Advanced technology for orthopedic rehabilitation – knee replacement via additive manufacturing

During his time studying engineering at university, Mike Geldart suffered a severe knee injury in a racing accident. Following surgery, he received a rigid knee prosthesis that was poorly fitted and unsuitable for a swift recovery. Now serving as CEO of GRD Biomechanics, Geldart has transformed his challenging recovery experience into the inspiration behind a groundbreaking knee prosthesis. Utilizing additive manufacturing, this advanced design promotes faster recovery and minimizes the need for surgeries for patients who receive timely medical attention.

Below, Geldart explains why 3D printing offers the next generation of medical applications for lower extremity recovery.

Innovative recovery of the lower limbs

Basic lower limb recovery care has seen little change over the past 50 years, with current prosthetics consisting of simple metal frames, foam and plastic parts. The purpose of these devices is simple: to keep the patient’s leg in the correct position until it heals. According to Geldart, this view of bone and muscle healing is not based on hard evidence.

“These devices provide long treatment times, a suboptimal experience and are not very effective in patient care,” he said.

To change the way the market thinks about leg and knee recovery, the GRD team began prototyping dozens of new devices aimed at strengthening muscles instead of reducing patient movement. Over time, the team decided to combine molds for 3D printing with end-use parts for additive manufacturing, and the result? Ascend knee brace.

The main strap that holds the Ascend device on the leg is a final part molded directly from Tough 2000 resin. This part is under constant pressure, adjusted daily by the patient and exposed to daily wear and tear. Because of the shape of the ribbon, Geldart said “it would be difficult to machine or shape this part, so we print it directly on the Form 3.”

The ability to print functional parts for end use represents a significant cost and time saving for a small business. According to Geldart, “By using the Form 3, we are making more complex geometries that fit every application, and we’re doing it for less money.”

The Geldart team also prints molds for two internal zippers. This allows the team to access small-batch production with the 3D printer, ensuring cost-effectiveness despite each patient requiring a customized machine. Using these two methods – final production and 3D printed molds – demonstrates the versatility of in-house printing for start-ups like GRD. For patients, this means that it is possible, for the first time, to have access to truly personalized medical solutions, speeding up recovery times.

When looking to invest in a new 3D printer, Geldart considers several vital components, of which material properties are the most important. For Ascend, the design requirements come directly from each customer and therefore there can be no compromises. The goal is for each Ascend to fit perfectly. The parts must be durable but not fragile, flexible but strong. Each brace requires parts with different material properties, which means a 3D printer must be able to handle multiple demands.

Small businesses are acutely aware of the waste of time and resources, which for GRD can improve relationships with doctors and patients waiting for prosthetics. That’s why the second most important feature Geldart looks for is reliability. He said:

«We can’t use a printer that takes 18 or 20 hours to print and then breaks down. We’re looking for a printer that will be used partly for production. So we want a reliable printer that can run 24 hours a day.»

Initial success: Avoid surgery

The company saw early successes with Ascend. In one case, a young woman was on her way to her fifth knee surgery before she was connected to GRD. They created a device specifically for the patient and the surgery was cancelled. The patient recovered quickly, saving time and money and avoiding a fifth surgery. Faster recovery times also allow healthcare providers to focus on other patients, eliminating multiple unnecessary surgeries for the same patient.

Knee pads are especially important for runners. One patient GRD worked with had suffered from «runner’s knees» for years. After using Ascend, he was able to run five miles without experiencing severe pain. This type of patient outcome is only possible with cutting-edge, customer-specific medical devices.

One day, Geldart expects these types of stories to become common. “I think the market is moving towards a mix of standardized and customized manufacturing. We envision a world where we can manufacture to design rather than design to produce. Right now we’re making more complex geometries that fit application requirements, and we’re doing it for less money than traditional manufacturing.” Until then, he expects to continue refining his design with endless prototypes in research and development, saying, «I’ve lost count of the number of prototypes I’ve made. 3D printing effectively allows you to make endless prototypes until we get the right part.»

More information on Module 3

The GRD team currently has four Form 3s and three Form 2s.

This allows for flexibility, allowing you to use all seven printers simultaneously for maximum productivity when demand is high or to reserve some printers for research and development. At the moment, the team is happy with their fleet of SLA printers, but is always looking towards future expansion. According to Geldart, “we are interested in printing with nylon and Fuse 1. We currently use nylon parts on the prosthetic base and see opportunities for exploration and expansion in that area as well.”