The spine journal : official journal of the North American Spine Society
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Novel dual-threaded screws are configured with overlapping (doubled) threads only in the proximal shaft to improve proximal cortical fixation. ⋯ Although dual-threaded screws required higher insertion torque than standard screws in bone and low density foam, dual-threaded and standard pedicle screws exhibited equivalent axial pullout and cyclic fatigue endurance. Unlike single-threaded screws, the mechanical performance of dual-threaded screws in bone was relatively independent of BMD. In foam, the mechanical performance of both types of screws was highly dependent on porosity.
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There is currently no reliable technique for intraoperative assessment of pedicle screw fixation strength and optimal screw size. Several studies have evaluated pedicle screw insertional torque (IT) and its direct correlation with pullout strength. However, there is limited clinical application with pedicle screw IT as it must be measured during screw placement and rarely causes the spine surgeon to change screw size. To date, no study has evaluated tapping IT, which precedes screw insertion, and its ability to predict pedicle screw pullout strength. ⋯ Our findings suggest that tapping IT directly correlates with pedicle screw IT, pedicle screw pullout strength, and optimal pedicle screw size. Therefore, tapping IT may be used during thoracic pedicle screw instrumentation as an adjunct to preoperative imaging and clinical experience to maximize fixation strength and optimize pedicle "fit and fill" with the largest screw possible. However, further prospective, in vivo studies are necessary to evaluate the intraoperative use of tapping IT to predict screw loosening/complications.
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Despite significant advances in the development of diagnostic technology, the diagnosis of cervical myelopathy (CM) still remains based on the clinical findings, which do not provide the means for a sufficiently accurate diagnosis. Furthermore, conventional magnetic resonance imaging (MRI) using T1- and T2-weighted sequences lacks sensitivity to detect and characterize spinal cord lesions. Considering these uncertainties, several investigators have assessed the diagnostic value of diffusion tensor imaging (DTI), an advanced MRI technique that measures the diffusion of water molecules. ⋯ Use of DTI to quantitatively compare compression in the cervical spinal cords of CM subjects and healthy controls explained individual differences in the clinical findings in the subjects. These findings even applied to CM subjects whose compressed spinal cords looked similar on conventional T2-weighted MRI. Therefore, DTI provided more accurate and reliable information than did conventional T2-weighted MRI about the relationship between spinal cord structure and clinical presentation of CM. Based on our DTI findings, we hypothesized that different clinical findings in CM are attributable to the stage of progression and the severity of pathologic change at presentation. We anticipate that the use of DTI to quantify the extent of myelopathological changes in CM could be more reliable than any other existing diagnostic tools and might provide invaluable information about selecting the optimal treatment for CM and predicting surgical outcomes and prognosis.
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In patients with structural lumbar curves, several studies have shown the advantages of stopping fusion at L3 and saving L4. However, fusing the L4 may still be deemed necessary in a significant number of patients with structural lumbar curves (ie, Lenke types 3 and 6) when fusion levels are selected by using traditional flexibility X-ray (TXR) methods such as supine side bends and traction. ⋯ TrUGA may be an alternative method for selection of fusion levels and may help to save L4 when compared with traditional radiograph methods in surgical treatment of Lenke types 3 and 6 curves.
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Recent research describes the use of a nerve root sedimentation sign to diagnose lumbar spinal stenosis (LSS). The lack of sedimentation of the nerve roots (positive sedimentation sign) to the dorsal part of the dural sac is the characteristic feature of this new radiological parameter. ⋯ The sedimentation sign is a new measurement tool that can enable physicians to objectively assess and quantify spinal stenosis. The sign is most often present in patients who have clinically significant lumbar stenosis and require surgery.