The effect of six degree of freedom loading sequence on the in-vitro compressive properties of human lumbar spine segments

Amin, Dhara B.; Lawless, I.M.; Sommerfeld, Dana; Stanley, Richard M.; Ding, Boyin; Costi, John J.

doi:10.1016/j.jbiomech.2016.09.009

Cited by 25 publications

(39 citation statements)

References 41 publications

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“…While the strain magnitude applied to IVD was higher than the levels of nominal strain (ie, endplate-endplate strain) generally observed in vivo, it was within the range of local strains that occur in human discs in experimentally simulated physiological conditions. 33 The frequency range (0.1-15 Hz) encompassed both slow movements (0.1 Hz), ambulation (~1 Hz), and high frequency vibrations experienced while using heavy equipment (3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15). Just as we found increased viscoelastic heating at higher frequencies, exposure of tractor, bus and heavy equipment drivers to high frequency vibrations is associated with increased risk of back pain.…”

Section: Discussionmentioning

confidence: 99%

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Viscoelastic heating of insulated bovine intervertebral disc

2018

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Back pain is the leading cause of disability globally and the second most common cause of doctors' visits. Despite extensive research efforts, the underlying mechanism of back pain has not been fully elucidated. The intervertebral disc (IVD) is a viscoelastic tissue that provides flexibility to the spinal column and acts as a shock absorber in the spine. When viscoelastic materials like the IVD are cyclically loaded, they dissipate energy as heat. Thus, diurnal, regular movements of the vertebral column that deform the IVD could increase disc temperature through viscoelastic heating. This temperature rise has the potential to influence cell function, drive cell death and induce nociception in innervating nociceptive neurons within the IVD. The present study was conducted to investigate the capacity of IVD to increase in temperature due to viscoelastic heating. Insulated caudal bovine IVD were subjected to physiological cyclic uniaxial compression over a range of frequencies (0.1-15 Hz) and loading durations (1-10 min) ex vivo, and the temperature rise in the tissue was recorded. According to our findings, the IVD can experience a temperature rise of up to 2.5 C under cyclic loading. Furthermore, under similar conditions, the inner nucleus pulposus exhibits more viscoelastic heating than the outer annulus fibrosis, likely due to its more viscous composition. The measured temperature rise of the disc has physiological relevance as degenerative IVD tissue has been shown to produce a sensitization of nociceptive neurons that spontaneously fire at 37 C, with a T50 response at 37.3 C and a maximum response at 38 C. Our results suggest that viscoelastic heating of IVD could interact with sensitized nociceptive neurons in the degenerative IVD to play a role in back pain.

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Section: Discussionmentioning

confidence: 99%

“…In vivo, IVD undergo cyclic multiaxial deformations, including axial compression, as a result of regular movements, physical activities, and exposure to vibrations. Individuals operating heavy machinery, such as construction equipment, experience full body vibrations up to and exceeding 15 Hz .…”

Section: Introductionmentioning

confidence: 99%

Viscoelastic heating of insulated bovine intervertebral disc

2018

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“…Segments were tested using a state‐of‐the‐art hexapod system that simultaneously controls and measures all six DOFs . The protocol consisted of an axial compression preload followed by six sequential tests, subsequently called “DOF tests,” each of which applied cyclic loading to one target DOF (Figure ).…”

Section: Methodsmentioning

confidence: 99%

“…The protocol consisted of an axial compression preload followed by six sequential tests, subsequently called “DOF tests,” each of which applied cyclic loading to one target DOF (Figure ). A novel hybrid control system was used, for details of the apparatus and control system, please see previous publications . In each DOF test, prescribed cyclic loading was applied to the target DOF in position or load control, and the off‐axis DOFs were load controlled in real time to maintain (approximately) zero off‐axis forces and moments .…”

Section: Methodsmentioning

confidence: 99%

“…For example, applying axial compression increases stiffness in the rotational DOFs (Rx, Ry, Rz) . In this study, we sequentially tested the disc's response to cyclic loading in each of the six DOFs, using a state‐of‐the‐art hexapod system to measure both same‐axis and off‐axis responses . We hypothesized that applied loading in each DOF would generate coupled off‐axis motions (translations and rotations) in the other five DOFs, and we tested this hypothesis by correlating, for each DOF, the applied motion vs measurements of the resulting five off‐axis motions.…”

Section: Introductionmentioning

confidence: 99%

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Off‐axis response due to mechanical coupling across all six degrees of freedom in the human disc

et al. 2019

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The kinematics of the intervertebral disc are defined by six degrees of freedom (DOF): three translations (Tz: axial compression, Tx: lateral shear, and Ty: anterior‐posterior shear) and three rotations (Rz: torsion, Rx: flexion‐extension, and Ry: lateral bending). There is some evidence that the six DOFs are mechanically coupled, such that loading in one DOF affects the mechanics of the other five “off‐axis” DOFs, however, most studies have not controlled and/or measured all six DOFs simultaneously. Additionally, the relationships between disc geometry and disc mechanics are important for evaluation of data from different sized donor and patient discs. The objectives of this study were to quantify the mechanical behavior of the intervertebral disc in all six degrees of freedom (DOFs), measure the coupling between the applied motion in each DOF with the resulting off‐axis motions, and test the hypothesis that disc geometry influences these mechanical behaviors. All off‐axis displacements and rotations were significantly correlated with the applied DOF and were of similar magnitude as physiologically relevant motion, confirming that off‐axis coupling is an important mechanical response. Interestingly, there were pairs of DOFs that were especially strongly coupled: lateral shear (Tx) and lateral bending (Ry), anterior‐posterior shear (Ty) and flexion‐extension (Rx), and compression (Tz) and torsion (Rz). Large off‐axis shears may contribute to injury risk in bending and flexion. In addition, the disc responded to shear (Tx, Ty) and rotational loading (Rx, Ry, and Rz) by increasing in disc height in order to maintain the applied compressive load. Quantifying these mechanical behaviors across all six DOF are critical for designing and testing disc therapies, such as implants and tissue engineered constructs, and also for validating finite element models.

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Development and validation of a biomechanically fidelic surgical training knee model

Bennett,

Foroutan,

Fairweather

et al. 2024

Journal Orthopaedic Research

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Knee arthroplasty technique is constantly evolving and the opportunity for surgeons to practice new techniques is currently highly dependent on the availability of cadaveric specimens requiring certified facilities. The high cost, limited supply, and heterogeneity of cadaveric specimens has increased the demand for synthetic training models, which are currently limited by a lack of biomechanical fidelity. Here, we aimed to design, manufacture, and experimentally validate a synthetic knee surgical training model which reproduces the flexion dependent varus‐valgus (VV) and anterior‐posterior (AP) mechanics of cadaveric knees, while maintaining anatomic accuracy. A probabilistic finite element modeling approach was employed to design physical models to exhibit passive cadaveric VV and AP mechanics. Seven synthetic models were manufactured and tested in a six‐degree‐of‐freedom hexapod robot. Overall, the synthetic models exhibited cadaver‐like VV and AP mechanics across a wide range of flexion angles with little variation between models. In the extended position, two models showed increased valgus rotation (<0.5°), and three models showed increased posterior tibial translation (<1.7 mm) when compared to the 95% confidence interval (CI) of cadaveric measurements. At full flexion, all models showed VV and AP mechanics within the 95% CI of cadaveric measurements. Given the repeatable mechanics exhibited, the knee models developed in this study can be used to reduce the current reliance on cadaveric specimens in surgical training.

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The effect of six degree of freedom loading sequence on the in-vitro compressive properties of human lumbar spine segments

Cited by 25 publications

References 41 publications

Viscoelastic heating of insulated bovine intervertebral disc

Viscoelastic heating of insulated bovine intervertebral disc

Off‐axis response due to mechanical coupling across all six degrees of freedom in the human disc

Development and validation of a biomechanically fidelic surgical training knee model

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