Human facet cartilage: swelling and some physicochemical characteristics as a function of age. Part 2: Age changes in some biophysical parameters of human facet joint cartilage.

This study was aimed at investigating, in relating to aging, some of the biochemical and biophysical characteristics of the facet cartilage that determine the functional behavior of this tissue. In addition, facets and discs from the same segment were graded according to their macroscopic appearance. The proportion of severely degenerate discs was low in young subjects and increased with age; by contrast, the proportion of coarsely fibrillated and/or ulcerated facets was high in spines from young adults and remained constant throughout adulthood. Unlike discs, facets do not show an age-related loss of proteoglycans or a consequent decrease in the resistance to a compressive load. However, even in relatively young age groups (30-50 years) a high hydration was observed more often in facet joints than in cartilage from other joints studied. These characteristics are known to accompany damage of the collagen network and cartilage degeneration. Unlike normal femoral head cartilage, facet cartilage does not show a rise in fixed charge density with age. The cartilage from the superior processes (concave) is thicker than that from the inferior processes (convex) and has a higher fixed charge density. At the same time it has a higher water content, which indicates that damage occurs more frequently.