[Lumbar spinal stenosis. An overview 50 years following initial description]

About 50 years after the first descriptions of lumbar stenosis and its most frequent symptom, neurogenic intermittent claudication, this update gives an overview of present-day concepts of the disease and of new experience in this area. Stenosis of the central and lateral lumbar spine is chiefly held to be one of the results of segmental degenerative instability throughout the several stages of spondylosis. The degenerative process of the spine has its starting point in regressive changes of the disc. This leads to instability of the motion segment, which explains the pathophysiological dynamics of the stenosis and its symptoms, including intermittent neurogenic claudication. Segmental instability is the crucial lesion causing all the changes in the degenerative process, which are not to be considered as separate entities but as part of the dynamics of the same disease. The spine's congenital anatomic individual patterns, which confirm the population thinking of the evolutionary biology (since they are different from one motion segment to the other) help to determine the outline of single cases. The disparity between radiological and clinical patterns is pointed out: severe stenosis may be asymptomatic or cause just modest monoradicular trouble as well as serious multiradicular deficit. The reason for the discrepancy is unknown. One must be careful to avoid surgery on a silent, purely radiological stenosis. Experience of more than 15 years confirms the uselessness of performing a complete laminectomy to achieve sufficient decompression. The author's method of selective decompression is described briefly. The English term "undercutting decompression" runs the risk of being misunderstood, since it is also used for rather destroying procedures. Finally, we point out that surgery for spinal stenosis must resolve both root compression and degenerative instability in the majority of cases. In most cases of lumbar stenosis, if decompression alone is performed, only the consequence, and not the cause of the disease, segmental degenerative instability, is treated. Osteophyte formation is an attempt by nature to stabilize the motion segments by stiffening its components. Spinal fusion tries to achieve the same effect. For most cases of spinal stenosis, we suggest our own technique, which combines safe and preserving ("selective") decompression according to Benini [1,7] with the translaminar screw fixation of Magerl [7]. In cases of degenerative spondylolisthesis, however, transpeduncular fusion is mandatory.