3D printed hand prosthesis to be attached to the patient's container, replacing the prosthetic "hook", providing safety and resistance in its performance.
Hacklab prosthesis design
This work was promoted by the HackLab research group of Escuela Universitaria Centro de Diseño de Uruguay, funded by the National Agency for Research and Innovation (ANII) and sponsored by the State Insurance Bank (BSE).
Work duration: 12 - 18 months.
Role: Research and design assistant
Hacklab prosthesis printed 3D
Working with real users
A group of patients was defined by the rehabilitation team; 5 patients forearm amputated with stumps of different lengths. All the patients of the reduced sample are discharged, which implies that they have been reintegrated into their work activities with follow-up of the BSE.
Anthropometric analysis with a 3D scanner was carried out on each patient as a complement to the Questionnaire.
Three open source prosthesis models were selected in order to be evaluated for their assemble, failures and ergonomics.
In terms of performance, these models were tested by real amputees.
Duration: 2 weeks each model.
During that time, we evaluated the prosthesis with a two method combination: the ARAT (Action Research Arm Test) and Activities of Daily Living evaluation.
ARAT test
Insights
Based on the systems studied, the version developed enhances the following aspects:
+ Progressive closure of the phalanges.
+ The fingers can continue their journey even when one or more fingers bumps up with an object.
+ Easy assembly system and safety in its execution.
+ Accessible inputs.
Design and Validation
Approximately 9 versions of the Hacklab prosthesis were made and tested until the final design was reached.
Features
The coupling of objects was improved through palm and fingers design, the tension system and the creation of different textures.
In the new design, the contact areas, such as the palm and fingertips, are printed in flexible material similar to a pad, which seeks to resemble the the natural texture of the hand.
Intuitive assembly, each part has an indicator to facilitate the assembly.
Safe and precise tensioning system.
Performance: sequence closure system so that fingers close gradually.
Parametric modeling: the prosthesis is automatically customized once the patient's measurements are completed in Autodesk Inventor.
Testing and ARAT evaluation
Final thoughts
The design provides greater firmness and therefore a feeling of trust and security. An improvement in grip is highlighted, attributed to the fingers path and the flex pieces that surround them.
However, in practice it shows some difficulties. Among them, it does not get a successful fine clamp, so it would be necessary to check the position, opening and direction of the thumb.
Due to the required test and iteration times, it was not possible to design a solution with a voluntary opening system (hook terminal mechanism), which is considered more appropriate for the physical integrity and patient safety.
