The 3D-printed Quatro socket uses Freeform to deliver unprecedented customization
There are 2.7 million Americans living with limb loss, a number that is expected to nearly double by 2050.* For those with a lower-limb amputation, regaining mobility depends on a prosthesis that both functions properly and fits well. These two factors are very much interrelated, as a poor fit can greatly hinder function and comfort.
Nowhere is this more apparent than in the prosthetic socket, the interface between the residual limb and the prosthesis. These sockets are traditionally made with a plaster cast that is customized for the individual user and then laminated using carbon and resin. After multiple fittings, the final socket is often made from carbon fiber, fiberglass, or nylon.
Here’s the problem: even the most accurately customized socket will eventually fit poorly because the residual limb is not static. Not only does it change in shape and volume during the first 12 to 18 months after the initial surgery, but its volume continues to fluctuate as much as 11% or 12% daily. This can lead to sockets that don’t fit well, cause a great deal of pressure and discomfort, and ultimately make it very difficult to control the prosthesis.
Enter Quorum Prosthetics, a Colorado-based company behind the Quatro, a 3D-printed socket with a patented design that allows users to change the volume and compression of the socket with adjustable reels and interchangeable comfort cells that combine to provide a better overall fit and a better comfort.
Freeform, developed by Oqton, is the software that enabled Quorum Prosthetics to bring the idea to life.
Quorum Prosthetics CEO Joe Johnson has firsthand experience of the difference this design makes. He has worn a Quatro socket for more than three years.
“It’s a lot safer wearing a prosthesis that has these integrated cells because I can feel where my foot is in space,” he says. “The Quatro uses opposing forces that transfer compression into the socket and that leads to better proprioception, which is your sense of limb position and movement. It also provides a better, snugger fit for the user. They can control the fit with micro-adjustments on the dial.”
Quorum Prosthetics uses Freeform to design their patented 3D-printed socket, the Quatro.
The degree to which the Quatro socket can be adjusted is a big reason for its success. Conventional sockets are manufactured with an accuracy range of approximately 3mm. But the Quatro has an accuracy range of less than one millimeter.
“It’s much more accurate,” Johnson says. “That's important. When we do the refit, we can reproduce that exactly on the inside of the socket if the person has lost volume since the previous fitting, which they nearly always do. Previously, you couldn't do that. Or, if you could, it just wasn’t very accurate.”
Quorum first started using Freeform almost four years ago to bring Quatro to market.
“We had a patent for the Quatro socket with a very specific design requirement and Freeform fit the need perfectly,” Johnson says. “Basically, we make custom-fitting sockets for each patient, so each shape looks very different. But the layout of the adjustment lines and the whole Quatro system has been standardized in Freeform to make the design process quick and easy.”
The process starts with a diagnostic socket made by a clinical practitioner, which the Quorum team brings into the Freeform digital design environment via high-fidelity 3D scanning. Next, Quorum designer Sean McClure arranges the base plate, housings and other CAD-created components within the space of the mold.
“This is where the higher accuracy really comes into play,” McClure says. “Traditionally, you could expect to get within an eighth of an inch. With Freeform we can get much more precise.”
The Quatro uses opposing forces that transfer compression into the socket and that leads to better proprioception, or the sense of limb position and movement.
With the components in place, mold modifications begin in a digital clay model. Freeform includes a wide range of tools for carving and shaping clay, including razors, knife cutters, and scrapers, all of which provide haptic feedback. Then McClure traces the brim line, makes the base socket, and proceeds with the design of the patented Quatro technologies.
“The haptic technology within Freeform allows us to create these very highly controlled curves, which enables us to incorporate standardized design features within a fully customized shape,” McClure says. “It’s by no means a template. Our number one goal is making a socket that fits one specific person and functions the way they need it to.”
At this point in the process, McClure combines the original solid model, the clay model, and a mesh model to arrive at a final design that is ready for 3D printing with an HP 4200 MultiJet Fusion Printer. The final step in the process is vapor polishing to achieve the right surface quality.
Using a more traditional approach, creating this kind of socket design would take as long as 12 hours. With Freeform, the Quorum team can finish a design in four to six hours, although some have been done in as little as three. When four sockets are ready to go, they can all be 3D printed simultaneously for a dramatic boost in efficiency.
“We wait until we have four sockets ready to print so we’re maximizing the capacity of our printer,” Johnson says. “Total manufacturing time from end to end is typically a week, but we’ve done it in three days in some cases. And a lot of that is printing and cooling and post-processing. Together, Freeform and 3D printing allow us to cut our production time in half.”
Johnson also notes that a secondary benefit to 3D printing is that they can run unattended overnight, which not only improves overall efficiency but helps avoid the need to hire and retain machine operators during a labor shortage.
“Skilled labor is one of the biggest cost centers in any manufacturing company right now,” he says. “And it’s only getting more expensive. Our 3D printer just needs some maintenance from time to time, and it can deliver four sockets in the same time it takes a traditional technician to do just one.”
According to Quorum Prosthetics CEO Joe Johnson Freeform remains essential to their work.
Right now, Quorum is a fast-growing company with a strong footprint in the local Colorado area. Despite its relative youth in the highly competitive medical device industry, Quorum is increasing its reach purely by word of mouth and social media.
“Typically it is patients that seek us out directly,” Johnson says. “Prosthetic patients tend to be more tech savvy than the average person. They do extensive research and find us through any number of platforms. We’ve even had a few orders come in through TikTok.”
Unfortunately, the primary driver in this scenario is the relatively poor quality of the average carbon fiber socket, which does not always provide a consistently comfortable experience.
“I would love every amputee to have access to the Quatro socket,” Johnson says. “Because it has been life-changing for me. The patients we work with are ecstatic when they receive their sockets. They like being more in control of their prosthesis. They feel like they are part of the whole process. They can even add a special logo or pattern to their socket.”
Freeform remains essential to the work that Quorum Prosthetics does, both in terms of its functionality and the efficiency it brings to the process, according to Johnson.
“We have a tagline on the door of our facility that says, ‘This is where ideas become reality,’” he says. “And that’s really because of Freeform. Without the componentry and haptics of the Freeform software, there is no way we could accomplish what we do at the speed we aspire to.”
* Amputee Coalition. Limb Loss and Limb Difference Awareness Month. Accessed July 31, 2023. https://www.amputee-coalition.org/events-programs/limb-loss-awareness-month/