In:
Journal of Neurosurgery: Spine, Journal of Neurosurgery Publishing Group (JNSPG), Vol. 14, No. 2 ( 2011-02), p. 226-234
Abstract:
Posterior screw-rod fixation for thoracic spine trauma usually involves fusion across long segments. Biomechanical data on screw-based short-segment fixation for thoracic fusion are lacking. The authors compared the effects of spanning short and long segments in the thoracic spine. Methods Seven human spine segments (5 segments from T-2 to T-8; 2 segments from T-3 to T-9) were prepared. Pure-moment loading of 6 Nm was applied to induce flexion, extension, lateral bending, and axial rotation while 3D motion was measured optoelectronically. Normal specimens were tested, and then a wedge fracture was created on the middle vertebra after cutting the posterior ligaments. Five conditions of instrumentation were tested, as follows: Step A, 4-level fixation plus cross-link; Step B, 2-level fixation; Step C, 2-level fixation plus cross-link; Step D, 2-level fixation plus screws at fracture site (index); and Step E, 2-level fixation plus index screws plus cross-link. Results Long-segment fixation restricted 2-level range of motion (ROM) during extension and lateral bending significantly better than the most rigid short-segment construct. Adding index screws in short-segment constructs significantly reduced ROM during flexion, lateral bending, and axial rotation (p 〈 0.03). A cross-link reduced axial rotation ROM (p = 0.001), not affecting other loading directions (p 〉 0.4). Conclusions Thoracic short-segment fixation provides significantly less stability than long-segment fixation for the injury studied. Adding a cross-link to short fixation improved stability only during axial rotation. Adding a screw at the fracture site improved short-segment stability by an average of 25%.
Type of Medium:
Online Resource
ISSN:
1547-5654
DOI:
10.3171/2010.10.SPINE09785
Language:
Unknown
Publisher:
Journal of Neurosurgery Publishing Group (JNSPG)
Publication Date:
2011
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