Development of a simple stance-control system for persons with poliomyelitis and an associated gait analysis

A simple stance-control system (SSCS) was developed, which is a new device attached to the upper lateral frame of a carbon fiber-reinforced plastic knee-ankle-foot orthosis (carbon KAFO). The SSCS consisted of two pressure sensors beneath the heel and metatarsal phalangeal joints, connecting cables, microcomputer, motor controlling the lever of Swiss-lock knee joint, and battery box. Normally the SSCS is off, and the Swiss-lock knee joint is mechanically fixed in the extended position, whereas the SSCS is on during the swing phase according to the information from the pressure sensors, and the Swiss-lock knee joint is released by pulling up the lever. Therefore, a patient using a carbon KAFO with SSCS can flex his/her knee joint during the swing phase and to maintain it in the extended position during the stance phase. The safety while using the SSCS was confirmed in four healthy men and the gait pattern was measured by using a three-dimensional motion analysis and force plate system. These results revealed that the SSCS attached to a carbon KAFO did not unlock the Swiss-lock knee joint on the five conditions in daily living activities, and enabled a patient to control his/her lower limb during the stance phase and flex it during the swing phase.