MORPHOLOGY OF THE ARTICULAR SURFACES OF THE DISTAL RADIO-ULNAR JOINT

BACKGROUND: The two articular surfaces of the distal ulna get an important role in load transmission and stabilization of the distal radio-ulnar joint. The present study describes the morphology of the distal radio-ulnar joint surfaces in terms of the functional relationships between the shape of the ulnar articular facets and the predominant contact situation in this joint. METHODS: Besides macroscopic dissection and radiological investigation the model of the "inclined plane" has been used to simulate force transmission across the radio-ulnar joint concerning the angle between the distal and the radial articular surfaces of the ulnar head. RESULTS: The presented morphological parameters of the radio-ulnar joint surfaces verify that the transmitted forces are effective in both a radio-ulnar and an axial direction. The protection and the captaincy of this joint are limited by its great mobility. The investigations show that signs of an increased load pressure are frequently found in the joints that also show degenerative changes. As a morphological sign of the force transmission, distinct spongious trabecles are formed perpendicularly to the articular circumference in those ulnar heads that show a stolid angle between their articular facets. CONCLUSIONS: Because of the individuality of the morphological data only qualitative statements can be made both the predominant shapes of the ulnar head, in particular about the loading of its articular surfaces. The angle between its two articular facets influences the force transmission through the radio-ulnar joint as well as the spongious architecture of the subchondral bone of the ulnar head.