Transmission of Force in the Lumbosacral Spine During Backward Falls

Toen, Carolyn Van; Sran, Meena M.; Robinovitch, Stephen N.; Cripton, Peter A.

doi:10.1097/brs.0b013e31823ecae0

Cited by 17 publications

(15 citation statements)

References 43 publications

(25 reference statements)

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“…Although this reduced the biofidelity of the simulation, it allowed us to isolate and characterize the force-deflection characteristics of each individual flooring system (as opposed to overall 'system' characteristics). An added benefit is that this floor-specific compliance data can be incorporated into mathematical models of impact that require explicit stiffness parameters for both floors and impacting body parts [17,37,38].…”

Section: Discussionmentioning

confidence: 99%

Characterization of the protective capacity of flooring systems using force-deflection profiling

Glinka¹,

Karakolis²,

Callaghan³

et al. 2013

Medical Engineering & Physics

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Section: Discussionmentioning

confidence: 99%

Characterization of the protective capacity of flooring systems using force-deflection profiling

Glinka¹,

Karakolis²,

Callaghan³

et al. 2013

Medical Engineering & Physics

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“…The stiffness and damping characteristics of the intervertebral disk form a critical component in determining the spine’s dynamic response [27, 39, 44, 63, 64]. In this study, the dynamic stiffness computed for the lumbar spine (having two disks in series) can be compared to previous experiments using a single functional spinal unit by doubling the stiffness and damping values measured in this study.…”

Section: Discussionmentioning

confidence: 99%

“…Assuming the subject would land in a seated position, such a fall was modeled to produce a high rate axial load and thus would produce a compression fracture. Although little is known about the magnitude and type of forces or the moments to which the thoraco-lumbar spine is exposed due to a backward fall [44, 45], the model predicted a 10% increase in the stiffness of the segment to yield an increase of 2–5% in the peak forces acting on the vertebrae [43]. This increase in peak forces, may increase the risk of vertebral fracture (VFx) in osteoporotic individuals.…”

Section: Introductionmentioning

confidence: 99%

“…Degenerative changes in the annulus and nucleus, which strongly affect their static and viscoelastic material properties [52–54] and the associated loss of hydration [55–57], result in the degradation of the FSU’s long-term creep behavior and energy dissipation [24, 28, 57]. Although hydration and the degenerative state of the disk are important determinants of the spine’s stiffness and damping characteristics, little is known about their effect on the failure load of elderly spines under high rate loading [29, 44, 58]. In view of the intimate relationship between the disk’s hydration and its mechanical competence, we hypothesize that MR classification of degenerative changes will be associated with loss of the dynamic stiffness and damping properties of the spinal segments.…”

Section: Introductionmentioning

confidence: 99%

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The degenerative state of the intervertebral disk independently predicts the failure of human lumbar spine to high rate loading: An experimental study

Alkalay

Vader

Hackney

2015

Clinical Biomechanics

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Background In the elderly, 30–50% of patients report a fall event to precede the onset of vertebral fractures. The dynamic characteristics of the spine determine the peak forces on the vertebrae in a fall. However, we know little about the effect of intervertebral disk degeneration on the failure of human spines under the high loading rates associated with such falls. We hypothesized that MR estimates of disk hydration and viscoelastic properties will provide better estimates of failure strength than bone density alone. Methods Seventeen L1–L3 human spine segments were imaged (Magnetic Resonance imaging, Dual-energy X-ray absorptiometry), their dynamic responses quantified using pendulum based impact, and the spines tested to failure under high rate loading simulating a fall event. The spines’ stiffness and damping constants were computed (Kelvin–Voigt model) with disk hydration and geometry assessed from T2 and proton density images. Findings Under impact, the spines exhibited a second-order underdamped response with stiffness and damping ranging (17.9–754.5)kN/m and (133.6–905.3)Ns/m respectively. Damping, but not stiffness, was negatively correlated with higher ultimate strength (p<0.05). Higher bone mineral density and MR-estimated disk hydration correlated with higher ultimate strength (p<0.01 for both). No such correlations were observed for the T2 values. Adding disk hydration yielded a 20% increase in the model’s association with failure load compared to bone density alone (MANOVA, p<0.001). Interpretation The strong correlation between disk viscoelastic properties and MR-estimated hydration with the spine segments ultimate strength clearly demonstrate the need to include disk degeneration as part of fracture risk assessment in the elderly spine.

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“…Though several previous studies have investigated the response of the spine to dynamic loading (Kong and Goel, 2003; Guo and Teo, 2005; Guo et al, 2009), high-rate loading (Belytschko and Privitzer, 1978; Belytschko et al, 1978; Luo and Goldsmith, 1991), and force on the buttocks in subinjurious fall (Sran and Robinovitch, 2008; Van Toen et al, 2012), these models pertain mostly to the young to middle age, male population that might be subject to workplace injuries. Wilson and Myers (1998), employing an optimization based geometric model of osteopenic thoraco-lumbar spine, predicted the stiffness and damping characteristics of the spinal segments to influence the peak forces sustained by the vertebrae due to a backwards fall from standing height.…”

Section: Introductionmentioning

confidence: 99%

Effect of the Degenerative State of the Intervertebral Disk on the Impact Characteristics of Human Spine Segments

Wilson

Alkalay

Myers

2013

Front. Bioeng. Biotechnol.

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Models of the dynamic response of the lumbar spine have been used to examine vertebral fractures (VFx) during falls and whole body vibration transmission in the occupational setting. Although understanding the viscoelastic stiffness or damping characteristics of the lumbar spine are necessary for modeling the dynamics of the spine, little is known about the effect of intervertebral disk degeneration on these characteristics at high loading rates. We hypothesize that disk degeneration significantly affects the viscoelastic response of spinal segments to high loading rate. We additionally hypothesize the lumbar spine stiffness and damping characteristics are a function of the degree of preload. A custom, pendulum impact tester was used to impact 19 L1–L3 human spine segments with an end mass of 20.9 kg under increasing preloads with the resulting force response measured. A Kelvin–Voigt model, fitted to the frequency and decay response of the post-impact oscillations was used to compute stiffness and damping constants. The spine segments exhibited a second-order, under-damped response with stiffness and damping values of 17.9–754.5 kN/m and 133.6–905.3 Ns/m respectively. Regression models demonstrated that stiffness, but not damping, significantly correlated with preload (p < 0.001). Degenerative disk disease, reflected as reduction in magnetic resonance T2 relaxation time, was weakly correlated with change in stiffness at low preloads. This study highlights the need to incorporate the observed non-linear increase in stiffness of the spine under high loading rates in dynamic models of spine investigating the effects of a fall on VFx and those investigating the response of the spine to vibration.

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Transmission of Force in the Lumbosacral Spine During Backward Falls

Abstract: Lowering the floor stiffness (from 400 to 59 kN/m) can attenuate peak lumbosacral spine forces in a backward fall onto the buttocks from standing by 46% (average peak from 6.9 to 3.7 kN at L4/L5) to values closer to the average tolerance of the spine to fracture (3.4 kN).

Cited by 17 publications

References 43 publications

Characterization of the protective capacity of flooring systems using force-deflection profiling

Characterization of the protective capacity of flooring systems using force-deflection profiling

The degenerative state of the intervertebral disk independently predicts the failure of human lumbar spine to high rate loading: An experimental study

Effect of the Degenerative State of the Intervertebral Disk on the Impact Characteristics of Human Spine Segments

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