A prosthetic hand structure (100) comprises at least one mechanical finger (110a-e) comprising in turn a metacarpal support (111) and a proximal stiff link (112) connected to the metacarpal, support (111) by a proximal cylindrical joint (113). The mechanical finger (110a-e) also comprises a transmission member (116, 117) connected to the proximal stiff link (112). The transmission member (116, 117) is adapted to actuate the proximal stiff link and a flexible rack (117) having a first end portion (117a), pivotally connected to the metacarpal support (111), and a second end portion (117b) arranged to engage with the threaded profile of the worm screw (116).
