[Extension of the fingers. IV. Morphologic and structural study].

The putting in tension of the dorsal aponeurosis of the digits induces its retraction and the nearness of its insertions on the basis of the 3 phalanges. It depends on the extensor digitorum, interosseous and lumbrical muscles. The aponeurosis is not a single driving belt, but set off in itself 3 types of reaction: 1) The gliding on the sides of the pyramid, which constitute the proximal epiphyses of the phalanges. It suppresses the central dorsal-ward tensions. 2) The displacement of the axes of insertion and rotation of retinacular ligaments inducing collateral volar-ward tractions. 3) The modifications of the way of the structures of transmission: at one time the lengthening of the way is induced by the interactions of the fibers; at other times a shortening is suppressed by the extension of the close proximal joint. Analysis of the different fibrous and fascicular interactions and translations.