Insight on the Mechanical and Tribological Characteristics of Ball-on-Socket Artificial Disc under Alternate Motion of Flexion Extension–Axial Rotation and Lateral Bending–Axial Rotation

Object. The authors compared the biomechanical performance of the human cadaveric spine implanted with a metallic ball-and-cup artificial disc at L4–5 with the spine's intact state and after anterior discectomy. Methods. Seven human L2—S1 cadaveric spines were mounted on a biomechanical testing frame. Pure moments of 0, 1.5, 3.0, 4.5, and 6.0 Nm were applied to the spine at L-2 in six degrees of motion (flexion, extension, right and left lateral bending, and right and left axial rotation). The spines were tested in the intact state as well as after anterior L4–5 discectomy. The Maverick disc was implanted in the discectomy defect, and load testing was repeated. The artificial disc created greater rigidity for the spine than was present after discectomy, and the spine performed biomechanically in a manner comparable with the intact state. Conclusions. The results indicate that in an in vitro setting, this model of artificial disc stabilizes the spine after discectomy, restoring motion comparable with that of the intact state.

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Effect of position and height of a mobile core type artificial disc on the biomechanical behaviour of the lumbar spine

Proceedings of the Institution of Mechanical Engineers Part H Journal of Engineering in Medicine ◽

10.1243/09544119jeim241 ◽

2008 ◽

Vol 222 (2) ◽

pp. 229-239 ◽

Cited By ~ 18

Author(s):

A Rohlmann ◽

T Zander ◽

B Bock ◽

G Bergmann

Keyword(s):

Lumbar Spine ◽

Facet Joint ◽

Axial Rotation ◽

Intradiscal Pressure ◽

Upper Body ◽

Artificial Disc ◽

Lateral Bending ◽

Implant Position ◽

Joint Force ◽

Flexion Extension

The extent of natural disc removal and the implant position and height of an artificial disc with a mobile core were studied for their effects on intersegmental rotation, intradiscal pressure, and facet joint force. A validated finite element model of the lumbar spine was used. The model was loaded with the upper body weight, a follower load, and muscle forces to simulate standing, flexion, extension, lateral bending, and axial rotation. The implant position was varied up to 2 mm in an anterior and posterior direction and up to 3 mm in a lateral direction. Three different implant heights were simulated. The effect of removing the lateral parts of the annulus was also studied. The implant position and height markedly affect intersegmental rotation and facet joint forces but have hardly any influence on intradiscal pressure in the adjacent discs. Removing the lateral parts of the annulus increases intersegmental rotation and facet joint force mainly for lateral bending and axial rotation. The calculated translation of the mobile implant core is about 1 mm at most, and thus its effect is often overestimated. Great care should be taken to choose the optimal implant height and to insert the implant in the best position for each individual patient.

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Biomechanical Analysis of Cervical Artificial Disc Replacement Using Cervical Subtotal Discectomy Prosthesis

Frontiers in Bioengineering and Biotechnology ◽

10.3389/fbioe.2021.680769 ◽

2021 ◽

Vol 9 ◽

Author(s):

Jin Wo ◽

Zhenjing Lv ◽

Jing Wang ◽

Kui Shen ◽

Haoran Zhu ◽

...

Keyword(s):

Facet Joint ◽

Wear Test ◽

Axial Rotation ◽

Fe Analysis ◽

Fe Model ◽

Artificial Disc ◽

Lateral Bending ◽

Bone Implant ◽

Joint Force ◽

Flexion Extension

Background: Anterior cervical discectomy and fusion (ACDF) sacrifices segmental mobility, which can lead to the acceleration of adjacent segment degeneration. The challenge has promoted cervical artificial disc replacement (CADR) as a substitute for ACDF. However, CADR has revealed a series of new issues that are not found in ACDF, such as hypermobility, subsidence, and wear phenomenon. This study designed a cervical subtotal discectomy prosthesis (CSDP) consisting of a cervical disc prosthesis structure (CDP structure), cervical vertebra fixation structure (CVF structure), link structure, and locking screw, aiming to facilitate motion control and reduce subsidence. The aim of this study was to assess the biomechanics of the CSDP using finite element (FE) analysis, friction-wear test, and non-human primates implantation study.Study Design: For the FE analysis, based on an intact FE C2-C7 spinal model, a CSDP was implanted at C5-C6 to establish the CSDP FE model and compare it with the Prestige LP prosthesis (Medtronic Sofamor Danek, Minneapolis, MN, United States). The range of motion (ROM), bone-implant interface stress, and facet joint force were calculated under flexion extension, lateral bending, and axial rotation. In addition, CSDP was elevated 1 mm to mimic an improper implantation technique to analyze the biomechanics of CSDP errors in the FE model. Moreover, the friction-wear test was conducted in vitro to research CSDP durability and observe surface wear morphology and total wear volume. Finally, the CSDP was implanted into non-human primates, and its properties were evaluated and verified by radiology.Results: In the FE analysis, the ROM of the CSDP FE model was close to that of the intact FE model in the operative and adjacent segments. In the operative segment, the CSDP error FE model increased ROM in flexion extension, lateral bending, and axial rotation. The maximum stress in the CSDP FE model was similar to that of the intact FE model and was located in the peripheral cortical bone region. The facet joint force changes were minimal in extension, lateral bending, and axial rotation loads in CSDP. In the friction-wear test, after the 150-W movement simulation, both the CVF-link-junction and the CDP-link-junction had slight wear. In the CSDP non-human primate implantation study, no subsidence, dislocation, or loosening was observed.Conclusion: In the FE analysis, the biomechanical parameters of the CSDP FE model were relatively close to those of the intact FE model when compared with the Prestige LP FE model. In terms of CSDP error FE models, we demonstrated that the implantation position influences CSDP performance, such as ROM, bone-implant interface stress, and facet joint force. In addition, we performed a friction-wear test on the CSDP to prove its durability. Finally, CSDP studies with non-human primates have shown that the CSDP is effective.

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Range of motion change after cervical arthroplasty with ProDisc-C and Prestige artificial discs compared with anterior cervical discectomy and fusion

Journal of Neurosurgery Spine ◽

10.3171/spi-07/07/040 ◽

2007 ◽

Vol 7 (1) ◽

pp. 40-46 ◽

Cited By ~ 70

Author(s):

Ung-Kyu Chang ◽

Daniel H. Kim ◽

Max C. Lee ◽

Rafer Willenberg ◽

Se-Hoon Kim ◽

...

Keyword(s):

Range Of Motion ◽

Axial Rotation ◽

Anterior Cervical Discectomy ◽

Artificial Disc ◽

Lateral Bending ◽

Cervical Arthroplasty ◽

Cervical Discectomy ◽

Motion Modes ◽

Adjacent Segments ◽

The Prestige

Object Range of motion (ROM) changes were evaluated at the surgically treated and adjacent segments in cadaveric specimens treated with two different cervical artificial discs compared with those measured in intact spine and fusion models. Methods Eighteen cadaveric human cervical spines were tested in the intact state for the different modes of motion (extension, flexion, lateral bending, and axial rotation) up to 2 Nm. Three groups of specimens (fitted with either the ProDisc-C or Prestige II cervical artificial disc or submitted to anterior cervical discectomy and fusion [ACDF]) were tested after implantation at C6–7 level. The ROM values were measured at treated and adjacent segments, and these values were then compared with those measured in the intact spine. Results At the surgically treated segment, the ROM increased after arthroplasty compared with the intact spine in extension (54% in the ProDisc-C group, 47% in the Prestige group) and in flexion (27% in the ProDisc-C group, 10% in the Prestige group). In bending and rotation, the postarthroplasty ROMs were greater than those of the intact spine (10% in the ProDisc-C group and 55% in the Prestige group in bending, 17% in the ProDisc-C group and 50% in the Prestige group in rotation). At the adjacent levels the ROMs decreased in all specimens treated with either artificial disc in all modes of motion (< 10%) except for extension at the inferior the level (29% decrease for ProDisc-C implant, 12% decrease for Prestige disc). The ROM for all motion modes in the ACDF-treated spine decreased at the treated level (range 18–44%) but increased at the adjacent levels (range 3–20%). Conclusions Both ProDisc-C and Prestige artificial discs were associated with increased ROM at the surgically treated segment compared with the intact spine with or without significance for all modes of testing. In addition, adjacent-level ROM decreased in all modes of motion except extension in specimens fitted with both artificial discs.

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How the height and the area of the annulus fibrosus affect the range of motion behavior: A stochastic analysis

Proceedings of the Institution of Mechanical Engineers Part L Journal of Materials Design and Applications ◽

10.1177/1464420718805896 ◽

2018 ◽

Vol 233 (10) ◽

pp. 1985-1992

Author(s):

Héctor E Jaramillo S

Keyword(s):

Finite Element ◽

Range Of Motion ◽

Annulus Fibrosus ◽

Element Model ◽

Axial Rotation ◽

Disc Height ◽

Lateral Bending ◽

Analytic Equation ◽

Geometrical Properties ◽

Flexion Extension

The annulus fibrosus has substantial variations in its geometrical properties (among individuals and between levels), and plays an important role in the biomechanics of the spine. Few works have studied the influence of the geometrical properties including annulus area, anterior / posterior disc height, and over the range of motion, but in general these properties have not been reported in the finite element models. This paper presents a probabilistic finite element analyses (Abaqus 6.14.2) intended to assess the effects of the average disc height ( hp) and the area ( A) of the annulus fibrosus on the biomechanics of the lumbar spine. The annulus model was loaded under flexion, extension, lateral bending, and axial rotation and analyzed for different combinations of hpand A in order to obtain their effects over the range of motion. A set of 50 combinations of hp(mean = 18.1 mm, SD = 3.5 mm) and A (mean = 49.8%, SD = 4.6%) were determined randomly according to a normal distribution. A Yeoh energy function was used for the matrix and an exponential function for the fibers. The range of motion was more sensitive to hpthan to A. With regard to the range of motion the segment was more sensitive in the following order: flexion, axial rotation, extension, and lateral bending. An increase of the hpproduces an increase of the range of motion, but this decreases when A increases. Comparing the range of motion with the experimental data, on average, 56.0% and 73.0% of the total of data were within the experimental range for the L4–L5 and L5–S1 segments, respectively. Further, an analytic equation was derived to obtain the range of motion as a function of the hpand A. This equation can be used to calibrate a finite element model of the spine segment, and also to understand the influence of each geometrical parameter on the range of motion.

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Hybrid dynamic stabilization: a biomechanical assessment of adjacent and supraadjacent levels of the lumbar spine

Journal of Neurosurgery Spine ◽

10.3171/2012.6.spine111054 ◽

2012 ◽

Vol 17 (3) ◽

pp. 232-242 ◽

Cited By ~ 18

Author(s):

Prasath Mageswaran ◽

Fernando Techy ◽

Robb W. Colbrunn ◽

Tara F. Bonner ◽

Robert F. McLain

Keyword(s):

Lumbar Spine ◽

Lumbar Fusion ◽

Industrial Robot ◽

Pedicle Screws ◽

Axial Rotation ◽

Dynamic Stabilization ◽

Follower Load ◽

Lateral Bending ◽

Intact Specimen ◽

Flexion Extension

Object The object of this study was to evaluate the effect of hybrid dynamic stabilization on adjacent levels of the lumbar spine. Methods Seven human spine specimens from T-12 to the sacrum were used. The following conditions were implemented: 1) intact spine; 2) fusion of L4–5 with bilateral pedicle screws and titanium rods; and 3) supplementation of the L4–5 fusion with pedicle screw dynamic stabilization constructs at L3–4, with the purpose of protecting the L3–4 level from excessive range of motion (ROM) and to create a smoother motion transition to the rest of the lumbar spine. An industrial robot was used to apply continuous pure moment (± 2 Nm) in flexion-extension with and without a follower load, lateral bending, and axial rotation. Intersegmental rotations of the fused, dynamically stabilized, and adjacent levels were measured and compared. Results In flexion-extension only, the rigid instrumentation at L4–5 caused a 78% decrease in the segment's ROM when compared with the intact specimen. To compensate, it caused an increase in motion at adjacent levels L1–2 (45.6%) and L2–3 (23.2%) only. The placement of the dynamic construct at L3–4 decreased the operated level's ROM by 80.4% (similar stability as the fusion at L4–5), when compared with the intact specimen, and caused a significant increase in motion at all tested adjacent levels. In flexion-extension with a follower load, instrumentation at L4–5 affected only a subadjacent level, L5–sacrum (52.0%), while causing a reduction in motion at the operated level (L4–5, −76.4%). The dynamic construct caused a significant increase in motion at the adjacent levels T12–L1 (44.9%), L1–2 (57.3%), and L5–sacrum (83.9%), while motion at the operated level (L3–4) was reduced by 76.7%. In lateral bending, instrumentation at L4–5 increased motion at only T12–L1 (22.8%). The dynamic construct at L3–4 caused an increase in motion at T12–L1 (69.9%), L1–2 (59.4%), L2–3 (44.7%), and L5–sacrum (43.7%). In axial rotation, only the placement of the dynamic construct at L3–4 caused a significant increase in motion of the adjacent levels L2–3 (25.1%) and L5–sacrum (31.4%). Conclusions The dynamic stabilization system displayed stability characteristics similar to a solid, all-metal construct. Its addition of the supraadjacent level (L3–4) to the fusion (L4–5) did protect the adjacent level from excessive motion. However, it essentially transformed a 1-level lumbar fusion into a 2-level lumbar fusion, with exponential transfer of motion to the fewer remaining discs.

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The cervical end of an occipitocervical fusion: a biomechanical evaluation of 3 constructs

Journal of Neurosurgery Spine ◽

10.3171/spi/2008/9/9/296 ◽

2008 ◽

Vol 9 (3) ◽

pp. 296-300 ◽

Cited By ~ 24

Author(s):

Michael A. Finn ◽

Daniel R. Fassett ◽

Todd D. Mccall ◽

Randy Clark ◽

Andrew T. Dailey ◽

...

Keyword(s):

Tracking System ◽

Plate Fixation ◽

Axial Rotation ◽

Lateral Mass ◽

Lateral Bending ◽

Cross Link ◽

3D Tracking ◽

Flexion Extension ◽

Biomechanical Evaluation ◽

Rotation Motion

Object Stabilization with rigid screw/rod fixation is the treatment of choice for craniocervical disorders requiring operative stabilization. The authors compare the relative immediate stiffness for occipital plate fixation in concordance with transarticular screw fixation (TASF), C-1 lateral mass and C-2 pars screw (C1L-C2P), and C-1 lateral mass and C-2 laminar screw (C1L-C2L) constructs, with and without a cross-link. Methods Ten intact human cadaveric spines (Oc–C4) were prepared and mounted in a 7-axis spine simulator. Each specimen was precycled and then tested in the intact state for flexion/extension, lateral bending, and axial rotation. Motion was tracked using the OptoTRAK 3D tracking system. The specimens were then destabilized and instrumented with an occipital plate and TASF. The spine was tested with and without the addition of a cross-link. The C1L-C2P and C1L-C2L constructs were similarly tested. Results All constructs demonstrated a significant increase in stiffness after instrumentation. The C1L-C2P construct was equivalent to the TASF in all moments. The C1L-C2L was significantly weaker than the C1L-C2P construct in all moments and significantly weaker than the TASF in lateral bending. The addition of a cross-link made no difference in the stiffness of any construct. Conclusions All constructs provide significant immediate stability in the destabilized occipitocervical junction. Although the C1L-C2P construct performed best overall, the TASF was similar, and either one can be recommended. Decreased stiffness of the C1L-C2L construct might affect the success of clinical fusion. This construct should be reserved for cases in which anatomy precludes the use of the other two.

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Biomechanical evaluation of the ProDisc-C stability following graded posterior cervical injury

Journal of Neurosurgery Spine ◽

10.3171/2018.3.spine171248 ◽

2018 ◽

Vol 29 (5) ◽

pp. 515-524

Author(s):

Michael D. Staudt ◽

Doron Rabin ◽

Ali A. Baaj ◽

Neil R. Crawford ◽

Neil Duggal

Keyword(s):

Axial Rotation ◽

Control Group ◽

Lateral Bending ◽

Cervical Injury ◽

Cervical Arthroplasty ◽

Posterior Surgery ◽

Flexion Extension ◽

Posterior Element ◽

And Control ◽

Flexion And Extension

OBJECTIVEThere are limited data regarding the implications of revision posterior surgery in the setting of previous cervical arthroplasty (CA). The purpose of this study was to analyze segmental biomechanics in human cadaveric specimens with and without CA, in the context of graded posterior resection.METHODSFourteen human cadaveric cervical spines (C3–T1 or C2–7) were divided into arthroplasty (ProDisc-C, n = 7) and control (intact disc, n = 7) groups. Both groups underwent sequential posterior element resections: unilateral foraminotomy, laminoplasty, and finally laminectomy. Specimens were studied sequentially in two different loading apparatuses during the induction of flexion-extension, lateral bending, and axial rotation.RESULTSRange of motion (ROM) after artificial disc insertion was reduced relative to that in the control group during axial rotation and lateral bending (13% and 28%, respectively; p < 0.05) but was similar during flexion and extension. With sequential resections, ROM increased by a similar magnitude following foraminotomy and laminoplasty in both groups. Laminectomy had a much greater effect: mean (aggregate) ROM during flexion-extension, lateral bending, and axial rotation was increased by a magnitude of 52% following laminectomy in the setting of CA, compared to an 8% increase without arthroplasty. In particular, laminectomy in the setting of CA introduced significant instability in flexion-extension, characterized by a 90% increase in ROM from laminoplasty to laminectomy, compared to a 16% increase in ROM from laminoplasty to laminectomy without arthroplasty (p < 0.05).CONCLUSIONSForaminotomy and laminoplasty did not result in significant instability in the setting of CA, compared to controls. Laminectomy alone, however, resulted in a significant change in biomechanics, allowing for significantly increased flexion and extension. Laminectomy alone should be used with caution in the setting of previous CA.

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Biomechanical Analysis of an Anterior Cervical Discectomy and Fusion Pseudarthrosis Model Revised With Machined Interfacet Allograft Spacers

Global Spine Journal ◽

10.1177/2192568219884265 ◽

2019 ◽

Vol 10 (8) ◽

pp. 973-981

Author(s):

Raymond J. Hah ◽

Ram Alluri ◽

Paul A. Anderson

Keyword(s):

Range Of Motion ◽

Study Design ◽

Axial Rotation ◽

Biomechanical Analysis ◽

Anterior Cervical Discectomy ◽

Lateral Bending ◽

Cervical Discectomy ◽

Single Level ◽

Flexion Extension ◽

Potential Applications

Study Design: Biomechanics study. Objectives: To evaluate the biomechanical advantage of interfacet allograft spacers in an unstable single-level and 2-level anterior cervical discectomy and fusion (ACDF) pseudoarthrosis model. Methods: Nine single-level and 8 two-level ACDF constructs were tested. Range of motion in flexion-extension (FE), lateral bending (LB), and axial rotation (AR) at 1.5 N m were collected in 4 testing configurations: (1) intact spine, (2) ACDF with interbody graft and plate/screw, (3) ACDF with interbody graft and plate/loosened screws (loose condition), and (4) ACDF with interbody graft and plate/loosened screws supplemented with interfacet allograft spacers (rescue condition). Results: All fixation configurations resulted in statistically significant decreases in range of motion in all bending planes compared with the intact spine ( P < .05). One Level. Performing ACDF with interbody graft and plate on the intact spine reduced FE, LB, and AR 60.0%, 64.9%, and 72.9%, respectively. Loosening the ACDF screws decreased these reductions to 40.9%, 44.6%, and 52.1%. The addition of interfacet allograft spacers to the loose condition increased these reductions to 74.0%, 84.1%, and 82.1%. Two Level. Performing ACDF with interbody graft and plate on the intact spine reduced FE, LB, and AR 72.0%, 71.1%, and 71.2%, respectively. Loosening the ACDF screws decreased these reductions to 55.4%, 55.3%, and 51.3%. The addition of interfacet allograft spacers to the loose condition significantly increased these reductions to 82.6%, 91.2%, and 89.3% ( P < .05). Conclusions: Supplementation of a loose ACDF construct (pseudarthrosis model) with interfacet allograft spacers significantly increases stability and has potential applications in treating cervical pseudarthrosis.

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