Sensory feedback is largely unavailable for persons with upper-limb amputation with conventional prostheses. The current study created a portable vibratory haptic feedback system integrated into the prosthesis to test its usefulness in gripping objects during daily life.
Development involved optimizing a mapping algorithm between the force sensor and the feedback tactor vibration, developing a custom process for mounting a wireless force sensor onto the prosthetic thumb with reliable output, and developing an instrumented object for testing grip force accuracy. Clinical testing involved optimizing tactor placement, measuring grip force accuracy, measuring the ability to perform daily gripping tasks, and surveying prosthetic users' opinion of the system after using the vibratory haptic device at home. A total of six individuals with unilateral transradial amputation participated in this study.
The results demonstrated optimal tactor placement more proximal versus distal on the forearm. Accuracy with haptic versus no haptic feedback demonstrated that haptic feedback improved the grip force accuracy by 129% (adjusted P = 0.041) for light grip force target (2 lb or 0.9 kg) in the nonportable system and 21% (adjusted P = 0.051) for medium grip force target (10 lb or 4.5 kg) in the portable system. Haptic feedback did not statistically improve grip accuracy at strong grip forces (20 lb or 9.1 kg). Haptic feedback improved the gripping technique during the Assessment of Capacity for Myoelectric Control (ACMC) by 1.22 points, although this was not statistically significant (P = 0.27, n = 4). The participants provided specific positive examples of how the vibratory haptic system was useful at home. The overall usability score was 3.6 where 4 indicated excellent and 0 indicated poor.
This kind of system has potential to improve the lives of upper-limb prosthetic users.
TERI ROSENBAUM-CHOU, PhD, is affiliated with Modus Health LLC.
WAYNE DALY, RAY AUSTIN, and DAVID A. BOONE are affiliated with Orthocare Innovations LLC, Edmonds, WA.
PRAVIN CHAUBEY is affiliated with DWFritz Automation Inc., Wilsonville, OR.
Disclosure: The authors declare no conflict of interest.
The work was supported by National Institute on Disability and Rehabilitation Research (NIDRR) under the Department of Education through grant number H133S10094. The work would not have been possible without valuable input from subjects who participated in the study.
Correspondence to: Teri Rosenbaum-Chou, PhD, Modus Health LLC, 123 2nd Avenue S., Edmonds, WA 98020; email: email@example.com