[Morphology of the distal radio-ulnar joint. Surgical orthopedic consequences].

Morphologic and biomechanical changes are often the causes of osteoarthrosis in a joint. Complete integrity is necessary, if a joint will be intact the whole life. This integrity is very often disturbed in the distal radio-ulnar joint by trauma and also by surgical treatment. To avoid any incongruence in this joint, which seemed to be neglected by surgeons and orthopaedics, in 1985 about 700 wrists were examined by X-ray, to study the exact morphology with regard to the relation between ulna, radius, declinations and lengths. The aim was to avoid failures in future by all therapeutic procedures. 31 negative ulnar variances (4.4%) and 9 (1.4%) non-traumatic positive variances with a difference of more than 2 mm were revealed. The declination of the distal radio-ulnar joint in relation to the axis of the radius was measured by a special goniometer. To find out the three-dimensional structure of this joint, oblique X-ray photographs were also taken. The results were: in joints with negative ulnar variance declinations of 100 degrees and more were found, and the stereoscopic pictures were conical; in the presence of positive ulnar variance the declinations amounted to 80 degrees or less and the distal radio-ulnar joint surfaces were spherical; in neutral ulnar variances the angle was found to be about 90 degrees and the joints were cylindrical in form. Nearly all operative or traumatic changes were associated with incongruence of this joint. Therefore all therapeutic methods must be planned exactly with reference to this stereoscopic relations between radius and ulna. In traumatic cases the three-dimensional integrity must be reconstructed.(ABSTRACT TRUNCATED AT 250 WORDS)