Posterior lumbar apophyseal fractures.

The radiographic findings in 4 patients with fractures of the lumbar vertebral ring apophysis are reported. All patients had a bony ridge or fragment projecting into the spinal canal, usually from the lower border of L4; a defect in the postero-inferior aspect of the vertebral body; and either an anterior extradural impression or complete blockage on the myelogram. Computed tomography was performed on one patient and appears to be helpful in demonstrating bone within the spinal canal. Preoperative diagnosis can facilitate selection of the appropriate surgical approach.