Vertebral burst fractures: CT analysis of the retropulsed fragment.

Ten cases of retropulsed thoracolumbar vertebral body fragments that had been documented by CT were reviewed to define and characterize the nature, appearance, and position of the retropulsed fragment. All of the retropulsed fragments arose from the superior aspect of the vertebral body. Five of ten patients had a vertical fracture within the retropulsed fragment. Three of ten fragments had anteriorly rotated 90 degrees +/- 60 degrees, so that the cartilaginous end plate faced anteriorly; also, they had migrated 3-8 mm in a craniad or caudad direction. Six of ten patients had an associated vertical or Y-shaped fracture originating from the region of the basivertebral foramen and passing into the inferior one-half of the vertebral body. The presence of a retropulsed fragment is nearly pathognomonic of an axial compression injury. Characteristics of this lesion that may hinder surgical reduction are the intra-fragment fracture, rotation, and craniocaudad movement.