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.
|A||Oblique radiograph of the lumbar spine. This shows a pars defect.|
|B||Opposite oblique radiograph of the lumbar spine. This shows another pars defect at L5-S1.|
|C||Coned radiograph of the L5-S1 region. The abnormalities are difficult to appreciate.|
|D||Axial CT. This image confirms bilateral pars defects at L5-S1.|
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