Evaluation of Posterior Element Injury in Traumatic Thoraco-Lumbar Burst Fractures

Purpose : The purpose of this study is to examine the frequency of posterior element injury in patients with traumatic thoraco-lumbar burst fractures and to evaluate the correlation between the MR imaging and CT findings. Materials and Methods : The MR images of 38 patients with 39 thoraco-lumbar burst fractures and the results of the CT examinations of 28 patients with 29 fractures were retrospectively analyzed. Both procedures were performed within two weeks of injury. Twenty-one males and 17 females were included ; their average age was 51.3 (range, 11-75) years. MR images were evaluated for injury to the posterior ligamentous complex, comprising the supraspinous ligament(SSL), the interspinous ligament(ISL), the flaval ligament(FL), and the capsule of facets. Analysis of the CT findings focused on the posterior bony elements of the lamina, pedicle, spinous process, and facet joint. Results : MR imaging revealed posterior ligamentous injuries in 18(46.2 %) of 39 burst fractures ; there was tearing of the ISL in 15 cases(38.5 %), of the SSL in 11(28.2 %), of the capsule of facets in 11(28.2 %), and of the FL in nine(23.1 %). Among the 29 burst fracture cases examined by CT, posterior bony injuries were detected in 13(44.8 % ). Lamina and facet joint fractures were detected in six cases(20.7 %), facet separation or dislocation in six(20.7%), and spinous process and pedicle fracture in one(3.4 %). In 29 burst fracture cases, both MRI and CT were performed. Among the 18 cases in which MR imaging revealed posterior ligamentous injuries, CT failed to demonstrate posterior element fractures in seven. On the other hand, among the 13 cases in which CT indicated posterior bony fractures, MR failed to reveal posterior ligamentous injuries in two. Conclusion : Posterior element injury is frequently found in patients with traumatic thoraco-lumbar burst fractures demonstrated by MR imaging(46.2 %) and CT(44.8 % ). Both MRI and CT are useful tools for the evaluation of posterior element injury, which determines the degree of instability of traumatic burst fracture.