Flexion distraction fractures of the thoracolumbar spine.

Holdsworth’s classification of injuries of the lumbar spine in I 963 has done much to further our understanding of the pathomechanics of these fractures. Four major types were described: flexion, flexion and rotation, extension, and compression. Nicoll had previously reviewed a series offlexion and flexion-rotation fractures of the thoracolumbar spine in miners. He stressed the importance of the integrity of the posterior interspinous ligaments in the stability of these fractures. Rotational forces were believed responsible for all fractures involving the neural arch and articular processes, and he concluded that fracture of the pedicles was an extremely rare injury which probably occurred only as a part of a severe fracture-dislocation. Chance had described three cases of fracture of the lumbar spine in which there was a horizontal splitting of the vertebral body and neural arches through the pedicles. He illustrated the description with line drawings and roentgenograms of one fracture. These injuries were surmised to be the result of a pure flexion injury but their mechanism was thought to be an anatomical mystery. Recent experience with two similar cases prompted us to re-examine the theoretical pathomechanics of this kind of fracture. It would appear that it may be produced by flexion and distraction, a combination not included in Holdsworth’s schema.