Bypass sockets allow researchers to perform tests of prosthetic systems from the prosthetic user's perspective. We designed a modular upper-limb bypass socket with 3D-printed components that can be easily modified for use with a variety of terminal devices. Our bypass socket preserves access to forearm musculature and the hand, which are necessary for surface electromyography and to provide substituted sensory feedback. Our bypass socket allows a sufficient range of motion to complete tasks in the frontal working area, as measured on non-amputee participants. We examined the performance of non-amputee participants using the bypass socket on the original and modified Box and Block Tests. Participants moved 11.3 ± 2.7 and 11.7 ± 2.4 blocks in the original and modified Box and Block Tests (mean ± SD), respectively, within the range of reported scores using amputee participants. Range-of-motion for users wearing the bypass socket meets or exceeds most reported range-of-motion requirements for activities of daily living. The bypass socket was originally designed with a freely rotating wrist; we found that adding elastic resistance to user wrist rotation while wearing the bypass socket had no significant effect on motor decode performance. We have open-sourced the design files and an assembly manual for the bypass socket. We anticipate that the bypass socket will be a useful tool to evaluate and develop sensorized myoelectric prosthesis technology.A 1534-4320 (c)

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Many presently available prostheses lack a functional wrist. To fill this niche and to better 9 understand the impact a wrist has in prosthetic functionality, we designed a low-cost, adaptable, 3D-10 printable prosthetic wrist that can be adapted to various prosthetic hands and sockets. The wrist 11 utilizes inexpensive but powerful servo motors to provide simultaneous and proportional control of 12 two degrees of freedom: pronation/supination and flexion/extension or radial/ulnar deviation. 13Participants used both our wrist and a commercially available wrist (DEKA "LUKE" Arm) to complete a 14 modified version of the clothespin relocation task with and without the wrists enabled. Through use 15 of the NASA Task Load Index we found that both wrists significantly reduced the subjective workload 16 associated with clothespin relocation task (p < 0.05). However, we found no significant difference in 17 task completion speed, presumably due to compensation strategies. This inexpensive and adaptable 18 prosthetic wrist can be used by amputees to reduce task workload, or by researchers to further 19 explore the importance of wrist function. 20 21 24 functional disability [1-3]. The current standard of care, often a body-powered hook or 25 myoelectric prosthetic hand, is unsatisfactory, causing up to 50% of amputees to abandon their 26 prostheses [4]. Transradial amputees have expressed their top priorities for useful prostheses (in 27 order of importance): wrist rotation, simultaneous movements, wrist deviation, wrist 28 flexion/extension, increased automaticity [5]. Additional priorities include reduced weight, 29 improved durability, and increased strength [5].30 Functional wrist motion is important in reducing biomechanical strain. Without a wrist, 31amputees are forced to compensate with unnatural movements to complete standard activities of 32 daily living (ADLs) [6][7][8]. The continual use of these motions causes further damage to the 33 musculoskeletal system over long periods [9,10]. 343D-printing has provided new and innovative solutions to address several of the above 35 issues with prosthetics. For example, 3D-printing has considerably lowered the cost and weight 36 of prostheses [11][12][13], and several 3D-printed prosthetic hands are currently available [14][15][16]. 37 Traditionally, wrists have been excluded from the design of 3D-printed and commercial 38 prosthetic arms to conserve space and to focus on the implementation of a more dexterous hand 39 [17]. Commercially available prosthetic hands without an active wrist include the Michelangelo 40 [18], i-limb Ultra [19], TASKA [20], and bebionic [21]. 41Although these commercially available prosthetic hands can be paired with a wrist, few 42 commercial active wrists exist, and none provide more than 1 active degree of freedom [22,23]. 43There are many dedicated, passive wrists with varying degrees of freedomsuch as the bebionic 44 [21]but these are unnatural since the wrist must be manually adjusted by the intact 45 contralateral hand of the user...

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