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About six years ago my father gave me a book titled, Fabricated: The New World of 3D Printing. At the time, he told me that this would be coming to the field of prosthetics soon. It took me a while to get through the book because I didn’t initially see how it would apply to prosthetics. 3D printers were expensive. Materials used for the printer were very limited. Durability of the printed product was suspect as well. I thought it would be a long time before the field of prosthetics would feel any impact from 3D printing.
Then and Now
Charles W. Hull is generally credited with creating the first 3D printer in the mid-1980s. The cost was somewhere around $100,000, equivalent to about $250,000 today. Fast forward to present day, and you can buy a small 3D printer online for less than $200. The original use of 3D printing was for prototyping of design concepts. While this is still one of the biggest uses of 3D printing, people today combine materials to print a wide range of items. Guitars, flutes, acrylic camera lenses, food, clothing—you name it! You could get a bikini custom made from a nylon material to your scanned shape. One of our engineers at College Park even 3D printed a 3D printer! Think about that one for a minute.
3D printing can have impactful benefits in the medical field. Doctors can 3D print internal organs from a CT scan that can be used to practice complicated and delicate procedures before operating on a patient. Artificial heart valves and other anatomical parts and pieces are being printed with stem cells and a protein substrate to match more closely the internal anatomy of a patient and reduce the need for anti-rejection medication. Here at College Park, we use 3D printing to model prototypes of new product. This can be done with both metal and plastic materials. It saves time, effort, and money by helping determine the efficacy of future product designs before a large investment is made in production tooling and processing.
What to Consider With Prosthetics
3D printing in prosthetic design and manufacturing has certainly taken hold, and not without controversy. When we consider medical devices, prosthetics in particular, there are always concerns about liability. This is a gray area with 3D printed devices. Who is responsible when a prosthetic product that was 3D printed by an individual in their home breaks and causes bodily harm? Who is ensuring that the device was built to quality and strength standards?
Let’s start with a look at historical and current prosthetic design vs. 3D printed designs. First, the socket—as prosthetists, this is where we believe true skill and experience is paramount. This is also the area of the field that is most overlooked by those outside of the industry. The devil is in the details here. Historically, the socket was carved out of a block of willow wood, fit and re-fit until a level of comfort was achieved. Currently, sockets are still handcrafted, either with plaster or scanning technology, by the prosthetist. If the socket isn’t right, it doesn’t matter what technology in the form of a knee, foot, hand, wrist, or elbow is attached to it; a successful outcome is not likely. The materials chosen for the socket construction are selected for strength and weight characteristics that meet the patient’s needs. There are industry standards for weight rating and durability. If the socket fails for some reason, it is the prosthetists’ responsibility to repair or replace as needed.
The second consideration is the connective components of the prosthesis. Historically, exoskeletal designs made from wood, again, evolved into laminated outer covering materials that can still be used today. Today’s industry standard of endoskeletal components to connect lower-extremity sockets to the hips, knees, and feet all have weight ratings and require rigorous testing to ensure a minimal likelihood of catastrophic failure with possible injury to the patient.
Finally, the products incorporated into a prosthesis in the way of hips, knees, feet, hands, wrists, and elbows need to be considered. These products must go through extensive testing including submission to the FDA for some products to ensure safety to the consumer and mitigate any risk to the end-user. Manufacturers have specific testing guidelines for durability and patient safety. We test our endoskeletal componentry, knees, and feet between 2 to 7 million cycles at 2 to 6 hertz to ensure they will hold up to the expected lifetime of a prosthesis (3-5 years). The Espire Pro elbow system had to withstand 120 volts and not pass the voltage through the system to the patient’s socket. College Park uses Intelliweave® composite technology for our feet. It’s made of fibers woven by hand in a 3D pattern for ultimate durability and precision gait matching. Each part of College Park’s prosthetic products is tested individually before being assembled together.
The question is, who is responsible for this testing with 3D printed medical products? If each part is built individually with no standardization of product, how can durability testing be established? Open Bionics has introduced the first medically approved 3D printed prosthetic device with the Hero Arm. The Open Bionics team went through several years of clinical trials to achieve this great success and the product is limited to transradial amputees only at this time. Translating this same type of technology to transhumeral amputees with the added degree of freedom of the elbow, or lower limb amputees with the added requirement of weight bearing on the device certainly will add to the level of durability required for functional use.
Benefits and Future Prosthetics
There are certainly benefits to 3D printing if and when these questions of durability, adjustability, and liability are answered.
- Cost: The Hero Arm can be 1/10th the cost of a traditional myoelectric transradial prosthesis. If there is an issue with fit, design, or durability, there is the option of modifying and reprinting the device. The cost savings is particularly beneficial in those areas of the world without a robust healthcare system.
- Remote Access: There is the potential for “one visit delivery.” The patient could be scanned directly, the model rectified, and device fabricated, and delivered remotely. For those with limited access or mobility, this could clearly be a benefit.
- Customization: Literally, your imagination is your only limitation when it comes to 3D printing. Whether it be an external shape like Iron Man, or a transtibial prosthesis shaped like a bowling pin, it can be done with 3D printing.
I think many people in the O&P industry have traditionally seen 3D printing as a threat. The recent article in the O&P Edge by Maria St. Louis-Sanchez, From Disruptor to Partner, explores this idea. Even if the fabrication process becomes automated with 3D printing, the creative process of socket design and the interactive process of fitting and alignment will still require the level of expertise of the O&P professional. One thing is clear, 3D printing is not going away. It will soon play a big role in the field of Orthotics & Prosthetics.