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Adjacent segments biomechanics following lumbar fusion surgery: a musculoskeletal finite element model study

Ebrahimkhani, M ; Sharif University of Technology | 2022

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  1. Type of Document: Article
  2. DOI: 10.1007/s00586-022-07262-3
  3. Publisher: Springer Science and Business Media Deutschland GmbH , 2022
  4. Abstract:
  5. Purpose: This study exploits a novel musculoskeletal finite element (MS-FE) spine model to evaluate the post-fusion (L4–L5) alterations in adjacent segment kinetics. Methods: Unlike the existing MS models with idealized representation of spinal joints, this model predicts stress/strain distributions in all passive tissues while organically coupled to a MS model. This generic (in terms of musculature and material properties) model uses population-based in vivo vertebral sagittal rotations, gravity loads, and an optimization algorithm to calculate muscle forces. Simulations represent individuals with an intact L4–L5, a preoperative severely degenerated L4–L5 (by reducing the disc height by ~ 60% and removing the nucleus incompressibility), and a postoperative fused L4–L5 segment with either a fixed or an altered lumbopelvic rhythm with respect to the intact condition (based on clinical observations). Changes in spine kinematics and back muscle cross-sectional areas (due to intraoperative injuries) are considered based on in vivo data while simulating three activities in upright/flexed postures. Results: Postoperative changes in some adjacent segment kinetics were found considerable (i.e., larger than 25%) that depended on the postoperative lumbopelvic kinematics and preoperative L4–L5 disc condition. Postoperative alterations in adjacent disc shear, facet/ligament forces, and annulus stresses/strains were greater (> 25%) than those found in intradiscal pressure and compression (< 25%). Kinetics of the lower (L5–S1) and upper (L3–L4) adjacent segments were altered to different degrees. Conclusion: Alterations in segmental rotations mainly affected adjacent disc shear forces, facet/ligament forces, and annulus/collagen fibers stresses/strains. An altered lumbopelvic rhythm (increased pelvis rotation) tends to mitigate some of these surgically induced changes. © 2022, The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature
  6. Keywords:
  7. Adjacent segments ; Lumbar fusion surgery ; Musculoskeletal finite element model ; Spine loads ; Biomechanics ; Clinical observation ; Controlled study ; Finite element analysis ; Force ; Gravity ; Human ; In vivo study ; Intervertebral disk ; Kinematics ; Musculoskeletal system ; Preoperative evaluation ; Rotation ; Simulation ; Spine fusion ; Biomechanics ; Joint characteristics and functions ; Lumbar vertebra ; Physiology ; Procedures ; Surgery ; Biomechanical phenomena ; Humans ; Intervertebral disc ; Lumbar vertebrae ; Range of motion, articular ; Spinal fusion
  8. Source: European Spine Journal ; Volume 31, Issue 7 , 2022 , Pages 1630-1639 ; 09406719 (ISSN)
  9. URL: https://link.springer.com/article/10.1007/s00586-022-07262-3