Compact Transhumeral Prosthesis Mechanism with Integrated Flexo-Extension and Prone-Supination Movements

In this work, the mechanical aspect of a compact prototype of transhumeral prosthesis with flexo-extension and prone-supination movements is presented. The torque and maximum speed of the elbow and wrist joints were established based on activities of daily living. Lengths, circumferences, and maximum weight were adjusted to anthropometric measurements of the Latin American population. Materials and transmission mechanisms were selected using property pondering matrices. Safety factors and displacements were checked by means of numerical simulation. The parts were manufactured by machining and 3D printing. The mechanism was assembled and validated using the design loads. The mechanism measures 7 cm from the elbow to the arm coupling. It can move objects up to 450 g with retention and up to 2 kg without retention, with maximum speeds of 30 rpm and 20 rpm for the elbow and wrist joints, respectively. The ranges of movement are flexion, 130°; extension, 30°; pronation, 90°; supination, 90°. The prototype is compact enough to be used in cases of long amputation. The speeds, ranges of motion and load capabilities are suitable for most activities of daily life.