荷重線リアルタイム表示システムの開発と下腿義足アライメント調整への応用

抄録

A general method to get the best alignment of trans-tibial (BK) prostheses was analysed on the basis of mechanics and it was concluded that useful information is supplied by a system which can display mechanical quantities (forces and moments) exerted on a trans-tibial prosthesis in real time. From this viewpoint, a system containing a pylon load cell installed in the shank of the prosthesis to measure six quantity forces, flexible electro goniometers made of electroconductive rubber placed on the side of ankle and/or knee joint, and a portable data processing subsystem was developed. The whole system weighs less than 10kg, and is movable anywhere. From the output of the transducers, the load line on which the resultant force and moment work and are parallel to each other is calculated and displayed on the graphic plane of the micro computer in real time. With this system, prosthetic alignments and prosthetic functions were measured and evaluated. The load lines in standing posture and in level walking were measured and compared with the process of aligning a trans-tibial prosthesis by some skilled prosthetists on the same amputee. After each stage of bench, static and dynamic alignment, load line shows a peculiar pattern of its own. The resultant moment (torque on the load line) tends to decrease from bench to static and from static to dynamic alignment. The stance phase control function of a prosthetic knee joint was measured in a trans-femoral (AK) amputee for level walking and ramp descent. The amount of knee braking on stance phase was set in the three positions of free, normal and lock. With the knee braking mechanism working, load line comes to pass behind the knee axis in level walking. In ramp descent, more significant phenomena were observed compared than in level walking. From the real-time display of the load line acting on the prosthesis, problems of static alignment, dynamic alignments and functions of joints will be made clear and the way to get better alignment and better function can be easily estimated.