Surgical treatment of degenerative spondylolisthesis in the lumbar spine: no reposition without prior decompression.

In the present note, the cause of root compression in cases with degenerative lumbar spondylolisthesis is discussed in order to clarify the best method of surgery and to avoid iatrogenic damage of the cauda equina if a transpedicular fusion is going to be performed. The root compression is due to osteophytes growing out from the upper articular facets and from the upper ridge of the lamina of the lower vertebra. Therefore, the repositioning of the anteriorly displaced vertebra by the instrumentation could lead to the squeezing of the cauda equina between the withdrawn vertebral body and the degeneratively enlarged and hypertrophic facet joints of the lower vertebra. The reposition (even if incomplete) must always be preceded by decompression on both sides, even if radicular complaints are unilateral.