The erosive front: a topographic study of the junction between the pannus and the subchondral plate in the macerated rheumatoid metacarpal head.

The junction between cellular pannus and cartilage/bone was identified grossly on rheumatoid metacarpal heads. Its topography was displayed by scanning electron microscopy using macerated samples. A uniform pattern of resorption bays, typical of osteoclastic activity, was seen spreading over the surfaces of both calcified cartilage and subchondral bone. The contact area between pannus and cartilage/bone was found to represent an erosive front. Morphologic evidence suggested that osteoclasts were primarily responsible for the destructive process.