Influence of different artificial disc kinematics on spine biomechanics

doi:10.1016/j.clinbiomech.2008.11.008

Clinical Biomechanics

Volume 24, Issue 2, February 2009, Pages 135-142

https://doi.org/10.1016/j.clinbiomech.2008.11.008 Get rights and content

Abstract

Background

There are several different artificial discs for the lumbar spine in clinical use. Though clinically established, little is known about the biomechanical advantages of different disc kinematics.

Methods

A validated finite element model of the lumbosacral spine was used to compare the results of total disc arthroplasty at level L4/L5 performed by simulating the kinematics of three established artificial disc prostheses (Charité, ProDisc, Activ L). For flexion, extension, lateral bending, and axial torsion, the intervertebral rotations, the locations of the helical axes of rotation, the intradiscal pressures, and the facet joint forces were evaluated at the operated and adjacent levels.

Findings

After insertion of an artificial disc, intervertebral rotation is reduced for flexion and increased for extension, lateral bending, and axial torsion for all studied discs at implant level. The positions of the helical axes are altered especially for lateral bending and axial torsion. Increased facet joint contact forces are predicted for the Charité disc during extension – influenced by the existence of anterior scar tissue – and for the ProDisc and the Activ L during lateral bending and axial torsion. The studied artificial discs have only a minor effect on the adjacent levels.

Interpretations

For some load cases, total disc arthroplasty leads to considerably altered kinematics and increased facet joint contact forces at implant level. The spinal kinematic alterations due to an artificial disc exceed by far the inter-implant differences, while facet joint contact force alterations are strongly implant and load case dependent. The importance of implant kinematics is often overestimated.

Introduction

Total disc arthroplasty is becoming more and more common in regard to the surgical treatment of discogenic spinal pathology. Many implants have been designed for the arthroplasty of lumbar discs in the last years (Mayer, 2005). From the mechanical point of view, disc prostheses are defined mainly by their kinematics, and these are distinctly different from disc to disc. Typically, the artificial discs consist of two or three functional components. There are always two disc plates, the relative movements of which are determined by a core. The core is either separate or it is connected to the lower plate. While the CHARITÉ^® Artificial Disc (DePuySpine, Inc., Raynham, MA, USA) has a lentoid core with two articulating surfaces, the ProDisc^® (Synthes, Inc., West Chester, PA, USA) has an inlay with a fixed centre of rotation. The disc Activ L (Aesculap, Inc., Center Valley, PA, USA) has a core that can slide in the anterio-posterior direction. The core of the Mobidisc^® (LDR Médical, Troyes, France) can additionally slide laterally. Another difference is the core’s radius of curvature. The Maverick™ prosthesis (Medtronic, Inc., Minneapolis, MN, USA) and the Flexicore^® (Stryker, Kalamazoo, MI, USA) both have a relatively small radius, but the position of the centre of the core differs. The Maverick’s centre of rotation is located more posteriorly than that of the Flexicore.

Several retrospective and some prospective studies (Blumenthal et al., 2005, Delamarter et al., 2003, Huang et al., 2003, Shim et al., 2007, Siepe et al., 2007, Tournier et al., 2007) show the usefulness of total disc arthroplasty as a surgical procedure which can provide pain relief while maintaining mobility, but only few experimental studies have been performed focussing on the mechanical characteristics of artificial discs. Panjabi et al. performed in vitro tests with the Charité disc (Panjabi et al., 2007b) and the ProDisc (Panjabi et al., 2007a) in order to investigate if effects on adjacent levels can be predicted. They did not find any remarkable changes at the adjacent discs for one level total disc arthroplasty. O’Leary et al. (2005) measured the intervertebral rotations of specimen with and without a Charité disc. They found an increased mobility after implantation but did not compare different implant types. Tournier et al. (2007) studied 105 patients with the Maverick disc, the Charité disc and the ProDisc with X-rays in vivo and measured the range of motion, the mean centre of rotation, and the balance. They found no difference in the ranges of motion between the three prostheses.

An implant is unlikely to provide the exact characteristics of native anatomy and different disc kinematics will probably influence relative motion of the adjacent vertebrae, the facet joint forces and adjacent disc loads. But the multitude of biological factors existing in experimental studies impedes an exploration of the pure biomechanical influence of artificial discs. Investigating the isolated influence of the disc kinematics is possible only in simulation studies. Several studies exist which reveal the biomechanical influence of artificial discs (Denoziere and Ku, 2006, Grauer et al., 2006, Rohlmann et al., 2005, Rohlmann et al., 2008, Zander et al., 2007) but these studies were carried out for a different purpose than for studying inter-implant differences and were build up and loaded differently which prevents comparability.

The relative motion of adjacent vertebrae can be characterized in different ways. The clinical relevance of the centre of rotation was pointed out by Pearcy and Bogduk (1988). For movements that cannot be described in two dimensions like lateral bending or axial torsion, the main motion alone does not provide a complete description of the movement. Therefore Baeyens et al. (2005) proposed to describe the motion patterns with the finite helical axes which also have a communicative meaning: The motion of a body can always be described as a rotation around, and a superimposed translation along this axis.

The objective of the present study is to predict differences in the intervertebral rotation, to describe the vertebral kinematics and to estimate the facet loads and the intradiscal pressures in the adjacent discs for the load cases flexion, extension, lateral bending and axial torsion. Kinematics considered in this study are those of the artificial discs Charité, ProDisc, and Activ L.

Section snippets

Intact model

A validated three-dimensional finite element model for static analyses of the lumbar spine ranging from vertebra L1 to the lumbosacral disc L5/S1 was used (Fig. 1). It is build up by about 60,000 elements the nodes of which have about 200,000 degrees of freedom. It incorporates non-linearities originating from material behaviour, contact conditions in the facet joints and from large deflections. The dimensions and orientations of the intervertebral discs and the vertebrae including the curved

Relative intervertebral rotation

The relative rotation of adjacent vertebrae around their helical axes is changed after the insertion of an intervertebral disc prosthesis. Above and below the treated level, there is a small decrease in rotation (Fig. 4, top and bottom) in most of the cases. The decrease is between 5% and 34% of the value for the intact situation when no scar tissue was simulated at the treated level. For extension, simulated scar tissue leads to a small increase of relative rotation at the adjacent levels of

Discussion

The influence of the different design concepts of artificial discs on intervertebral rotation, helical axes of motion, facet joint forces, and on the intradiscal pressure was studied. The kinematical differences between three concepts realized for clinically-used lumbar intervertebral disc prostheses were investigated for different load cases.

Although emphasis was laid on model validation, each model is limited to what it was created for and has its own shortcomings: The present model does not

Conclusions

Total disc arthroplasty inherently alters the kinematics at implant level for all clinically-used prostheses. Compared to these alterations inter-implant differences are small. This result is supported by the clinical outcome available until now, which shows similar success rates for the available artificial discs (Mayer, 2005). By contrast, facet joint forces are strongly dependent on the implant kinematics and on the load case. Only long term clinical results can show if the increased facet

Acknowledgements

This work was supported by the Deutsche Forschungsgemeinschaft, Bonn, Germany (Ro 581/17-2). We thank Dr. W. Baumann and Dr. R. Ehrig from Konrad-Zuse-Zentrum für Informationstechnik Berlin (ZIB), Germany, for computational assistance. Finite element analyses were performed at the Norddeutscher Verbund für Hoch- und Höchstleistungsrechnen (HLRN).

References (36)

G. Denoziere et al.
Biomechanical comparison between fusion of two vertebrae and implantation of an artificial intervertebral disc
J. Biomech.
(2006)
J.N. Grauer et al.
Biomechanics of two-level Charite artificial disc placement in comparison to fusion plus single-level disc placement combination
Spine J.
(2006)
F. Heuer et al.
Stepwise reduction of functional spinal structures increase range of motion and change lordosis angle
J. Biomech.
(2007)
P. O’Leary et al.
Response of Charite total disc replacement under physiologic loads: prosthesis component motion patterns
Spine J.
(2005)
M.M. Panjabi
Hybrid multidirectional test method to evaluate spinal adjacent-level effects
Clin. Biomech.
(2007)
A. Rohlmann et al.
Determination of trunk muscle forces for flexion and extension by using a validated finite element model of the lumbar spine and measured in vivo data
J. Biomech.
(2006)
M.A. Rousseau et al.
Disc arthroplasty design influences intervertebral kinematics and facet forces
Spine J.
(2006)
F.E. Veldpaus et al.
A least-squares algorithm for the equiform transformation from spatial marker co-ordinates
J. Biomech.
(1988)
D.C. Wilson et al.
Accuracy and repeatability of a new method for measuring facet loads in the lumbar spine
J. Biomech.
(2006)
J.P. Baeyens et al.
Measurement of three-dimensional intra-articular kinematics: methodological and interpretation problems
Ergonomics
(2005)

S. Blumenthal et al.

A prospective, randomized, multicenter food and drug administration investigational device exemptions study of lumbar total disc replacement with the CHARITE artificial disc versus lumbar fusion: part I: Evaluation of clinical outcomes

Spine

(2005)

C. Boulay et al.

Sagittal alignment of spine and pelvis regulated by pelvic incidence: standard values and prediction of lordosis

Eur. Spine J.

(2006)

R.B. Delamarter et al.

ProDisc artificial total lumbar disc replacement: introduction and early results from the United States clinical trial

Spine

(2003)

H. Haberl et al.

Kinematic response of lumbar functional spinal units to axial torsion with and without superimposed compression and flexion/extension

Eur. Spine J.

(2004)

R.C. Huang et al.

Long-term flexion-extension range of motion of the prodisc total disc replacement

J. Spinal Disord. Tech.

(2003)

A. Kettler et al.

Finite helical axes of motion are a useful tool to describe the three-dimensional in vitro kinematics of the intact, injured and stabilised spine

Eur. Spine J.

(2004)

Y. Masharawi et al.

Facet orientation in the thoracolumbar spine: three-dimensional anatomic and biomechanical analysis

Spine

(2004)

Y. Masharawi et al.

Facet tropism and interfacet shape in the thoracolumbar vertebrae: characterization and biomechanical interpretation

Spine

(2005)

Cited by (105)

Hybrid cortical bone trajectory and modified cortical bone trajectory techniques in transforaminal lumbar interbody fusion at L4-L5 segment: A finite element analysis
2024, Heliyon
The academia has increasingly acknowledged the superior biomechanical performance of the hybrid fixation technique in recent years. However, there is a lack of research on the hybrid fixation technique using BCS (Bilateral Cortical Screws) and BMCS (Bilateral Modified Cortical Screws). This study aims to investigate the biomechanical performance of the BCS and BMCS hybrid fixation technique in transforaminal lumbar interbody fusion (TLIF) at the L4-L5 segment in a complete lumbar-sacral finite element model.
Three cadaver specimens are used to construct three lumbar-sacral finite element models. The biomechanical properties of various fixation technologies (BCS-BCS, BMCS-BMCS, BMCS-BCS, and BCS-BMCS) are evaluated at the L4-5 segment with a TLIF procedure conducted, including the range of motion (ROM) of the L4-5 segment, as well as the stress experienced by the cage, screws, and rods. The testing is conducted under specific loading conditions, including a compressive load of 400 N and a torque of 7.5Nm, subjecting the model to simulate flexion, extension, lateral bending, and rotation.
No significant variations are seen in the ROM at the L4-5 segment when comparing the four fixation procedures during flexion and extension. However, when it comes to lateral bending and rotation, the ROM is ordered in descending order as BCS-BCS, BCS-BMCS, BMCS-BMCS, and BMCS-BCS. The maximum stress experienced by the cage is observed to be highest within the BMCS-BCS technique during movements including flexion, extension, and lateral bending. Conversely, the BMCS-BMCS technique exhibits the highest cage stress levels during rotational movements. The stress applies to the screws and rods order the sequence of BCS-BCS, BCS-BMCS, BMCS-BCS, and BMCS-BMCS throughout all four working conditions.
The BMCS-BCS technique shows better biomechanical performance with less ROM and lower stress on the internal fixation system compared to other fixation techniques. BMCS-BMCS technology has similar mechanical performance to BMCS-BCS but has more contact area between screws and cortical bone, making it better for patients with severe osteoporosis.
Cadaveric biomechanical studies of ADDISC total lumbar disc prosthesis
2024, Clinical Biomechanics
Most total disc replacements provide excessive mobility and not reproduce spinal kinematics, inducing zygapophyseal joint arthritic changes and chronic back pain. In cadaveric lumbosacral spines, we studied if a new lumbar disc prosthesis kinematics mimics the intact intervertebral disc.
In eight cold preserved cadaveric lumbosacral spines, we registered the movement ranges in flexion, extension, right and left lateral bending, and rotation in the intact status, post-discectomy, and after our prosthesis implantation, comparing them for each specimen.
Comparing the intact lumbosacral spine with the L₄-L₅ prosthesis implanted specimens, we saw statistically significant differences in lateral bending and right rotation but not in the full range of rotation. Analyzing segments, we also noticed statistically significant differences at L₄-L₅ in flexion-extension and rotation. On the other hand, the L₄-L₅ discectomy, compared to the baseline spine condition, showed a statistically significant mobility increase in flexion, extension, lateral bending, and axial rotation, with an abnormal instantaneous center of rotation, which destabilizes the segment partly due to anterior annulus surgical removal. Disc prosthesis implantation reversed these changes in instantaneous center of rotation, but the prosthesis failed to restore the initial range of motion due to the destabilization of the ligaments in the operated disc.
The ADDISC total disc replacement reproduces the intact disc kinematics and Instantaneous Center of Rotation, but the prosthesis fails to restore the initial range of motion due to ligament destabilization. More studies will be necessary to define a technique that restores the damaged ligaments when implanting the prosthesis.
Yeditepe spine mesh: Finite element modeling and validation of a parametric CAD model of lumbar spine
2022, Medical Engineering and Physics
Finite element analysis is a powerful tool that is often used to study the biomechanical response of the spine. The primary objective of this study was to illustrate the mechanical behavior of a previously proposed parametric CAD spine model in comparison with a segmented FSU model and the literature. In this study, two finite element models of the L4-L5 spinal level were developed from the same patient’s CT scan data. The first was developed using well-known segmentation methods, whereas the second was developed from the new by using a novel parametric CAD model. Both models were subjected to the same loading and boundary conditions to perform flexion, extension, lateral bending and axial rotation motions. The segmented finite element model was observed to be in good agreement with the literature. The parametric finite element model results were also observed to be in good agreement with the segmented finite element model and with the literature except under extension.
Meta-analyses comparing spine simulators with cadavers and finite element models by analysing range-of-motion data before and after lumbar total disc replacement
2020, Journal of Advanced Research
Range-of-motion (ROM) data generated by the in vitro test methods of spine simulators with cadavers (SSCs) and finite element models (FEMs) are used alternatively and complementarily for in vitro evaluations.
Our purpose is to compare exemplary segmental ROM data from SSCs and FEMs before and after ball-and-socket total disc replacement (bsTDR) to determine whether the two test methods provide the same data for the same evaluation subjects.
We performed 70 meta-analyses (MAs) and 20 additional comparative analyses based on data from 21 SSC studies used for 39 MAs and 16 FEM studies used for 31 MAs. Only fifty-nine percent (n = 23/39) of SSC MAs show a restored ROM after bsTDR, whereas in FEM MAs, the ROM is restored in ninety percent (n = 28/31). Among the analyses comparing data from the same spinal segments, motion directions and bsTDR, SSC and FEM data are significantly different in ten percent (n = 2/20). According to our results, data generated by SSCs and FEMs cannot be used as alternative and complementary data without restriction. The quality of the evaluation methods itself as well as potential technical reasons for the discrepant results were not our evaluation target. Further SSC and FEM data should be compared using the same approach.
Thoracic vertebra fixation with a novel screw-plate system based on computed tomography imaging and finite element method
2020, Computer Methods and Programs in Biomedicine
The traditional pedicle screw-rod internal fixation system has been widely used for thoracic diseases in clinical practice, but its high profile increases the damage to soft tissue, leading to long-term intractable back stiffness. The purpose of this study is to compare biomechanical advantages between the new spine pedicle screw-plate internal fixation system and traditional pedicle screw-rod internal fixation system using finite element analysis.
Based on computed tomography (CT), four three-dimensional finite element models of T7-T9 were constructed. The downward concentrated force of 150 N and the moment of 5 Nm was applied to the models to simulate six physiological activities, including flexion, extension, left and right lateral bending, left and right axial torsion. The maximum displacement, range of motion (ROM) and maximum stress of the two models in six physiological activities, was measured to evaluate the biomechanical advantages of the novel pedicle screw-plate internal fixation system.
The novel pedicle screw-plate internal fixation system has a lower profile than the traditional pedicle screw-rod internal fixation system. With regards to the stability, the maximum displacement of the models of two internal fixation systems decreased by 56.2%–91.4% under the six motion status when comparing with the unstable model. Meanwhile, the ROM remained unchanged between the two models of internal fixation systems besides the left lateral bending. However, there is no significant difference in the ROM between the models of the two internal fixation systems in left lateral bending motion (P = 0.203). In terms of the strength, the maximum stress in the model with the new pedicle screw-plate internal fixation system was higher than that of model with the traditional pedicle screw-rod internal fixation system in every motion status but left and right lateral bending motion.
The novel pedicle screw-plate internal fixation system has lower profile in orthopedics and higher strength, However, it has no disadvantage when comparing with the traditional pedicle screw-rod internal fixation system in terms of the stability. In summary, we suggest that the novel spine pedicle screw-plate system can be used as a new internal fixation and provide better comfort for patients.
A braced arm-to-thigh (BATT) lifting technique reduces lumbar spine loads in healthy and low back pain participants
2020, Journal of Biomechanics
Citation Excerpt :
Intervertebral motion was assumed to be a pure rotation (no translation) about a fixed centre of rotation (Pearcy and Bogduk, 1988). However, the in vivo location of the centre of rotation varies throughout the range of motion and is dependent on the participant and the activity (Zander et al., 2009, Kettler et al., 2004, Wachowski et al., 2009), leading to up to 30% differences in joint load estimates (Ghezelbash et al., 2015). Shifting the joint centre posteriorly increases the net external moment due to gravity and decreases extensor moment arms, thus resulting in larger muscle forces and joint loads, while the opposite results occur when shifting the joint anteriorly (Ghezelbash et al., 2018).
Despite the common use of one-handed lifting techniques for activities of daily living, these techniques have received little attention in the biomechanics literature. The braced arm-to-thigh technique (BATT) is a one-handed lifting method in which the dominant hand picks up objects, while the free hand braces the trunk on the ipsilateral thigh. The aim of this study was to compare the BATT to two-handed or unsupported one-handed lifting techniques with loads of 2 and 10 kg, by evaluating trunk motion and spine loading at L4/L5. Twenty healthy participants (30–70 years old) matched in age and sex to 18 participants with low back pain were recruited to the study. A three-axis load cell secured to the distal anterior thigh measured the bracing forces applied by the hand. The OpenSim Lifting Full-Body model was used to estimate trunk kinematics and spinal loading at L4/L5. Linear mixed-effects models were developed to compare trunk angles and L4/L5 moments and forces between lifting techniques. Trunk flexion angles were significantly reduced for the BATT lift compared to one-handed and two-handed stoop lifts (9–20%). However, the BATT also increased asymmetric trunk kinematics and moments at L4/L5. The BATT produced significantly lower moments (28–38%), and compressive (25–32%) and antero-posterior shear (25–45%) forces at L4/L5, compared to unsupported lifting techniques. Bracing the hand on the thigh to support the trunk can substantially reduce low back loading during lifting tasks of 2 to 10 kg.

View all citing articles on Scopus

View full text

Influence of different artificial disc kinematics on spine biomechanics

Abstract

Background

Methods

Findings

Interpretations

Introduction

Section snippets

Intact model

Relative intervertebral rotation

Discussion

Conclusions

Acknowledgements

J. Biomech.

Spine J.

J. Biomech.

Spine J.

Clin. Biomech.

J. Biomech.

Spine J.

J. Biomech.

J. Biomech.

Measurement of three-dimensional intra-articular kinematics: methodological and interpretation problems

Ergonomics

A prospective, randomized, multicenter food and drug administration investigational device exemptions study of lumbar total disc replacement with the CHARITE artificial disc versus lumbar fusion: part I: Evaluation of clinical outcomes

Spine

Sagittal alignment of spine and pelvis regulated by pelvic incidence: standard values and prediction of lordosis

Eur. Spine J.

ProDisc artificial total lumbar disc replacement: introduction and early results from the United States clinical trial

Spine

Kinematic response of lumbar functional spinal units to axial torsion with and without superimposed compression and flexion/extension

Eur. Spine J.

Long-term flexion-extension range of motion of the prodisc total disc replacement

J. Spinal Disord. Tech.

Finite helical axes of motion are a useful tool to describe the three-dimensional in vitro kinematics of the intact, injured and stabilised spine

Eur. Spine J.

Facet orientation in the thoracolumbar spine: three-dimensional anatomic and biomechanical analysis

Spine

Facet tropism and interfacet shape in the thoracolumbar vertebrae: characterization and biomechanical interpretation

Spine