. However, when comparing the means of correction (postoperative values- preoperative values), all radiographic parameters were found to be significantly better in PLIF group. Additionally, SA and DH showed significantly less correction loss in the PLIF group. ODI and VAS scores improved significantly in both groups during the final follow-up, with no significant differences between the two groups. Changes in ODI and VAS were significantlycorrelated with changes in SD, DH, and LL. Conclusion: PLIF exhibits greater strength in correcting sagittal radiographic parameters. Nevertheless, this difference does not seem to influence short-term clinical results. Notably, changes in DH, SA, and LL displayed significant correlations with changes in ODI and VAS, underscoring the importance of restoring disc height, rectifying slip angle, and reestablishing normal lumbar lordosis as crucial steps in the surgical management of isthmic spondylolisthesis. Trial registration ClinicalTrials.gov Identifier: NCT03877341, registered on March 15, 2019.