Preliminary Kinematic and Kinetic Evaluation of a Modular Microprocessor-Controlled Stance-Control Knee-Ankle-Foot Orthosis

Abstract

Stance-control knee-ankle-foot orthoses (SCKAFO) permit free knee motion during swing and knee flexion resistance during stance for individuals with knee-extensor muscle weakness. Microprocessor-controlled SCKAFO use electronic sensors and control algorithms to dictate when knee flexion resistance engages or disengages. Many SCKAFO require full leg extension to engage flexion resistance, and provide no support at other knee angles. This research presents a preliminary biomechanical evaluation of a novel local sensor-based (i.e., thigh, knee) variable knee-flexion resistance microprocessor SCKAFO (VSCKAFO) that was designed to address these limitations while maintaining stance-control functionality across various gait modes. Five able-bodied male participants were fit with the VSCKAFO and device settings were adjusted to each participant during an accommodation period. A lower body, six degree-of-freedom marker set (30 markers) was affixed to each participant. Kinematic data were collected for stand-to-sit and stair descent in a motion lab with a 10-camera Vicon system. Kinetic data were recorded for stand-to-sit with two force plates. Inertial measurement unit data were also recorded from sensors on the instrumented orthosis. It was found that the novel VSCKAFO sufficiently resisted knee flexion during weight-bearing stair descent and stand-to-sit activities. Successful biomechanical analysis with able-bodied individuals supports further testing with persons who have knee-extensor muscle weakness.