500 Section - Evaluation of stability and efficiency during stand to sit activity in unilateral transfemoral amputee with New-Developed Prosthetic Knee made in Korea

Objectives : The purpose of this study was to investigate whether the newly developed mechanical polycentric knee prosthesis, First-K1, improves load distribution and compensatory movements during stand-to-sit activity in unilateral transfemoral amputees. Specifically, we compared knee joint motion, trunk compensation, and intact-limb contribution between the First-K1 and a conventional prosthesis using 3D motion analysis.

Design:

Four unilateral transfemoral amputees participated in this study. A 3D motion analysis system (Motion Analysis®) was used to collect full-body kinematic and kinetic data during the stand-to-sit task. Participants stood with their feet shoulder-width apart and sat down on a chair with their arms crossed in front of the chest. For both the intact limb and the prosthetic limb, trunk lateral bending and knee joint angular velocity in the frontal plane were calculated to assess compensatory movement. Vertical ground reaction force, impulse, and joint moment were also computed to determine load distribution differences between limbs. In addition, a symmetry index was derived from these variables to quantify the degree of inter-limb asymmetry. Each participant performed the task using both a conventional knee prosthesis and the First-K1 prosthesis, allowing direct comparison of biomechanical performance between the two devices.

Results: With the First-K1, vertical GRF and impulse decreased on the intact limb and increased on the amputated limb, resulting in significantly improved limb-loading symmetry (p< 0.05). These findings indicate a redistribution of load toward the prosthetic side. However, trunk lateral bending and frontal-plane knee angular velocity showed no statistically significant differences between prostheses.

Conclusion: The First-K1 reduced excessive loading on the intact limb during stand-to-sit movement, enhancing symmetry. Further research with a larger sample size is required to confirm broader functional effects.