Session V Spine and Pediatrics

Traumatic Ligamentous Disruptions of the Cervical Spine: Correlation of MRI Appearance and Operative Findings

W. A. Cohen, J. R. Chapman, MD, L. C. Blake, M. S. Grady, W. D. Robertson, W. A. McAuliffe, S. Mirza

University of Washington-Harborview Medical Center, Seattle, WA

Purpose: Patients with significant cervical spine trauma have MR signal abnormality in ligaments, discs, and soft tissue structures of the spinal axis. Although the spinal abnormalities are often extensive, the significance of the soft tissue changes in relation to spinal stability is conjectural. We correlated MR abnormalities with injuries found at surgery in a group of patients with acute cervical spine injury. We hypothesize that there are specific MR findings which suggest instability of the spine.

Materials and Methods: Prospective evaluation was performed on 20 patients with acute cervical spine injury who underwent operative decompression/stabilization. The MR and operative procedure were performed as a routine part of the patient's clinical management. The MR protocol including T1, T2-weighted fast spin echo with frequency selective fat saturation, fast STIR, and axial gradient echo sequences. Peripheral gating was used with FSE and STIR sequences. MR examinations were evaluated independently by two readers blinded to the patients' clinical status and surgical findings. Discordances were resolved by a third reader. Appearance of ligaments, disc spaces, and facet joints were recorded at the time of surgery. Patients undergoing an anterior surgical approach had evaluation of the anterior tissues, those with posterior surgery had a similar evaluation of posterior structures. Disc abnormalities and spinal instability were evaluated in both groups. Correlation was performed between the findings noted at surgery and the abnormalities demonstrated on MR.

Results: Twenty patients with acute cervical spine injury (15 men and 5 women ranging in age from 16-63 years) underwent 21 operative stabilization procedures, 15 from an anterior approach and 6 from posterior. MR was performed within 2 days of injury. Fifteen patients underwent surgery within 3 days of the MR examination, and all were operated on within 5 days of imaging.

Increased signal on FSE/STIR sequences was present in prevertebral space in 16/20, 13 of whom had abnormal disc signal/configuration. Three with normal disc signal and abnormal prevertebral soft tissue signal (PVSTS) had vertebral body fracture, facet injury, or degenerative disc spaces. In 8 of 13 with anterior surgery and PVSTS, this abnormal signal correlated with edematous tissues. In this group, 11 were clearly unstable and 1 was minimally unstable intraoperatively. Twelve with abnormal signal in a disc space underwent anterior surgery. Intraoperative instability was present in 9. Anterior longitudinal ligament was thought to be abnormal on MR in 10, only 3 of which were torn at surgery, and intact in 3, 2 of which were torn at surgery.

Evaluation of posterior structures was more difficult because of the small size of the operative group. Nuchal ligament had increased T2 signal in all 6, 4 of whom demonstrated hemorrhage or tears. Interspinous ligament was abnormal in 5, 4 of which were lax or torn at surgery. PLL was abnormal in 2, one of which was lax at surgery. In the entire group of 20 patients, PLL appeared discontinuous or displaced in 7 with intraoperative motion and appeared normal in 5 with intraoperative motion.

Conclusion: Abnormal MR signal in prevertebral soft tissues correlates with injury to disc space, and abnormal signal in disc spaces is associated with instability in 75% of patients. Detection of injury to ALL and PLL with MR is less accurate.