​The Polymers Powering Prosthetic Fabrication

Introduction

Plastics play a critical role in prosthetic manufacturing by providing the ideal balance of durability, flexibility, and comfort for amputees. For decades, prosthetists relied on traditional materials like wood, leather, and steel for artificial limbs.

While functional, these conventional elements were often heavy, uncomfortable, and prone to breakage. The evolution to high performance polymer materials marks a pivotal shift towards fabrics that can meet the diverse needs of prosthetic users.

Lightweight plastics like polyethylene, polypropylene, and thermoplastics introduced more dynamic solutions. They provided elasticity for improved gait, allowed for custom limb fabrication with 3D printing, and enabled thinner, sleeker limb designs.

But the demand from amputees for maximum function and aesthetics continues to drive innovation. That's why contemporary prosthetic manufacturing focuses on materials that are not only cost effective but deliver enhanced mobility, resilience, realistic visual properties, and the highest quality of life possible.

Material Trends

The prosthetics industry is continuously innovating to meet the diverse needs of users requiring orthotic and prosthetic support. One key area of focus is developing advanced polymer sheet materials that offer an optimal balance of durability, flexibility, and stiffness.

Recent trends showcase a shift towards new formulations of ethylene-vinyl acetate (EVA) copolymers designed specifically for prosthetic fabrication. These low-friction, silicone-free EVA materials aim to enhance both performance and manufacturing characteristics.

Product developers are introducing modified EVA compositions capable of maintaining superior forming and seaming qualities while resisting cold-flow deformation over time. Tests indicate that these next-generation EVA thermoplastics retain their original malleability and fabrication properties better than traditional alternatives during the thermoforming processes integral to prosthetic socket manufacturing.

The development of innovative polymer sheets with ideal stiffness, flexibility, and fabrication traits continues to be a high priority for both materials scientists and prosthetists focused on optimizing form, function and comfort.

Fabrication Materials and Techniques

The prosthetics industry has seen a major shift towards using carbon fiber-reinforced thermoplastics for definitive sockets. The carbon fiber reinforcement polymer offers improved stiffness and support for patients compared to traditional plastic sockets.

Thermoplastics reinforced with carbon fibers provide excellent durability and allow for customization to each patient's needs. They are also much lighter than old-fashioned plastic and metal sockets.

Another important material innovation is the development of advanced release sprays for use during the prosthetic fabrication process. These sprays are essential for simplifying the separation of the prosthetic socket from foam molds.

Water-based release agents provide an eco-friendly alternative to older solvent-based formulas. They allow prosthetists to quickly detach the formed thermoplastic or carbon fiber socket from the positives after molding and curing are complete. This streamlines the entire fabrication workflow.

The combination of carbon fiber-reinforced thermoplastics and advanced water-based release sprays demonstrates the prosthetics industry's commitment to utilizing innovative new materials. These technologies enable prosthetists to improve the fit, function and comfort of prosthetic devices.

Cosmetic and Functional Enhancements

Transfer papers are revolutionizing the prosthetics industry by allowing for more vibrant and appealing graphics on devices, especially pediatric prosthetics. Traditionally, prosthetics were available in limited color options like skin tones, blacks, and browns. But transfer papers with high quality printed graphics are opening up countless new aesthetic possibilities.

Vibrant images and designs can now be printed onto transfer paper using sublimation technology and heat transferred onto a prosthetic. This not only provides endless options for visual customization, but has been shown to greatly increase patient satisfaction and emotional wellbeing. Pediatric patients especially benefit from being able to personalize their prosthetics with fun graphics from movies, TV shows, video games, and other interests.

Beyond aesthetics, transfer papers are being applied as wearable sensors to collect data on how prosthetics are being used. Printed sensor arrays on transfer paper can track stress, movement, and other variables when applied to the prosthetic. This data can then optimize fitting, performance, and user comfort. Transfer papers have also been used to create custom measurement grids for enhanced fit.

The possibilities are endless when it comes to using printed transfer papers to enhance both the form and function of modern prosthetics through graphics and sensor applications. As materials and printing techniques continue to advance, high quality transfer printing will become a standard part of prosthetic design and manufacturing.

Commonly Used Plastics

Polypropylene, polyethylene, and thermoplastics are among the most common plastics used in prosthetic manufacturing due to their beneficial properties.

Thermoplastics

Thermoplastic materials like polycarbonate, acrylic, nylon, and acetal polymers bring transparency, impact resistance, and customizability to prosthetic fabrication.

They can be thermoformed into complex shapes using molds, vacuum forming, or 3D printing. Carbon fiber-reinforced thermoplastics combine the strength and stiffness of carbon fiber with the ability to mold the material. This enables optimized mechanical properties and patient-specific customization.

Polypropylene

Polypropylene is one of the most widely used plastics in prosthetics manufacturing due to its durability, chemical resistance, and flexibility. There are several grades of polypropylene that each offer distinct benefits for prosthetic applications:

Standard Polypropylene

• -Highly rigid and lightweight making it suitable for structural components in prostheses.
• -Offers high impact strength even at low temperatures.
• -Widely used for definitive and check sockets in lower limb prosthetics.

Co-Polymer Polypropylene

• -Exhibits enhanced flexibility and elongation compared to standard polypropylene.
• -Provides excellent chemical resistance.
• -Commonly used for flexible inner socket liners that cushion the residual limb.

Orthopedic Polypropylene

• -Specifically formulated for increased elasticity and pliability.
• -Allows for easy thermoforming to custom-fit orthopedic braces and supports.
• -Used in ankle-foot orthoses and knee-ankle-foot orthoses to provide durability combined with flexibility.

The unique benefits of the different polypropylene grades make this plastic versatile for a wide variety of prosthetic and orthotic applications where rigidity, strength, and formability are required. The continual development of specialized orthopedic polypropylene formulations helps improve patient comfort and performance.

Low-Friction EVAs

EVA, or ethylene vinyl acetate, is a copolymer plastic that offers an optimal balance of flexibility, durability, and chemical resistance for prosthetic applications. Recently, EVA formulations have been enhanced to reduce friction and improve performance.

These low-friction EVA materials utilize additives that act as internal lubricants. Silicone is typically added to EVA to reduce friction, but new alternatives eliminate silicone from the formulation. This is crucial because silicone can slowly migrate to the surface of the EVA over time, leaving a tacky residue that attracts dirt and debris.

Silicon-free options such as those using emulsified wax technology maintain the low-coefficient and non-tack performance qualities of silicone while avoiding the drawbacks.

The low friction minimizes abrasion and allows layers of an orthosis or prosthesis to glide smoothly over one another with movements. This results in greater comfort for the patient and protects sensitive skin from chafing and irritation.

Low-friction EVAs also demonstrate high shape retention and stability over time. Advanced formulations resist cold flow deformation, which helps prosthetics maintain their prescribed shape and function at body temperature.

Overall, these next-generation EVA materials deliver key advantages for overall prosthetic performance, improving fabrication traits while creating a better patient experience. Their durability, chemical stability, and friction properties make low-friction EVAs a versatile choice for inner and outer prosthetic liners, pads, and sheaths.

Conclusion

Continuous innovation in prosthetic materials is critical to meet the diverse and changing needs of individuals who require orthotic and prosthetic devices. As material science and fabrication techniques advance, we can expect to see further improvements in the performance, comfort, and aesthetics of prosthetics.

Lightweight, flexible, and realistic materials will enable greater mobility, functionality, and self-esteem. Carbon fiber-reinforced thermoplastics and vibrant graphic transfer papers are just the beginning. We foresee the integration of robotics and biotechnology for a more intuitive, natural user experience. With a user-centered design approach, materials engineering and 3D printing will transform personalized prosthetics.

Forward-thinking providers stay at the forefront by evaluating and integrating promising new materials. However, the true measure of success is the positive impact on users' quality of life.

The needs and priorities of patients should remain central when exploring new materials and fabrication methods in this rapidly evolving field. By maintaining a compassionate, human-focused approach, providers can deliver individualized solutions that help patients thrive.