Tech Trends-Restoring Lives with Rapid Prototyping

30 Jun, 2006 By: Kenneth Wong

3D digitizing technologies help create prosthetics.

After making its way through Baghdad's security gantlet and U.S. Customs' scrutiny, a package containing a plaster cast arrived at St. Charles, Missouri. It finally came to Bill Macy, chief technology officer of REALADI (, a company founded by several former Boeing engineers. The cast gave Macy the necessary specifications to manufacture something for a 37-year-old Iraqi man who had sustained a traumatic injury. Macy was going to build a new leg for him.

Figure 1. Using proprietary rapid prototyping technologies, REALADI and its partners remotely manufactured a prosthetic leg to restore mobility to an injured 37-year-old Baghdad resident. They created digital casts of a leg (top left) and a prosthesis (bottom left), which they used to create a digital rendering of a prosthesis (top right) and finally a finished prosthetic leg (bottom right).
Figure 1. Using proprietary rapid prototyping technologies, REALADI and its partners remotely manufactured a prosthetic leg to restore mobility to an injured 37-year-old Baghdad resident. They created digital casts of a leg (top left) and a prosthesis (bottom left), which they used to create a digital rendering of a prosthesis (top right) and finally a finished prosthetic leg (bottom right).

Baghdad Calls

In 2005, REALADI was contacted by Stratasys (, a rapid prototyping technology and services provider. Stratasys invited Macy and his partners to participate in a project called RP4Baghdad (, which was organized and supported by leaders in the rapid prototyping industry. According to RP4Baghdad's concept statement on its site, "While helping people in serious need, the [rapid prototyping] industry wants to demonstrate how its technology can fundamentally influence peoples' lives for the better." The initiative involves using technology to produce prosthetic devices for injured Baghdad residents. As it happened, Macy and his partners were exploring creative ways to deploy 3D digitizing solutions in the medical prosthesis field. They had, in fact, developed methods for acquiring data, processing it, and producing wearable prosthetics. So they signed up, agreeing to produce the first prosthetic leg under the program.

The Human Factor

Stratasys has been REALADI's partner in developing the socket, the load-bearing component that joins the remaining limb with the mechanical parts. This "human–machine interface," as Macy calls it, presents some of the greatest challenges in manufacturing prosthetics. "Every patient has different types of soft tissues, bones structures and external and internal compositions, so the socket is dynamic," Macy explains. "To make a properly fitted socket, a prosthetist [a medical specialist in artificial body parts] has to go through a series of iterations. Depending on how good the prosthetist is, it can be two to three iterations, or it can take a long time."

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3D digital scanners can be used to capture the necessary shape, but it's not as easy as it first appears. "If you hold your limb straight, it's in one shape. If you hold it over your head, it's in another shape. If you bend your knee or straighten it, it's in yet another shape," Macy points out. "So just capturing the external shape of the limb does not solve all the problems in obtaining a good fit."

Macy has seen patients who've spent years with poorly fitted sockets. He predicts patients will benefit tremendously when his company, or anyone else, discovers a way to reliably and accurately acquire the shape of the residual limb and generate a custom-fitted socket with emphasis on affordability.

The Cost Factor

The technology at REALADI, Macy noted, is in the R&D stage and not appropriate for high-volume production, but he anticipates that success stories will reach the ears of the right investors.

"The software costs a lot," he admits. "Optimization can solve this problem. For instance, Rapidform or Geomagic [software companies that develop and market point-cloud data processing solutions] have developed a specific algorithm—a subroutine—for processing hearing aids, and that individual capability can be purchased much more affordably."

In addition, the FDM (fused deposition modeling) process used in rapid prototyping currently has a premium cost because, Macy observes, in the past is was confined to making low-volume samples and prototypes—not for high-volume end-product creation. When the process becomes a mainstream practice, then prosthetics manufacturing may become an affordable medical option and a sustainable business at the same time.

The Process

Using proprietary fitting methods, REALADI's partner, investor and prosthetist Steve Peeples of Peeples Orthotics & Prosthetics developed the shape of the patient's limb based on the cast received. "Then we imported that into the computing environment, processed the data, exported the requirements and generated a part," said Macy. Steve Peeples oversaw the tricky fitting process. Because the patient wasn't physically available for fittings, they used a combination of virtual and physical fitting methods to ensure that the finished product would suit the patient. Macy imagines that, with the right infrastructure in place, it would be relatively easy to acquire the patient's data digitally in Iraq, transmit it to the U.S. for processing and then remotely manufacture the prosthetic limb closer to where the patient resides using rapid prototyping technologies and the Internet.

But that's in the future. For now, the finished prosthetics must circulate through the postal system and the Customs Service and be subject to strict clearance requirements like everything else destined for that region. "It's possible to complete [the prosthetics] in five days, assuming everyone is available," Macy estimates. "In the future, with regular production, there is nothing preventing a one-day cycle time and the opportunity to build the digital socket anywhere in the world." It took REALADI and its partners about two weeks to produce the artificial leg for the 37-year-old Iraqi patient. It took months for the shipment to get to its new owner.

More Information

Macy was happy to report that REALADI's first artificial leg for RP4Baghdad, once received, "provided a good fit and the patient was very happy to have restored mobility." REALADI and its partners are also responsible for helping a 45-year-old man and a 28-year-old man injured in Iraq. In addition to prosthetics, REALADI also provides solutions for capturing 3D data, converting them to editable CAD data and CNC (computer numeric controlled) production of prototypes for traditional manufacturing sectors.

Wohlers Associates (, one of the sponsors of RP4Baghdad, reports that "more than 40 medical models have been produced and shipped to Baghdad to support teams of doctors with complex reconstructive surgeries of the head and face . . . In August 2005, more than 300 civilians were on a waiting list for an artificial leg at one of three medical centers in Baghdad. It is believed that scores of others have not registered for a prosthetic because of the extensive backlog."

RP4Baghdad's sponsors include Z Corp. (, a developer of 3D printers; 3D Systems (, a rapid prototyping technology provider; Medical Modeling (, a tactile imagery provider for reconstructive surgery; and many others.

Editors' Note

RP4Baghdad has a big need for supplies, equipment and cash donations. Please be aware that the RP4Baghdad Web site contains some graphic images of patients.

Kenneth Wong is a former editor of Cadence magazine. As a freelance writer, he explores innovative use of technology and its implications. E-mail him at kennethwongsf at

About the Author: Kenneth Wong