The rib perichondrium. An anatomical study in sheep of a tissue used as transplant in the treatment of hyaline-cartilage defects.

Perichondrial tissue is of great importance as a transplant for the repair of hyaline-cartilage defects of synovial joints because of its potential to produce hyaline-like cartilage. The histological and histochemical character and fiber orientation of rib perichondrial grafts prior to a transplantation procedure for the repair of full-thickness hyaline-cartilage defects is analyzed in a sheep model. Compared to other descriptions of the rib perichondrium of other different species and humans, the perichondrial architecture of different origins demonstrates the same histological, histochemical character and fiber orientation. The three different layers of this tissue are: the outer fibrous layer, the central part called proliferation zone and the inner part towards the underlying rib called transition zone. The fibrous layer demonstrates a wave-like extracellular configuration and contains a few fibrocytes. The proliferation zone is only a few cell rows thick and contains single cells with an oval shape and longitudinal fibrocyte-like nucleus. Because of the potential of these cells to produce cartilage this layer is called proliferation or cambium layer. The transition zone contains more oval-shaped cells with rounded nuclei and demonstrates a more chondrocytic character. Some cells lie in groups of 2 and more cells like in chondrons. The extracellular matrix shows an increasing stain towards the rib cartilage indicating new cartilage production. The fiber orientation is longitudinal in the fibrous part and vertical in the transition zone. Between these layers, fibers deviate from the longitudinal to the vertical orientation corresponding to the light-microscopically visible proliferation zone.