Evaluation of the intervertebral disk angle for the assessment of anterior cervical diskoligamentous injury

The anterior diskoligamentous complex is important for cervical spinal stability. Subjective widening of the disk space after trauma has been used to gauge disruption of the anterior diskoligamentous complex on CT scanning, but no quantitative CT measurements exist to evaluate injury. The purpose of our study was to evaluate if an increased intervertebral disk angle could serve as a more sensitive, reproducible indicator of disruption of the anterior diskoligamentous complex compared with subjective assessment. The intervertebral disk angle was retrospectively measured on CT scanning for 122 disk levels with disruption of the anterior diskoligamentous complex by MR imaging and 1095 disk levels with an intact anterior diskoligamentous complex by MR imaging. The intervertebral disk angle was measured between the anterior superior endplate and anterior inferior endplate, with angle apex at the midposterior disk. Area under the receiver operating characteristic curves for subjective disk widening and specific angle values were obtained. Intervertebral disk angle reproducibility was also evaluated. Intervertebral disk angle measurements were "substantially reproducible." No disk with an intact anterior diskoligamentous complex had an intervertebral disk angle greater than 18° or 2 standard deviations from the average intervertebral disk angle of the remaining disks. The area under the receiver operating characteristic curve for a criterion of subjective disk widening was 0.58. The area under the receiver operating characteristic curve for objective criteria, an intervertebral disk angle greater than 13 or above 1 standard deviation from normal values, was 0.85. The maximal area under the receiver operating characteristic curve was achieved if an intervertebral disk angle greater than 2 SD from the average angle of the other disks was used (0.86). Subjective disk widening does not accurately detect disruption of the anterior diskoligamentous complex on CT scanning; an elevated intervertebral disk angle provides a more sensitive and objective measurement to help direct further imaging in trauma patients.