Radiological lumbar stenosis severity predicts worsening sagittal malalignment on full-body standing stereoradiographs

Publication date: Available online 17 May 2017
Source:The Spine Journal
Author(s): Aaron J. Buckland, Subaraman Ramchandran, Louis Day, Shay Bess, Themistocles Protopsaltis, Peter G. Passias, Bassel G. Diebo, Renaud Lafage, Virginie Lafage, Akhila Sure, Thomas J. Errico
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) measures.MethodsDLS patients 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 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. HRQoL measures were also analyzed in relation to severity of stenosis.Results125 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<0.05). No significant difference was found in Pelvic Incidence, supine lordosis, thoracic kyphosis, or T1 Spinopelvic Inclination between central stenosis groups. Despite similar supine lordosis between stenosis groups, patients with grade 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.



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