The coordinate movement of the interphalangeal joints. A cinematic study

No agreement exists on how coordinate flexion and extension movements of the interphalangeal joints of the long fingers of the hand are performed. A cinematic study in 18 healthy volunteers was done to assess the objective sequence of beginning and ending of movement in the eight free movements of the hand in which these joints flex and extend. The results show that the proximal interphalangeal joint is the one that first initiates the four analyzed movements in which these interphalangeal joints flex and the four movements in which these interphalangeal joints extend. The distal interphalangeal joint is the one that ends first in these two groups of movements. These results confirm that the coordinated movements of the interphalangeal joints may be explained based exclusively on the tendinous system and especially on the setup and balance that exists between the components of the extensor apparatus (longitudinal sliding of the central slip and lateral bands and either the dorsal to palmar or palmar to dorsal displacement of the lateral bands with respect to the rotation axis of the proximal interphalangeal joint).