A newly developed wearable cyborg leg can help people with neuromuscular disorders, such as spinal muscular atrophy (SMA), walk again, a recent study has found. Researchers from several hospitals across Japan conducted a clinical trial to study the safety and efficacy of the Hybrid Assistive Limb in people with neuromuscular disorders undergoing physical therapy.
Developed by Japan’s Tsukuba University and robotics company Cyberdyne, the HAL connects to the wearer’s central nervous system (CNS) through electrodes placed on the skin. This allows for bio-electric signals for movement to be sent from the brain to the device, which helps the wearer move.
“Using these signals, HAL allows the wearer to perform the desired movements with their voluntary commands,” according to Brooks Rehabilitation. “The physical therapist can see these signals and adjust settings on the robot suit to amplify weak signals and focus on desired signals. Active use of these neural pathways for voluntary movement with feedback to the brain leads to an improved ability for the wearer to walk on their own.”
Movement and Neuromuscular Disorders
Neuromuscular disorders are conditions in which there is damage to the nerve cells involved in movement. They are usually caused by rare changes in DNA that make it difficult for nerve cells to send signals for movement. In spinal muscular atrophy, the survival motor neuron (SMN) genes are mutated, so they cannot make enough healthy SMN proteins.
Assistive devices are available to help those with SMA, such as canes, walkers, and wheelchairs. However, for those who have more serious mobility issues, these devices may not be enough. Rehabilitation programs for individuals with neuromuscular disorders are useful in many cases but cannot restore muscle function.
According to the researchers, the HAL device is a safer, more effective alternative to traditional assistive devices used in rehabilitation programs. “In SMA, exercise training and active exercise therapy have been considered harmful because overexertion may worsen the disease,” Dr. Takashi Nakajima, director of Niigata National Hospital, told mySMAteam. “In contrast, gait exercise therapy with the newly developed HAL lower limb is safe and effective in improving gait function in patients with SMA and other neuromuscular disorders.”
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The study included a total of 24 participants with SMA, muscular dystrophy, and other neuromuscular disorders. The participants were divided into groups A and B, which determined what treatment they would receive first. Those in group A performed walking tests using only an assistive hoist — used as a control. Those in group B performed walking tests using the HAL. After nine sessions, the groups switched treatments so that they could be compared.
The two-minute walking test (2MWT) is a standard mobility test used to measure how far a person can walk in two minutes. Overall, the HAL significantly improved participants’ 2MWT score by almost 10.1 percent, helping them walk farther than with an assistive hoist alone. Researchers also saw significant improvements in speed and rate of walking — known as cadence — for the 10 minute walking test (10MWT).
The authors noted that it takes around five minutes to put the HAL on, and it was found to be safe for all users. Some participants reported side effects using the HAL, including back pain and skin irritation from the device and electrodes. These side effects were all manageable for the participants.
The authors told mySMAteam that they are interested in studying whether using the HAL together with other SMA treatments — such as nusinersen — can improve motor function in people with SMA type 2. They would also like to investigate whether the HAL combined with medication can be used to treat people with chronic type 3 SMA to improve and maintain gait.
Researchers in Japan have begun an observational study to answer these questions and better understand how HAL can be used to improve the lives of people with SMA.