An evaluation of contralateral hand involvement in the operation of the Delft Self-Grasping Hand, an adjustable passive prosthesis

Abstract

The Delft Self-Grasping Hand is an adjustable passive prosthesis operated using the concept of tenodesis (where opening and closing of the hand is mechanically linked to the flexion and extension of the wrist). As a purely mechanical device that does not require harnessing, the Self-Grasping Hand offers a promising alternative to current prostheses. However, the contralateral hand is almost always required to operate the mechanism to release a grasp and is sometimes also used to help form the grasp; hence limiting the time it is available for other purposes. In this study we quantified the amount of time the contralateral hand was occupied with operating the Self-Grasping Hand, classified as either direct or indirect interaction, and investigated how these periods changed with practice. We studied 10 anatomically intact participants learning to use the Self-Grasping Hand fitted to a prosthesis simulator. The learning process involved 10 repeats of a feasible subset of the tasks in the Southampton Hand Assessment Procedure (SHAP). Video footage was analysed, and the time that the contralateral hand was engaged in grasping or releasing was calculated. Functionality scores increased for all participants, plateauing at an Index of Functionality of 33.5 after 5 SHAP attempts. Contralateral hand involvement reduced significantly from 6.47 (first 3 attempts) to 4.68 seconds (last three attempts), but as a proportion of total task time remained relatively steady (increasing from 29% to 32%). For 9/10 participants most of this time was supporting the initiation of grasps rather than releases. The reliance on direct or indirect interactions between the contralateral hand and the prosthesis varied between participants but appeared to remain relatively unchanged with practice. Future studies should consider evaluating the impact of reliance on the contralateral limb in day-to-day life and development of suitable training methods.

A quantitative comparison between the mHand Adapt passive adjustable hand prosthesis and its predecessor, the Delft Self-Grasping Hand

“…In this study, comparisons were drawn to existing data from a study of the SGH [ 4 ]. The methodology for data capture was matched as closely as possible to that described in the previous paper.…”

“…They were all right-handed, anatomically intact, and had no upper-limb impairments. As the previous trial had limited information on the demographics of its participants, it was decided to source individuals for the mHand trial from the same location as those who took part in the SGH trial, the University of Salford [ 4 ]. Though this does not guarantee the populations to be equivalent, it is believed that this would aid in achieving this goal.…”

“…Previous studies explored the performance of the SGH with both anatomically intact participants using a prosthesis simulator [ 4 ], and with prosthesis users making use of the hand in their day-to-day lives [ 5 ]. Both studies highlighted the release switch as a limitation to the design of the SGH.…”

Reimagining Prosthetic Control: A Novel Body-Powered Prosthetic System for Simultaneous Control and Actuation

“…BP prosthesis users' design priorities and needs have remained virtually unchanged for decades [33,44,49,50], and little attention has been given to broadening the design choices available to them. Recently, the "Self-Grasping Hand" was developed (for adults with hand absence) at the Delft University of Technology [57,58] to address the need for a purely mechanical device that does not require harnessing. However, the Self-Grasping Hand is a passive-adjustable device that does not provide the user with continuous control over grasping movement compared to active UL prostheses.…”

Real-World Testing of the Self Grasping Hand, a Novel Adjustable Passive Prosthesis: A Single Group Pilot Study

“…We asked participants to use the SGH over two weeks in their own Initial laboratory testing of the SGH, with healthy anatomically intact adult volunteers performing activities of daily living using the SGH fitted to a prosthesis simulator, was promising, indicating that it was used more frequently than a conventional passive hand [6,7]. Further lab-based testing, also with anatomically intact adult volunteers performing the Southampton Hand Assessment Procedure (SHAP), quantified the amount of contralateral hand involvement in the operation of the SGH [8]. They found that the percentage of task time where the user was reliant on the contralateral hand remained relatively unchanged (~30%) with practice.…”