Preoperative disc angle is an important predictor of segmental lordosis after degenerative spondylolisthesis fusion

• Published in: Canadian Journal of Surgery 2022-12, Vol.65, p.S157-S157
• Main Authors: Thornley, Patrick, Glennie, Andrew, Alahmari, Abdulmajeed, Al-Jahdali, Fares, Fisher, Charles, Rampersaud, Raja, Urquhart, Jennifer, Bailey, Chris
• Format: Article
• Language: English
• Subjects: Vertebrae
• ISSN: 0008-428X; 1488-2310

Background: The aim of this study was to determine the effect of interbody cages inserted via the posterior approach on segmental lordosis in the setting of preoperative lordotic versus kyphotic/neutral disc spaces in patients with lumbar degenerative spondylolisthesis (LDS). Methods: Five consecutive years of retrospective data from a Canadian Spine Outcomes and Research Network (CSORN) prospective study on the assessment and management of patients with LDS were collected from 2 contributing centres of consecutively enrolled patients. Patients were analyzed preoperatively and at 12-month follow-up with standing lumbar radiographs. At the spondylolisthesis level, segmental lumbar lordosis (SLL) was measured from the upper end plate of the proximal vertebra to the lower end plate of the distal vertebra. Patients were stratified into 4 groups on the basis of the index level disc angle and the type of procedure performed: preoperative lordotic posterolateral fusion (PLF) (group 1), preoperative neutral/kyphotic PLF (group 2), preoperative lordotic interbody fusion (IF) (group 3) and preoperative neutral/kyphotic IF (group 4). Results: A total of 100 of 111 (90 %) patients completed 1-year follow-up. Twenty-three patients underwent PLF with 18 (18%) in group 1 and only 5 (5%) in group 2. Eighty-eight patients underwent IF, with 40 (40%) in group 3 and 48 in group 4 (48%). Among patients with preoperatively lordotic disc angles, group 3 patients had a greater magnitude of worsening in SLL than group 1 patients, with significant differences persisting at 1 year (mean difference 2.3°, 95% confidence interval 0.3 to 4.3, p = 0.029). Patients in group 4 were more likely to achieve improvement in SLL at 1 year than those in group 3 (67% v. 44%, p = 0.046), with similar mean improvement magnitude between groups 3 and 4 (-1.1, 95% CI -3.7 to 1.6, p = 0.42). Conclusion: In the setting of an index-level preoperative lordotic disc angle, the magnitude of segmental lordosis worsening was more pronounced when an interbody cage was used versus PLF. Patients who have kyphotic or neutral disc space preoperatively are more likely to gain lordosis when an interbody cage is used.