STUDY DESIGN: Biomechanical cadaveric study. OBJECTIVE: The aim of this study is to evaluate the effect of degeneration on biomechanical properties of the passive structures of the lumbar spine. SUMMARY OF BACKGROUND DATA: While the load apportionment among the passive structures in healthy spines follows well-defined contribution patterns, it remains unknown how this load distribution and sagittal preload changes by degenerative processes of the intervertebral disc (IVD). METHODS: 50 lumbar spinal segments were tested in a displacement-controlled stepwise reduction study in flexion, extension, axial rotation, lateral bending, anterior, posterior and lateral shear. The intertransverse ligaments (ITL), supraspinous and interspinous ligaments (ISL&SSL), facet joint capsules (FJC), facet joints (FJ), ligamentum flavum (LF), posterior longitudinal ligament (PLL), anterior longitudinal ligament (ALL) and spondylophytes (SP) were subsequently reduced. The results were set in relation to IVD-degeneration, quantified with Pfirrmann classification. RESULTS: In flexion, a load redistribution from LF (-28% n.s.) and PLL (-13% n.s.) towards the IVD (+9%, n.s.) is observed comparing grade 2 to 5 IVD degeneration, while in all other loading directions, a reduction of IVD-contribution from -12% to -53% is recorded. In axial rotation, anterior and lateral shear, more load is shared by the FJ (+4% n.s., +23% *, +13% n.s.). The preload of the ALL, LF, PLL and IVD is reduced ranging from -0.06 Nm to -0.37 Nm. CONCLUSION: IVD-degeneration is related to notable load-redistributions between the passive spinal structures. With further degeneration, reduced contribution of the LF and PLL and higher loads on the IVD are observed in flexion. In the other tested loading directions, the relative load on the IVD is reduced, while higher FJ-exposure in axial rotation, anterior and lateral shear is observed. Furthermore, the preload of the spinal structures is reduced. These observations can further the understanding of the degenerative cascade in the spine.Level of Evidence: N/A.
STUDY DESIGN: Biomechanical cadaveric study. OBJECTIVE: The aim of this study is to evaluate the effect of degeneration on biomechanical properties of the passive structures of the lumbar spine. SUMMARY OF BACKGROUND DATA: While the load apportionment among the passive structures in healthy spines follows well-defined contribution patterns, it remains unknown how this load distribution and sagittal preload changes by degenerative processes of the intervertebral disc (IVD). METHODS: 50 lumbar spinal segments were tested in a displacement-controlled stepwise reduction study in flexion, extension, axial rotation, lateral bending, anterior, posterior and lateral shear. The intertransverse ligaments (ITL), supraspinous and interspinous ligaments (ISL&SSL), facet joint capsules (FJC), facet joints (FJ), ligamentum flavum (LF), posterior longitudinal ligament (PLL), anterior longitudinal ligament (ALL) and spondylophytes (SP) were subsequently reduced. The results were set in relation to IVD-degeneration, quantified with Pfirrmann classification. RESULTS: In flexion, a load redistribution from LF (-28% n.s.) and PLL (-13% n.s.) towards the IVD (+9%, n.s.) is observed comparing grade 2 to 5 IVD degeneration, while in all other loading directions, a reduction of IVD-contribution from -12% to -53% is recorded. In axial rotation, anterior and lateral shear, more load is shared by the FJ (+4% n.s., +23% *, +13% n.s.). The preload of the ALL, LF, PLL and IVD is reduced ranging from -0.06 Nm to -0.37 Nm. CONCLUSION:IVD-degeneration is related to notable load-redistributions between the passive spinal structures. With further degeneration, reduced contribution of the LF and PLL and higher loads on the IVD are observed in flexion. In the other tested loading directions, the relative load on the IVD is reduced, while higher FJ-exposure in axial rotation, anterior and lateral shear is observed. Furthermore, the preload of the spinal structures is reduced. These observations can further the understanding of the degenerative cascade in the spine.Level of Evidence: N/A.
Authors: Marco D Burkhard; Frédéric Cornaz; José Miguel Spirig; Florian Wanivenhaus; Rafael Loucas; Marie-Rosa Fasser; Jonas Widmer; Mazda Farshad Journal: N Am Spine Soc J Date: 2021-11-17