Journal of spinal disorders
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Impressive clinical reports have come from several major spinal research centers regarding the results of using the AO spinal internal fixator, a recently released pedicle screw rod system. A retrospective review of the first 2 years of clinical results from a diverse group of orthopedic surgeons using this device at a Canadian University center may provide some insight into potential clinical outcomes in general use. These results contrast with the outcome data provided to date, which have been presented by expert academic spinal surgeons. The results suggest that there may be room for considering limited release of this device, perhaps with the requirement for special certification in its application.
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We carried out experiments on whole cadaveric lumbar spines in order to determine the role that each of the capsulo-ligamentous structures play in axial rotation in the neutral position and in the flexed position. Eight specimens were first tested intact, then after division of all the apophyseal joint capsules between L1 and the sacrum. Another five specimens were also first tested intact, then after division of the supra- and interspinous ligaments and yellow ligament, and finally after cutting the posterior longitudinal ligament and posterior annulus at each level as well. ⋯ The apophyseal joint capsules limit rotation both in neutral and flexed positions. In flexion, the amplitude of rotation in the lumbar spine is reduced. Of the capsulo-ligamentous structures, it is the posterior annulus and the posterior longitudinal ligament that seem to play the more important role in limiting axial rotation while the spine is flexed.