Journal of neurosurgery. Spine
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In generalized osteoporosis, instrumentation with cement-augmented pedicle screws is an amplification of the therapeutic spectrum. Early clinical results are promising for both solid and cannulated screws; however, there are concerns regarding the revision characteristics of these screws, especially for the cannulated-fenestrated type with its continuous cement interconnection from the core of the screw to surrounding bone tissue. In a human cadaver model, bone mineral density (BMD) was assessed radiographically. ⋯ Thus, the revision characteristics of cement-augmented, cannulated-fenestrated pedicle screws are not problematic, even in cases of severe osteoporosis. The winglike cement interconnection between the screw core and surrounding bone tissue is fragile enough to break off in the event of an extraction torque and to release the screw. There is no proof to support the theoretical fear that while trying to remove a screw, the composite of screw and cement would not break but instead would rotate as a whole in the osteoporotic vertebral body.
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The authors' experience with treatment of 8 patients with "vertical mobile and reducible" atlantoaxial dislocation is reviewed. The probable pathogenesis, radiological and clinical features, and management issues in such cases are discussed. ⋯ Vertical mobile and reducible atlantoaxial dislocation is a discrete clinical entity. Abnormal inclination and incompetence of the facet joint appears to be the primary causative factor that resulted in vertical dislocation or basilar invagination. Posterior fixation in the reduced dislocation position forms the basis of treatment.
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Spontaneous spinal epidural hematoma (SSEH) is rare. Its etiology remains controversial; however, spinal venous wall susceptibility to intravenous pressure change and the resultant venous rupture seem to be involved. ⋯ This neurological false localizing sign seems to have resulted from counterforce by preexisting asymptomatic cervical intervertebral disc herniation at the C6-7 levels inducing direct pressure on the anterior spinal cord. This case is the first reported instance of posterior cervical SSEH manifesting acute anterior spinal cord syndrome as its false localizing sign.