Biomechanical Comparison of Posterior Fixation Combinations with an Allograft Spacer between the Lateral Mass and Pedicle Screws
Open Access
- 19 October 2020
- journal article
- research article
- Published by MDPI AG in Applied Sciences
- Vol. 10 (20), 7291
- https://doi.org/10.3390/app10207291
Abstract
Background: There are a few biomechanical studies that describe posterior fixation methods with pedicle screws (PS) and lateral mass screws (LMS); the combination of both screw types and their effect on an allograft spacer in a surgically treated cervical segment is unknown. Methods: Finite element model (FEM) analyses were used to investigate the effects of a hybrid technique using posterior PS and LMS. Stress distribution and subsidence risk from a combination of screws under hybrid motion control conditions, including flexion, extension, axial rotation, and lateral bending, were investigated to evaluate the biomechanical characteristics of different six-screw combinations. Findings: The load sharing on the allograft spacer in flexion mode was highest in the LMS model (74.6%) and lowest in the PS model (35.1%). The likelihood of subsidence of allograft spacer on C6 was highest in the screws from the distal LMS (type 5) model during flexion and extension (4.902 MPa, 30.1% and 2.189 MPa, 13.4%). In lateral bending, the left unilateral LMS (type 4) model screws on C5 (3.726 MPa, 22.9%) and C6 (2.994 MPa, 18.4%) yielded the greatest subsidence risks, because the lateral bending forces were supported by the LMS. In counterclockwise axial rotation, the left unilateral LMS (type 4) model screws on C5 (3.092 MPa, 19.0%) and C6 (3.076 MPa, 18.9%) demonstrated the highest subsidence risks. Conclusion: The asymmetrical ipsilateral use of LMS and posterior PS in lateral bending and axial rotation demonstrated the lowest stability and greatest subsidence risk. We recommend bilateral symmetrical insertion of LMS or posterior PS and posterior PS on distal vertebrae for increased stability and reduced risk of allograft spacer subsidence.This publication has 34 references indexed in Scilit:
- Comparison of Cervical Spine Biomechanics After Fixed- and Mobile-Core Artificial Disc ReplacementSpine, 2011
- Posterior cervical fixation following laminectomy: a stress analysis of three techniquesEuropean Spine Journal, 2011
- Do design variations in the artificial disc influence cervical spine biomechanics? A finite element investigationEuropean Spine Journal, 2009
- In vitro study of accuracy of cervical pedicle screw insertion using an electronic conductivity device (ATPS part III)European Spine Journal, 2009
- Hybrid multidirectional test method to evaluate spinal adjacent-level effectsClinical Biomechanics, 2007
- Finite element analysis of moment-rotation relationships for human cervical spineJournal of Biomechanics, 2006
- P66. How to Avoid Fatal Vascular Complications Caused by Cervical Pedicle Screws: A New Surgical Strategy and Techniques for Safe Screw PlacementThe Spine Journal, 2006
- Cobb Method or Harrison Posterior Tangent MethodSpine, 2000
- The Thickness of Human Vertebral Cortical Bone and its Changes in Aging and Osteoporosis: A Histomorphometric Analysis of the Complete Spinal Column from Thirty-Seven Autopsy SpecimensJournal of Bone and Mineral Research, 1997
- Transpedicular Screw Fixation for Traumatic Lesions of the Middle and Lower Cervical SpineJournal of SPINAL DISORDERS, 1994