Enhanced Load-Bearing Capacity in Transmetacarpal Amputation: Development of a Flex Sensor-Based Thumb Prosthesis Through Additive Manufacturing

Escalante N.T.A.; Galarza R.J.G.; Tacza Y.V.; Mamani J.M.Z.; Rios R.J.C.; Vela-Anton P.; Shah D.; Kunkel M.E. · IFMBE Proceedings (2025) · DOI: 10.1007/978-3-031-93646-3_19

Resumen

The thumb, crucial for dexterity and manual skill in daily tasks, executes precise and forceful movements. Thumb amputation significantly reduces overall hand function, resulting in a 60% functionality decrease, a 20% grip strength reduction, and a 49.2 pinch frequency decline. While open-source mechanical upper limb prostheses exist, their thumb traction mechanism is limited to palmar grip. Hence, a customized mechanical thumb prosthesis with a flex sensor system was developed to aid interphalanges flexion with opposition, addressing transmetacarpal amputation users’ specific needs. The design facilitates three thumb joint movements through interaction with a flex sensor system on the index finger, activated during flexion, and considers user aesthetics. Prototyping and manufacturing occurred at the Prototyping Laboratory of the Universidad Peruana Cayetano Heredia (UPCH), utilizing advanced CAD/CAE/CAM tools. Additive manufacturing with polylactic acid (PLA) material is considered user-specific anatomical and biomechanical aspects. Integrated hardware includes 270° a servomotor for distal (90°) and proximal (35°) phalanges movement and metacarpophalangeal joint (36°) movement in response to index finger flex sensor readings. Prosthesis software aligns with biomechanical analysis, ensuring precise and strong robust movements during pinch activities for secure object handling across four tests. After multiple load-bearing tests, the prosthesis withstood up to 2 kg without structural alteration or fatigue, effectively meeting user needs. This interdisciplinary approach highlights promising advancements in prosthetic design, particularly for transmetacarpal amputation cases. © Brazilian Society of Biomedical Engineering 2025.

Instituciones: Universidad Peruana Cayetano Heredia