A Lightweight, Untethered Ankle Exoskeleton Can Help Improve Energy Cost of Walking in Cerebral Palsy Patients

A Lightweight, Untethered Ankle Exoskeleton Can Help Improve Energy Cost of Walking in Cerebral Palsy Patients

A lightweight, untethered ankle exoskeleton can lead to clinically significant improvements in walking economy in children and young adults with cerebral palsy, a study shows.

The study, “An untethered ankle exoskeleton improves walking economy in a pilot study of individuals with cerebral palsy,” was published in IEEE Transactions on Neural Systems and Rehabilitation Engineering.

Abnormal gait patterns — the manner in which a person walks — can affect an individual’s quality of life by requiring more effort and energy to walk.

Improving walking efficiency remains an important task for physicians treating children and young adults with gait disorders, particularly ones caused by cerebral palsy (CP).

The energy cost of walking can be two to three times greater in people with CP compared to their healthy peers.

There is also a strong negative correlation between how much energy is required to walk and the amount of physical activity undertaken in individuals with CP, highlighting the need for new strategies to improve walking economy.

Assistive devices that can reduce the effort it takes patients to walk will likely contribute to increased quality of life through improved and prolonged independent mobility. In particular, powered assistance provided to the ankle joint has been shown to reduce the energy cost of walking.

Recently, tethered powered assistance — in which not all of the components needed to provide assistance are worn by the user  has been shown to improve walking economy in stroke victims.

Whether the device is tethered or untethered is an important distinction, as carrying the extra weight of the power supply can negate the benefit of powered assistance.

No studies have reported improvements in the energy cost of walking using an untethered exoskeleton in patients with neurological gait impairment, including individuals with CP.

Among the two untethered exoskeletons that have been shown to reduce the energy cost of transport in healthy adults, neither was optimally designed for children and adolescents with gait impairments.

Therefore, researchers set out to design and assess a battery-powered, untethered ankle exoskeleton that was specifically intended to improve walking economy in children and young adults with neuro-motor impairment.

The lightweight device had a waist- or torso-mounted control and actuator, and a cable connecting it to an ankle assembly. Two differently sized devices were created to accommodate the body mass of the individual.

Researchers conducted a device feasibility and pilot clinical evaluation study with five individuals ages 5-30 diagnosed with gait deficits from CP.  The participants’ body mass varied widely (15.7-51.1 kg) as did levels of impairment.

Participants completed an evaluation and assessment, four to 10 exoskeleton training visits, and a final data collection visit. On average, individuals completed 130 minutes of exoskeleton-assisted walking practice.

Results showed an average of 19% improvement in the energy cost of walking with untethered exoskeleton assistance compared to how participants walked in the beginning of the study.

Individually, patients required less energy when walking with exoskeleton assistance, ranging from 4-29% lower net metabolic cost of transport for the best-case trials.

All participants perceived higher exertion during walking with exoskeleton assistance, three participants preferred walking with exoskeleton assistance, one participant preferred the normal condition, and one was undecided. Three participants also believed the device’s assistance helped them walk.

“These preliminary findings support the future investigation of powered ankle assistance for improving mobility in this patient population,” researchers said.

“[T]his pilot study provides evidence that a lightweight, untethered ankle exoskeleton can result in clinically significant improvements in walking economy for children and young adults with CP,” they concluded.

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