Affordable 3D-printed tendon prosthetic hands: Expectations and benchmarking questioned

The popularization of 3D-printing has allowed enhancing affordable prostheses for persons with amputations in developing countries, yet manufacturers are not subjected to any control from any medical regulatory authority. Adopted evaluation protocols seem to cherish optimistic expectations. A reduced performance test, derived from the Southampton Hand Assessment Procedure and two bench tests, to evaluate the mechanical advantage in the fingers and the slip resistance, are proposed to assess affordable tendon-driven devices. Ultimately, five models amongst those most commonly found in the scientific literature and the Internet have been evaluated. Three subjects participated with the aid of an able-bodied adaptor. The reduced test of performance provides consistent results but with a more direct interpretation of the failed patterns of prehension. All these models create far more expectations than the results deliver. With the supplementary material provided, an affordable benchmarking can be established with this reduced performance test and the two bench tests. They can lead to improved designs, prescriptions and regulations.