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Designing Prosthetics: When Customization is Crucial

Naked Prosthetics uses 3D printing to create biomechanical prosthetic fingers, such as the PIPDriver, pictured here. Image courtesy of Naked Prosthetics.

Naked Prosthetics uses 3D printing to create biomechanical prosthetic fingers, such as the PIPDriver, pictured here. Image courtesy of Naked Prosthetics.

Today’s prosthetic applications are an example of the intersection of design, technology and science. Going beyond traditional molding techniques and labor-intensive processes presents new opportunities for medical device design and patient data collection.

Despite its long history, 3D printing is just now flourishing in the medical sector, especially for generating prosthetics. Engineers and medical professionals are collaborating on a new generation of technology and design processes based on the quick customization enabled by 3D printing.

“With the use of 3D printing, a designer and prosthetist can work together to design a prosthetic using modern tools in combination with age-old techniques like plaster casting, to create prosthetics faster and more efficiently at a lower cost,” says Ava DeCapri, industrial designer at FATHOM, a Stratasys 3D printer reseller and service provider.

Get Involved

Because open source is a large part of the 3D-printed prosthetic movement, organizations have popped up to take advantage of the technology for philanthropy. If you’re interesting in helping, check out these causes:

e-NABLE: One of the largest groups in the community, e-NABLE delivers prosthetics globally and its Raptor hand design has become mainstream for similar charities.

The Helping Hand Project: Based out of UNC Chapel Hill, the group can make a prosthetic hand design for less than $40.

Open Bionics: Going beyond 3D printing, this company has a developer community for users to help shape prosthetic designs and devices.

For example, Travis Bellicchi, Maxillofacial Prosthodontic resident at Indiana University’s School of Dentistry, is working with a host of students and faculty to develop a new mandible prosthesis for a patient. They’re using a new digital workflow that includes 3D printing.

Knowing the final product would be produced with FDA-grade silicone, Bellicchi and his team decided to integrate 3D printing as part of the design process. “It’s easily iterative. If you’re working with plaster in the lab to make your molds, it’s quite easy to crack, fracture [or] get totally destroyed. There’s a real delicacy to a mold.” Additionally, there’s a higher resolution quality to some of the printing materials, which is especially important when figuring out how to place a prosthesis near a jaw or under skin.

To develop a new mandible, Bellicchi collaborated with the School of Informatics and Computing: Department of Media Arts and Science, School of Mechanical Engineering and Herron School of Art. Their work not only created a new mandible, but also produced a digital workflow that combined 3D scanning, CAD and 3D printing — something that’s relatively new to the field. “In the past, our work felt very traditional and bogged down in this analog process,” he says.

By being able to gather digital data and print multiple prototypes, Bellichi says his team was able to automate a lot of the time-consuming lab work by referring to patient data every time they wanted to tweak the design, instead of starting from scratch.

Comfort is Key in Prosthetics

When addressing form, fit and function in prosthetic design, “fit” is king for creating a device that will be used every day.

“We get a lot of customers who [have gotten] prosthetics developed and they just end up sitting in a drawer,” says Tony Peto, senior engineer at Naked Prosthetics. “That’s not what we want.”

3D printing allows the fit to be customized for each patient. Peto says engineers at Naked work on a patient-to-patient basis to ensure that the design will be beneficial to its user once it leaves production.

Movement is another key requirement, especially for more advanced prostheses, according to Travis Bellicchi, Maxillofacial Prosthodontic resident at Indiana University. When generating solutions that are integrated into the jaw or face, for example, part of the patient experience is how movement affects the prosthetic material and positioning.

The form of the design is also important, but it’s not as challenging from a design perspective. “The aesthetic needs are actually quite [streamlined] for a prosthesis,” Bellicchi explains. “Both for internal characterization and external characterization, making it look lifelike is relatively straightforward.”

Making prosthetics look cooler than lifelike is also an option with 3D printing. For example, Open Bionics has teamed up with The Walt Disney Company to provide Frozen, Marvel and Star Wars inspired prosthetic hands to kids. Others are using the technology to create artistic prosthetics that are both lightweight and customized.

Collaboration is also helping to drive lower costs. “The largely open-source prosthetic 3D printing community shares designs and concepts at high speed, constantly 3D printing, testing and improving available designs … leading to faster innovation in the industry as a whole,” FATHOM’s DeCapri notes. This type of open-source design can be seen through organizations such as e-NABLE, The Helping Hand Project, Open Bionics and others who are focused on providing affordable and free 3D printed prosthetics to those in need.

While one of the main benefits of using 3D printing for prosthetics is reduced cost, there are other benefits that might not immediately be considered. “There is less risk and lower cost involved in designing and creating 3D printed prosthetics vs. traditionally fabricated prosthetics, so the technology allows for greater exploration of unprecedented design concepts. For the many people who have unique cases, traditional options [which may require surgery] can seem overwhelming,” says DeCapri.

Beyond the cost and time savings for digital development, Bellicchi hopes using tools such as 3D printing and basic design software could also help medical professionals directly within hospitals. “There’s a missing link in healthcare [when it comes to] digital design. Day-to-day, there’s a need for more simplistic rapid prototyping that doesn’t necessarily justify the thousands of dollars of design support, but still can be beneficial for patients.”

Getting Technical

3D printing is just the beginning of offering customized medical devices. Affordable, accessible technologies are also ushering in an era of prosthetics and medical devices that integrate sensors for smart prosthetics and tailored feedback. Some examples include the BOOMcast from FATHOM and the limbU design. Both of these applications focus around connecting technology and augmenting the patient’s use of a prosthetic or cast.

“With BOOMcast, the FATHOM team saw the opportunity as a challenge,” DeCapri explains. “How can we rethink a medical cast? What are the possibilities that haven’t been tapped into? What if this leg cast could actively facilitate the healing process and give doctors additional medical data?”

Some of the technology that was used in the BOOMcast was implemented to gather technical data — including an accelerometer, gyroscope, magnetometer and an Intel Edison compute module. Because the wearer, Mike North, was constantly moving around the globe for his job, having connectivity allowed doctors assess his medical state from afar and make adjustments as needed.

While the technology helped doctors monitor patient statics, it also served as a bigger part of the user experience. Bluetooth-enabled speakers and LED lighting added a new layer of customization. But, it wasn’t entirely decorative; the speakers emitted low-frequency tones that researchers concluded did ultimately help heal the bone, says DeCapri.

The integration of different technologies such as 3D printing, sensors and computer processors is just the beginning for prostheses.

“Despite promising advances in medical technology, prostheses that can match their biological counterparts are currently confined to the realms of science fiction. This limitation, however, does not restrict us from exploring new forms and functions for which the prosthetic limb is uniquely situated,” says Troy Baverstock, designer.

The limbU prosthetic device integrates sensors and lights for data collection and customization. Image courtesy of Troy Baverstock.

The limbU prosthetic device integrates sensors and lights for data collection and customization. Image courtesy of Troy Baverstock.

Baverstock has designed limbU to push the boundaries of prosthetics and advance the current offerings. The device, which is a prosthetic add-on, currently sports a USB charger, stereo amplifier and speakers, GPS, microcontrollers, barometer, accelerometer and gyroscope. Ultimately, the wearer will not only be able to monitor daily activity, but also their environment around them. “limbU seeks to redefine a wearer’s relationship with their limb by allowing the opportunity to co-­create its form and function to suit their personal lives,” he says.

But, even with these advanced devices, Peto says that the technology for truly advanced prosthetics right now is currently ahead of the implementation. Still, with the lower costs of 3D printing methods and the trend toward connectivity, it’s helping more patients get better devices and paving the way for even more innovative prosthetics.

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About Jess Lulka

Jess Lulka is a former associate editor for Digital Engineering. Contact her via de-editors@digitaleng.news.