<p>Prosthetics remain as a salient need for developing countries due to the increased volume of recently amputated patients. The vast majority of these inflicted individuals are above the knee amputees meaning they have lost both knee and ankle in this scenario. Currently, these designs remain exceedingly expensive and unavailable in developing regions because of the vast amount of machinery used as well as being exported from first-world countries. Children remain the most in need by having to adopt the use of heavy metallic knee joints when their bodies are not fully matured in addition to the repeated expenses of multiple prosthetics due to their growing limbs. The most vital criteria being observed in this development is the need for lightweight prosthetics for children, improved measurements to prevent buckling and the use of a human-like gait. </p><p>This study presents a passive, self-actuated, 3D printed compliant knee joint for children in developing regions to decrease the overall expense of above knee prosthetics as well as increase the ease to print multiple prosthetics during their growing cycle. Compliant mechanisms replace the traditional joints with their equivalent flexure hinges thereby eliminating the need of the assembly process. They use the material properties of the flexible links to maximize a singular deflection into a convenient desired movement. A single piece designed five-bar mechanism is proposed to provide adequate human-like gait instead of the traditional pegleg gait provided in previous rigid models. This gait is achieved through the use of both compliant links as well a novel 3D printed approach which is more accustomed to children because of the mechanism’s light weight. In addition to the compliant knee joint, a compliant ankle possessing flexure hinge placed at the toe is also designed to provide required bending during the gait cycle. The approach of using a fully passive knee joint enables to limit the weight of the prosthetics to create less of a burden to children and by isolating the need to utilize motors.  A test bench consisted of a rack-pinion, two parallel rods, supports and two servo motors are fabricated to experiment the performance of the knee joint. While the test bench is 3D printed using polylactic acid (PLA), the compliant knee joint is 3D printed in thermoplastic polyurethane (TPU) to emulate the gestures of a real human leg. The results from this project could be used for enhances to the knee design and gait improvements. Using the MATLAB program, simulations are performed to validate that the proposed knee joint mimics the human knee and desired angles.</p>

Preliminary Design and Experimental Studies of a Compliant Knee Joint for Pediatric Above Knee Amputees

Paper Proceedings: https://asmedigitalcollection.asme.org/IMECE/IMECE2021/volume/85543

ASME 2021 International Mechanical Engineering Congress and Exposition (IMECE2021)

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