Kinematic analysis of the space available for cord and disc bulging of the thoracic spine using kinematic magnetic resonance imaging (kMRI)

Publication date: Available online 14 November 2017
Source:The Spine Journal
Author(s): Permsak Paholpak, Ishan Shah, Lou-Anne Acevedo-Moreno, Koji Tamai, Jeffrey C. Wang, Zorica Buser
Background ContextThe thoracic spine was previously known as a relatively stable region in human spine. Several studies reported motion of the thoracic spine and changes in the cross-sectional area of the spinal cord changed with positions in sagittal plane. The kinematic relationship between the thoracic disc and space available for cord with the positional change is still not well investigated.PurposeTo evaluate the kinematic change of the intervertebral disc and space available for the spinal cord of the thoracic spine using kMRI.Study designRetrospective study.Patient Sample105 patients who underwent thoracic spine kMRI.Outcome MeasurementDisc bulging and the space available for cord were evaluated from T4/5 to T11/12 in flexion, neutral, and extension positions.MethodsMRAnalyzer3 (TrueMRI Corp., Bellflower, CA) was used to analyze disc bulging and space available for cord (SAC) from T4/5 to T11/12. Friedman's test was used to analyze the differences in disc bulging and space available for cord between neutral, flexion, and extension positions at each segment. The Wilcoxon-signed rank test was used for post hoc analysis for the significant levels from Friedman's test.ResultsThe mean value of the thoracic intervertebral disc area from T4-5 to T11-12 tended to be larger in flexion than in extension. Initial analysis with Friedman's test revealed a significant difference in disc bulging at T8-9, T9-10, and T11-12 among the three positions (p<0.05). Post hoc analysis showed that disc bulging was only significant at T8-9 between flexion and extension (p<0.001), T9-10 between neutral and flexion (0.003), and T9-10 between flexion and extension (p=0.004). The SAC from T4-5 to T11-12 tended to be widest in extension and narrowest in flexion. Only T5-6 exhibited a statistically significant difference in SAC between flexion and extension (p=0.002).ConclusionsThe thoracic discs and SAC from T4-5 to T11-12 showed kinematic changes from flexion to extension. The thoracic spinal canal tended to be narrowest in flexion and widest in the extension. Thus, kyphotic deformities could be one of the etiologies for neurogenic deterioration in patients with thoracic myelopathy.



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