The association between spinal cord compression and functional deficits following cervical spine trauma has been well studied using both CT and MRI. However, until now, there was little data evaluating whether that same association is true for thoracic spine injuries. In the February 21, 2018 edition of The Journal, Skeers et al. identified the same correlations between canal compromise, cord compression, and functional outcome in the T1 to L1 region.
Using retrospective data, the authors showed that the severity of neurologic deficits was associated with the amount of maximal cord compression, as measured with advanced imaging. More specifically, their univariate analysis showed that cord compression >40% was associated with a tenfold greater likelihood of complete spinal cord injury compared to cord compression <40%. This study also found that MRI measures osseous canal compromise more accurately than CT, probably because it more clearly visualizes soft tissue changes related to the posterior longitudinal ligament, ligamentum flavum, and facet capsule.
A major issue with this study (and with almost all studies that evaluate spine trauma) is that these advanced imaging techniques are temporally static; even when they’re obtained relatively soon after injury, they cannot capture the position of vertebral body fragments and posterior structure deformities that existed upon impact. This shortcoming is probably more relevant for younger patients, who are more likely to experience higher-velocity trauma.
The population in the Skeers et al. study is skewed a bit toward older patients (mean age 34.8) with relatively severe spinal injuries (mean TLICS of 7.8 and mean cord compression of 40%). These factors may highlight the roles that lower bone density and decreased soft tissue elasticity play in the setting of high-energy spine trauma.
Although the data reflect some variability, this study should help spine surgeons counsel patients and their families following these tragic injuries. The more severe the initial cord compression in the thoracic spine, the more likely there is to be severe neurologic injury without improvement.
Marc Swiontkowski, MD