[The quadrate pronator muscle--a morphological and functional analysis].

Based upon the findings of dissections and of histological investigations, the m. pronator quadratus was found to be composed of 2 heads. In the majority of the cases an oblique superficial head entirely covered a deep head, whose fasciculi were oblique from the ulnar origin to the distal volar surface of the radius. The fibers of both heads were arranged obliquely to the axis of rotation. From this both heads by contraction will develop a rotatory and a shunt force, the shunt components acting antagonistically. The superficial head is the rotator for pronation, whereas the deep head is well located for maintenance of transverse forces at the distal radioulnar joint. Moreover, the two heads insert into the capsule of the articulatio radioulnaris distalis.