Acute injuries of the axis vertebra.

A retrospective analysis of 165 patients admitted to Hermann Hospital with acute injuries of the axis vertebra revealed 68 (41%) dens fractures, 62 (38%) cases of traumatic spondylolisthesis ("hangman's" fracture), 21 (13%) extension teardrop fractures, 10 (6%) hyperextension dislocations, and 2 (1.0%) fractures each of the laminae and spinous processes. Of the 68 dens fractures, none (0%) were of the Anderson and D'Alonzo Type I; 21 (31%) were Type II ("high"); and 47 (69%) were Type III ("low"). The 62 traumatic spondylolistheses included 13 (21%) Effendi type I, 35 (56%) type II and 3 (5%) type III. This review disclosed an additional 11 (18%) patients with an atypical variety of traumatic spondylolisthesis, not previously reported, in which one or both fractures involved the posterior cortex of the axis body. Of the axis injuries 31 (18%) were limited to the axis body alone. Of these, 21 (61%) were hyperextension teardrop fractures and 10 (32%) were hyperextension dislocations. Axis injuries were associated with acute injuries of other cervical vertebrae in 14 (8%) of the patients.