Assessment of injury to the thoracolumbar posterior ligamentous complex in the setting of normal-appearing plain radiography

Background context: The posterior ligamentous complex (PLC) is thought to contribute significantly to the stability of thoracolumbar spine. Obvious translation or dislocation of an interspace clearly denotes injury to the PLC. A recent survey of the Spine Trauma Study Group indicated that plain radiographic findings, if present, are most helpful in determining PLC injury. However, confusion exists when plain radiography shows injury to the anterior spinal column without significant kyphosis or widening of the posterior interspinous space. Purpose: The objective of this study is to identify imaging parameters that may suggest a disruption of the posterior ligamentous complex of the thoracolumbar spine in the setting of normal-appearing plain radiographs. This study was performed, in part, as a pilot study to determine critical imaging parameters to be included in a future prospective, randomized, multicenter study. Study design/setting: Survey analysis of the Spine Trauma Study Group. Patient sample: None. Outcome measures: Compilation and statistical analysis of survey results. Methods: Based on a systematic review of the English literature from 1949 to present, we identified a series of traits not found on plain X-rays that were consistent with PLC injury. This included five imaging findings on either computed tomography (CT) scans or magnetic resonance imaging (MRI) and several physical examination features. These items were placed on a survey and sent to the members of the Spine Trauma Study Group. They were asked to rank the items from most important to least important in representing an injury to the PLC in the setting of normal-appearing plain radiographs. Results: Thirty-three of 47 surveys were returned for final analysis. Thirty-nine percent (13/33) of the members ranked "disrupted PLC components (i.e., interspinous ligament, supraspinous ligament, ligamentum flavum) on T1 sagittal MRI" as the most important factor in determining disruption of PLC. When analyzed with a point-weighted system, "diastasis of the facet joints on CT" received the most points, indicating that this category was ranked high by the majority of the members of the group. The members were also given freedom to add other criteria that they believed were important in determining PLC integrity in the setting of normal-appearing plain radiograph. Of the other criteria suggested, one included a physical finding and the other a variant of MR sequencing. Conclusions: In a setting of normal-appearing plain radiographs, PLC injury as displayed on T1-weighted MRI and diastasis of the facet joints on CT scan seem to be the most popular determinants of probable PLC injury among members of the Spine Trauma Study Group. Between MRI and CT scan, most members feel that various characteristics on MRI studies were more helpful.