Low-Cost Upper‑Limb Prosthetic

Three CAD components rendered against a dark background — a white upper-arm section with a shaped cup, a beige tapered forearm section with two pin holes, and a grey hook terminal device on a short post with a cable stud. — The main components modelled in Autodesk Inventor: upper-arm section, forearm section and hook.

Maximum displacement, at the hook tipsSimulation result: 0.016 in
Peak von Mises stress, concentrated in the hookSimulation result: 3.73 ksi

Objective

Prosthetic arms often cost thousands of dollars and need professional fitting, which puts them out of reach for most amputees in Nepal, especially in rural areas far from rehabilitation centres. The goal was a functional, affordable arm that could be made, fitted and repaired locally.

Design approach

The arm is body-powered. A shoulder harness and control cable let the user open and close the hook with shoulder and chest movement, so there are no electronics, motors or batteries to fail or replace. We modelled the arm in Autodesk Inventor, with a lightweight frame that follows the arm’s natural movement at the elbow and the hook, for everyday tasks like holding utensils, a cup or a bag.

Materials

Every material was chosen because it is common in Nepal:

PVC for the upper arm, which a technician can heat and shape from pipe to fit each user.
High-density polyethylene for the forearm.
Canvas or nylon webbing for a figure-8 shoulder harness, with locally available buckles and straps.

Constraints

Cost: under $20 per device, with a hard limit of $50.
Simplicity: few moving parts, so there are fewer ways to fail.
Fit: one design adaptable to different limb sizes and lengths.
Repair: it can be taken apart and reassembled with basic tools, so no glued or fused parts.
Climate: it has to cope with cold, sun, dust and monsoon humidity.

Analysis

We ran displacement and von Mises stress simulations on the full arm in Autodesk Inventor. Stress stays near zero through the upper arm and forearm and concentrates in the hook, which peaks at 3.73 ksi. The hook tips deflect at most 0.016 in. These are simulation results; the design was not built or physically tested as part of the project.

Team

A three-person team project for the Fundamentals of Rehabilitation Engineering course at the University of Central Florida, from January to April 2025.

Von Mises stress plot of the full prosthetic arm in Autodesk Inventor. Almost the whole arm is blue, near zero stress, with green and yellow areas on the hook. The scale runs from 0 to 3.728 ksi. — Von Mises stress across the full arm (simulation). The peak, 3.73 ksi, sits in the hook.

Displacement plot of the hook and forearm end in Autodesk Inventor. The forearm is blue, near zero, while the hook tips shade through green to red. The scale runs from 0 to 0.01608 inches. — Displacement at the hook (simulation). The tips move at most 0.016 in.

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