[Blast injuries of the 1st commissure]

Explosions are responsible for severe hand injuries. Due to their extremely important functional role, lesions of the thumb and first commissure must be identified separately during assessment of the lesions. No classification of these injuries has been proposed since the one defined by Mac Gregor and Jackson. Based on their experience of 11 injuries, the authors propose a classification divided into four stages of increasing severity. In the emergency situation, the severe forms with disruption of the blood supply have a very poor prognosis. In the other forms, the degree of opening of the first commissure is of fundamental importance. Secondarily, the functional prognosis of the hand is dominated by retraction of the first commissure, ankylosis of the trapezo-metacarpal joint or its preservation during amputations.