[Mechanical consequences of the surgical treatment of lumbar stenosis].

In a series of 84 cases of lumbar stenosis duly controlled with lateral X-rays at each visit, 7 post-operative slips were discovered (8 p. cent). They occur very early, are moderate and do not seem to become worse. The functional repercussion was actually present on only 2 instances. 5 occurred spontaneously, 2 represented the aggravation of an arthritic spondylolisthesis. The preferred localization is L4-L5 and the slip seems to develop especially on pinched but still thick discs, and spines with an over-lordosis. Multi-levels total lamino-arthrectomy promotes slipping but this wide resection is not an exclusive factor. The knowledge of anatomical factors of risk enables to limit the indication of a stabilizing arthrodesis and the low slipping risk versus the much higher percentage of failure because of insufficient resection, prompts the author to keep performing wide releases on demand.