Spondylolysis refers to failure of fusion of the pars interarticularis, most often at the lower lumbar spine. This is usually a congenital defect, although it may occasionally be post-traumatic. The process may affect one or both sides of the spine. Oblique radiographs are best for the detection of this abnormality.
Oblique radiograph of the lumbar spine. This shows a pars defect.
Opposite oblique radiograph of the lumbar spine. This shows another pars defect at L5-S1.
Coned radiograph of the L5-S1 region. The abnormalities are difficult to appreciate.
Axial CT. This image confirms bilateral pars defects at L5-S1.
