Only approximately twenty-five percent of patients with spondylolysis develop spondylolisthesis. Progression to significant slippage is uncommon.

Spondylolisthesis associated with spondylolysis is most common at L5-S1, approximately 90% of cases. The remainder usually occur at L4-L5. Spondylolisthesis associated with degenerative disease is most common at L4-L5.

Pars interarticularis defects are considered to represent fatigue stress fractures. Most are believed to develop in childhood. They are especially common in athletic children.

Dx -

Imaging should begin with conventional radiographs. The lateral and oblique views are nearly equally sensitive in diagnosing the defect. CT also easily displays the lesion. SPECT imaging can be useful in identifying pars interarticularis defects that are symptomatic. Magnetic resonance imaging plays little role. Difficulty in recognizing an intact pars interarticularis leads to a low positive predictive value.