• Zhiwei Ren, An Liu, Kaixiang Yang, Dalin Wang, Zorica Buser, and Jeffrey C Wang.
• Department of Orthopaedic Surgery, Elaine Stevely Hoffman Medical Research Center, Keck School of Medicine, University of Southern California, HMR 710, 2011 Zonal Avenue, Los Angeles, CA, 90033, USA.
• Eur Spine J. 2017 Aug 1; 26 (8): 1999-2006.

PurposeTo investigate the changes of lumbar neural foramina size during dynamic motion using positional MRI.MethodsTwo hundred and fifty neural foramina from 50 patients were analyzed. Lumbar foraminal height, width, and area parameters from L1 to S1 were evaluated for changes in extension, neutral, and flexion positions on T2 parasagittal positional MRI images, and were correlated to lumbar angular motion. One-way analysis of variance (ANOVA) and post hoc analysis were used to examine the differences between levels and positions.ResultsCompared to the neutral position, almost all lumbar foraminal parameters (height, width at inferior level, and area) increased in flexion and decreased in extension at all levels, except for L5-S1 foraminal width at superior and middle levels. The foraminal height and area in all lumbar segments except L5-S1 increased as the lumbar angular motion changed from extension to flexion in <40° group. The foraminal width increased significantly at L3-4 and L4-5 among all groups.ConclusionLumbar foraminal dimensions increased in flexion compared to neutral and extension positions. Lumbar angular motion contributed to the changes of foraminal height and area at most of the segments, while it affected foraminal width only at L3-4 and L4-5. This information can be useful in the understanding of patient symptoms and the correlation with the imaging studies with dynamic foraminal stenosis. Furthermore, data from our study may help with patient positioning for foraminal injections or endoscopic surgery.

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