Congenital deficiency of the vertebral pedicle

Abstract Three examples of unilateral partial absence of the vertebral pedicle have been described, involving respectively a last lumbar and a first and a second sacral vertebra. The condition in the first sacral vertebra is associated with spina bifida occulta, so that part of the vertebral arch forms an independent bony element. In the lumbar vertebra the deficiency is anterior to the transverse process, but does not involve the costal element; in the sacral vertebrae it is between the transverse and superior articular processes. The superior articular process of the lumbar vertebra on the affected side is deformed so that the direction of its articular surface is reversed. It is suggested that pedicle defects result from degenerative changes in the neural process prior to ossification. Deformities of the articular processes may be related to the occasional presence of a separate center of ossification for the inferior articular process.