[Simultaneous functional testing of the metacarpophalangeal joints of the thumb in hyperpronation using a simple device].

For the diagnosis of rupture of the ulnar ligaments of MP joint of the thumb functional X-rays are required. The best position for this investigation seems to be - contrary to the routine - overpronation where the metacarpal and the proximal phalanx are both lying nearly straight on the board. If the patient pushes the pulp of his thumb against a barrier he produces stress in abdduction. Both hands can be tightly bandaged together in this uncomfortable position for a certain time. This permits a symmetrical and simultaneous image of both stressed thumbs on only one X-ray film. For this purpose we use a simple wooden board with two small borders which is placed over the film case.