Abstract
Roughly one quarter of active upper limb prosthetic technology is rejected by the user, and user surveys have identified key areas requiring improvement: function, comfort, cost, durability, and appearance. Here we present the first systematic, clinical assessment of a novel prosthetic hand, the SoftHand Pro (SHP), in participants with transradial amputation and age-matched, limb-intact participants. The SHP is a robust and functional prosthetic hand that minimizes cost and weight using an underactuated design with a single motor. Participants with limb loss were evaluated on functional clinical measures before and after a 6–8 hour training period with the SHP as well as with their own prosthesis; limb-intact participants were tested only before and after SHP training. Participants with limb loss also evaluated their own prosthesis and the SHP (following training) using subjective questionnaires. Both objective and subjective results were positive and illuminated the strengths and weaknesses of the SHP. In particular, results pre-training show the SHP is easy to use, and significant improvement in the Activities Measure for Upper Limb Amputees in both groups following a 6–8 hour training highlights the ease of learning the unique features of the SHP (median improvement: 4.71 and 3.26 and p = 0.009 and 0.036 for limb loss and limb-intact groups, respectively). Further, we found no difference in performance compared to participant’s own commercial devices in several clinical measures and found performance surpassing these devices on two functional tasks, buttoning a shirt and using a cell phone, suggesting a functional prosthetic design. Finally, improvements are needed in the SHP design and/or training in light of poor results in small object manipulation. Taken together, these results show the promise of the SHP, a flexible and adaptive prosthetic hand, and pave a path forward to ensuring higher functionality in future.
Highlights
The human hand is important for many activities of daily living (ADL), including self-feeding, tool use, and recreation, and loss of the upper extremity has a large impact on functional independence, psychological well-being, and overall quality of life [1]
Participants performed significantly better with their own prosthesis compared to the SoftHand Pro (SHP) on the Box and Blocks (B&B) (Fig 5C; median difference (MD): 13 blocks; IQR: 0–21 blocks; p = 0.042) and on three Jebsen subtasks: lifting small, common objects (Fig 5B), stacking checkers, and lifting large, heavy objects (MD, IQR: 70, 43–103; 22, 16–95; 9, 3–12 seconds and p = 0.021, 0.044, and 0.018, respectively)
The results show that, as an adaptive, anthropomorphic hand, the SHP is easy to use and highly functional both for individuals experienced in myoelectric prosthetic control and novices
Summary
The human hand is important for many activities of daily living (ADL), including self-feeding, tool use, and recreation, and loss of the upper extremity has a large impact on functional independence, psychological well-being, and overall quality of life [1]. Despite advances in technology since their debut, upper extremity prosthetic function and satisfaction remain low: the adult rejection rate for myoelectric upper limb prostheses is estimated at 23% [4]. Most often, these prostheses resemble a human hand, but have an internal tri-digit structure that closes in a C-shape for power or pinch grasp. Less common are myoelectric greifers and similar technologies that offer higher grip force and are more amenable to manual labor but are not anthropomorphic Both types of devices allow simple, voluntary control in both open and close directions and perform a single, rigid grasp. The control complexity of such a device demands a higher cognitive burden on the part of the user to fully access the widened feature set [6] and may result in a prosthesis that is not utilized to its capacity
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