3D Printing Gains Momentum in Clinical O&P

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By Miki Fairley

Technologies in 3D printing are moving further into mainstream O&P clinical use beyond their now-familiar role in producing prosthetic covers, foot orthotics, and somewhat controversial volunteer-produced hand devices. Within the last three to five years, new printers and materials, including some developed especially for prosthetics and orthotics, are driving the momentum. Some devices have even been tested to meet ISO 10328 strength standards.

The O&P EDGE  spoke with experts in newer 3D-printing companies and early adopters who have been using 3D printing clinically for several years to gain insight into how the technology is being used in practices, its advantages, its pitfalls, and possible trends for the future.

Early Adopters Forge Ahead

Jeff Erenstone, CPO, owner of Create Orthotics and Prosthetics, Lake Placid, New York, and Mountain Orthotic & Prosthetic Services, Lake Placid, is an early adopter of 3D-printing technologies in humanitarian work as well as at his clinical facility.

Continuing his interest in 3D printing, Erenstone has developed a complete 3D-printing system. With Create O&P's Rapid Socket System, clinicians can go from cast to fit in three hours, Erenstone says. The system includes a professional-grade printer specifically designed for O&P use and web-based modification software that uses an iPad touch screen for clinicians to modify digital plaster with movements and techniques that are familiar, he explains. "Using a touch screen, you can shape things and modify the digital model similarly to using a plaster model. We're used to using our hands; if you have to relearn how to do something, that's going to slow you down and make you less efficient."

"We've built a start-to-finish process…. [You] can scan the limb with scanner on your iPad, upload it to the CAD, open it with the iPad, and use the modification tools on that same device without even leaving the patient room. The front-end user then doesn't have to worry about converting a CAD STL file to a G Code file for the printer." The user simply decides what kind of device he or she wants to make and presses a button, according to Erenstone. Clinicians can email the file to a technician who inserts the SD card in the printer and starts printing. A check socket typically takes about two hours to print.

However, Erenstone sees a continuing role for traditional materials and fabrication methods and uses both 3D printing and conventional fabrication in his clinic. "You have to consider not just what you can 3D print, but what you should 3D print." Erenstone says 3D printing should be used when it is more efficient, cost-effective, and provides the necessary quality and durability.

Other early adopters of 3D printing are William (Bill) Layman, CPO, BOCPO, and Sharon Layman, COF/CMF, owners of Innovative Orthotics & Prosthetics of Louisiana, Kenner, and their son, Brian Layman, CP, BOCPO, who operates a sister company, Innovative Digital Manufacturing, Kenner. They began exploring the technology seven years ago. The company is using 3D printing to fabricate sockets and protective covers in a variety of designs. "At this time, we are adding one layer of carbon fiber over our prints for strength and durability. We are also able to print housings in our sockets for different types of shuttle locks and elevated vacuum and expulsion valves," Bill Layman says. After a patient is fitted with a check socket, the interior and exterior of that aligned check socket are scanned. The two scans are merged to provide a complete scan from which a 3D-printed definitive socket can be fabricated from ABS or nylon 12 material.

"We recently received a patent (#10,010,433) on the added techniques that we use to make our sockets' appearance acceptable," adds Sharon Layman. "With this technique, the sockets are tumbled for a period of time and an epoxy sealant is added inside the socket." She adds that laminating over prints is combination of old and new school techniques that work well together.

Prosthetic Design Inc. (PDI), Clayton, Ohio, is another O&P pioneer in clinical use of 3D printing. "PDI's sister company, Dayton Artificial Limb Clinic (DALC), began selectively fitting patients with PDI-printed sockets in 2009," says Tracy Slemker, CPO, FAAOP, president and founder of PDI and DALC, Clayton. "After observing a better fitting device and satisfied patients, DALC converted all patients to PDI-printed sockets in 2013."

Besides its 3D printing and conventional central fabrication services and various O&P-related products, several of which were developed by the company, PDI also offers a 3D printer specially designed for O&P with strength, durability, and speed in mind.

The Squirt Shape machine was developed in the late 1980s by doctoral student Josh Rolock at Northwestern University. After the project ran out of funding, PDI privately funded and further developed the machine, Slemker says. The printer operates under an AXZ axis orientation as opposed to XYZ. "The rotational A axis allows for a constant spiral motion so there is no disconnect between layers," Slemker explains. "It also allows for a larger extruder to be attached to the printer that allows 18 times more plastic to be extruded at any given time. Average print time for a transtibial socket is one and a half hours."

The printer utilizes a proprietary virgin plastic (made from original rather than recycled materials) pelletized copolymer formula that has exceeded performance testing including destructive and cyclic testing by third-party material testing facilities, Slemker notes. PDI produces 3D-printed check and definitive sockets, flexible inner sockets, liners, and tooling. PDI also can print flexible inner sockets; products include spinal orthoses, knee bracing, and cranial helmets, he adds.

Innovators Launch O&P-focused Enterprises

Extremiti3D, Johns Island, South Carolina, is a young company founded by CEO Barry D. Hand and Chief Marketing and Sales Officer James H. Price, both of whom have decades of medical device experience. Extremiti3D has developed an O&P-focused 3D-printing manufacturing process and a proprietary blend of thermoplastic and carbon fiber materials to create precisely fitted definitive transtibial and transfemoral prosthetic sockets, along with prosthetic covers and flexible inner sockets. Using the company's C-Fit Carbon Fiber Infill Technology, the sockets pass stringent ISO 10328 strength and cycle testing standards and qualify for the ultralight socket L-Code.

Extremiti3D has strategically leveraged the power of partnership and alliances by collaborating with other companies: Friddle's Orthopedic Appliances, Honea Path, South Carolina; Vorum, Vancouver, British Columbia, Canada; Standard Cyborg, San Francisco, California; and Click Medical, Steamboat Springs, Colorado.

Noting some of the advantages of the 3D socket technology over traditional fabrication methods, Hand points out that since the residual limb is scanned to exact measurement rather than thermoformed over a mold, there are no pulling deformities. If needed, slight modifications can be made to the definitive socket with a heat gun. Fabrication costs and time are reduced, thus increasing time spent seeing patients. The carbon reinforcement combined with plastic enables the sockets to have softness in the proximal part of the socket but stiffness in the distal part. "Patients have commented on how comfortable they are," Hand says. "Working with Friddle's, we have made a traditional carbon-fiber socket and one fabricated with our technology for some patients—they wear one and then the other—and every single time, they've chosen the 3D-printed socket over the traditional carbon fiber one."

3D printing is not the sole technology Extremiti3D uses. "Our liners and protective covers are entirely 3D printed, but our sockets go through additional post-processing steps to produce strength and durability." Future plans include orthotics as well.

Like many other innovative O&P companies, Naked Prosthetics, Olympia, Washington, was launched by a person with an amputation who created the prosthetic device he needed. After losing most of his right middle finger in an accident in 2010, Colin Macduff, an experienced fabricator and welder, made his own prosthetic finger out of bicycle parts. Soon after, he and current CEO Bob Thompson founded an enterprise providing functional biomechanical fingers to other people with digit amputations.

Today, Naked Prosthetics, under the leadership of Thompson and a strong team of engineers and customer care specialists, has moved far beyond bicycle parts into sophisticated fabrication of highly customized finger and thumb prostheses.

Using 3D printing alone or, for some products, in combination with traditional machine milling, Naked Prosthetics manufactures three products: the MCPDriver, which mimics the flexion and extension of a natural finger through movement of the metacarpophalangeal (MCP) joint; the PIPDriver for amputations distal to the proximal interphalangeal joint (PIP) joint; and the ThumbDriver, which provides opposition and strength and is driven off the carpometacarpal (CMC) and MCP joints. All the prosthetic digits are sleek and slender; multiple devices can be worn on the same hand.

"The population we see are often active men, working with their hands, often working outside," says Vice President of Engineering KT Treadwell. "They may have had an on-the-job injury. We put a lot of effort into making our products robust, so they can go back to those jobs. About 50 percent of persons who lose fingers can't go back to the same job, so we're very proud of the fact that we get a lot of guys back to work."

She adds, "Until we had access to 3D printing, nobody was able to provide functional [biomechanical] finger replacements because it was too difficult to make a completely custom device for each person. We absolutely could not do what we do well without it." However, Treadwell sees 3D printing as an important tool, but not the only one. "Our PIPDriver is 3D printed, but our MCPDriver is produced by a combination of 3D printing and traditional machining. So it really depends on the requirements of the device."

3D printing central fabrication facility Protosthetics, Fargo, North Dakota, which launched in November 2015, got its start when Cofounder and Chief Futurist Cooper Bierscheid, lead engineer, was still in college. He and some classmates designed and created a microprocessor-controlled arm utilizing 3D printing, which led Bierscheid to continue pursuing 3D printing in the O&P industry. Bierscheid partnered with Josh Teigen, the company's cofounder and chief visionary, who brought the medical device background and startup experience, and together they started Protosthetics.

The Protosthetics team of engineers constructs its printers in-house, "giving us the capability to design and assemble them to specifications that will give us the best results for O&P applications," say Teigen and Emma Ilvedson, director of business development. "Our Tallboy printers can print up to 28 inches high and in over 30 different materials ranging from flexible urethanes to rigid fiber-reinforced copolymers."

Protosthetics and c2renew, Fargo, have partnered to create a proprietary new material using industrial polymers and unique strengthening fibers to create definitive sockets that will "improve safety, usability, and patient quality of life," according to Teigen and Ilvedson.

"However, we have learned that the best approach to fabrication right now is a blend of traditional fab and CAD/CAM/3D printing," Teigen and Ilvedson add. "3D printing may not always be directly involved in the end product, but it is almost always involved in the manufacturing process at some point."

The company offers 3D-printed check and definitive sockets, prosthetic cosmetic covers, and 3D-printed orthoses including fully custom pectus carinatum braces, functional foot orthotics, UCBs, non-ambulatory AFOs, and its Amphibian water leg. The water leg's cosmetic cover, designed to match the patient's sound limb, and part of the definitive socket are 3D printed; the leg is partnered with a waterproof Niagara foot and the AquaPaw, a neoprene treaded slip-on foot cover.

3D PrintingAdvantages and Challenges

Advantages

A benefit of 3D printing is being able to create completely customized devices, Treadwell notes.

"The printer can do a large portion of the labor while technicians are working on laminating or finishing other orders," Teigen and Ilvedson say. "We can even start prints before leaving for the night and come back in the morning to completed sockets."

Slemker sees the advantages to 3D printing as fabrication speed, strength, socket design freedom, and research capability. "3D [printing] allows research access to fabrication of unlimited number of identical sockets or even as specific as creating a precise void for placement of internal sensors."

Challenges

"3D printing in general was rolled out to the masses about six to eight years ago; people were eager to try it but didn't really understand how the process works or how the materials behave," Hand says. "Early on, 3D printing got the reputation of being experimental, not always reliable, and not ready for prime time manufacturing. At the onset of utilizing this additive manufacturing process for prosthetics and orthotics, there were questions of strength and reliability. It was also seen as just another way to make something that's already made by other processes. Our challenge was, and to some extent still is, getting people to see that our technology has become much better with new machines and materials combined with an engineering-focused process."

Although material quality and technologies are reaching the point where 3D printing can be used for durable devices rather than mainly printing prototypes and concepts, products still must be engineered, Treadwell points out. "You still have to deal with stress concentrations, material properties, and design factors, as well as reliability and fatigue [the weakening of a material caused by repeatedly applied loads]."

"Since there are not currently many central fabrication facilities for 3D-printed O&P devices, practitioners interested in utilizing 3D printing technologies may feel they must purchase their own printers and learn the modification software on their own," Teigen and Ilvedson point out. "This is a large capital investment, especially for small clinics. Our goal is to allow practitioners a path where they take advantage of this technology at low cost and without taking on a huge learning curve."

Slemker sees technical and clinical acceptance as the biggest challenges. "3D printing is a significant paradigm shift. Practitioners and technicians must have a willingness to learn new skill sets."

Looking to the Future

All those interviewed foresee a promising future and a bigger role for 3D printing as printing technologies and materials become better and less expensive. For instance, Treadwell mentions some new materials that are isotropic, providing the same strength in all directions rather than being stronger in one direction than another. Unequal directional strengths are likely to cause parts failure and breakage due to stress exerted on the weaker directions.

However, interviewees do not see 3D printing as ever replacing traditional fabrication and manufacturing technologies, but rather as an increasingly useful tool in the toolbox.

"3D printing will become more widely accepted in the O&P industry in the near future," Teigen and Ilvedson say. "It is important to view 3D printing not as an end-all/solve-all solution. Rather, it is a tool that can increase accuracy, repeatability, efficiency, and ultimately save the clinic and practitioner time and money while maintaining a high level of patient care."

Slemker points out another valuable role for 3D printing in O&P. "3D [printing] technology can be a resource of significant improvement to access for those in need," he says. Citing information from the World Health Organization 2017 Standards for Prosthetics and Orthotics, he notes, "There are 35-40 million people globally who require prosthetics and orthotics services…. The harsh reality in many countries is that 85-95 percent of the people who could benefit from assistive products do not have access to them…including prostheses and orthoses."

"We have solved the challenges and can now produce strong and durable prosthetic devices with the right fit for each patient," Hand says. "Research and development will continue for ongoing ‘mass customization,' that is, individually customized products on a large scale. Better technology and materials, along with skilled engineering, will continue to create promising technologies and solutions for our patients. It will happen."

Miki Fairley is a freelance writer based in southwest Colorado. She can be contacted at miki.fairley@gmail.com.