[Lesions of the ulnar collateral ligament of the metacarpo-phalangeal joint of the thumb: anatomic study and classification].

The collateral ulnar ligament of the first metacarpo-phalangeal joint was studies in anatomical specimens in order to evaluate the relationship between pathological anatomy of the lesion and joint laxity. The clinical and X-ray evaluation of the valgus stretched joint led to the correct indications for treatment.