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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A new fixation device for C1-C2 fusion is presented. It consists of a claw construct for the C1 arch that is rigidly attached to C1-C2 transarticular screws to form an instrument that combines anterior and posterior fixation in the same construct. The new device was successfully applied in a case with failed C1-C2 fusion that was initially stabilized with transarticular screws alone, where the usual posterior wiring was omitted due to a defect of the posterior C1 arch.
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Loosening of the pedicle screws with subsequent non-union or loss of correction is a frequent problem in spinal instrumentation. In a clinical pilot study, coating of pedicle screws with plasma-sprayed hydroxyapatite (HA) resulted in a significant increase of removal torque. An experimental study was performed to investigate the effects of HA coating on the pull-out resistance. ⋯ At 12 weeks, the average stiffness was significantly higher for the HA-coated screws, while there was no significant differences in stiffness between the two screw types at 0 and 6 weeks. Energy to failure was significantly higher for coated screws when compared to the uncoated screws at all three time points. HA coating improves fixation of loaded pedicle screws, with increased pull-out resistance and reduced risk of loosening.
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Stabilizing a lumbar spine with an implant alters the mechanical properties of the bridged region. In order to determine whether this procedure is associated with higher loads in the adjacent segments, seven lumbar cadaver spines were mounted in a spine tester and loaded with pure moments of flexion/extension, left and right lateral bending, and left and right axial rotation. The material studied comprised intact lumbar spines, intact spines with bisegmental internal spinal fixators, and postcorpectomy spines both with a graft and fixators and with fixators alone. ⋯ Highly significant differences in these regions (P<0.01) were far below the interspecimen range. We did not find any case where both intradiscal pressure changes and intersegmental motion showed highly significantly differences in the regions adjacent to the bridged one. Our results suggest that disc degeneration, which is sometimes found at the level directly above and below the fixators, is not caused by mechanical factors.
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Comparative Study
Role of cortical and cancellous bone of the vertebral pedicle in implant fixation.
An experimental study was conducted to determine the role of cancellous and cortical bone of vertebral pedicles in the fixation of pedicular screws. Ten segments of the lumbar spinal column removed from adults at autopsy were used. Direct measurements were made to obtain the total diameter of the pedicles from L1 to L5 plus the diameter of cancellous bone and the diameter of cortical bone. ⋯ The screws used ranged in diameter from 3 to 12.5 mm, with progressive 0.5-mm increments. The analysis of the alterations in pedicle structure was performed by considering total diameter, spongy bone diameter, cortical bone diameter, and diameter of the screw used to produce the structural alteration. The results showed that the screws in general presented fixation mainly in the cancellous bone portion of the vertebral pedicle, whereas a small percentage of cortical bone was used for fixation.
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No results on long-term outcome in terms of health-related quality of life (HRQL) have previously been presented for patients treated for adolescent idiopathic scoliosis. A consecutive series of patients with adolescent idiopathic scoliosis, treated between 1968 and 1977 before the age of 21, either with distraction and fusion using Harrington rods [surgical treatment group (ST), n=156; 145 females and 11 males] or with a brace [brace treatment group (BT), n=127; 122 females and 5 males] were followed at least 20 years after completion of the treatment. Ninety-four percent of ST and 91% of BT patients filled in a questionnaire comprising the SF-36, Psychological General Well-Being Index (PGWB), Oswestry Disability Back Pain Questionnaire, parts of SRS/MODEM'S questionnaire and study-specific questions concerning the treatment, as a part of an unbiased personal follow-up examination including radiography and clinical examination. ⋯ No correlation was found between the outcome scores and curve size after treatment, curve type, total treatment time or age at completed treatment. Patients treated for adolescent idiopathic scoliosis were found to have approximately the same HRQL as the general population. A minority of the patients (4%) had a severely decreased psychological well-being, and a few (1.5%) were severely physically disabled due to the back.