Congenital laminar defect of the upper lumbar spine associated with pars defect. A report of eleven cases.

Lumbar spondylolysis generally is considered to be a fatigue fracture of the pars interarticularis, and no unequivocal case of congenital spondylolysis has been reported. The authors describe 11 cases of unilateral spondylolysis (possibly congenital laminar defect associated with pars defect) of the upper lumbar spine. They have roentgenographic characteristics distinct from conventional spondylolysis of the lumbar spine, including hypoplasia of the spinal accessory process, rotation of the spinous process contralaterally to the spondylolysis, and prominent ipsilateral lamina. The anomaly found in these 11 patients probably is congenital, and its clinical significance is not known.