Detailed observation of axis ring fractures using computed tomography: a retrospective analysis of 202 cases

Abstract

Background: There is a dearth of research observing the precise anatomical location, pattern, and frequency of the fracture lines in axis ring fractures based on large size sample database and deducing the possible injury mechanism for such fractures. The study aimed to observe the anatomical features of axis ring fractures and evaluate the probable mechanism of injury.Methods: 202 patients with axis ring fractures were identified. According to the involvement of anatomical structures, the axis ring injuries were classified into facet joint injury and pure bony injury. The axis ring was also divided into: anterior, middle, and posterior elements. The anatomical structures involvement and fracture patterns of such fractures were observed using CT. Result: 501 anatomical structures of the axis ring were involved in 202 patients, including 288 facet joints injuries and 213 bony injuries. For facet joints injuries, the most common injuries were superior articular facet injuries, and for pure bony injuries, the most common injuries were pediculoisthmic component fractures. In regard to different element of the axis ring, the injuries of anterior element were more common than that of middle or posterior element. Most of (76.2%) axis ring fractures were asymmetrical, with different elements of the axis ring damaged on different side. Conclusion: In axis ring fractures, fracture lines could occur in any part of the ring. Facet joints injuries were more common than pure bony injuries, and the injuries of anterior element were more common than that of middle or posterior element. The probable mechanism of such injuries might be hyperextension and axial load, with an additional rotational load.