Most people with cerebral palsy (CP) suffer from impaired walking ability and pathological gait patterns. Seeking to improve the effectiveness of gait training in this patient population, this study developed and assessed the feasibility of a real-time biofeedback mechanism to augment untethered ankle exoskeleton-assisted walking performance in individuals with CP. We selected step length as a clinically-relevant gait performance target and utilized a visual interface with live performance scores. An adaptive ankle exoskeleton control algorithm provided assistance proportional to the real-time ankle moment. We assessed lower-extremity gait mechanics and muscle activity in seven ambulatory individuals with CP as they walked with adaptive ankle assistance alone and with ankle assistance plus step-length biofeedback. We achieved our technical validation goal by demonstrating a strong correlation between estimated step length and real step length (R = 0.771, p <; 0.001). We achieved our clinical feasibility goal by demonstrating that biofeedback-plus-assistance resulted in a 14% increase in step length relative to baseline (p ≤ 0.05), while no difference in step length was observed for assistance alone. Additionally, we observed near immediate improvements in lower-extremity posture, moments, and positive power relative to baseline for biofeedback-plus-assistance (p <; 0.05), with none, or more-limited improvements observed for assistance alone. Our findings suggest that providing real-time biofeedback and using step length as the target can be effective for increasing the rate at which individuals with CP improve their gait mechanics when walking with wearable ankle assistance.

Objective: Many individuals with cerebral palsy (CP) experience gait deficits resulting in metabolically-inefficient ambulation that is exacerbated by graded walking terrains. The primary goal of this study was to clinically-validate the accuracy and efficacy of adaptive ankle exoskeleton assistance during steady-state incline walking and stair ascent in individuals with CP. Exploratory goals were to assess safety and feasibility of using adaptive ankle exoskeleton assistance in real-world mixed-terrain settings. Methods: We used a novel battery-powered ankle exoskeleton to provide adaptive ankle plantar-flexor assistance during stance phase. Seven ambulatory individuals with CP completed the study. Results: Adaptive controller accuracy was 85% for incline walking and 81% for stair-stepping relative to the biological ankle moment. Assistance improved energy cost of steady-state incline walking by 14% (p = 0.004) and stair ascent by 21% (p = 0.001) compared to walking without the device. Assistance reduced the muscular demand for the soleus and vastus lateralis during both activities. All participants were able to safely complete the real-world mixed-terrain route, with adaptive ankle assistance resulting in improved outcomes compared to walking with the device providing zero-torque; no group-level differences were found compared to walking without the device, yet individuals with more impairment exhibited a marked improvement. Conclusion: Adaptive ankle exoskeleton assistance can improve the energy cost of steady-state incline walking and stair ascent in individuals with CP. Significance: As the first study to demonstrate safety and performance benefits of ankle assistance on graded terrains in CP, these findings encourage further investigation in free-living settings.

Despite medical treatment focused on addressing walking disability, many millions of people with neurological conditions, like cerebral palsy (CP), struggle to maintain independent mobility. Lower limb exoskeletons and exosuits may hold potential for augmenting walking ability. However, it remains unknown whether these wearable robots are safe and beneficial for use outside of highly controlled laboratory environments, the demonstration of which is necessary for clinical translation. Here, we show that a lightweight, portable, ankle exoskeleton with an adaptable one-size-works-for-all assistance controller can improve energy efficiency and walking speed for individuals with CP spanning a wide spectrum of lower limb impairment in a multi-terrain real-world environment. Tested on an outdoor walking route with level, sloped, and stair terrain, robotic assistance resulted in a 15–18% (p ${=}$ 0.013–0.026) reduction in estimated energy cost and a 7–8% (p ${=}$ 0.001–0.004) increase in average walking speed across “shorter” 6-minute and “longer” 20-minute walking durations relative to unassisted walking. This study provides evidence that wearable robots may soon improve mobility in neighborhood, school, and community settings for individuals with CP.

People with lower-limb hemiparesis have impaired function on one side of the body that affects their walking ability. Wearable robotic assistance has been investigated to treat hemiparetic gait by applying assistance to the paretic limb. In this exploratory case series, we sought to compare the effects of bilateral vs. paretic-limb-only ankle exoskeleton assistance on walking performance in a case series of three heterogeneous presentations of lower-limb hemiparesis. A secondary goal was to validate the use of a real-time ankle-moment-adaptive exoskeleton control system for effectively assisting hemiparetic gait; the ankle moment controller accuracy ranged from 72–90% across all conditions and participants. Compared to walking without the device, both paretic-limb-only and bilateral assistance resulted in greater average total ankle power (up to 72%), improved treadmill walking efficiency (up to 28%), and increased over-ground walking distance (up to 41%). All participants achieved a more symmetrical, efficient gait pattern with bilateral assistance, indicating that assisting both limbs may be more beneficial than assisting only the paretic side in people with hemiparetic gait. The results of this case series are intended to inform future clinical studies and exoskeleton designs in a wide range of patient populations.

Musculoskeletal health is critical for physical and mental well-being. Most people with cerebral palsy (CP) experience gait disorders that are associated with increased joint loading, pain, and degeneration. Wearable assistive devices can improve mobility and gait mechanics in those with CP, but their effects on joint loads remain unknown. This study sought to quantify the effects of ankle exoskeleton assistance on knee contact force in people with CP. Eleven children and young adults with CP walked on a treadmill with just shoes (Shod) and with ankle exoskeleton assistance (Exo). Muscle forces were estimated using an electromyography-informed (EMG-informed) modeling approach, where EMG signals from eight lower limb muscles were used to constrain muscle activations. Compressive knee contact force was then quantified based on estimated muscle forces. Ankle assistance reduced peak late-stance knee contact force by 9.3 ± 7.3% and average stance-phase knee contact force by 7.2 ± 4.6% compared to Shod (p ≤ 0.003). Ankle assistance also reduced stance-phase quadriceps muscle force by 9.1 ± 10.9% compared to Shod (p = 0.015). Exo-induced reduction in quadriceps force was associated with lower knee contact force (p < 0.001). Despite the lack of group-level differences in gastrocnemius force or joint kinematics between Shod and Exo, greater knee extension, greater ankle plantarflexion, and lower gastrocnemius force were associated with lower knee contact force (p ≤ 0.022). Our study indicates that ankle assistance may decrease knee loading in people with CP due to changes in knee extensor muscle forces during walking.