The spine journal : official journal of the North American Spine Society
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Posterolateral fusions of the lumbar spine have nonunion rates as high as 35%. The availability of autologous bone to promote fusion is limited, particularly for multilevel fusions. Bone substitutes have been proposed to augment or replace autologous bone for spinal surgery. Calcium sulfate offers high porosity, osteoconductivity, and high resorption rate. This material has been used successfully for treatment of long bone defects but has not been investigated as a bone graft substitute for spinal fusions. ⋯ This study found that calcium sulfate as a bone graft substitute was unsuccessful in promoting spine fusion in a rabbit model. There was radiographic evidence of rapid resorption of the calcium sulfate within 4 weeks after surgery. The use of electrical stimulation created a dose-dependent increase in mechanical competence of the bony mass. However, the addition of direct current (DC) current did not significantly alter fusion rates with calcium sulfate used as the bone graft substitute in this model.
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Biomechanical studies show that bone-mineral density, pedicle morphology, and screw thread area affect pedicle screw pullout failure. The current literature is based on studies of cylindrical pedicle screw designs. Conical screws have been introduced that may provide better "fit and fill" of the dorsal pedicle as well as improved resistance to screw bending failure. However, there is concern about loss of fixation if conical screws must be backed out after insertion. ⋯ Conical screws offer improved initial fixation strength compared with cylindrical screws of the same size and thread design. Our results suggest that appropriately designed conical screws can be backed out 180 to 360 degrees for intraoperative adjustment without loss of pullout strength, stiffness or work to failure. Intraoperative adjustments of these specific conical screws less than 360 degrees should not affect initial fixation strength. These results may not hold true for screws with a smaller thread area or larger minor diameter.
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Discography is used today as the basis of the diagnosis of discogenic back and neck pain. As such, it plays a pivotal role in the formulation of treatment plans for patients complaining of chronic axial spine pain. ⋯ Clinicians who use discography to determine treatment pathways for their patients need to critically examine the validity of the test. Recent studies examining the specificity of discography have led us to proceed much more cautiously in interpreting the results of discography.
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Clinical Trial
Segmental instrumentation for thoracic and thoracolumbar fractures: prospective analysis of construct survival and five-year follow-up.
Segmental instrumentation systems have replaced nonsegmental systems in all areas of spine surgery. Construct patterns for fracture stabilization have been adapted from deformity experience and from biomechanical studies using nonsegmental systems. Few studies have been completed to validate the use of these implants in trauma or to assess their relative strengths and weaknesses. ⋯ Segmental instrumentation allowed immediate mobilization of these severely injured patients, eliminating thromboembolic and pulmonary complications, and reducing overall morbidity and mortality. Segmental instrumentation produced a high rate of fusion with no rod breakage or hook failure. Pedicle screw constructs had a high rate of screw complications associated with anterior column insufficiency, but revision was not always necessary. Eighty percent of these severely injured patients were capable of returning to full-time employment, and 70% did so.
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Results of subsequent surgical intervention in patients with intractable pain after lumbar spine surgery are typically worse than for initial surgery, particularly in those with predominant complaints of back pain rather than lower extremity pain. Spinal cord stimulation (SCS) has been found to yield good results in patients with primary complaints of intractable lower extremity pain. Technological advances have broadened the indications for this treatment. ⋯ In this retrospective study, the majority of patients were satisfied with the results of SCS and would have the procedure again knowing what their outcome would be. These results suggest that further investigation of SCS is warranted in this difficult to treat patient population presenting with predominant complaints of chronic, intractable, axial low back pain.