Spondylolysis

One of the more important developmental anomalies of the lumbar vertebrae, and one which affects the stability of the spinal column, is a failure in ossification of the laminae between the superior and inferior articular processes. This is actually a radiological finding wherein a break is demonstrated in the pars interarticularis or isthmus on one or both sides of the neural arch. When this defect is not associated with a subluxation of the vertebral segment anterior to the lesion, it is usually referred to as spondylolysis. The condition has also been called spondyloschisis, and occasionally the term "prespondylolisthesis" is used to describe the defect. This latter term is unfortunate because it implies the later development of a condition which actually may never take place. I feel that we should report the anatomic variation as it is found and avoid any confusion or unfounded supposition that another pathologic entity may be