General Session: MIS-1
Presented by: C.H. Kim - View Audio/Video Presentation (Members Only)
C.H. Kim(1), C.K. Chung(1)
(1) Seoul National University Hospital, Neurosurgery, Seoul, Korea, Republic of
Background: Lumbar spinal stenosis (LSS) is the most common lumbar degenerative disease, and sagittal imbalance is uncommon. Forward-bending posture, which is primarily caused by buckling of the ligamentum flavum, may be improved via simple decompression surgery.
Purpose: The objectives of this study were to identify the risk factors for sagittal imbalance and to describe the outcomes of simple decompression surgery.
Study Design: Retrospective nested case-control study
Patient Sample: This was a retrospective study that included 83 consecutive patients (M:F = 46:37; mean age, 68.5 ± 7.7 years) who underwent decompression surgery and a minimum of 12 months of follow-up. Outcome measurement: The primary endpoint was normalization of sagittal imbalance after decompression surgery.
Materials and Methods: Sagittal imbalance was defined as a C7-sagittal vertical axis (SVA) ≥ 40 mm on a 36-inch-long lateral whole spine radiograph. Logistic regression analysis was used to identify the risk factors for sagittal imbalance. Bilateral decompression was performed via a unilateral approach with a tubular retractor. The SVA was measured on serial radiographs performed 1, 3, 6 and 12 months postoperatively. The prognostic factors for sagittal balance recovery were determined based on various clinical and radiological parameters.
Results: Sagittal imbalance was observed in 54% (45/83) of patients, and its risk factors were old age and a large mismatch between pelvic incidence and lumbar lordosis. The 1-year normalization rate was 73% after decompression surgery, and the median time to normalization was 1 to 3 months. Patients who did not experience SVA normalization exhibited low thoracic kyphosis (HR, 1.04; 95% CI, 1.02 - 1.10) (p < 0.01) and spondylolisthesis (HR, 0.33; 95% CI, 0.17 - 0.61) prior to surgery.
Conclusions: Sagittal imbalance was observed in more than 50% of LSS patients, but this imbalance was correctable via simple decompression surgery in 70% of patients.