Human facet cartilage: swelling and some physico-chemical characteristics as a function of age. Part 1: Swelling of human facet joint cartilage.

Abstract

The hydration of cartilage from human facet joints was measured after the joints had been subjected to different treatments. One group of facets was opened and directly exposed to physiologic saline solution before extraction of cartilage plugs. The plugs were weighed, re-equilibrated in fluid, and weighed again. The swelling results obtained under these conditions were compared with those when similar plugs of cartilage were excised from joints that had not been exposed to solution or had been exposed to solution while still closed. It was found that swelling was least (and similar in value to hip cartilage) for joints that had been exposed open to saline solution, highest for joints that had not been exposed to solution, and intermediate for joints that had been exposed to solution while still closed. The same trends were observed whether the cartilage on the joint was intact or fibrillated, although in each group the swelling and the final hydration were higher for fibrillated than for intact tissue. It was concluded that facet cartilage, unlike human hip or knee cartilage, is underhydrated when excised from the joint. This underhydration is thought to reflect the permanent presence of stresses in vivo on some part of the facet joints, the position of the loaded site changing with time. The authors attempted to distinguish between the swelling caused by this underhydration and that from disruption of the collagen network in the case of fibrillated specimens.