Biomechanics of a Posterior Lumbar Motion Stabilizing Device: In Vitro Comparison to Intact and Fused Conditions
Abstract
Nondestructive flexibility tests were performed in vitro, comparing multiple conditions of fixation in a single group of specimens. To compare the biomechanical behavior of the lumbar spine in the intact condition, after implanting a novel motion stabilizer, and after implanting a rigid fixator. Two specific scenarios that may benefit from dynamic lumbar stabilization are single-level moderate instability, where the stabilizing tissues are relatively incompetent, and juxta-level to fusion, where the last instrumented level requires intermediate stiffness ("topping off") to prevent transfer of high stresses from the stiffer fusion construct to the intact adjacent levels. Both scenarios were evaluated in vitro. Seven human cadaveric L2-S1 segments were tested (1) intact, (2) after moderate destabilization, (3) after 2-level hybrid posterior fixation, consisting of bilateral dynamic pedicle screws at L4 interconnected with rigid rods to standard pedicle screws at L5 and S1, (4) after 2-level rigid fixation, (5) after 1-level (L4-L5) dynamic fixation, and (6) after 1-level rigid fixation. In each condition, angular range of motion (ROM) and sagittal instantaneous axis of rotation (IAR) were assessed. In 1-level constructs, dynamic ...Continue Reading
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Thoracolumbar deformity arthrodesis stopping at L5: fate of the L5-S1 disc, minimum 5-year follow-up
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Biomechanics
Biomechanics examines the generation of internal forces within the body and investigates the effects and control of forces that act on or are produced on tissues. Here are the latest discoveries.