• Aaron J Buckland, Subaraman Ramchandran, Louis Day, Shay Bess, Themistocles Protopsaltis, Peter G Passias, Bassel G Diebo, Renaud Lafage, Virginie Lafage, Akhila Sure, and Thomas J Errico.
• Division of Spine Surgery, Department of Orthopaedic Surgery, NYU Hospital for Joint Diseases, 306 East 15th St, New York, NY 10003, USA. Electronic address: aaronbuckland@me.com.
• Spine J. 2017 Nov 1; 17 (11): 1601-1610.

Background ContextPatients with degenerative lumbar stenosis (DLS) adopt a forward flexed posture in an attempt to decompress neural elements. The relationship between sagittal alignment and severity of lumbar stenosis has not previously been studied.PurposeWe hypothesized that patients with increasing radiological severity of lumbar stenosis will exhibit worsening sagittal alignment.Study DesignThis is a cross-sectional study.Patient SampleOur sample consists of patients who have DLS.Outcome MeasuresStanding pelvic, regional, lower extremity and global sagittal alignment, and health-related quality of life (HRQoL) were the outcome measures.MethodsPatients with DLS were identified from a retrospective clinical database with corresponding full-body stereoradiographs. Exclusion criteria included coronal malalignment, prior spine surgery, spondylolisthesis>Grade 1, non-degenerative spinal pathology, or skeletal immaturity. Central stenosis severity was graded on axial T2-weighted magnetic resonance imaging (MRI) from L1-S1. Foraminal stenosis and supine lordosis was graded on sagittal T1-weighted images. Standing pelvic, regional, lower extremity, and global sagittal alignment were measured using validated software. The HRQoL measures were also analyzed in relation to severity of stenosis.ResultsA total of 125 patients were identified with DLS on appropriate imaging. As central stenosis grade increased, patients displayed significantly increasing standing T1 pelvic angle, pelvic tilt, sagittal vertical axis, and pelvic incidence-lumbar lordosis (p<.05). No significant difference wasfound in pelvic incidence, supine lordosis, thoracic kyphosis, or T1 spinopelvic inclination between central stenosis groups. Despite similar supine lordosis between stenosis groups, patients with Grades 2 and 3 stenosis had less standing lordosis, suggesting antalgic posturing. Upper lumbar (L1-L3) stenosis predicted worse alignment than lower lumbar (L4-S1) stenosis. Increasing severity of foraminal stenosis was associated with reduced lumbar lordosis; however, no significant postural difference in lordosis, thoracolumbar, or lower extremity compensatory mechanisms were noted between foraminal stenosis groups. Stenosis grading did not predict worsening HRQoLs in central or foraminal stenosis.ConclusionsSeverity of central lumbar stenosis as graded on MRI correlates with severity of sagittal malalignment. These findings support theories of sagittal malalignment as a compensatory mechanism for central lumbar stenosis.Copyright © 2017 Elsevier Inc. All rights reserved.

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