Observations on the pathomorphology of spinal stenosis.

Verbiest was the first to describe in detail the pathological anatomy of the stenotic spinal canal. He mentioned that lumbar spinal stenosis is characterized by developmental narrowing of the spinal canal in the mid-sagittal plane and that spondylotic changes may only act as additional constrictive agents [21, 22]. In contrast with this interpretation, the opinion has subsequently emerged that degenerative changes of the bony components of the spinal canal are in most cases the only cause of lumbar spinal stenosis [4, 5, 8]. Furthermore, it is recognised that the dimensions of the spinal canal may change under dynamic conditions, particularly in flexion-extension and rotation movements of the spine [10, 18]. In the 1980's, CT scanning has significantly contributed to the knowledge of the pathomorphology of lumbar spinal stenosis. In particular, it has allowed precise measurements of the dimensions of the spinal canal so that the constrictive effects of facet joint hypertrophy and the evaluation of the role of soft tissue changes in compression of the neural and vascular contents of the canal can be assessed [6, 11, 16, 17]. Nevertheless, the pathomorphology of lumbar stenosis still remains somewhat unknown or controversial. Furthermore, controversy and confusion still exists on the definition and classification of the various types of spinal stenosis.