The coordinate movement of the interphalangeal joints - A cinematic study

No agreement exists on how coordinate flexion and extension movements of th e interphalangeal joints of the long fingers of the hand are performed. A c inematic study in 18 healthy volunteers was done to assess the objective se quence of beginning and ending of movement in the eight free movements of t he hand in which these joints flex and extend. The results show that the pr oximal interphalangeal joint is the one that first initiates the four analy zed movements in which these interphalangeal joints flex and the four movem ents in which these interphalangeal joints extend. The distal interphalange al joint is the one that ends first in these two groups of movements. These results confirm that the coordinated movements of the interphalangeal join ts may be explained based exclusively on the tendinous system and especiall y on the setup and balance that exists between the components of the extens or apparatus (longitudinal sliding of the central slip and lateral bands an d either the dorsal to palmar or palmar to dorsal displacement of the later al bands with respect to the rotation axis of the proximal interphalangeal joint).