by the gearing of the worm gear 52 as is shown in fig3 and fig4 the device is mounted on the palmar aspect of the forearm for motion of the thumb the device thus rotates in a plane parallel to the plane of the user 39 s hand about an axis transverse to the plane the thumb is drawn by a finger attachment through a spiral which is shortened from that traveled when the device is used on the fingers for use with the thumb the device is attached to a mount 116 on the palmar side of the splint the mount 116 comprises a splint pivot clamp 106 which engages the rotator shaft 12 the actuating arm 118 is shortened so as to preclude interference with the fingers as an alternative embodiment of the invention the linear actuator could comprise a belt drive of course it should be understood that the belt drive can be a toothed belt or a linked chain similarly the motor may be mounted outside the housing on a axis parallel to the pivot bar and appropriate gearing may be used to drive the actuators the batteries used to drive the motor are mounted in a compartment 60 in the housing 10 and are thus concealed the relay circuit further includes a reversing mechanism so that the motor will reverse upon encountering a preset load.