European spine journal : official publication of the European Spine Society, the European Spinal Deformity Society, and the European Section of the Cervical Spine Research Society
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Recently, lateral interbody fusion (LIF) has become more prevalent, and evaluation of lumbar nerves has taken on new importance. We report on the assessment of anatomical relationships between lumbar nerves and vertebral bodies using diffusion tensor imaging (DTI). ⋯ The L3/4 and L4/5 nerve roots are located posterior to the vertebral body center. These were found to be offset to the rear when the hip is flexed or the lateral decubitus position is assumed. The present study is the first to elucidate changes in the course of the lumbar nerves as this varies by position. The lateral decubitus position or the position supine with hips flexed may be useful for avoiding nerve damage in a direct lateral transpsoas approach. Preoperative DTI seems to be useful in evaluating the lumbar nerve course as it relates anatomically to the vertebral body.
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Cement augmentation is an established method to increase the pedicle screw (PS) anchorage in osteoporotic vertebral bodies. The ideal timing for augmentation when a reposition maneuver is necessary is controversial. While augmentation of the PS before reposition maneuver may increase the force applied it on the vertebrae, it bears the risk to impair PS anchorage, whereas augmenting the PS after the maneuver may restore this anchorage and prevent early screw loosening. The purpose of the present study was to evaluate the effect of cement application timing on PS anchorage in the osteoporotic vertebral body. ⋯ The time of cement application has an effect on PS anchorage in the osteoporotic vertebral body if a reposition maneuver of the instrumented vertebrae is carried out. PS augmented after the reposition maneuver showed a significant higher number of load cycles until screw loosening.
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To assess the pull-out strength of thoracolumbar pedicle screws implanted via either a patient-specific template-guided or conventional free-hand fluoroscopically controlled technique in a randomized cadaveric study, and to evaluate the influence of local vertebral bone density, quantified by Hounsfield units (HU), on pedicle screw pull-out strength. ⋯ There was a significantly higher pull-out strength of thoracolumbar pedicle screws when inserted via a patient-specific template-guided versus conventional free-hand fluoroscopically controlled technique, potentially associated with screw trajectory.
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Implant failure is a frequent complication in corrective surgery for early onset scoliosis, since considerable forces are acting on small and fragile vertebrae. Osseointegration showing biomechanical and histological improvement in bone-implant interface (BII) after dental implant placement has been well investigated. However, there are no studies regarding osseointegration in immature vertebral bone. The purpose was to evaluate the timecourse of biomechanical and histological changes at BII after pedicle screw placement using in vivo immature porcine model. ⋯ Improved stability at BII caused by osseointegration was confirmed by in vivo immature porcine model. A two-stage operation is proposed based on the osseointegration theory, in which an implant is installed in advance in the vertebrae at the first stage and deformity correction surgery is performed after sufficient stability is obtained by osseointegration at a later stage.
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To evaluate the influence of the position of the arms on the location of the body's gravity line. ⋯ We conclude in a validation of the data of the barycentremeter, as well as of the data obtained by the force platforms as long as the artifact of the position of the arms is taken into account.