Fracture of the transverse process of the fifth lumbar vertebra.

Fracture of the transverse process of the fifth lumbar vertebra is caused by traction through the iliolumbar ligament by the vertically and proximally or medially dislocated hemipelvis. This fracture is therefore associated with the vertical shearing force of Malgaigne's fracture-dislocation of the pelvis or the lateral crush fracture-dislocation of the pelvis. In the absence of evidence on a radiograph of a fracture through the sacroiliac area or dislocation or subluxation of the sacroiliac joint, the fracture of the transverse process of the fifth lumbar vertebra may be the only radiological evidence for posterior instability of the ipsilateral hemipelvis.