We are pleased to share that our team recently delivered two custom transradial prostheses to one of our clients. Both devices are body-powered systems, a reliable, durable, and highly functional option for many individuals with upper-limb limb loss. Body-powered prostheses use a simple but effective cable-and-harness mechanism, allowing the user to control the terminal device through shoulder and arm movements.
In the photo, the prosthesis on the left is a voluntary-opening design, while the prosthesis on the right is a voluntary-closing design. Although they may look similar, these two systems function quite differently and offer unique benefits depending on the user’s needs, goals, and daily activities.
What Is a Voluntary-Opening Prosthesis?
A voluntary-opening (VO) prosthesis operates by using tension applied through the harness to open the terminal device (such as a prosthetic hook). When the user relaxes the tension, the device naturally returns to the closed position through rubber bands or internal springs.
Key Features of Voluntary-Opening Systems
✔ Quick and easy opening with minimal sustained effort
✔ Automatic return to closed position for simple grasping tasks
✔ Great for tasks requiring frequent opening, such as picking up or releasing objects
This design is often preferred for users who want an intuitive, low-maintenance system that supports everyday activities without requiring continuous muscle engagement.
What Is a Voluntary-Closing Prosthesis?
A voluntary-closing (VC) prosthesis works in the opposite way. With this design, the terminal device closes when the user applies tension through the harness, and it opens when the tension is released.
Key Features of Voluntary-Closing Systems
✔ Precise control over grip strength
✔ Ability to apply a stronger, adjustable gripping force
✔ Useful for tasks where securely holding objects is essential
Because the user directly controls how firmly the device closes, voluntary-closing prostheses can provide a more natural sense of grip control, making them ideal for tasks that require stability, such as carrying bags, holding tools, or manipulating small items.
Choosing the Right System
There is no single “best” option—both systems offer valuable advantages. During the assessment and fitting process, our clinicians work closely with each client to understand their lifestyle, daily demands, comfort preferences, and long-term goals. Factors such as work tasks, hobbies, strength, range of motion, and cosmetic needs all contribute to the final recommendation. Some clients even benefit from having both styles, using each device for different tasks depending on the day.
Our Commitment to Personalized, Functional Prosthetic Care
At Pentland’s, we are proud to support our clients with prosthetic solutions that are tailored to their needs, thoughtfully designed, and backed by clinical expertise. Delivering these two transradial prostheses reflects our ongoing commitment to helping individuals regain independence, function, and confidence in their daily lives.
If you have questions about body-powered prostheses or would like to learn more about upper-limb prosthetic options, our team is always here to help.