Almost 30 million people in China have physical disabilities according to most recent figures, and the majority rely on prosthetic devices to restore some of the functions of the missing body part. Conventional methods used to manufacture assistive devices fall short of delivering good fit and functionality. The Hubei Rehabilitation Assistive Technology Center (HRATC) in China set out to change the experience of wearing prostheses and achieved this with cutting-edge additive manufacturing technology and Freeform software.
Mr Lu, based in Wuhan City, is a beneficiary of the technology. Having lost both his legs in a work-related injury in his youth, he initially used traditionally-manufactured prosthetic legs. His first prostheses had two major drawbacks – they were heavy and airtight, causing perspiration and itchiness when walking.
To address Mr Lu’s issues, the team at HRATC successfully designed new prosthetic legs with Geomagic Freeform. “I used to feel like a burden to my family. Since wearing the additive manufactured assistive legs, I can do some of the household chores, such as grocery shopping, cooking, laundry and even carrying gas cylinders.” Lu said, “I once walked 2,500 meters. The technology has empowered people with disabilities like me.”
Mr Lu is just one of a multitude of patients that have benefited from HRATC’s forward-thinking approach to assistive device manufacturing. The center works in R&D, provision and distribution of prosthetic devices for people with disabilities and elderly patients. Since 2014, the center has taken the lead in exploring the application of additive manufacturing technology to make crus prostheses, spinal orthoses, and orthotics.
Reshaping prostheses manufacturing
Conventionally, prostheses are made of leather, aluminum and other materials. The most common technology for fitting resin sockets, the device that joins the residual limb to the prosthesis, uses plaster bandages to create a mould for a duplicate of the limb. From start to finish, the process involves trimming, moulding and assembly with resin materials. The process is labor intensive and time-consuming and the end product is heavy and non-waterproof.
Additive manufacturing brought about a sea change in prosthetic device production, with massive improvements to fit and comfort. To implement this new technology, Wan Liu, Deputy Chief of the Technology and Quality Management Section at HRATC, and his coworkers first had to overcome a series of difficulties in manufacturing and material selection. They developed a series of 3D-printed rehabilitation aids with independent intellectual property rights, which are now available for patients. "We hope to design each piece of an assistive device as a work of art through Freeform. We will forge ahead with our patients towards a happy life," Liu said.
The production of a 3D-printed prosthesis starts with an optical 3D-scan of the limbs. The non-contact nature of a 3D-scan allows staff to avoid secondary injuries which can occur when using a traditional process with plaster. Computer-aided design (CAD) software will be introduced to complete the structural modeling and form a model precisely matching the patient's condition. The entire process takes 24 hours.
Geomagic Freeform, developed by Oqton, is a key tool in HRATC's production. Freeform is a 3D-design software used with touch-based haptic devices to create an organic, digital design for custom manufacturing making it an ideal tool for prosthetics design. The haptic device simulates three-dimensional sculpting, allowing users a more intuitive way to learn to sculpt shapes digitally and shortening the learning curve.
For any prosthesis to function well, a good shape and fit of the socket are paramount. The slightest misalignment can result in intense discomfort and biomechanical dysfunction. Additive manufacturing comes with a higher degree of freedom than would normally be possible, allowing the HRATC technical team to make sockets with an optimized fit and ventilating structure. Freeform gives users complete control of design parameters such as mesh pattern, density, and size, with a high level of precision to create optimal sockets and other components for each patient's physiological conditions and use habits.
One of the key advantages of Freeform is that assistive devices designed in the software can also be printed directly. The model is transferred to industrial-grade additive manufacturing equipment with a single click, sidestepping the usual problems that come with model conversion and data incompatibility.
The breadth of enhancements made possible with Freeform and 3D printing is well represented in the crus prosthesis that HRATC created (see picture below). The team developed multi-layer breathable micro-pores and a hollowed-out mesh to facilitate perspiration in the special inner lining sleeve or silicone sleeve. In addition, the crus is easy to clean as it doesn't have any metal parts. The final result is a prosthesis that's lighter but robust, water-resistant as well as breathable.
More customisation and better performance
HRATC has made a tremendous contribution to the understanding of assistive devices. The center gathered over 100 cases of models and data on AM-made prostheses, with patients aged from 7 to 93, the longest exceeding 72 months. Their efforts have been rewarded with seven national patents, one software copyright, and numerous national awards for assistive devices. The center's products have been showcased at China International Rehabilitation Expo for five consecutive years.
To further promote the improvement of assistive devices and prosthetic fitting technology in the national industry, the HRATC established a Digital Technology Service Center in 2022. With advanced hardware and software tools, like Oqton's Freeform, and with a novel integration of digital and traditional processes, the HRATC will create more customized high-performance assistive devices and promote the development of rehabilitation assistive devices.
Geomagic Freeform is not a medical device and Oqton makes no claims that it is intended to treat, plan, or diagnose. However, there is evidence and publicly available research that indicates many customers are successful using Geomagic Freeform in their own patient-specific solution workflows. It is the responsibility of these customers to follow all local regulatory requirements.