Biomechanical Analysis of a Pedicle Screw-Rod System with a Novel Cross-Link Configuration.
Yasuhiro Nakajima,Masahito Hara,Daisuke Umebayashi,Shoichi Haimoto,Yu Yamamoto,Yusuke Nishimura,Toshihiko Wakabayashi +6 more
TL;DR: A novel cross- link configuration that features cross-link devices passing through the base of the spinous processes increased the mechanical resistance in pullout and flexion-compression testing compared to un-cross-link constructs.
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Abstract: STUDY DESIGN The strength effects of a pedicle screw-rod system supplemented with a novel cross-link configuration were biomechanically evaluated in porcine spines. PURPOSE To assess the biomechanical differences between a conventional cross-link pedicle screw-rod system versus a novel cross-link instrumentation, and to determine the effect of the cross-links. OVERVIEW OF LITERATURE Transverse cross-link systems affect torsional rigidity, but are thought to have little impact on the sagittal motion of spinal constructs. We tested the strength effects in pullout and flexion-compression tests of novel cross-link pedicle screw constructs using porcine thoracic and lumbar vertebrae. METHODS Five matched thoracic and lumbar vertebral segments from 15 porcine spines were instrumented with 5.0-mm pedicle screws, which were then connected with 6.0-mm rods after partial corpectomy in the middle vertebral body. The forces required for construct failure in pullout and flexion-compression tests were examined in a randomized manner for three different cross-link configurations: un-cross-link control, conventional cross-link, and cross-link passing through the base of the spinous process. Statistical comparisons of strength data were analyzed using Student's t-tests. RESULTS The spinous process group required a significantly greater pullout force for construct failure than the control group (p=0.036). No difference was found between the control and cross-link groups, or the cross-link and spinous process groups in pullout testing. In flexion-compression testing, the spinous processes group required significantly greater forces for construct failure than the control and cross-link groups (p<0.001 and p=0.003, respectively). However, there was no difference between the control and cross-link groups. CONCLUSIONS A novel cross-link configuration that features cross-link devices passing through the base of the spinous processes increased the mechanical resistance in pullout and flexion-compression testing compared to un-cross-link constructs. This configuration provided more resistance to middle-column damage under flexion-compression testing than conventional cross-link configuration.
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Citations
Finite element analysis of human lumbar vertebrae in internal fixation system model with different bone density trajectories
TL;DR: Compared to traditional pedicle screw and traditional CBT, MCBT has better mechanical stability, and it is of certain clinical application value.
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TL;DR: In this paper , the authors evaluated the effects of cross-links insertion between rods on the fusion rates and post-surgical patients' satisfaction among patients with traumatic thoracolumbar fractures who underwent posterior spinal fixation with pedicle screws.
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The role of cross-link augmentation on fusion rate and patient satisfaction among patients with traumatic thoracolumbar spinal fracture: A randomized clinical trial.
Farhad Mirzaei,Arad Iranmehr,Ghaffar Shokouhi,Masoud Khadivi,Moslem Shakeri,Mohamad Namvar,Ebrahim Rafiei,Bagher Matloubi +7 more
TL;DR: In this paper, the authors evaluated the effects of cross-links insertion between rods on the fusion rates and post-surgical patients' satisfaction among patients with traumatic thoracolumbar fractures who underwent posterior spinal fixation with pedicle screws.
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References
Evaluation of proximal junctional kyphosis in adolescent idiopathic scoliosis following pedicle screw, hook, or hybrid instrumentation.
Melvin D. Helgeson,Suken A. Shah,Peter O. Newton,David H. Clements,Randal R. Betz,Michelle C. Marks,Tracey P. Bastrom +6 more
TL;DR: Adjacent level proximal kyphosis was significantly increased with pedicle screws, but the clinical significance of this is unclear, and a potential solution is the substitution of hooks at the upper-instrumented vertebrae, but further investigation is required.
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Mechanical evaluation of cross-link designs in rigid pedicle screw systems.
TL;DR: The use of cross‐linkage in spinal fusion increases torsional stiffness in pedicle screw and hook constructs and it is demonstrated that cross‐links do not increases stiffness in the lateral flexion mode.
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Mechanical stability of thoracolumbar pedicle screw fixation. The effect of crosslinks.
TL;DR: The rotational and bending stiffness values of thoracolumbar fractures fixed by the AO's internal fixation system with zero, one, or two crosslinks were determined and showed a clear trend toward increased stiffness with crosslinks.
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A modular spinal rod linkage system to provide rotational stability
Marc A. Asher,William L. Carson,Charles F. Heinig,Walter E. Strippgen,Marcia Arendt,Richard Lark,Mark Hartley +6 more
TL;DR: Cross linkage used in conjunction with sublaminar wires significantly improved torsional stability, improved lateral bending stability, and had no adverse affect on stability for axial, forward flexion, or extension loading when studied in an unstable fracture model using calf spine segments.
49
Torsional rigidity of scoliosis constructs.
TL;DR: With pedicle screws as distal anchors in scoliosis constructs, cross-linking with one or two devices adds very little additional rotational stiffness and may be unnecessary in many cases.
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