S-line as Predictor of Clinical Outcome for Patients Undergone Transforaminal Lumbar Interbody Fusion for Lumbar Spinal Stenosis

Background: Some have speculated that LSTV has an impact on lumbar curve. A retrospective study was conducted to evaluate S-line as predictor of clinical outcome for patients undergone transforaminal lumbar interbody fusion for lumbar spinal stenosis.Methods: 126 patients undergoing transforaminal lumbar interbody fusion were enrolled. S-line stands for the connecting line between the highest points of the iliac crests on both sides. The patients were divided into two groups according to the position of S-line, S-line (-) group included patients whose S-line were between L4 and L5, and S-line (+) group included patients whose S-line is above or below this range, which were divided into two subgroups. Their pre-operative imaging data about sagittal alignment were collected, including lumbar lordosis (LL), sacral slope (SS), pelvic incidence (PI) and pelvic tilt (PT). Clinical outcomes were measured using Japanese Orthopaedic Association (JOA) scores, the Oswestry disability index (ODI), visual analog scale (VAS) before the surgery and postoperatively. The correlation of S-line and clinical outcomes, as well as sagittal alignment and clinical outcomes, were analyzed.Results: LL, SS, PI, PT and PI minus(-) LL of S-line (-) group were (45.39°±12.68°), (30.27°±10.55°), (43.32°±12.22°), (13.05°±6.52°), (-2.07°±8.20°), respectively, and those parameters of S-line (+) group were (40.29±14.92), (35.70°±14.09°), (52.59°±17.07°), (16.89°±8.24°), (12.30°±9.98°), respectively. Significant difference were seen in the above parameters between S-line (-) and S-line (+) group. For S-line (-) and S-line (+) group, post-operative JOA score were (22.39±2.12), (20.26±2.46), post-operative VAS were (2.07±0.88), (3.14±1.47), the post-operative ODI were (8.36±3.28), (11.82±3.32), the improvement rate is (0.61±0.13), (0.55±0.15), Significant differences of those parameters are seen between S-line (-) group and S-line (+) group.Conclusion: S-line is a reliable predictor of clinical outcome for patients undergone transforaminal lumbar interbody fusion for lumbar spinal stenosis.