Comparative Development and Engineering Evaluation of Low-Cost Individualized Hand Rehabilitation Orthoses with Alternative Finger Actuation Mechanisms

Vollständiger Abstract

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Hand rehabilitation orthoses play an important role in restoring upper-limb function in individuals with impaired grasp ability; however, selecting an actuation mechanism that balances functional performance, manufacturing complexity, and production cost remains a significant engineering challenge. This study aimed to develop and compare three low-cost hand and forearm rehabilitation orthosis prototypes within a common subject-specific digital workflow based on three-dimensional (3D) scanning, computer-aided design (CAD), and fused deposition modeling (FDM). Three finger actuation mechanisms—a cable-driven mechanism powered by two DC motors, an arc-based mechanism driven by a DC motor, and an arc-based mechanism driven by a linear actuator—were integrated into subject-specific orthotic structures. The prototypes were evaluated on a single healthy subject by comparing manufacturing time, material consumption, weight, production cost, finger range of motion (ROM), and angular velocity, supplemented by a simplified theoretical mechanical analysis. Prototype 2 achieved the highest total finger ROM (186.66 ± 5.35°) and the greatest angular velocity during extension (177.71 ± 30.03°/s) and flexion (183.16 ± 81.16°/s), while maintaining a low production cost of €18.33. The proposed workflow enabled systematic comparison of the three implemented actuation mechanisms and identified Prototype 2 as providing the most favorable balance between kinematic performance, manufacturing requirements, and practical scalability under the tested conditions. Its simple, modular, and customizable architecture provides a suitable basis for subsequent multi-finger development.