Elbow Flexion Assist Orthosis for Arthrogryposis.

People with arthrogryposis multiplex congenita (AMC) often have muscle weakness in the biceps that makes elbow flexion difficult. An elbow-flexion assist orthosis was designed using the force of springs, combined with a sliding joint, to apply appropriate elbow torque to aid a user in lifting her hand to her mouth. The sliding joint allows an increasing elbow torque despite a decreasing spring force. The device was prototyped for a user with AMC. An occupational therapist measured the user's flexion with and without the device. Benchtop torque measurements were also determined and compared with user trials. The assist orthosis applied an increasing torque as the elbow flexed, thereby allowing the subject to reach her mouth for feeding and then extend her elbow to a position of no applied torque. Without the device, the subject had active elbow flexion of 87 degrees. With the device, this flexion increased to 120 degrees. The novel prototype is a lightweight, spring-powered flexion orthosis which can be made relatively easily and is potentially concealed under clothing. It provides the appropriate torque to move the hand against gravity and increases elbow-flexion of the user.