Histomorphology of the peritendinous tissue of the phalangeal extensor apparatus.

The phalangeal extensor tendon is surrounded and fixed by connective tissue showing differently extended expansions of its intercellular spaces. This connective tissue runs in horizontal lamellae and forms connective tissue spaces around the dorsal extensor apparatus. The clinical importance of the connective tissue spaces is in the formation of gliding spaces and the diffusion of phlegmonas or purulent infection processes. The morphological differentiation of the cellular and intercellular elements of the dorsal connective tissue lamellae shows that the peritendinous gliding spaces around the dorsal aponeurosis are bordered by synovia-like cellular and noncellular structures. Besides mast cells and histiocytes many cells are seen that show all signs of activated fibroblasts. They form small groups of cells. These cells produce a mucoid dense bordering lamella that is opposite to the collagenous fibers of the dorsal aponeurosis. The intercellular matrix has importance both in fixing and mobilizing the phalangeal extensor tendons in the sheathless parts of the phalangeal extensor tendon.