Clinical biomechanics
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Clinical biomechanics · Jan 2016
Antiglide plating of vertical medial malleolus fractures provides stiffer initial fixation than bicortical or unicortical screw fixation.
Vertical shear fractures of the medial malleolus (44-A2 ankle fractures) occur through a supination-adduction mechanism. There are numerous methods of internal fixation for this fracture pattern. ⋯ An antiglide plate construct provides the stiffest initial fixation while withstanding higher load to failure for vertical medial malleolus fractures when compared to unicortical and bicortical screw fixation.
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Clinical biomechanics · Jan 2016
Biomechanics of posterior instrumentation in L1-L3 lateral interbody fusion: Pedicle screw rod construct vs. transfacet pedicle screws.
The use of pedicle screws is the gold standard for supplemental posterior fixation in lateral interbody fusion. Information about the performance of transfacet pedicle screws compared to standard pedicle screws and rods in the upper lumbar spine with or without a lateral interbody fusion device in place is limited. ⋯ Posterior fixation with transfacet pedicle screws provides equivalent immediate stability to similarly sized pedicle screws. However, in the presence of a lateral interbody fusion device, pedicle screws seem to resist loosening more and may be a better option for fusion in the upper lumbar spine.
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Clinical biomechanics · Dec 2015
Biomechanical effects of fusion levels on the risk of proximal junctional failure and kyphosis in lumbar spinal fusion surgery.
Spinal fusion surgery is a widely used surgical procedure for sagittal realignment. Clinical studies have reported that spinal fusion may cause proximal junctional kyphosis and failure with disc failure, vertebral fracture, and/or failure at the implant-bone interface. However, the biomechanical injury mechanisms of proximal junctional kyphosis and failure remain unclear. ⋯ The results of this study demonstrate that more distal fusion levels, particularly in spinal fusion including the L5-S1 level, lead to greater increases in the risk of proximal junctional kyphosis and failure, as evidenced by larger ranges of motion, higher stresses on fibers of the annulus fibrosus and vertebra at the adjacent segment, and higher axial forces on the screw at the uppermost instrumented vertebra in flexion-extension. Therefore, fusion levels should be carefully selected to avoid proximal junctional kyphosis and failure.
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Clinical biomechanics · Dec 2015
Biomechanical response to ankle-foot orthosis stiffness during running.
The Intrepid Dynamic Exoskeletal Orthosis (IDEO) is an ankle-foot orthosis developed to address the high rates of delayed amputation in the military. Its use has enabled many wounded Service Members to run again. During running, stiffness is thought to influence an orthosis' energy storage and return mechanical properties. This study examined the effect of orthosis stiffness on running biomechanics in patients with lower limb impairments who had undergone unilateral limb salvage. ⋯ Ankle-foot orthosis stiffness affected ankle joint stiffness but did not influence other biomechanical parameters of running in individuals with unilateral limb salvage. Foot strike asymmetries may have influenced the kinetics of running. Therefore, a range of stiffness may be clinically appropriate when prescribing ankle-foot orthoses for active individuals with limb salvage.
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This study has been designed to ascertain whether a standard configuration Ilizarov tibial frame can control shear motion at the fracture site of an oblique fracture within acceptable limits for axial micro-motion, and therefore promote bony union. If not, are there simple modifications to the frame design that can achieve this? ⋯ This is one of only two studies to look at circular frame fracture site control in oblique fractures. This is the only study to characterise Ilizarov frame stiffness in oblique fractures. We have shown that the standard Ilizarov frame design is inadequate for control of oblique fractures in this mechanical model. Our data show that with the application of simple principles, the Ilizarov frame can be modified to provide better fracture site control. These frame designs can be applied clinically to reduce fracture site shear motion in oblique fractures, resulting in improved union rates.