Grade1 anterolisthesis of L5 on S1, congenital anterior wedge deformities of T12 L1 present. Bilateral L5 pars interarticularis defects. Means what?

The tiny plates. which help stabilize the veterbrae one with another are missing at the 5th Lumbar Veertebral level causing a SLIPPAGE of the L-5 veterbrae on the sacrum (S1). this is associated with a smaller height of two of the veterbrae ABOVE the defect T-12 (the lowest chest (thoracic) veterbrae and the highest Lumbar (low back) veterbrae..... Hope this helps..difficult to explain without a "pointer"