3D-printed mold made in an acrylate-based material.
3D touch-enabled modeling helps build an organically designed nasal prosthetic for a skin cancer patient who lost his nose.
When we hear someone is going to get a nose job it usually involves fixing a broken nose or hiding a physical insecurity. But more and more we are hearing stories of doctors performing facial miracles on war, burn, and cancer victims who have lost part of their face and need to have it replaced with facial prosthetics.
Traditionally, the facial prosthetic design process was as traumatic as the initial injury that caused the disfigurement. The patient sat through several sessions that involved scanning the damaged areas and then producing a mold -- a process that could be very painful at times.
The turnaround time for traditional design processes could be anywhere from several days to weeks and involved several labor intensive and invasive stages. An impression material was first applied directly to the area fitted for a prosthetic.
This was then turned into a replica of the defect, on to which a wax pattern was carved. Long consultations were required whilst the design was fitted and refitted to the patient to make sure it blended in with the rest of the surrounding anatomy.
An Organic Design Solution
Dominic Eggbeer using the Sensable Freeform 3D design system with its Phantom haptic device.
Sensable's Freeform, 3D touch-enabled modeling solution not only shortens the design and review process for patients in need of facial prostheses, but it moves designs into the prototyping and manufacturing phases more efficiently, reducing costs and time for both the patients and medical professionals.
Most importantly, it creates a lifelike representation with a natural appearance that fits more attractively with the surrounding anatomy and eliminates the messy techniques that are associated with traditional manual processes, creating a more comfortable experience for patients.
CARTIS (The Centre for Applied Reconstructive Technologies in Surgery) -- a unique partnership between Product Design & Development Research (PDR) at the University of Wales Institute, Cardiff (UWIC), and Morriston Hospital (both in the UK) -- used Freeform to produce an organically-designed nasal prosthetic for an older gentleman who lost his nose due to a squamous-cell carcinoma, the second most common cancer of the skin. The prosthesis -- made from a silicone elastomer -- featured skin pores, brow creases, and was secured on the patient's face by two magnets, which were surgically implanted into the facial bones.
"Freeform is better for working with the complex geometry of the human anatomy," says Dominic Eggbeer, research officer and head of medical applications at CARTIS. "It helps to add subtle detailing that makes it successful in reaching its end goal of proper prosthetic reconstruction."
Flexibility & Efficiency
Freeform's digital workflow not only achieved finely sculpted curves, gentle feathering of the edges, and realistic textures that made the nose prosthesis appear more authentic, but it reduced the time that the patient had to sit in a chair for the design and fitting of the prosthesis.
"Part of the research here is to figure out the most efficient way of producing prostheses," says Eggbeer. "From the start, we used 3D surface scanning to capture the facial anatomy. That information goes straight into Freeform, which then gets designed into the pattern and mold tool that makes the final prosthesis. The final prosthesis mold tool then gets 3D printed."
The sequence of events made it extremely flexible for both the patient and prosthetist, says Eggbeer. A more efficient design was created without requiring the patient to sit in a chair for long periods of time. The prosthetist was also able to evaluate the shape from various angles (many that were typically hard to view) in order to evaluate the outcome before creating a final prosthesis.
Nasal prosthesis molded in a soft, flexible elastomer.
Physical Space vs. Computer Space
While Freeform enabled CARTIS to produce a realistic nose prosthetic with a high-degree of flexibility and intuitive use, it did present some challenges concerning the maneuverability of the tool.
"One idiosyncrasy of using it is that you're confined to working with the haptic arm which provides you with feedback and has a relatively limited space to maneuver around in the physical environment," says Eggbeer.
Eggbeer points out that users are provided with infinite space in the computer environment, which can be a good thing, but it can cause users to get lost and confused about where their tool is between the physical and computer environments. "But once you get used to it, it's like any other computer software," says Eggbeer.
Final nasal prosthesis.
Another challenge during the nasal prosthetic design procedure concerned the edges of the prosthesis in creating thin margins that would blend into the surrounding anatomy. "The idea is when you frown or you smile and your facial expressions change, the edges will stick to your skin and remain invisible without making you feel like there is something static on your face," says Eggbeer. "There is also the challenge of making it look correct in terms of color and texture."
Subtle Smoothing & Smudging
Considering the complexity of the human anatomy, the ability to make subtle smoothing and smudging proved to be the most useful for CARTIS. "You can feel what you're working on, so you can make very subtle changes to the anatomy that you can't really do when working with conventional CAD," says Eggbeer. "The ability to make various textures is also very powerful."
Freeform provides the ability for designers to quantify the changes they make, and help them analyze how much material they have used and moved. "It kind of works in real-time as well, which is also very useful," says Eggbeer.
The all-digital approach made it easier for CARTIS to develop a nasal prosthesis from the patient's existing one, which faded in color and no longer fitted properly. The digital files will also provide an excellent starting point for future replacement prostheses, allowing a prosthetist to print a replacement mold from the digital file. They will make it easier to create different prostheses for various weather conditions and lifestyles in which patients will be able to apply make-up and other accessories.
