A chronic flexion-distraction injury with a “fistulous wither” on the split spinous process of the L1 vertebra—a case report of a modified transpedicle wedge osteotomy

Flexion-distraction injuries (FDIs) are caused by high-energy force and momentum on the spine. In general, the posterior column and the posterior wall of the affected vertebra have failed in distraction, and the anterior column has failed in compression based on Denis’ three column theory [ 1 ]. Hoshikawa et al. has proposed a motion axis of FDIs, which is defined as a transitional line from the anterior compression to the posterior splitting failure [ 2 ]. In terms of biomechanics, the integrity of the posterior tension band of the affected vertebrae has failed in FDIs. As a result of this loss of integrity of the posterior element, kyphotic deformity easily develops and remains unless proper treatment has been optioned in FDIs.