Biomechanical Assessment of Anchored Cervical Interbody Cages: Comparison of 2-Screw and 4-Screw Designs

2014 ◽  
Vol 10 (3) ◽  
pp. 412-417 ◽  
Author(s):  
Marco T. Reis ◽  
Phillip M. Reyes ◽  
Neil R. Crawford
Keyword(s):  
Axial Rotation ◽  
Anterior Plate ◽  
Biomechanical Assessment ◽  
Loading Mode ◽  
Variable Angle ◽  
Flexion Extension ◽  
Standard Plate ◽  
Vertebral Bodies ◽  
The Stability

Abstract BACKGROUND: A new anchored cervical interbody polyetheretherketone spacer was devised that uses only 2 integrated variable-angle screws diagonally into the adjacent vertebral bodies instead of the established device that uses 4 diagonal fixed-angle screws. OBJECTIVE: To compare in vitro the stability provided by the new 2-screw interbody spacer with that of the 4-screw spacer and a 4-screw anterior plate plus independent polyetheretherketone spacer. METHODS: Three groups of cadaveric specimens were tested with 2-screw anchored cage (n = 8), 4-screw anchored cage (n = 8), and standard plate/cage (n = 16). Pure moments (1.5 Nm) were applied to induce flexion, extension, lateral bending, and axial rotation while measuring 3-D motion optoelectronically. RESULTS: In all 3 groups, the mean range of motion (ROM) and lax zone were significantly reduced relative to the intact spine after discectomy and fixation. The 2-screw anchored cage allowed significantly greater ROM (P < .05) than the standard plate during flexion, extension, and axial rotation and allowed significantly greater ROM than the 4-screw cage during extension and axial rotation. The 4-screw anchored cage did not allow significantly different ROM or lax zone than the standard plate during any loading mode. CONCLUSION: The 2-screw variable-angle anchored cage significantly reduces ROM relative to the intact spine. Greater stability can be achieved, especially during extension and axial rotation, by using the 4-screw cage or standard plate plus cage.

Numerical investigation on the stability of human upper cervical spine (C1–C3)

2021 ◽  
pp. 1-13
Author(s):  
Waseem Ur Rahman ◽  
Wei Jiang ◽  
Guohua Wang ◽  
Zhijun Li
Keyword(s):  
Finite Element ◽  
Cervical Spine ◽  
Axial Rotation ◽  
Upper Cervical Spine ◽  
Fe Model ◽  
Facet Joints ◽  
Flexion Extension ◽  
Upper Cervical ◽  
The Stability

BACKGROUND: The finite element method (FEM) is an efficient and powerful tool for studying human spine biomechanics. OBJECTIVE: In this study, a detailed asymmetric three-dimensional (3D) finite element (FE) model of the upper cervical spine was developed from the computed tomography (CT) scan data to analyze the effect of ligaments and facet joints on the stability of the upper cervical spine. METHODS: A 3D FE model was validated against data obtained from previously published works, which were performed in vitro and FE analysis of vertebrae under three types of loads, i.e. flexion/extension, axial rotation, and lateral bending. RESULTS: The results show that the range of motion of segment C1–C2 is more flexible than that of segment C2–C3. Moreover, the results from the FE model were used to compute stresses on the ligaments and facet joints of the upper cervical spine during physiological moments. CONCLUSION: The anterior longitudinal ligaments (ALL) and interspinous ligaments (ISL) are found to be the most active ligaments, and the maximum stress distribution is appear on the vertebra C3 superior facet surface under both extension and flexion moments.

scholarly journals Biomechanical evaluation of an integrated fixation cage during fatigue loading: a human cadaver study

2017 ◽  
Vol 26 (4) ◽  
pp. 524-531 ◽  
Author(s):  
Vivek Palepu ◽  
Jonathan H. Peck ◽  
David D. Simon ◽  
Melvin D. Helgeson ◽  
Srinidhi Nagaraja
Keyword(s):  
Mechanical Stability ◽  
Fatigue Testing ◽  
Plate Fixation ◽  
Fatigue Loading ◽  
Axial Rotation ◽  
Cadaver Study ◽  
Anterior Plate ◽  
Stability Parameters ◽  
Loading Mode ◽  
Flexion Extension

OBJECTIVE Lumbar cages with integrated fixation screws offer a low-profile alternative to a standard cage with anterior supplemental fixation. However, the mechanical stability of integrated fixation cages (IFCs) compared with a cage with anterior plate fixation under fatigue loading has not been investigated. The purpose of this study was to compare the biomechanical stability of a screw-based IFC with a standard cage coupled with that of an anterior plate under fatigue loading. METHODS Eighteen functional spinal units were implanted with either a 4-screw IFC or an anterior plate and cage (AP+C) without integrated fixation. Flexibility testing was conducted in flexion-extension (FE), lateral bending (LB), and axial rotation (AR) on intact spines, immediately after device implantation, and post-fatigue up to 20,000 cycles of FE loading. Stability parameters such as range of motion (ROM) and lax zone (LZ) for each loading mode were compared between the 2 constructs at multiple stages of testing. In addition, construct loosening was quantified by subtracting post-instrumentation ROM from post-fatigue ROM. RESULTS IFC and AP+C configurations exhibited similar stability (ROM and LZ) at every stage of testing in FE (p ≥ 0.33) and LB (p ≥ 0.23) motions. In AR, however, IFCs had decreased ROM compared with AP+C constructs at pre-fatigue (p = 0.07) and at all post-fatigue time points (p ≤ 0.05). LZ followed a trend similar to that of ROM in AR. ROM increased toward intact motion during fatigue cycling for AP+C and IFC implants. IFC specimens remained significantly (p < 0.01) more rigid than specimens in the intact condition during fatigue for each loading mode, whereas AP+C construct motion did not differ significantly (p ≥ 0.37) in FE and LB and was significantly greater (p < 0.01) in AR motion compared with intact specimens after fatigue. Weak to moderate correlations (R2 ≤ 56%) were observed between T-scores and construct loosening, with lower T-scores leading to decreased stability after fatigue testing. CONCLUSIONS These data indicate that a 4-screw IFC design provides fixation similar to that provided by an AP+C construct in FE and LB during fatigue testing and better stability in AR motion.

In vitro biomechanical analysis of three anterior thoracolumbar implants

2000 ◽  
Vol 93 (2) ◽  
pp. 252-258 ◽  
Author(s):  
Patrick W. Hitchon ◽  
Vijay K. Goel ◽  
Thomas N. Rogge ◽  
James C. Torner ◽  
Andrew P. Dooris ◽  
...  
Keyword(s):  
Axial Rotation ◽  
Biomechanical Analysis ◽  
Rigid Fixation ◽  
Angular Rotation ◽  
Content Type ◽  
Light Emitting ◽  
Vertebral Bodies ◽  
The Stability ◽  
Fine Print

Object. The goal of this study was to evaluate the comparative efficacy of three commonly used anterior thoracolumbar implants: the anterior thoracolumbar locking plate (ATLP), the smooth-rod Kaneda (SRK), and the Z-plate. Methods. In vitro testing was performed using the T9—L3 segments of human cadaver spines. An L-1 corpectomy was performed, and stabilization was achieved using one of three anterior devices: the ATLP in nine spines, the SRK in 10, and the Z-plate in 10. Specimens were load tested with 1.5-, 3-, 4.5-, and 6-Nm in flexion and extension, right and left lateral bending, and right and left axial rotation. Angular motion was monitored using two video cameras that tracked light-emitting diodes attached to the vertebral bodies. Testing was performed in the intact state in spines stabilized with one of the three aforementioned devices after the devices had been fatigued to 5000 cycles at ± 3 Nm and after bilateral facetectomy. There was no difference in the stability of the intact spines with use of the three devices. There were no differences between the SRK- and Z-plate—instrumented spines in any state. In extension testing, the mean angular rotation (± standard deviation) of spines instrumented with the SRK (4.7 ± 3.2°) and Z-plate devices (3.3 ± 2.3°) was more rigid than that observed in the ATLP-stabilized spines (9 ± 4.8°). In flexion testing after induction of fatigue, however, only the SRK (4.2 ± 3.2°) was stiffer than the ATLP (8.9 ± 4.9°). Also, in extension postfatigue, only the SRK (2.4 ± 3.4°) provided more rigid fixation than the ATLP (6.4 ± 2.9°). All three devices were equally unstable after bilateral facetectomy. The SRK and Z-plate anterior thoracolumbar implants were both more rigid than the ATLP, and of the former two the SRK was stiffer. Conclusions. The authors' results suggest that in cases in which profile and ease of application are not of paramount importance, the SRK has an advantage over the other two tested implants in achieving rigid fixation immediately postoperatively.

scholarly journals Evaluation of Two Novel Integrated Stand-Alone Spacer Designs Compared with Anterior and Anterior-Posterior Single-Level Lumbar Fusion Techniques: An <italic>In Vitro</italic> Biomechanical Investigation

2017 ◽  
Vol 11 (6) ◽  
pp. 854-862 ◽  
Author(s):  
Craig A. Kuhns ◽  
Jonathan A. Harris ◽  
Mir M. Hussain ◽  
Aditya Muzumdar ◽  
Brandon S. Bucklen ◽  
...  
Keyword(s):  
Lumbar Fusion ◽  
Pedicle Screws ◽  
Axial Rotation ◽  
Disc Disease ◽  
Screw Design ◽  
Biomechanical Investigation ◽  
Flexion Extension ◽  
The Stability ◽  
Marginal Improvement

<sec><title>Study Design</title><p><italic>In vitro</italic> biomechanical investigation.</p></sec><sec><title>Purpose</title><p>To compare the biomechanics of integrated three-screw and four-screw anterior interbody spacer devices and traditional techniques for treatment of degenerative disc disease.</p></sec><sec><title>Overview of Literature</title><p>Biomechanical literature describes investigations of operative techniques and integrated devices with four dual-stacked, diverging interbody screws; four alternating, converging screws through a polyether-ether-ketone (PEEK) spacer; and four converging screws threaded within the PEEK spacer. Conflicting reports on the stability of stand-alone devices and the influence of device design on biomechanics warrant investigation.</p></sec><sec><title>Methods</title><p>Fourteen cadaveric lumbar spines were divided randomly into two equal groups (n=7). Each spine was tested intact, after discectomy (injured), and with PEEK interbody spacer alone (S), anterior lumbar plate and spacer (AP+S), bilateral pedicle screws and spacer (BPS+S), circumferential fixation with spacer and anterior lumbar plate supplemented with BPS, and three-screw (SA3s) or four-screw (SA4s) integrated spacers. Constructs were tested in flexion-extension (FE), lateral bending (LB), and axial rotation (AR). Researchers performed one-way analysis of variance and independent <italic>t</italic>-testing (<italic>p</italic>≤0.05).</p></sec><sec><title>Results</title><p>Instrumented constructs showed significantly decreased motion compared with intact except the spacer-alone construct in FE and AR (<italic>p</italic>≤0.05). SA3s showed significantly decreased range of motion (ROM) compared with AP+S in LB (<italic>p</italic>≤0.05) and comparable ROM in FE and AR. The three-screw design increased stability in FE and LB with no significant differences between integrated spacers or between integrated spacers and BPS+S in all loading modes.</p></sec><sec><title>Conclusions</title><p>Integrated spacers provided fixation statistically equivalent to traditional techniques. Comparison of three-screw and four-screw integrated anterior lumbar interbody fusion spacers revealed no significant differences, but the longer, larger-diameter interbody spacer with three-screw design increased stabilization in FE and LB; the diverging four-screw design showed marginal improvement during AR.</p></sec>

Is intervertebral disc degeneration related to segmental instability? An evaluation with two different grading systems based on clinical imaging

2017 ◽  
Vol 59 (3) ◽  
pp. 327-335 ◽  
Author(s):  
David Volkheimer ◽  
Fabio Galbusera ◽  
Christian Liebsch ◽  
Sabine Schlegel ◽  
Friederike Rohlmann ◽  
...  
Keyword(s):  
Intervertebral Disc Degeneration ◽  
Statistical Significance ◽  
Axial Rotation ◽  
Spinal Motion ◽  
X Ray ◽  
Grading Systems ◽  
Flexion Extension ◽  
The Difference ◽  
Magnetic Resonance Imaging Mri

Background Several in vitro studies investigated how degeneration affects spinal motion. However, no consensus has emerged from these studies. Purpose To investigate how degeneration grading systems influence the kinematic output of spinal specimens. Material and Methods Flexibility testing was performed with ten human T12-S1 specimens. Degeneration was graded using two different classifications, one based on X-ray and the other one on magnetic resonance imaging (MRI). Intersegmental rotation (expressed by range of motion [ROM] and neutral zone [NZ]) was determined in all principal motion directions. Further, shear translation was measured during flexion/extension motion. Results The X-ray grading system yielded systematically lesser degeneration. In flexion/extension, only small differences in ROM and NZ were found between moderately degenerated motion segments, with only NZ for the MRI grading reaching statistical significance. In axial rotation, a significant increase in NZ for moderately degenerated segments was found for both grading systems, whereas the difference in ROM was significant only for the MRI scheme. Generally, the relative increases were more pronounced for the MRI classification compared to the X-ray grading scheme. In lateral bending, only relatively small differences between the degeneration groups were found. When evaluating shear translations, a non-significant increase was found for moderately degenerated segments. Motion segment segments tended to regain stability as degeneration progressed without reaching the level of statistical significance. Conclusion We found a fair agreement between the grading schemes which, nonetheless, yielded similar degeneration-related effects on intersegmental kinematics. However, as the trends were more pronounced using the Pfirrmann classification, this grading scheme appears superior for degeneration assessment.

New anterior controllable antedisplacement and fusion surgery for cervical ossification of the posterior longitudinal ligament: a biomechanical study

2022 ◽  
pp. 1-9
Keyword(s):  
Fatigue Loading ◽  
Axial Rotation ◽  
Posterior Longitudinal Ligament ◽  
Cyclic Fatigue ◽  
Biomechanical Study ◽  
Biomechanical Stability ◽  
Loading Test ◽  
Crossover Effect ◽  
Flexion Extension

OBJECTIVE The traditional anterior approach for multilevel severe cervical ossification of the posterior longitudinal ligament (OPLL) is demanding and risky. Recently, a novel surgical procedure—anterior controllable antedisplacement and fusion (ACAF)—was introduced by the authors to deal with these problems and achieve better clinical outcomes. However, to the authors’ knowledge, the immediate and long-term biomechanical stability obtained after this procedure has never been evaluated. Therefore, the authors compared the postoperative biomechanical stability of ACAF with those of more traditional approaches: anterior cervical discectomy and fusion (ACDF) and anterior cervical corpectomy and fusion (ACCF). METHODS To determine and assess pre- and postsurgical range of motion (ROM) (2 Nm torque) in flexion-extension, lateral bending, and axial rotation in the cervical spine, the authors collected cervical areas (C1–T1) from 18 cadaveric spines. The cyclic fatigue loading test was set up with a 3-Nm cycled load (2 Hz, 3000 cycles). All samples used in this study were randomly divided into three groups according to surgical procedures: ACDF, ACAF, and ACCF. The spines were tested under the following conditions: 1) intact state flexibility test; 2) postoperative model (ACDF, ACAF, ACCF) flexibility test; 3) cyclic loading (n = 3000); and 4) fatigue model flexibility test. RESULTS After operations were performed on the cadaveric spines, the segmental and total postoperative ROM values in all directions showed significant reductions for all groups. Then, the ROMs tended to increase during the fatigue test. No significant crossover effect was detected between evaluation time and operation method. Therefore, segmental and total ROM change trends were parallel among the three groups. However, the postoperative and fatigue ROMs in the ACCF group tended to be larger in all directions. No significant differences between these ROMs were detected in the ACDF and ACAF groups. CONCLUSIONS This in vitro biomechanical study demonstrated that the biomechanical stability levels for ACAF and ACDF were similar and were both significantly greater than that of ACCF. The clinical superiority of ACAF combined with our current results showed that this procedure is likely to be an acceptable alternative method for multilevel cervical OPLL treatment.

In vitro 3D-kinematics of the upper cervical spine: helical axis and simulation for axial rotation and flexion extension

2009 ◽  
Vol 32 (2) ◽  
pp. 141-151 ◽  
Author(s):  
Pierre-Michel Dugailly ◽  
Stéphane Sobczak ◽  
Victor Sholukha ◽  
Serge Van Sint Jan ◽  
Patrick Salvia ◽  
...  
Keyword(s):  
Cervical Spine ◽  
Axial Rotation ◽  
Helical Axis ◽  
Upper Cervical Spine ◽  
3D Kinematics ◽  
Flexion Extension ◽  
Upper Cervical

Immediate Stiffness of the C5–C6 Segment after Discectomy with the Cloward Technique: An in Vitro Biomechanical Study on a Human Cadaveric Model

Neurosurgery ◽  
2001 ◽  
Vol 49 (6) ◽  
pp. 1399-1408 ◽  
Author(s):  
Andrzej Maciejczak ◽  
Michał Ciach ◽  
Maciej Radek ◽  
Andrzej Radek ◽  
Jan Awrejcewicz
Keyword(s):  
Interbody Fusion ◽  
Spinal Instrumentation ◽  
Axial Rotation ◽  
Postoperative Management ◽  
Biomechanical Study ◽  
Lateral Bending ◽  
Cervical Discectomy ◽  
Cloward Procedure ◽  
Flexion Extension

ABSTRACT OBJECTIVE To determine whether the Cloward technique of cervical discectomy and fusion increases immediate postoperative stiffness of single cervical motion segment after application of interbody dowel bone graft. METHODS We measured and compared the stiffness of single-motion segments in cadaveric cervical spines before and immediately after interbody fusion with the Cloward technique. Changes in range of motion and stiffness of the C5–C6 segment were measured in a bending flexibility test (flexion, extension, lateral bending and axial rotation) before and after a Cloward procedure in 11 fresh-frozen human cadaveric specimens from the 4th through the 7th vertebrae. RESULTS The Cloward procedure produced a statistically significant increase in stiffness of the operated segment in flexion and lateral bending when compared with the intact spine. The less stiff the segment before the operation, the greater the increase in its postoperative flexural stiffness (statistically significant). The Cloward procedure produced nonuniform changes in rotational and extensional stiffness that increased in some specimens and decreased in others. CONCLUSION Our data demonstrate that Cloward interbody fusion increases immediate postoperative stiffness of an operated segment only in flexion and lateral bending in cadaveric specimens in an in vitro environment. Thus, Cloward fusion seems a relatively ineffective method for increasing the stiffness of a construct. This may add to discussion on the use of spinal instrumentation and postoperative management of patients after cervical discectomy, which varies from bracing in hard collars through immobilization in soft collars to no external orthosis.

scholarly journals A Biomechanical Evaluation of a Next-Generation Integrated and Modular ACDF Device Possessing Full-Plate, Half-Plate, and No-Profile Fixation Iterations

2019 ◽  
Vol 9 (8) ◽  
pp. 826-833
Author(s):  
Ripul Panchal ◽  
Anup Gandhi ◽  
Chris Ferry ◽  
Sam Farmer ◽  
Jeremy Hansmann ◽  
...  
Keyword(s):  
Plate Fixation ◽  
Testing Machine ◽  
Axial Rotation ◽  
Biomechanical Study ◽  
The Novel ◽  
Novel Device ◽  
Plate Group ◽  
Flexion Extension ◽  
Group 2

Study Design: In vitro biomechanical study. Objectives: The objective of this in vitro biomechanical range-of-motion (ROM) study was to evaluate spinal segmental stability following fixation with a novel anterior cervical discectomy and fusion (ACDF) device (“novel device”) that possesses integrated and modular no-profile, half-plate, and full-plate fixation capabilities. Methods: Human cadaveric (n = 18, C3-T1) specimens were divided into 3 groups (n = 6/group). Each group would receive one novel device iteration. Specimen terminal ends were potted. Each specimen was first tested in an intact state, followed by anterior discectomy (C5/C6) and iterative instrumentation. Testing order: (1) novel device (group 1, no-profile; group 2, half-plate; group 3, full-plate); (2) novel device (all groups) with lateral mass screws (LMS); (3) traditional ACDF plate + cage; (4) traditional ACDF plate + cage + LMS. A 2 N·m moment was applied in flexion/extension (FE), lateral bending (LB), and axial rotation (AR) via a kinematic testing machine. Segmental ROM was tracked and normalized to intact conditions. Comparative statistical analyses were performed. Results: Key findings: (1) the novel half- and full-plate constructs provided comparable reduction in FE and LB ROM to that of traditional plated ACDF ( P ≥ .05); (2) the novel full-plate construct significantly exceeded all other anterior-only constructs ( P ≤ .05) in AR ROM reduction; and (3) the novel half-plate construct significantly exceeded the no-profile construct in FE ( P < .05). Conclusions: The novel ACDF device may be a versatile alternative to traditional no-profile and independent plating techniques, as it provides comparable ROM reduction in all principle motion directions, across all device iterations.

Biomechanics of a Novel Minimally Invasive Lumbar Interspinous Spacer: Effects on Kinematics, Facet Loads, and Foramen Height

2010 ◽  
Vol 66 (suppl_1) ◽  
pp. ons-126-ons-133 ◽  
Author(s):  
Bruno C.R. Lazaro ◽  
Leonardo B.C. Brasiliense ◽  
Anna G.U. Sawa ◽  
Phillip M. Reyes ◽  
Nicholas Theodore ◽  
...  
Keyword(s):  
Range Of Motion ◽  
Axial Rotation ◽  
Surface Strain ◽  
Interspinous Spacer ◽  
Instantaneous Axis Of Rotation ◽  
Flexion Extension ◽  
Before And After ◽  
Biomechanical Effect ◽  
Foraminal Height

Abstract Objective: To study the alteration to normal biomechanics after insertion of a lumbar interspinous spacer (ISS) in vitro by nondestructive cadaveric flexibility testing. Methods: Seven human cadaveric specimens were studied before and after ISS placement at L1–L2. Angular range of motion, lax zone, stiff zone, sagittal instantaneous axis of rotation (IAR), foraminal height, and facet loads were compared between conditions. Flexion, extension, lateral bending, and axial rotation were induced using pure moments (7.5 Nm maximum) while recording motion optoelectronically. The IAR was measured during loading with a 400 N compressive follower. Foraminal height changes were calculated using rigid body methods. Facet loads were assessed from surface strain and neural network analysis. Results: After ISS insertion, range of motion and stiff zone during extension were significantly reduced (P &lt; .01). Foraminal height was significantly reduced from flexion to extension in both normal and ISS-implanted conditions; there was significantly less reduction in foraminal height during extension with the ISS in place. The ISS reduced the mean facet load by 30% during flexion (P &lt; .02) and 69% during extension (P &lt; .015). The IAR after ISS implantation was less than 1 mm from the normal position (P &gt; .18). Conclusion: The primary biomechanical effect of the ISS was reduced extension with associated reduced facet loads and smaller decrease in foraminal height. The ISS had little effect on sagittal IAR or on motion or facet loads in other directions.

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