The MyoGrab Hand

Abstract

Background: Last decades myoelectric prostheses have become more usable, functional and reliable. Yet, the cost of myoelectric upper limb prostheses are still a hindering factor of widespread usage of the prostheses. In developing countries, where the demand for prostheses is relatively higher, commercial myoelectric prostheses are out of reach for the majority of amputees because of limited financial resources. Low cost myoelectric prostheses with the aim of use in developing countries are not commercially available at this moment.
Objectives: The goal of this study is to develop a functional low cost myoelectric upper limb prosthesis. The developed prosthesis will be tested with standardized and validated test methods, to evaluate if the prosthesis is usable and functional. The Box and Blocks Test (BBT) and the Southampton Hand Assessment Procedure (SHAP) will be used for this purpose.
Results: A low cost myoelectric prosthesis prototype was developed in this study; the MyoGrab Hand. The material cost of the prototype was 99.33 euro. The weight of the prosthesis was 352 g. The maximum pinch force of the hand prosthesis was 54.8 N. The MyoGrab Hand was tested by 20 able-bodied participants with BBT and the SHAP. In a first evaluation with ten participants, the prototype proved its functionality with an average score of 17.0 (± 2.2) with the BBT and an Index of Functionality (IoF) of average 41 (± 8.3) with the SHAP. After optimizing the Arduino code structure, the MyoGrab Hand was evaluated again. Ten able-bodied participants carried out the BBT. The average score on the BBT with the optimized MyoGrab Hand was 18.4 (± 2.4). The result of the BBT in the second evaluation was not significantly better than in the first evaluation (t = -1.3, df = 18, p = 0.21). In a durability experiment, critical failure of the prototype occurred after 16539 cycles of opening and closing of the hand.
Conclusion: The goal of this study, the development of a functional low cost myoelectric prosthesis, has been achieved. The MyoGrab Hand was evaluated with standardized and validated test methods and proved itself functional. This is one of the first studies that was focused on the functionality, usability and durability of a low cost myoelectric prosthesis. The functionality of the MyoGrab Hand does not equal the functionality of commercial myoelectric prostheses, commercial myoelectric prostheses are more functional. The MyoGrab Hand was able to perform most of the activities of daily life (ADL) tasks in the SHAP, however, carrying out these ADL tasks took longer, as compared to commercial prostheses. This study is a first step in the direction of making a functional myoelectric prosthesis available to larger part of the amputee population with limited financial resources. Future research should focus on a lower weight battery solution, waterproof design and testing in a non-clinical setting.