Design and analysis of a new medial reciprocal linkage using a lower limb paralysis simulator

Study design: A feasibility study on the effect of a new reciprocating orthosis on specific gait parameters for use by people with spinal cord injury. Objectives: The aim of this study was to design and develop a new medial linkage orthosis (MLO) mechanism incorporating a reciprocating motion and to determine its efficacy in improving specific spatiotemporal, kinematic and kinetic parameters while ambulating when worn by healthy subjects. This was achieved via the use of a lower limb paralysis simulator (LLPS). Methods: A reciprocating joint with a remote center of motion was designed for use as an MLO. A prototype was fabricated and incorporated into an orthosis and equipped with a saddle to make the reciprocating motion possible. The efficacy of the orthosis was evaluated on four able-bodied healthy subjects who were trained to walk with the MLO attached to the LLPS. Results: Mean walking speed, stride length, stride time and cadence was 0.09 +/- 0.007 ms(-1), 0.42 +/- 0.01 m, 4.89 +/- 0.45 s and 29.54 +/- 4.32 steps min(-1), respectively, when healthy subjects walked with the new orthosis. The mean hip joint torque produced was 0.36 +/- 0.13 Nm. Conclusion: In this study a new MLO was designed and fabricated that provided a reciprocating mechanism using a four-bar mechanism to set the virtual axis of the mechanism in a more proximal position than hinge-type joints. Further investigation is currently underway to assess its effect on gait parameters and energy expenditure in paraplegic patients.