K Wade1, N Berger-Roscher1, T Saggese1, V Rasche2,3, H Wilke4. 1. Trauma Research Center Ulm (ZTF), Institute of Orthopedic Research and Biomechanics, Ulm University, Helmholtzstraße 14, 89081, Ulm, Germany. 2. Department of Internal Medicine II, University Hospital Ulm, Ulm, Germany. 3. Small Animal MRI, Medical Faculty, Ulm University, Ulm, Germany. 4. Trauma Research Center Ulm (ZTF), Institute of Orthopedic Research and Biomechanics, Ulm University, Helmholtzstraße 14, 89081, Ulm, Germany. hans-joachim.wilke@uni-ulm.de.
Abstract
PURPOSE: Both posture and loading rate are key factors in the herniation process and can determine the mechanism of disc failure. The aim of this study was to test the hypothesis that disruption visible with HR-MRI post-testing corresponds with microstructural features and further elucidate the mechanism by which this disruption weakens the disc. This will enable us to gain new insights into the herniation process. METHODS: Thirty ovine lumbar spinal segments were subjected to combinations of four loading conditions (0-12° flexion, 0-9° lateral bending, 0-4° axial rotation, 0-1500 N axial compression) for 1000 loading cycles at 2 Hz in a dynamic disc loading simulator. The discs were scanned in an ultra-high field MRI (11.7 T) then examined using brightfield microscopy to examine their microstructure. RESULTS: Four discs herniated and seven discs suffered nucleus displacement. These discs contained pre-existing defects in the central posterior annulus. Generally, following testing discs contained more posterior annulus disruption, Microstructural investigation revealed there was clear correspondence between HR-MRI and microstructural observations, and that the mid-outer annular-endplate junction had failed in all discs examined in this study. CONCLUSIONS: While all discs suffered outer annulus damage, only the discs containing pre-existing defects herniated. These pre-existing defects weakened the inner and mid annulus, allowing herniation to occur once the mid and outer annular wall was compromised. We propose this can occur during the degenerative cascade.
PURPOSE: Both posture and loading rate are key factors in the herniation process and can determine the mechanism of disc failure. The aim of this study was to test the hypothesis that disruption visible with HR-MRI post-testing corresponds with microstructural features and further elucidate the mechanism by which this disruption weakens the disc. This will enable us to gain new insights into the herniation process. METHODS: Thirty ovine lumbar spinal segments were subjected to combinations of four loading conditions (0-12° flexion, 0-9° lateral bending, 0-4° axial rotation, 0-1500 N axial compression) for 1000 loading cycles at 2 Hz in a dynamic disc loading simulator. The discs were scanned in an ultra-high field MRI (11.7 T) then examined using brightfield microscopy to examine their microstructure. RESULTS: Four discs herniated and seven discs suffered nucleus displacement. These discs contained pre-existing defects in the central posterior annulus. Generally, following testing discs contained more posterior annulus disruption, Microstructural investigation revealed there was clear correspondence between HR-MRI and microstructural observations, and that the mid-outer annular-endplate junction had failed in all discs examined in this study. CONCLUSIONS: While all discs suffered outer annulus damage, only the discs containing pre-existing defects herniated. These pre-existing defects weakened the inner and mid annulus, allowing herniation to occur once the mid and outer annular wall was compromised. We propose this can occur during the degenerative cascade.
Authors: Meredith L Schollum; Richard C Appleyard; Christopher B Little; James Melrose Journal: Spine (Phila Pa 1976) Date: 2010-10-15 Impact factor: 3.468
Authors: Kelly R Wade; Meredith L Schollum; Peter A Robertson; Ashvin Thambyah; Neil D Broom Journal: Spine (Phila Pa 1976) Date: 2016-08-01 Impact factor: 3.468
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