Development of 6-Axis Material Tester for Measuring Mechanical Spine Properties

PurposeThere have been several reports on the pullout strength of cortical bone trajectory (CBT) screws, but only one study has reviewed the stability of functional spine units using the CBT method. The purpose of this study was to compare vertebral stability after CBT fixation with that after pedicle screw (PS) fixation.MethodsIn this study, 20 lumbar spine (L5–6) specimens were assigned to two groups: the CBT model group that underwent CBT screw fixation (n = 10) and the PS model group that underwent pedicle screw fixation (n = 10). Using a six-axis material testing machine, bend and rotation tests were conducted on each model. The angular displacement from the time of no load to the time of maximum torque was defined as range of motion (ROM), and then, the mean ROM in the bend and rotation tests and the mean rate of relative change of ROM in both the bend and rotation tests were compared between the CBT and PS groups.ResultsThere were no significant differences between the CBT and PS groups with regard to the mean ROMs and the mean rate of relative change of ROMs in both the bend and rotation tests.ConclusionIntervertebral stability after CBT fixation was similar to that after PS fixation.

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“…For the test, a six-axis material testing machine [ 8 – 10 ] developed in our laboratory (Fig. 4 ) was used.…”

Section: Methodsmentioning

confidence: 99%

A biomechanical comparison between cortical bone trajectory fixation and pedicle screw fixation

et al. 2015

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“…Wahba et al experimented with a burst fracture model and reported that the stiffness of the PS model was weaker than that of an intact model [ 5 ]. Lim et al experimented with a discectomy model and reported that the ROMs of the PS model were larger than those of an intact model [ 11 ]. We also performed biomechanical experiments with a facetectomy model and concluded that the ROMs of the PS model were larger than those of an intact model during rotation tests and that insufficient torsional stability might be the cause of pseudoarthrosis and implant failure.…”

Section: Discussionmentioning

confidence: 99%

“…For the biomechanical tests, a 6-axis material testing machine developed in our laboratory that allows motion with 6 degrees of freedom was used ( Figure 2 ) [ 11 ]. In this study, we performed both a bending test (anterior, right-anterior, right, right-posterior, posterior, left-posterior, left, and left-anterior bending) and a rotation test (right and left rotation).…”

Section: Methodsmentioning

confidence: 99%

Biomechanical Stability of a Cross-Rod Connection with a Pedicle Screw System

Mizuno

Sakakibara

Yoshikawa

et al. 2018

Med Sci Monit Basic Res

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BackgroundSurgery with pedicle screw instrumentation does not provide sufficient torsional stability. This leads to pseudoarthrosis, loosening of the pedicle screws, and, ultimately, implant failure.Material/MethodsFunctional spinal units from 18 deer were evaluated using a 6-axis material testing machine. As specimen models, we prepared an intact model, a damaged model, a cross-rod model, and a cross-link model. We measured the range of motion (ROM) during bending and rotation tests.ResultsThe range of motions of cross-rod model were almost equal to those of cross-link model during the bending test. In the rotation test, the average ranges of motion of the intact, cross-rod, and cross-link models were 2.9°, 3.1°, and 3.9° during right rotation and 2.9°, 3.1°, and 4.1° during left rotation, respectively. The range of motions of the cross-rod model were significantly smaller than those of the cross-link model during the rotation test. The range of motions of the intact model were significantly smaller than those of the cross-link model during the rotation test, but there were no statistically significant differences between the range of motions of intact model and cross-rod model during the rotation test.ConclusionsThe stability of spinal fixation such as cross-rod model is equal to the fixation using the pedicle screw system during bending tests and equal to that of the intact spine during rotation tests.

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“…For the tests, a six-axis material testing machine developed in our laboratory was used (Fig. 3 ) [ 15 ]. This testing machine adopts a parallel mechanism.…”

Section: Methodsmentioning

confidence: 99%

Trajectory of instantaneous axis of rotation in fixed lumbar spine with instrumentation

et al. 2017

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BackgroundSeveral studies showed instantaneous axis of rotation (IAR) in the intact spine. However, there has been no report on the trajectory of the IAR of a damaged spine or that of a fixed spine with instrumentation. It is the aim of this study to investigate the trajectory of the IAR of the lumbar spine using the vertebra of deer.MethodsFunctional spinal units (L5–6) from five deer were evaluated with six-axis material testing machine. As specimen models, we prepared a normal model, a damaged model, and a pedicle screw (PS) model. We measured the IAR during bending in the coronal and sagittal planes and axial rotation. In the bending test, four directions were measured: anterior, posterior, right, and left. In the rotation test, two directions were measured: right and left.ResultsThe IAR of the normal model during bending moved in the bending direction. The IAR of the damaged model during bending moved in the bending direction, but the magnitude of displacement was bigger compared to that of the normal model. In the PS model, the IAR during bending test hardly moved. During rotation test, the IAR of the normal model and PS model located in the spinal canal, but the IAR of the damaged model located in the posterior part of the vertebral body.ConclusionsIn this study, the IAR of damaged model was scattering and that of PS model was concentrating. This suggests that higher mechanical load applied to the dura tube and nerve roots in the damaged model and less mechanical load applied to that in the PS model.

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Development of 6-Axis Material Tester for Measuring Mechanical Spine Properties

Cited by 13 publications

References 6 publications

A biomechanical comparison between cortical bone trajectory fixation and pedicle screw fixation

A biomechanical comparison between cortical bone trajectory fixation and pedicle screw fixation

Biomechanical Stability of a Cross-Rod Connection with a Pedicle Screw System

Trajectory of instantaneous axis of rotation in fixed lumbar spine with instrumentation

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