Hypoplasia of the lumbar vertebral body simulating spondylolisthesis.

Fifty cases of spondylosis and spondylolisthesis were reviewed. In 9 of the 20 cases interpreted as Grade I spondylolisthesis at L5-S1, the sagittal diameter of L5 was shortened, creating a false impression of vertebral slippage. Such cases are felt to represent spondylolysis with hypoplasia of the vertebral body rather than true spondylolisthesis.