[Hangman's fracture in ventrally flexed traction].

Hangman's fracture in ventrally flexed traction between 10(6) and 75 degrees is analyzed on the basis of 220 fracture trials on plaster of real bone preparations of the atlas and axis of two adults. Hangman's fractures, which are usually regarded as a form of injury from dorsal flexion, occurred in 25% of the fracture trials under this kind of strain. Frequency depended on flexion angle, as well as on inclination of the dens axis. Thus Hangman's fractures occurred, as a whole, more frequently in the kyphotic dens type than in the lordotic type and were found as a rule at 75 degrees flexion. Furthermore, the investigations showed that pedicles can by no means be regarded as the sole predilection site for fracture. A detailed description is provided on why the Hangman's fracture type, due to ventrally flexed traction, can be included in the group of bone injuries arising from flexion, with tensile stress of the dorsal parts of the dens and the corpus axis, on the one hand, and the upper side of the axis arch on the other. Hence, the injury picture ranges from the dorsal arch fracture to the horizontal rupture through the superior articular facies and the corpus axis, as documented by substantial evidence.