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Researchers Create Perfect Fitting 3D Printed Transtibial Leg Socket for Prosthetic Legs
Posted by Matt
MEDICAL

By Eddie Krassenstein | 3D Print

I am fortunate enough to have both of my legs. I can run, jump, play football, and swim in the ocean. Unfortunately though, not everyone can say the same. There are individuals born with birth defects that bring them into this world with missing legs, and there are those who suffer an accident or disease which leave them missing one of their legs. Prosthetic legs have been increasing in popularity, and they have really been quite effective in providing amputees and others with missing legs, the opportunity to walk again.

I’ve spoken to many people over the years who use prosthetic legs. While they are typically pleased with the fact that they can now get around without the need for a wheelchair or crutches, there are still plenty of qualms on their behalf.

Quite simply put, it is usually a massive pain in the butt getting fitted for a prosthesis. This is because of the lack of customization provided by today’s sockets. The socket is the part of the prosthesis that meets the “stub” of the wearer’s leg. Usually it takes several fittings and adjustments, followed by several more, before a prosthetic leg will fit just right. Even then, “just right” is a term that can be overstated, as many times the fit never ends up being perfect.

For one biomedical engineer, named Lizbeth López, this simply was not enough. López has been working at Tec de Monterrey, in Monterrey City, Mexico under the guidance of her thesis advisor, Dr. Ciro Rodriguez. In a collaboration with Ottobock and cTI Renato Archer in Campinas, Brazil with Dr. Jorge V. Lopes’ guidance as well, López set out to create a 3D printed custom transtibial leg socket that fits just right.

“The main objective of this work was to fabricate a complete functional prosthesis, in this case oriented to transtibial amputees as the first group of test patients,” López tells 3DPrint.com. “The project began as a personal motivation to design and fabricate prosthesis well adapted to health needs of the patient.”

López and her team worked with two patients. One of these patients was in Mexico, and López was able to test the use of laser scanners and computer tomography in order to create many different iterations in several different types of software. This allowed her to choose the best option that she would use in order to begin 3D printing the transtibial socket, with hopes of it being used on a final prosthesis.

López then moved her research from Mexico to Brazil and started working with a second patient, in compliance with Ottobock.

“We decided to use a laser scanner and CT to capture the stump of the patient,” López explained. “Later the DICOM data from [the] CT was reconstructed as a 3D structure in InVesalius software, and then it was compared with data acquired from the laser scanner. Subsequently, we imported the files in .stl extension to CAD software to begin the process of design, based on the real anatomical data of the specific patient.”

One of the tremendous benefits of using this 3D data to create the socket, other than the customizability it provides, is that once the scans are taken, there really is no need to directly work with the patient any long, prior to the initial fitting. Once the team believed that they had the socket designed correctly, they had to put it through tests to ensure reliability.

“We tested the socket design with FEM analysis, just to make sure that load conditions were to show numerical results under the yield strength of material; so we can be confident about the mechanical resistance of [the] 3D printed socket before the patient tests it,” explained López.

Once the tests were complete, it was on to 3D printing the socket using an SLS HiQ 3D printer. Printed in polyamide, the process took about 17 hours to complete. The socket was then mounted and aligned to the complete prosthesis at Ottobock in Valinhos, Brazil, before the ultimate test was undertaken.

The prosthesis and this incredible 3D printed socket were fitted to the patient, and the results surprised just about everyone. The patient, who has been involved in many other prosthetic leg tests for Ottobock, couldn’t believe the results. The socket was completely comfortable from the first time he put it on, only requiring the adjustment of one single screw. In the past, this same patient was required to try on the same prosthesis over and over again in order to get just the right fit. This could take days between fittings, causing quite a bit of frustration and aggravation.

With 3D printing technology and the tremendous work of López and her team, no adjustments were required.

“Technical [personnel at] Ottobock pointed [out] that this kind of result is not seen every day,” explained López. “That’s really good because then we have a great approximation to the fantastic and ‘futuristic’ idea that it’s going be possible to adapt many prosthesis to many patients in one single day.”

3D printing is certainly showing its potential in the field of prostheses, allowing for complete customization on a one-to-one basis, making the entire process much faster and more efficient, leaving both patient and doctor happy.

What do you think about this potential that 3D printing has in the custom fitting of prostheses? Discuss in the 3D printed prosthetic leg socket forum thread on 3DPB.com. Check out the video provided to us below of López’s patient trying on his prosthetic leg.

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