(E-185) 3D Printing Cost-Effective Lower Extremity Prosthetic and Orthotic Devices

Introduction:: Approximately 30 million amputees residing in developing countries do not have access to prosthetic limbs due to the large ‘high cost to low income’ ratios for prosthetics in these countries. Since traditionally fabricated prosthetics and orthotics are very expensive, 3D printing can be used as a cost-effective alternative. The current gold standard of lower extremity fabrication is hand-casting with the disadvantages being that the process is labor-intensive, requires several visits to fit properly, and relies largely on prosthetist experience. In order to mitigate these issues along with the high cost of prosthetics and orthotics, 3D printing technology is being assessed as an efficient form of fabrication. Although the application of 3D printing as a manufacturing technique is becoming more widespread across several industries due to its compatibility with many types of materials, not all materials are cost-effective and weight resistant. Lower extremity prosthetics and orthotics are weight-bearing devices that must be able to withstand large magnitudes of force during the gait cycle. Materials, such as carbon fiber, are known for its strength and ultra-lightweight properties, however the high cost of manufacturing prevents it from being an applicable material for most users. Alternatively, many materials, such as polyethylene, that are low in cost, tend to have low strength and flexibility, creating lower extremity devices with short lifespans. By selecting materials that can support a patient’s weight without compromising the flexibility needed in the gait cycle, 3D printing lower extremity devices can provide better patient-specificity at a low cost for underdeveloped countries.

Materials and Methods:: An analysis of 3 different factors was performed to determine the feasibility of using 3D printing to manufacture low-cost lower extremity devices. The first factor that was considered was the properties of materials that are compatible with 3D printing and low in cost. Materials that are high in strength, needed to support the weight of the body and large forces exhibited during the gait cycle, as well as high in flexibility, required to prevent failure during ambulation, were evaluated. Next, tests conducted to determine the biomechanical effectiveness of the 3D printed devices were studied. Instron testing was implemented to assess the biomechanics of 3D printed devices, such as strength, stiffness, and resistance to deformation. Also, 3D gait analysis using motion capture helped understand the extent to which 3D printed devices can help improve the gait cycle. More specifically, the kinetics and kinematics of the 3D printed devices were compared to traditionally manufactured devices to draw clear conclusions on the advantages of implementing the 3D printing fabrication technique. Lastly, various patient satisfaction questionnaires and assessments were interpreted since it is a factor that is just as important as the aforementioned considerations. Although the materials may be compatible for the printing technique and the characteristics of the device are comparable to the gold standard, the preference of the user helps determine the widespread capability of using 3D printing to produce the devices. Once all three considerations are successfully met, 3D printing low-cost and long-lasting lower extremity devices can be easily implemented globally.

Results, Conclusions, and Discussions:: Results and Discussion: Many materials can be used to produce low-cost 3D printed prosthetics and orthotics. When assessing orthotics, 3D printed polyurethane (PE) resembled the gait cycle and resistance to deformation of traditionally fabricated orthotics while increasing patient satisfaction. Nylon-11 experienced the least amount of mechanical dampening and was able to withstand strength testing that caused failure in carbon fiber orthotics. 3D printed Nylon-12 showed no significant difference in biomechanical parameters but showed a significant increase in the range of motion of the limb. Polylactic acid (PLA) displayed similarities in the gait analysis of hand-casted orthotics and an increase in patient perceived fit since users felt the 3D printed device better fit their anatomy. Lastly, stress testing comparing acrylonitrile butadiene styrene (ABS) to PLA showed that ABS can withstand more compressive and tensile stress.
In terms of prosthetics, strength testing of three different sockets resulted in comparable ultimate strength between PETG thermoplastic and 3D-printed PLA although both were lower than carbon fiber. Also, PLA had the lowest deformation after the test was complete. Walking tests using 3D printed bridge nylon sockets showed no significant differences when compared to hand-casted sockets, therefore it is biomechanically equivalent. Fully-functional 3D printed PLA sockets manufactured in Cambodia were found to be extremely low-cost at about $20 per socket. Lastly, fill-compositing technology was used to reinforce sockets by using carbon fiber to strengthen the bond between layers. The resulting sockets had significant increases in strength and decreases in delamination of the socket. The results of these studies show that 3D printed devices provide equivalent biomechanical properties at lower cost and higher patient satisfaction with feasible alternatives to traditionally fabricated devices
Conclusion: The findings of this study prove an attainable cost decrease for lower extremity devices. 3D printed devices can change the lives of millions of users across the world that are unable to obtain the devices. The emergence of engineering-grade 3D printing materials helps produce prosthetics and orthotics with high strength, increased flexibility, and long durability. The implementation of 3D printing fabrication can bridge the gap between the need of devices across all low-income countries.

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