Stair ascent and descent biomechanical adaptations while using a custom ankle–foot orthosis

Abstract

The ability to navigate stairs step-over-step is an important functional outcome following severe lower leg injury and is difficult for many patients. Ankle–foot orthoses, such as the Intrepid Dynamic Exoskeletal Orthosis (IDEO), are often prescribed to improve function. This study compared stair climbing mechanics between IDEO users and able-bodied control participants. Thirteen IDEO users who sustained severe lower leg injury and 13 controls underwent biomechanical gait analysis. Participants ascended and descended a 16-step instrumented staircase without handrail use at a controlled cadence of 80 steps/min. Peak joint angles, moments, powers, and ground reaction forces, and integrated mechanical work were calculated. Independent t-tests with Bonferroni-Holm corrections were used to compare controls to IDEO and sound limbs. Reduced ankle range of motion on the IDEO limb resulted in compensatory strategies while ascending or descending stairs. During ascent, IDEO users had greater bilateral hip power during pull-up (p<0.007) to compensate for the IDEO limb׳s reduced ankle dorsiflexion (p<0.001) and knee extensor moment (p=0.001) while it was leading, and reduced ankle plantarflexor power while it was trailing (p<0.001). During stair descent, when the IDEO limb had was trailing, it had less ankle dorsiflexion during controlled lowering (p<0.001), resulting in greater vertical ground reaction force (p=0.005) and greater ankle and knee power absorption (p<0.001). Reduced IDEO limb ankle power absorption during weight acceptance (p<0.001) resulted in a large knee extensor moment (p<0.001) on the trailing sound limb to lower the body. Despite gait deviations, IDEO users were able to climb stairs step-over-step unassisted.