Xray: what are "spondylisthesis", "retrolisthesis", and "anterolisthesis" ? are they all the same thing?

Vertebral slippage: Spondylolisthesis refers to the forward (anterolisthesis) or backward (retrolisthesis) movement of one vertebral body relative to the vertebral body immediately below it. It can be a result of degenerative changes, prior direct trauma, repetitive micro trauma, birth defects and pathologic bone such as from tumor involvement.