May 4, 2016 | By Kira
Properly fitted sockets are essential for prosthetic limb wearers, ensuring comfort and mobility while preventing further pain or injury. The socket joins the prosthetic to the user’s residual limb, and is therefore the key connecting piece of the puzzle. All-too-often, however, sockets are either ill-fitted, causing the person to stop wearing their prosthetic, or, when they are custom-made, they can be extremely expensive and time-consuming to produce.
Using low-cost 3D scanning, 3D CAD, and 3D printing technology, a student from Lund University in Sweden has now developed a streamlined, step-by-step process for 3D printing custom-fitted prosthetic limb sockets that can provide significant cost and time savings (up to 400 hours and $30K per year), even for prosthetists who have no previous experience with 3D technology.
Emelie Strömshed is a master’s student in Product Development at the School of Engineering at Lund University. For this project, her goal was twofold: first, to benefit prosthetists by making custom sockets easier, faster, and cheaper to produce; and second, to benefit the clients themselves by providing a perfectly-fitting socket every time.
Strömshed worked under the supervision of Christian Veraeus, prosthetist at Aktiv Ortopedteknik, and Olaf Diegel, professor of Product Development. If that last name sounds familiar, it’s because Diegel is no stranger to 3D printing or to 3Ders.org. Previously, the Lund University professor has helped develop a 3D construction printer and the world’s first 3D printed aluminum guitar.
As a professional in the field, Veraeus helped Strömshed and Diegel identify a key issue: custom socket manufacturing requires skilled craftsmanship, expertise, and materials that are not always available.
The traditional process begins with creating a negative mold from plaster, which is then used to create a positive cast of the residual limb. The limb cast is then manually modified, and through thermoforming, a prosthetic socket is formed. In some cases, the mold can be laminated with plastic resin or reinforced with fiber-glass, carbon fiber, or a silicone interface, requiring further equipment, materials, and processes.
Traditional cast-making process
Strömshed’s proposed solution eliminates much of the manual labor by utilizing precise yet low-cost 3D CAD and 3D scanning technology instead.
She began by using the iSense 3D scanner, a sub-$500 add-on that turns your iPad into a 3D scanning device, to capture digital images of the patient’s residual limb. These images are then uploaded into 3D CAD software, where she can shape the prosthetic socket by “offsetting the limb surface a distance equal to the desired thickness of the socket.” The original 3D scan is then subtracted from the 3D model, leaving an inner surface that perfect matches the patient’s residual limb.
Finally, the 3D file is sent to an SLS 3D printer, where it is 3D printed in durable and lightweight nylon material. This process can take just a few hours, and allows the patient to customize their prosthetic with colors or designs after the fact.
According to Lund University, since the process is straightforward and streamlined, even prosthetists with no previous 3D modeling experience can follow along. Another major advantage is that the process allows for the socket to be adapted for both passive and active myoelectric protheses. The pictures above show young Neya Pfannenstill using her custom 3D printed socket with a passive prosthesis (also custom 3D printed just for her), however the customization options for other patients are nearly unlimited.
The most substantial proof of Strömshed’s success, however, is in the numbers. The research team performed a time and cost comparison between the 3D printing process and traditional socket manufacturing. The results showed time savings of 400 hours per year, and cost reductions of 261,000 SEK (US$32,000) in the same period.
Detailed, step-by-step process for 3D printing custom prosthetic sockets
3D scanning and 3D printing technologies have been improving nearly every aspect of prosthetic design and production, yet as the connecting core, the time has come for custom 3D printed sockets to have their time in the limelight. For related 3D printing projects, check out E-NABLE’s sport-specific prosthetic attachment design challenge, or MIT Lab’s FitSocket limb measurement tool for better-fitting prosthetics.
Posted in 3D Printing Application
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