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  • Pull-out test  (2)
  • Arthrodèse lombaire  (1)
  • Failed-back syndrome  (1)
  • 1
    Electronic Resource
    Electronic Resource
    Springer
    European spine journal 4 (1995), S. 114-122 
    ISSN: 1432-0932
    Keywords: Thoracic spine ; Biomechanics ; Pedicle screw ; Pedicle hook ; Pull-out test
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Pedicle hooks which are used as an anchorage for posterior spinal instrumentation may be subjected to considerable three-dimensional forces. In order to achieve stronger attachment to the implantation site, hooks using screws for additional fixation have been developed. The failure loads and mechanisms of three such devices have been experimentally determined on human thoracic vertebrae: the Universal Spine System (USS) pedicle hook with one screw, a prototype pedicle hook with two screws and the Cotrel-Dubousset (CD) pedicle hook with screw. The USS hooks use 3.2-mm self-tapping fixation screws which pass into the pedicle, whereas the CD hook is stabilised with a 3-mm set screw pressing against the superior part of the facet joint. A clinically established 5-mm pedicle screw was tested for comparison. A matched pair experimental design was implemented to evauluate these implants in constrained (series I) and rotationally unconstrained (series II) posterior pull-out tests. In the constrained tests the pedicle screw was the strongest implant, with an average pull-out force of 1650 N (SD 623 N). The prototype hook was comparable, with an average failure load of 1530 N (SD 414 N). The average pull-out force of the USS hook with one screw was 910 N (SD 243 N), not significantly different to the CD hook's average failure load of 740 N (SD 189 N). The result of the unconstrained tests were similar, with the prototype hook being the strongest device (average 1617 N, SD 652 N). However, in this series the difference in failure load between the USS hook with one screw and the CD hook was significant. Average failure loads of 792 N (SD 184 N) for the USS hook and 464 N (SD 279 N) for the CD hook were measured. A pedicular fracture in the plane of the fixation screw was the most common failure mode for USS hooks. The hooks usually did not move from their site of implantation, suggesting that they may be well-suited for the socalled segmental spinal correction technique as used in scoliosis surgery. In contrast, the CD hook disengaged by translating caudally from its site of implantation in all cases, suggesting a mechanical instability. The differences in observed hook failure modes may be a function of the type and number of additional fixation screws used. These results suggest that additional screw fixation allows stable attachment of pedicle hooks to their implantation site. Hooks using additional fixation screws passing obliquely into the pedicle apparently provide the most rigid attachment. The second fixation screw of the prototype hook almost doubles the fixation strength. Thus, the prototype hook might be considered as an alternative to the pepdicle screw, especially in the upper thoracic region.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-0932
    Keywords: Rachis lombaire ; Arthrodèse lombaire ; Spondylolisthésis ; Echec de la chirurgie lombaire ; Biomécanique ; Lumbar spine ; Spinal fusion ; Spondylolisthesis ; Failed-back syndrome ; Biomechanics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Summary Various methods of lumbosacral fusions for the treatment of degenerative spinal diseases are used clinically. Results vary greatly depending on indication, type of fusion, implants, and method of evaluation. In a retrospective clinical and radiological examination after an average follow-up time of 3.9 years this study reports on the outcome of lumbosacral distraction spondylodesis (LSDS) in a consecutive series of 147 patients being fused for the treatment of spondylolisthesis, failed-back syndrome, or lumbar instability. LSDS consists of a posterolateral fusion together with an autologous corticocancellous H-graft wedged under distraction between the spinous processes of L4 and S1. With 81.0% good and excellent results this noninstrumented fusion technique showed the best outcome in patients with spondylolisthesis, while in cases with a failed-back syndrome or lumbar instability only 62.3% excellent to satisfying outcomes were noted. The rate of pseudarthrosis was 13.6% in the whole patient group; no major complications such as nerve root damage, postoperative neurological deficits, or spinal stenosis were found.
    Notes: Résumé Diverses méthodes de fusion lombo-sacrée sont utilisées dans le traitement des affections dégénératives rachidiennes. Les résultats sont très variables et dépendent de l'indicatio, du type de fusion, des implants et de la méthode d'évaluation. Par une analyse rétrospective clinique et radiologique après un délai postopératoire moyen de 3,9 mois, cette étude rend compte du résultat de la “spondylodèse lombo-sacrée en distraction” (LSDS) dans une série consécutive de 147 patients traités par arthrodèse pour spondylolisthésis, échec de la chirurgie lombaire ou instabilité lombaire. La LSDS consite en une greffe postéro-latérale associée à un greffon autologue cortico-spongieux en H enfoncé sous distraction entre les épineuses de L4 et de S1. Avec 81,0% de bons et excellents résultats, cette technique d'arthrodèse sans ostéosynthèse a montré ses meilleurs résultats dans le traitement des spondylolisthésis, tandis que dans les cas d'échec de la chirurgie lombaire ou d'instabilité lombaire il n'a donné que 62,3% des résultats excellents ou satisfaisants. Le taux de pseudarthroses était de 13,6% pour tout le groupe et l'on n'a pas trouvé de complications majeures comme une atteinte radiculaire, un déficit neurologique post-opératoire ou une sténose lombaire.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1432-0932
    Keywords: Thoracic spine ; Pedicle hook ; Fixation screw ; Biomechanics ; Pull-out test
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The pull-out force of thoracic spinal pedicle hooks secured by long fixation screws engaging the posterior portion of the vertebral endplate was measured. The perfomance of these hooks was compared with that of hooks using a shorter screw and different screw orientation such that the vertebral endplates were not perforated. The longer and differently angulated screws, engaging the endplate, significantly enhanced the fixation potential of the hooks.
    Type of Medium: Electronic Resource
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