In which cases do surgeons specializing in total disc replacement perform fusion in patients with cervical spine symptoms?

Various designs of cervical total disc replacement (CTDR) have been introduced and employed in an attempt to avoid disadvantages of the fusion surgery. The purposes of this study were to evaluate the effects of the range of motion (ROM), the instantaneous center of rotation (ICR) and the facet joint force (FJF) with different constrained types of CTDR devices. A three-dimensional finite element (FE) model of intact cervical spine (C3-7) was made from CT scans of a normal person and validated. Postoperative FE models simulating CTDR implantation at the C5-6 disc space were made for CTDR-I (constrained design) and CTDR-II (nonconstrained design), respectively. Hybrid protocol (intact: 1 Nm) with a compressive follower load of 73.6 N was applied at the superior endplate of the C3 vertebral body. The inferior endplate of C7 vertebral body was constrained in all directions. At the index level, CTDR-I showed a higher increase in segmental motion and FJF than CTDR-II in extension, lateral bending and axial rotation. The CTDR-II with an elastomer-type core reproduced a near physiological ICR of the intact model in extension and axial rotation. Abnormal kinetic and kinematic changes related to the CTDR may induce surgical level problems and cause long-term failure of spinal surgery.

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Investigation into Cervical Spine Biomechanics Following Single, Multilevel and Hybrid Disc Replacement Surgery with Dynamic Cervical Implant and Fusion: A Finite Element Study

Bioengineering ◽

10.3390/bioengineering9010016 ◽

2022 ◽

Vol 9 (1) ◽

pp. 16

Author(s):

Muzammil Mumtaz ◽

Iman Zafarparandeh ◽

Deniz Ufuk Erbulut

Keyword(s):

Cervical Spine ◽

Standard Procedure ◽

Total Disc Replacement ◽

Disc Replacement ◽

Von Mises Stress ◽

Adjacent Segment ◽

Fusion Model ◽

Hybrid Surgery ◽

Maximum Increase ◽

Flexion Extension

Cervical fusion has been a standard procedure for treating abnormalities associated with the cervical spine. However, the reliability of anterior cervical discectomy and fusion (ACDF) has become arguable due to its adverse effects on the biomechanics of adjacent segments. One of the drawbacks associated with ACDF is adjacent segment degeneration (ASD), which has served as the base for the development of dynamic stabilization systems (DSS) and total disc replacement (TDR) devices for cervical spine. However, the hybrid surgical technique has also gained popularity recently, but its effect on the biomechanics of cervical spine is not well researched. Thus, the objective of this FE study was to draw a comparison among single-level, bi-level, and hybrid surgery with dynamic cervical implants (DCIs) with traditional fusion. Reductions in the range of motion (ROM) for all the implanted models were observed for all the motions except extension, compared to for the intact model. The maximum increase in the ROM of 42% was observed at segments C5–C6 in the hybrid DCI model. The maximum increase in the adjacent segment’s ROM of 8.7% was observed in the multilevel fusion model. The maximum von Mises stress in the implant was highest for the multilevel DCI model. Our study also showed that the shape of the DCI permitted flexion/extension relatively more compared to lateral bending and axial rotation.

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Biomechanical Characteristics of Cervical Spine After Total Disc Replacement

Transactions of the Korean Society of Mechanical Engineers A ◽

10.3795/ksme-a.2009.33.7.637 ◽

2009 ◽

Vol 33 (7) ◽

pp. 637-644 ◽

Cited By ~ 1

Author(s):

Won-Man Park ◽

Jeung-Woo Joo ◽

Kyung-Soo Kim ◽

Ki-Seok Lee ◽

Yoon-Hyuk Kim

Keyword(s):

Cervical Spine ◽

Total Disc Replacement ◽

Disc Replacement

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Effects of Removal of Uncinate Process in a Cervical Disc Replacement Model: A Finite Element Based Study

ASME 2007 Summer Bioengineering Conference ◽

10.1115/sbc2007-176673 ◽

2007 ◽

Cited By ~ 1

Author(s):

A. Faizan ◽

V. K. Goel ◽

M. Krishna ◽

T. Friesem

Keyword(s):

Finite Element ◽

Cervical Spine ◽

General Procedure ◽

Total Disc Replacement ◽

Uncinate Process ◽

Disc Replacement ◽

Cervical Disc ◽

Fe Model ◽

Disc Space ◽

Cervical Disc Replacement

Anterior surgical approach is commonly used for Total Disc Replacement (TDR) surgeries in the cervical spine. The general procedure includes removal of the nucleus and anterior annulus of the intervertebral disc. Resection of Anterior Longitudinal Ligaments (ALL) is often performed to enter the disc space. The cervical spine also contains a unique anatomical feature called Luschka’s joints. These “joints” are actually fissures in the disc which run approximately parallel to the uncinate processes. These joints are thought to provide biomechanical stability to the cervical spine. However, sometimes surgeons have to sacrifice the uncinate processes at the involved level as well. We hypothesized that the cervical spine loses stability if the uncinate processes are removed along with disc replacement. We used a Finite Element (FE) model of cervical spine to prove the hypothesis (Fig1).

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