Author(s) :

Fakhruddin S. Kothari, Collin R.X. Pang.

Volume/Issue :

Abstract :

Upper limb amputees often face challenges and struggle performing everyday tasks that require dexterity, grip adaptability, and precise finger control. Although modern prosthetics have improved through advances in myoelectric control systems, improved materials, and even customizable manufacturing, many devices remain restricted by simplified mechanical joint designs. In particular, most prosthetic fingers rely on single-axis hinge joints that only allow flexion and extension, eliminating lateral motion and reducing the natural degrees of freedom in human metacarpophalangeal (MCP) joints. This mechanical constraint limits the effectiveness of advanced control systems and prevents hands from fully replicating natural finger movement. To address this limitation, our research proposes a prosthetic finger design that incorporates a constrained ball-and-socket joint at the MCP position to increase degrees of freedom (DOFs) while maintaining stability and control. The joint is engineered with internal mechanical stops that replicate ligament-like constraints, restricting motion to biologically realistic ranges of flexion, extension, and controlled adduction/abduction. The design is intended to integrate tendondriven actuation, myoelectric EMG-based interfaces, and vibrotactile feedback to support coordinated movement while minimizing cognitive load for the user. Additionally, manufacturing techniques such as 3D printing are proposed to enable lightweight, customizable, and cost-effective production. The functionality of the proposed prosthetic can be evaluated using standardized assessments, including the Prosthetic Hand Assessment Measure (PHAM) and the Box and Block Test (BBT), to determine whether increased mechanical degrees of freedom translate into measurable improvement in dexterity and task performance. As this is a conceptual design that has not yet been prototyped, the anticipated benefits described above are presented as hypotheses to be evaluated through future fabrication and testing. Overall, this design aims to narrow the gap between anatomical realism and practical prosthetic usability, with the potential to improve functional outcomes and accessibility for upper-limb amputees.