Full Leg Optimization (FLO): A Framework to Concurrently Design Low-Cost Passive Prosthetic Feet and Knees.

Abstract

The mobility and life quality of a user with an above-knee amputation depend on the performance of their prosthetic leg. Prosthetic leg performance is a result of the quality of the prosthetic components, the interaction between them, and the availability of continuous care. Access to these factors is limited in low- and middle-income countries where the majority of lower limb amputees live. This study presents a method to design prosthetic legs based on the operation of all components in tandem to minimize the time for adjustment and the cost of a prosthetic leg. The full leg optimization (FLO) framework provides a method to quantitatively design prosthetic legs by predicting the interaction of the prosthetic foot and prosthetic knee at the initiation of knee flexion during the late stance phase. A prosthetic leg was designed for a person with an above-knee amputation, consisting of a Hip Trajectory Error foot and a passive prosthetic knee. The leg was designed so that the prosthetic knee would unlock at <math xmlns="http://www.w3.org/1998/Math/MathML"><mrow><mn>72</mn> <mo>%</mo></mrow> </math> of stance based on the predicted interaction of the foot and knee. The preliminary results demonstrate consistent knee unlocking at <math xmlns="http://www.w3.org/1998/Math/MathML"><mrow><mn>73</mn> <mo>±</mo> <mn>3.8</mn> <mo>%</mo></mrow> </math> of stance after minimal acclimation time. This suggests that the FLO framework can accurately predict the interaction between the prosthetic foot and the prosthetic knee. Hence, the FLO framework is a design method for prosthetic legs for users with an above-knee amputation, providing a predictable performance, which would be beneficial for users living in low-resource settings.