Gait asymmetrical evaluation of lower limb amputees using wearable inertial sensors.

This study presents an analysis and evaluation of gait asymmetry (GA) based on the temporal gait parameters identified using a portable gait event detection system, placed on the lateral side of the shank of both lower extremities of the participants. Assessment of GA was carried out with seven control subjects (CS), one transfemoral amputee (TFA) and one transtibial amputee (TTA) while walking at different speeds on overground (OG) and treadmill (TM). Gait cycle duration (GCD), stance phase duration (SPD), swing phase duration (SwPD), and the sub-phases of the gait cycle (GC) such as Loading-Response (LR), Foot-Flat (FF), and Push-Off (PO), Swing-1 (SW-1) and Swing-2 (SW-2) were evaluated. The results revealed that GCD showed less asymmetry as compared to other temporal parameters in both groups. A significant difference (p < 0.05) was observed between the groups for SPD and SwPD with lower limb amputees (LLA) having a longer stance and shorter swing phase for their intact side compared to their amputated side, resulting, large GA for TFA compared to CS and TTA. The findings could potentially contribute towards a better understanding of gait characteristics in LLA and provide a guide in the design and control of lower limb prosthetics/orthotics.

Gait dynamic stability evaluation in patients undergoing hip joint fractures - tools to measure rehabilitation effectiveness.

A hip joint fracture includes a break in the thigh (femur) or coxa bone near the pelvis. During fracture healing, stability and weight bearing by the affected limb are key indicators to measure patients' improvement. Conventionally, the rehabilitation effectiveness is monitored through clinical examinations, patients' feedback, and few studies also reported instrumented gait evaluations. A gap remains there to numerically quantify the recovery in patients' stability and weight bearing in response to rehabilitation therapies. This study introduces Nyquist and Bode (N&B) methods to analyse the instrumented gait signals further and evaluate gait stability in hip fracture patients during weight loading and unloading transitions. The centre of pressure (CoP) data was recorded using force plates for conditions: coxa hip fracture (HC), femur hip fracture (HF), and normal hip joint (NH). The time rate of CoP signals illustrated two major impulses during the loading and unloading phases which were modelled in time and frequency domains. The frequency models were further analysed by applying N&B methods and stability margins were computed for both impaired and healthy conditions. Results illustrated a significant decrease (Kruskal-Wallis's test, p < 0.001) in the intralimb walking stability of both fracture conditions. Further, Spearman's correlation between CoP velocities of fractured and intact limbs illustrated significant interlimb dependencies to maintain walking stability (p < 0.001) during weight loading and unloading transitions. Overall, the HF impairment illustrated the least intralimb walking stability and relatively greater interlimb dependencies. Clinically, these methods and findings are important to measure the recovery in patients undergoing rehabilitation after a hip joint or other lower limb impairments.

Design optimization of powered ankle prosthesis to reduce peak power requirement.

The aim of the prosthetic devices is to replicate the able-bodied angle-torque profile of a healthy human during locomotion. A lightweight and energy-efficient ankle joint is able to lower the actuator peak power and/or energy consumption per gait cycle, while adequately fulfilling the profile matching constraints. This study presents the design optimization of the prosthetic ankle joint containing an elastic element and actuator coupled with a rigid triangular part. The dimensions of the ankle joint triangular part were optimized to minimize actuator peak power and maximize spring energy within its elastic limits. As a result of series simulation tests, at 1.1 and 1.6 m/s walking speeds, the simulation of dorsi/plantar flexion shows up to 78.8% and 66.98% reduction in motor peak power compared to a direct drive system, respectively. Low power ankle-prosthetic device that closely matches the angle-torque profile of a healthy human's ankle, is one of the key parameters for the cost-effectiveness of lower limb prostheses.

Evaluation of an ankle-foot orthosis effect on gait transitional stability during ramp ascent/descent.

Wearable ankle-foot orthoses (AFO) are widely prescribed clinically; however, their effect on balance control during ramp ascent/descent walk remains unknown. This study evaluates walking stability on a ramp during weight loading and unloading transitions of the stance phase with the effect of an adjustable AFO. An AFO is tuned firstly by tuning dorsiflexion only and then combining dorsi-plantarflexion adjustments. Gait stability is assessed from neuromotor input (centre-of-mass) and output (centre-of-pressure) responses obtained through motion-capture system and force platform. Stability margins are quantified from Nyquist and Bode methods illustrating the loading phase as stable and the unloading phase as unstable transition in all walking conditions. Further, a significant decrease in stability (p < 0.05) is observed by wearing AFO in its free mode which gets improved (p < 0.05) by tuning AFO. Results from neuromotor outputs also illustrated a strong interlimb correlation (p < 0.001), which implies a compensatory interaction between opposite limbs loading and unloading transitions. Neuromotor inputs illustrated unstable responses both in loading and unloading transitions and were observed to be greater in magnitudes compared with output margins. The overall results support the hypothesis that a wearable AFO affects gait stability during transitional phases, and by applying AFO adjustments, neuromotor balance control achieves stability margins closer to normal range.