Mechanical energy flow of gait in one normal subject and one complete spinal cord injured patient using reciprocal gait orthosis walking with crutches: A case study

Many benefits are associated with spinal cord injury patients using reciprocating gait orthoses instead of wheel chairs, such as fewer muscle contractures, reduced risk for bone fractures, better peripheral circulation, and less depression. However, high energy cost and a slow walking speed are two factors that limit the usage rate of reciprocating gait orthosis. In previous study, the data shows that SCI group walking with different gait patterns compared with normal subjects, they tend to flex the trunk to motivate the lower limbs into swing phase. The gait pattern might be the reasons why spinal cord injury patients walk inefficiently. Nevertheless, the reasons of high energy cost are still unclear. This article aims to figure out the cause of high energy cost by energy flow analysis. 1 SCI patient and 5 normal subjects were recruited for this study. All subjects practicd how to walk with the reciprocating gait orthosis and crutches before data collection. They walked at a self-selected speed along a 5 meter walkway equipped with an Optotrak system synchronized with AMTI force plates and single axis load-cells on the crutches. The kinetic, kinematic and temporal-spatial, energetic parameters were collected with this system and calculated by inversed dynamics. The energy flow parameters were then calculated from the kinetic and kinematic data. Finally, we discussed the energy flow data and walking strategy between two groups. The representative data showed one normal subject with RGO averaged over 5 trials; And we showed particular one trial without averaging for the SCI subject since the data varied too much from trial to trial. The representative trial shows most of the features found in the total data. The velocity of the SCI subject (0.06m/s) is very slow compared to the velocity of normal subject with RGO( 0.55m/s ), the result shows that normal subject with RGO use the mechanism of inverted pendulum that conserve energy by converting potential energy and kinetic energy to avoid energy consumption in double-limb support and acceleration period. However, the SCI subject reduce both potential energy and kinetic energy to the minimum in mid double-limb support period and rise both kinetic energy and potential energy up in late double-limb support period and acceleration period, thus, the energy can’t be conserved since the strategy contradict to the mechanism of inverted pendulum model. For SCI subject, power from the shoulder was used to create foot clearance during the preswing and acceleration period. The power would be consumed in deceleration (or late acceleration) period by friction and in double-limb support period by trunk-pelvis joint. The reason why the energy is not conserved but consumed is that the SCI subject adopt compensatory movements such as leaned forward trunk, simultaneously increases in PE and KE due to shoulder power, and a locked knee device that discourages the conversion of PE to KE, energy absorbed by joints or friction; If we can make the RGO equipped with artificial power source on hip or ankle joint and unlocked knee joint at good timing, that would help SCI subject to reduce of compensatory movement and friction.