Degenerative spondylolisthesis

Degenerative spondylolisthesis, described by McNab [18] as "spondylolisthesis with an intact neural arch," are most frequent at the L4-L5 level and may result in a stenotic condition. The term degenerative spondylolisthesis was coined by Newman [21]. The displacement due to facet hypertrophy can critically narrow the canal. In contrast to isthmic spondylolisthesis, degenerative spondylolisthesis is self-contained and rarely reaches grade II. Claudication, or much more often sciatic pain, are the encountered symptoms in stenosis secondary to degenerative spondylolisthesis. This is related to the fact that degenerative spondylolisthesis is usually at one level, and the two level pathogenesis described by Porter is not reached. Central stenosis is rare in lytic spondylolisthesis but in some cases of L5-S1 displacement the posterior element can be pulled forward against the body of S1, thus compressing the corda [35]. More often the loss of height of the disc induces a posterior bulging, which can trap the nerve root ion the foramen resulting in lateral stenosis. The osteofibrous callus present at the isth-mic fracture level can exceptionally become hypertrophic (Gill's nodules) [7] and compress the neural canal. Although those conditions are usually discovered in younger patients, they are occasionally be a problem in the elderly.

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