Design and Development of a Prosthetic Leg for People with Transfemoral Amputation Consisting of a Polycentric Knee Machined by Multi-Axis CNC and a Socket-Liner System with Simple Mechanical Adjustment

Miguel Ángel Escobar Guachambala; Ember Geovanny Zumba Novay; Edwin Rodolfo Pozo Safla; Jorge Sebastián Buñay Guamán; Luis Santiago Choto Chariguaman · International Journal of Drug Delivery Technology (2026) · DOI: 10.25258/ijddt.16.22s.9

Resumen

This study presents the design, simulation, and manufacturing of a transfemoral prosthetic knee based on a polycentric four-bar linkage mechanism, aimed at achieving an optimal balance between biomechanical performance, structural reliability, and cost-efficiency. The system was fabricated using 5-axis CNC machining, demonstrating its feasibility as a robust alternative to additive manufacturing for load-bearing biomedical components. Structural performance was evaluated through finite element analysis (FEM) under loading conditions defined by ISO 10328. Results indicate that the prosthesis operates within safe mechanical limits, with maximum stresses significantly below the yield strength of the selected materials and safety factors exceeding critical thresholds in both static and dynamic scenarios. Maximum deformation values remained below 2.5 mm under worst-case conditions, ensuring compliance with international standards and preserving functional integrity during the gait cycle. Fatigue analysis revealed that critical components exceed 10⁸ cycles, confirming high durability and long-term operational viability. From a biomechanical perspective, the polycentric mechanism reproduces a physiologically consistent motion trajectory, enabling a functional range of motion between 90° and 180°. The integration of a spring-based return mechanism improves energy efficiency during gait by facilitating energy storage and release without increasing system complexity. Additionally, the offset configuration of the upper connector enhances the moment arm, contributing to smoother limb advancement and a more natural walking pattern. A key innovation lies in the implementation of a fully mechanical socket-liner coupling system based on threaded adjustment, eliminating the need for costly imported technologies such as pin-lock or vacuum systems. This significantly reduces production and maintenance costs, making the solution suitable for low- and middle-income regions. Overall, this work provides a technically validated, economically viable, and scalable prosthetic solution, contributing to advancements in prosthetic knee design and improving accessibility for transfemoral amputees.

Instituciones: Universidad Nacional Mayor de San Marcos