Since 1984, 30 patients with burst fractures of the lower thoracic and lumbar spine were treated with AO internal spinal skeletal fixation system. All patients in this series had a minimum follow-up of 12 months. This new instrumentation is a posterior intrapedicular system developed by Dick in 1982. It allows stable fixation that is limited only to adjacent spinal segments. The internal fixator permits reduction in all three planes. Independently, it is possible to add distraction or compression to the involved segments. It also is able to reduce effectively the "middle column" which is thought to be accomplished by "ligamentotaxis." In this series there were 16 neurologically intact patients and 14 with partial or complete neurologic injury. There were two minor instrumentation loosenings early in the series. Most patients in this series had a near-anatomic reduction of all three columns in the involved segment. It was also possible to re-establish the normal lordosis of the lumbar spine. The device provided sufficient rigid fixation for rapid postoperative mobilization in a light external orthosis.