A study has been made of fifty-six patients suffering from rheumatoid arthritis in whom sixty-nine wrists were fused. The purpose of the investigation was to evaluate to what extent the position of the fused wrist influenced the position of the fingers in the frontal plane. All sixty-nine wrists were followed up by radiographic examination controls, and thirty-seven of the wrists were also examined clinically. The mean period of observation after operation was seven years and ten months.

The findings support the so-called "zigzag" theory based on the concept of carpus-metacarpus acting as Landsmeer's intercalated bone in a bi-articular system.

When the wrists were fused in more than 5 degrees of radial deviation seventeen of twenty hands showed ulnar drift of the fingers on radiographic examination. Of the nine patients in this group examined clinically, all showed ulnar drift.

A strong tendency to correction of the finger position is seen when the hands are pressed against the cassette. For this reason the clinical examination, during which the finger deviation was examined with the metacarpo-phalangeal joints in 30 degrees of flexion regularly revealed an ulnar deviation of 5 degrees more than that shown by radiographic examination.

In eighteen wrists the fusion had been done in more than 5 degrees of ulnar deviation. Fourteen of these hands showed a resulting radial deviation of the fingers on radiographic examination.

In a group of thirty-one wrists fused in neutral position (0 degrees±5 degrees) only six hands showed more than 5 degrees of finger deviation to either side.

The condition of the metacarpo-phalangeal joints asjudged from radiographs did not seem to influence the deviation of the fingers either in direction or in degree. The direction of the deviation of the fingers was almost regularly the opposite to that of the fused wrist. Five hands showing no visible pathological changes in the metacarpo-phalangeal joints displayed finger drift.