The Current Testing Protocols for Biomechanical Evaluation of Lumbar Spinal Implants in Laboratory Setting: A Review of the Literature

Gonzalez-Blohm, Sabrina A.; Doulgeris, James; Lee, William; Shea, Thomas M.; Aghayev, Kamran; Vrionis, Frank D.

doi:10.1155/2015/506181

Cited by 20 publications

(12 citation statements)

References 77 publications

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“…Biomechanical studies typically include assessments of load-displacement behavior of one or more functional spinal units (FSUs) under specific conditions. 8,13,21 The standard universal protocols include range of motion, stiffness, and hybrid testing. 13,21 The current study design mimics these protocols and prior PJK cadaveric studies in that specimens were unconstrained, with the magnitude and orientation of moments remaining the same with respect to the end vertebra.…”

Section: Current Study-biomechanical Analysismentioning

confidence: 99%

Biomechanical assessment of proximal junctional semi-rigid fixation in long-segment thoracolumbar constructs

Viswanathan

Ganguly

Minnema

et al. 2019

Journal of Neurosurgery: Spine

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OBJECTIVEProximal junctional kyphosis (PJK) and failure (PJF) are potentially catastrophic complications that result from abrupt changes in stress across rigid instrumented and mobile non-fused segments of the spine (transition zone) after adult spinal deformity surgery. Recently, data have indicated that extension (widening) of the transitional zone via use of proximal junctional (PJ) semi-rigid fixation can mitigate this complication. To assess the biomechanical effectiveness of 3 semi-rigid fixation constructs (compared to pedicle screw fixation alone), the authors performed cadaveric studies that measured the extent of PJ motion and intradiscal pressure changes (ΔIDP).METHODSTo measure flexibility and ΔIDP at the PJ segments, moments in flexion, extension, lateral bending (LB), and torsion were conducted in 13 fresh-frozen human cadaveric specimens. Five testing cycles were conducted, including intact (INT), T10–L2 pedicle screw-rod fixation alone (PSF), supplemental hybrid T9 Mersilene tape insertion (MT), hybrid T9 sublaminar band insertion (SLB1), and hybrid T8/T9 sublaminar band insertion (SLB2).RESULTSCompared to PSF, SLB1 significantly reduced flexibility at the level rostral to the upper-instrumented vertebral level (UIV+1) under moments in 3 directions (flexion, LB, and torsion, p ≤ 0.01). SLB2 significantly reduced motion in all directions at UIV+1 (flexion, extension, LB, torsion, p < 0.05) and at UIV+2 (LB, torsion, p ≤ 0.03). MT only reduced flexibility in extension at UIV+1 (p = 0.02). All 3 constructs revealed significant reductions in ΔIDP at UIV+1 in flexion (MT, SLB1, SLB2, p ≤ 0.02) and torsion (MT, SLB1, SLB2, p ≤ 0.05), while SLB1 and SLB2 significantly reduced ΔIDP in extension (SLB1, SLB2, p ≤ 0.02) and SLB2 reduced ΔIDP in LB (p = 0.05). At UIV+2, SLB2 similarly significantly reduced ΔIDP in extension, LB, and torsion (p ≤ 0.05).CONCLUSIONSCompared to MT, the SLB1 and SLB2 constructs significantly reduced flexibility and ΔIDP in various directions through the application of robust anteroposterior force vectors at UIV+1 and UIV+2. These findings indicate that semi-rigid sublaminar banding can most effectively expand the transition zone and mitigate stresses at the PJ levels of long-segment thoracolumbar constructs.

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Section: Current Study-biomechanical Analysismentioning

confidence: 99%

Biomechanical assessment of proximal junctional semi-rigid fixation in long-segment thoracolumbar constructs

Viswanathan

Ganguly

Minnema

et al. 2019

Journal of Neurosurgery: Spine

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“… 2010 ; Gonzalez-Blohm et al. 2015 ). In these tests, it is critical to know the liver’s response to a range of factors, such as puncturing, cutting, deformations and displacements.…”

Section: Introductionmentioning

confidence: 99%

Nonlinear viscoelastic constitutive model for bovine liver tissue

Capilnasiu

Bilston

Sinkus

et al. 2020

Biomech Model Mechanobiol

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Soft tissue mechanical characterisation is important in many areas of medical research. Examples span from surgery training, device design and testing, sudden injury and disease diagnosis. The liver is of particular interest, as it is the most commonly injured organ in frontal and side motor vehicle crashes, and also assessed for inflammation and fibrosis in chronic liver diseases. Hence, an extensive rheological characterisation of liver tissue would contribute to advancements in these areas, which are dependent upon underlying biomechanical models. The aim of this paper is to define a liver constitutive equation that is able to characterise the nonlinear viscoelastic behaviour of liver tissue under a range of deformations and frequencies. The tissue response to large amplitude oscillatory shear (1-50%) under varying preloads (1-20%) and frequencies (0.5-2 Hz) is modelled using viscoelastic-adapted forms of the Mooney-Rivlin, Ogden and exponential models. These models are fit to the data using classical or modified objective norms. The results show that all three models are suitable for capturing the initial nonlinear regime, with the latter two being capable of capturing, simultaneously, the whole deformation range tested. The work presented here provides a comprehensive analysis across several material models and norms, leading to an identifiable constitutive equation that describes the nonlinear viscoelastic behaviour of the liver.

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“…Although 2 preconditioning cycles are common, 23 Stolworthy et al 22 still found "significant residual changes in segmental flexibility" and recommended 20 cycles. These findings appear consistent to the findings in this study.…”

Section: Discussionmentioning

confidence: 99%

“…The torsion loading in each stage remained at +7.5 NÁm, as reported in comparable studies. [18][19][20]22,23 After initial testing in phase I, a pincer fracture was created in the mid-vertebra of the specimen 21 (either Th12 or L1). A wedged, V-shaped metal section ( Figure 3) was introduced laterally between the inferior endplate of the upper vertebral body and the intervertebral disc (IVD) until the IVD penetrated the superior endplate of the mid-vertebral body.…”

Section: Cyclic Testingmentioning

confidence: 99%

Lag-Screw Osteosynthesis in Thoracolumbar Pincer Fractures

Auerswald

Messer-Hannemann

Sellenschloh

et al. 2020

Global Spine Journal

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Study Design: Biomechanical. Objective: This study evaluates the biomechanical properties of lag-screws used in vertebral pincer fractures at the thoracolumbar junction. Methods: Pincer fractures were created in 18 bisegmental human specimens. The specimens were assigned to three groups depending on their treatment perspective, either bolted, with the thread positioned in the cortical or cancellous bone, or control. The specimens were mounted in a servo-hydraulic testing machine and loaded with a 500 N follower load. They were consecutively tested in 3 different conditions: intact, fractured, and bolted/control. For each condition 10 cycles in extension/flexion, torsion, and lateral bending were applied. After each tested condition, a computed tomography (CT) scan was performed. Finally, an extension/flexion fatigue loading was applied to all specimens. Results: Biomechanical results revealed a nonsignificant increase in stiffness in extension/flexion of the fractured specimens compared with the intact ones. For lateral bending and torsion, the stiffness was significantly lower. Compared with the fractured specimens, no changes in stiffness due to bolting were discovered. CT scans showed an increasing fracture gap during axial loading both in extension/flexion, torsion, and lateral bending in the control specimens. In bolted specimens, the anterior fragment was approximated, and the fracture gap nullified. This refers to both the cortical and the cancellous thread positions. Conclusion: The results of this study concerning the effect of lag-screws on pincer fractures appear promising. Though there was little effect on stiffness, CT scans reveal a bony contact in the bolted specimens, which is a requirement for bony healing.

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The Current Testing Protocols for Biomechanical Evaluation of Lumbar Spinal Implants in Laboratory Setting: A Review of the Literature

Cited by 20 publications

References 77 publications

Biomechanical assessment of proximal junctional semi-rigid fixation in long-segment thoracolumbar constructs

Biomechanical assessment of proximal junctional semi-rigid fixation in long-segment thoracolumbar constructs

Nonlinear viscoelastic constitutive model for bovine liver tissue

Lag-Screw Osteosynthesis in Thoracolumbar Pincer Fractures

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