Abstract:
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Purpose: Clearing the cervical spine in the acute trauma patient often leads to the question of ligamentous injury, especially in cases of normal or minimally abnormal cervical spine radiography. Patients are subsequently sent to MRI to evaluate ligament integrity. There is an inherent clinical assumption that an abnormal MRI indicates mechanical instability although the link between MRI signal abnormality and mechanical instability has not been firmly established. In this investigation we propose to correlate findings from cervical MRI with those of flexion-extension radiographs, the current accepted gold standard for assessing mechanical stability.
Methods and Materials: A retrospective review of medical and radiology records was performed from January 1999 and December 2001 for all trauma patients admitted to the emergency department who had both cervical spine MRI and flexion-extension views during the same admission. 72 patients were identified - 39 (54%) male, 33 (46%) female. There were no unconscious or obtunded patients. Active flexion-extension studies were performed and characterized as abnormal if a translation was noted between films. MRI was classified as abnormal if increased signal was present in the anterior or posterior longitudinal ligament, ligamenta flava or interspinous ligaments. Multivariate logistic regression analysis was performed using the dichotomized flexion-extension and MRI variables with subject age and gender included as covariates. Odds ratio and c2 analyses were performed along with sensitivity, specificity and positive and negative predictive values.
Results: Analysis revealed 6 true positive (abnormal MRI and abnormal flex-ex) and 5 false positive (abnormal MRI with normal flex-ex) MRI studies with 72 true negative MRIs and 8 false negative examinations. The multivariate logistic model produced an odds ratio of 3.7, correlation coefficient (r2) of 0.24 and a c2 p=0.102. Sensitivity and specificity for this correlation was 42.9 and 93.5 with positive and negative predictive values of 54.5 and 90% respectively.
Conclusion: Although a correlation between MRI ligament signal abnormality and translation on flexion and extension views exists, confidence of this statistic is reduced by poor correlation coefficient and statistical significance. Sensitivity and positive predictive values were low, but specificity and negative predictive values are high. This suggests that a negative MRI is likely to be associated with a stable cervical spine, although the converse is not necessarily true.
Questions about this event email: tptak@partners.org
Ptak MD, PhD, T,
An Evaluation of Magnetic Resonance Imaging in Predicting Mechanical Instability Due to Ligamentous Injury in Trauma Patients. Radiological Society of North America 2003 Scientific Assembly and Annual Meeting, November 30 - December 5, 2003 ,Chicago IL.
http://archive.rsna.org/2003/3108758.html
