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.Materials and Methods
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.Results
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.Conclusions
This kind of system has potential to improve the lives of upper-limb prosthetic users.