Analysis of a Minimally Invasive, Extension-limiting Device for the Spine
Analysis of a Minimally Invasive, Extension-limiting Device for the Spine
Object: Biomechanical testing and fluoroscopic imaging were used to study an extension-limiting device that has been developed to support and cushion the facet complex. It is a titanium screw-based system with a polycarbonate-urethane bumper that lies against the inferior articular process and is anchored into the pedicle by the screw for posterior dynamic stabilization (PDS).
Methods: Six human cadaveric spines were dissected from L-2 to L-5, leaving all ligamentous structures intact. The intact spines were first tested in flexion and extension, lateral bending, and axial rotation at ±7.5 Nm. The PDS devices were inserted at L3-4 and testing was repeated. Fluoroscopic analysis of posterior disc height and foraminal area of the intact and instrumented spines while loaded was performed. All test data were compared using a one-way analysis of variance (statistical significance was set at p < 0.05).
Instrumented spines had 62% less motion during flexion and 49% less motion during extension compared with the intact spines. Neuroimaging analysis showed 84% less compression of the posterior disc of the instrumented spines during extension, and no difference during flexion compared with intact spines. After instrumentation was affixed, the foraminal area was 36% larger than in intact spines during extension and 9% larger during flexion. During axial loading, compression of the posterior disc was decreased by 70%, and analysis showed 10% decompression prior to loading just from implanting the devices.
Conclusions: The PDS system has the benefit of being a completely percutaneous one, which can be used at all levels of the lumbar spine, including S-1. The PDS system limits spinal motion, enlarges the foramina, and achieves discal decompression.
Ainful conditions of the aging spine include degenerative disc disease, facet arthropathy, central and foraminal stenosis, and spondylolisthesis. There is significant clinical interest in developing technologies that would alleviate pain while maintaining the spine's natural biomechanics and not resorting to fusion. A novel percutaneous PDS device has been developed by Triage Medi cal, Inc. that is delivered bilaterally into the superior articular facet of the inferior VB for treating a given spinal motion segment. This device then acts as a mechanical stop between the articulating facets and theoretically should limit extension and thus compression of the central canal, the spinal foramen, and the posterior disc.
This study was designed to evaluate three biomechanical questions concerning this PDS device. First, we wanted to determine the differences in overall stiffness be tween intact and instrumented spinal motion segments. Second, we also measured the differences in relative intervertebral motion between intact and instrumented spinal motion segments. Third, we determined the differences in disc space height and spinal foramen size between intact and instrumented spinal motion segments.
Abstract and Introduction
Abstract
Object: Biomechanical testing and fluoroscopic imaging were used to study an extension-limiting device that has been developed to support and cushion the facet complex. It is a titanium screw-based system with a polycarbonate-urethane bumper that lies against the inferior articular process and is anchored into the pedicle by the screw for posterior dynamic stabilization (PDS).
Methods: Six human cadaveric spines were dissected from L-2 to L-5, leaving all ligamentous structures intact. The intact spines were first tested in flexion and extension, lateral bending, and axial rotation at ±7.5 Nm. The PDS devices were inserted at L3-4 and testing was repeated. Fluoroscopic analysis of posterior disc height and foraminal area of the intact and instrumented spines while loaded was performed. All test data were compared using a one-way analysis of variance (statistical significance was set at p < 0.05).
Instrumented spines had 62% less motion during flexion and 49% less motion during extension compared with the intact spines. Neuroimaging analysis showed 84% less compression of the posterior disc of the instrumented spines during extension, and no difference during flexion compared with intact spines. After instrumentation was affixed, the foraminal area was 36% larger than in intact spines during extension and 9% larger during flexion. During axial loading, compression of the posterior disc was decreased by 70%, and analysis showed 10% decompression prior to loading just from implanting the devices.
Conclusions: The PDS system has the benefit of being a completely percutaneous one, which can be used at all levels of the lumbar spine, including S-1. The PDS system limits spinal motion, enlarges the foramina, and achieves discal decompression.
Introduction
Ainful conditions of the aging spine include degenerative disc disease, facet arthropathy, central and foraminal stenosis, and spondylolisthesis. There is significant clinical interest in developing technologies that would alleviate pain while maintaining the spine's natural biomechanics and not resorting to fusion. A novel percutaneous PDS device has been developed by Triage Medi cal, Inc. that is delivered bilaterally into the superior articular facet of the inferior VB for treating a given spinal motion segment. This device then acts as a mechanical stop between the articulating facets and theoretically should limit extension and thus compression of the central canal, the spinal foramen, and the posterior disc.
This study was designed to evaluate three biomechanical questions concerning this PDS device. First, we wanted to determine the differences in overall stiffness be tween intact and instrumented spinal motion segments. Second, we also measured the differences in relative intervertebral motion between intact and instrumented spinal motion segments. Third, we determined the differences in disc space height and spinal foramen size between intact and instrumented spinal motion segments.
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