Morphological and functional changes of the lumbar spinous processes in the elderly.

Starting from about the 40th year of life the lumbar spinous processes of man undergo morphological changes, which mainly affect their posterior edges. These changes consist of asymptomatic osseous appositions or spurs radiologically visible in the lateral view, with a major incidence in the elderly. Spondyloarthritis is a constant accompanying finding. Histologically the condition corresponds' to a process of substitution by Haversian bone of a layer of calcified fibrocartilage, which constantly occupies the ligamentous and tendinous attachments for a variable distance. While in the young adult fibrocartilaginous metaplasia is limited to the bony attachments of the spinous ligaments, in the elderly it spreads to the greater part or to all of their thickness. The author believes that such a phenomenon is due to a reduced flexibility of the vertebral column as a whole and to exaggerated lumbar lordosis with ageing. The elongation of the lumbar spinous processes secondary to osseous appositions increases the posterior arm of the lever and favours the "extensores spinae" m.