Radiological Improvements in Global Sagittal Alignment After Lumbar Decompression Without Fusion

STUDY DESIGN.A retrospective, radiographical study. OBJECTIVE.To evaluate short-term radiological changes in sagittal alignment after lumbar decompression without fusion for lumbar canal stenosis. SUMMARY OF BACKGROUND DATA.Although the importance of global sagittal balance is underscored recently, little is known about the changes in sagittal alignment after lumbar canal decompression. METHODS.We retrospectively reviewed 88 patients who underwent lumbar decompression without fusion at a single institution between November 2008 and May 2013, with a minimum follow-up of 5 months. Standing radiographs at the preoperative period and the final follow-up were assessed. Radiological parameters included the sagittal vertical axis (SVA), lumbar lordosis (LL), pelvic tilt, pelvic incidence (PI), occipital 7th cervical angle, and thoracic kyphosis, which were measured by 2 spine surgeons. The Zurich Claudication Questionnaire and visual analogue scale scores were obtained to assess the patient-based clinical outcomes. RESULTS.Both LL and thoracic kyphosis significantly increased postoperatively, whereas SVA, PI-LL (PI minus LL), and pelvic tilt significantly decreased (P < 0.05). There were no significant differences between the preoperative and postoperative occipital 7th cervical angle and PI. The amount of increment in LL was greater in patients with small preoperative LL. The improvement in SVA was greater in those with a large preoperative SVA. The Zurich Claudication Questionnaire and visual analogue scale scores showed no significant correlation with the radiological parameters. CONCLUSION.Lumbar decompression without fusion can induce a reactive improvement in the lumbar and global sagittal alignment even if a sagittal imbalance exists preoperatively.Level of Evidence4