Shear fracture through the body of the axis vertebra.

STUDY
DESIGN: Three cases of a previously undescribed body fracture of the axis vertebra are presented.
OBJECTIVES: To describe the radiographic features of the fracture are described, and to point out the differences to other axis body fractures regarding the mechanism of injury, stability, and treatment. SUMMARY OF BACKGROUND DATA: Fractures involving the odontoid process usually are caused by indirect forces, and they are considered unstable injuries. Anderson and D'Alonzo Type III odontoid fractures usually are hyperflexion injuries. Superior articular process fractures with or without associated odontoid peg fractures are caused by lateral hyperflexion injuries.
METHODS: Three cases of body fractures of the axis vertebra are described. These fractures occur in an oblique plane shearing off in one piece the odontoid process together with one of the superior articular processes. The fragment displaces anterocaudally, and the odontoid process tilts toward the affected side.
RESULTS: All fractures were managed nonsurgically. The two displaced fractures did not reduce in traction, and they had united in the displaced position after the 12 weeks of halo treatment. One patient reported only minor problems, but showed radiologic evidence of facet joint arthritis at 20 months. The second patient was lost to follow-up after discontinuation of halo treatment at 12 weeks. The only undisplaced fracture was managed in a halo body jacket for 10 weeks. The patient was pain free and had regained a full range of movement at 7 months.
CONCLUSIONS: The presumed mechanism of injury in the described fracture is one of asymmetrical axial compression. The fracture can be managed safely in a halo jacket.