[The position of the os triquetrum in the classical roentgen picture. Clinical relevance].

The first carpal row acts as an important functional unit. The position of the lunate and scaphoid and their relationship within the wrist are wellknown. On the lateral radiography they are easily recognized so that one is able to define and measure accurately their relative position. The position of the triquetrum and its relationship to the adjacent bones have not been previously very well defined. However, it is possible to consistently identify the axis of the pisotriquetral joint on the lateral radiography. From this line the position of the triquetrum can be inferred. We measured the axis of the pisotriquetral joint in a random sample of 102 cases (40 men and 62 women), and compared it to the axis of the radius. Thus, using the pisiform axis as a marker, the position of the triquetrum can be accurately defined. Its movement correlates well with that of the adjacent bones.