Radiologic and Clinical Evaluation of Posterolateral Versus Transforaminal Interbody Fusion in Degenerative Lumbar Spondylolisthesis.

STUDY DESIGN: Retrospective cohort study.

OBJECTIVE: The primary objective is to compare foraminal height (FH) and disk height (DH) differences in posterolateral (PLF) and transforaminal interbody fusions (TLIFs) and secondarily correlate these measurements with patient-reported outcomes.

BACKGROUND: The impact FH has on patient outcomes in degenerative lumbar spinal fusion surgery is unknown. Postoperative FH change and how it relates to patient-reported outcomes in posteriorly based procedures has not been well evaluated.

METHODS: A retrospective review of a subset of patients from a prospective cohort from the Canadian Spine Outcomes and Research Network was undertaken. Radiographic assessment preoperatively, at 3 months and 1 year, with standing lumbar spine radiographs were completed. FH and DH were recorded at each time interval, differences between groups were compared, and correlations with patient-reported outcomes were assessed.

RESULTS: One hundred nine patients were included (23 PLF and 86 TLIF). At 3-month follow-up, the change in FH was greater in the TLIF group (mean difference =2.3; 95% CI: 0.8-3.5, P=0.002). The change in FH remained significantly different at 12 months (mean difference=1.6, 95% CI: 0.2, 3.0 mm, P=0.028). The change in DH was greater in the TLIF group, with a mean difference between groups of 4.1 mm (95% CI: 2.5, 5.7, P<0.001) and 3.6 mm (95% CI: 2.0, 5.3, P<0.001). A positive change in FH correlated with less back pain, less disability, and improved physical function in the TLIF group (P<0.05).

CONCLUSIONS: Patients treated with PLF lost FH over time. An increased difference in FH at 1 year was associated with improved function and less back pain in the TLIF group.