Journal of neurosurgery
-
Journal of neurosurgery · Jul 2003
Comparative StudyIn vitro biomechanical comparison of pedicle screws, sublaminar hooks, and sublaminar cables.
Three types of posterior thoracolumbar implants are in use today: pedicle screws, sublaminar titaniumcables, and sublaminar hooks. The authors conducted a biomechanical comparison of these three implants in human cadaveric spines. ⋯ These findings suggest that screws possess the greatest pullout strength of the three fixation systems. Sublaminar cables are the least rigid of the three. When screw failure occurred, the mechanism was generally screw back-out, without vertebral fractures.
-
Journal of neurosurgery · Jul 2003
Comparative StudyBiomechanical analysis of multilevel cervical corpectomy and plate constructs.
The authors compared the biomechanical stability of two multilevel cervical constructs involving the placement of equal size anterior cervical plates (ACPs) after decompressive surgery: the first is placed after three-level corpectomy with strut graft and the second after two-level corpectomy and aggressive discectomy with strut graft. In addition, both constructs were evaluated with and without the application of a screw attaching the ACP to the strut graft to determine whether the additional screw enhanced stability in any mode of loading. ⋯ The construct associated with the two-level corpectomy/discectomy provided better immediate postoperative stability than that associated with the three-level corpectomy. The addition of a screw to the strut graft conferred stability on the three-level construct but not the two-level construct.
-
Journal of neurosurgery · Jul 2003
Immunohistochemical analysis of the extracellular matrix in the posterior capsule of the zygapophysial joints in patients with degenerative L4-5 motion segment instability.
Although the hypertrophied shape of the zygapophysial joints in degenerative instability of the lumbar spine is well known, its underlying pathophysiological mechanism is unclear. The authors sought to provide evidence that there is increased fibrocartilaginous metaplasia in the posterior joint capsule resulting from greater mechanical loading; the authors suggest that these capsular changes are central to understanding the altered joint shape. ⋯ The results of this study provide molecular evidence for an altered loading history on the joint capsule. The pronounced loss of intervertebral disc height that occurred in all patients with severe degeneration of the lumbar motion segment promotes an increased range of axial rotation that places the posterior capsule under greater mechanical load. Compared with normal joints studied previously, the posterior capsules involved in these degenerative joint complexes were hypertrophied and fibrocartilaginous throughout. Cartilaginous metaplasia was especially pronounced at the attachment sites (entheses) where the fibrocartilage now extended beyond the original level of the joint space, and capped the osseous spurs arising from these attachment sites.
-
Journal of neurosurgery · Jul 2003
Comparative StudyAnterior cervical plate fixation: biomechanical effectiveness as a function of posterior element injury.
The primary goal of this study was to determine if the stabilization provided to the spine by anterior cervical fixation with plating (ACFP) was dependent on the degree of posterior element injury. The secondary goal was to evaluate the effectiveness of additional posterior screw/rod stabilization in these injuries. ⋯ Capsular ligaments and articular facets are important structures in limiting three-dimensional vertebral motion in the presence of an anterior plate. Supplementary posterior fixation does reduce motion for all injury conditions.
-
Journal of neurosurgery · Jul 2003
Case ReportsParamedian transmuscular access to C-3 dumbbell-type neurofibroma without paravertebral muscle dissection from the spinous process or facetectomy. Technical note.
The authors devised a paramedian transmuscular approach to the C2-3 facet joint that enabled total removal of C-3 dumbbell-type neurofibroma; dissection of the paravertebral muscles from the spinous process was not required and the facet joint was preserved. Only splitting or retraction of the paravertebral muscles was necessary. The anatomical features and procedures involved in muscle splitting are described.