  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.
