H.28 Soft Exoskeleton to assist kicking movements in preterm infants

It is estimated about 1 in 8 babies are born prematurely. The major neuropathology in preterm infants that has been associated with motor deficits (e.g. cerebral palsy) is thought to be cerebral white matter damage (WMD). Approximately 60-90% of infants with WMD are later diagnosed with cerebral palsy having varying grades of severity, especially with respect to their lower extremities, which limit the child’s daily function.

Kicking movement is one of the earliest coordinated behaviors in infancy. Kicking patterns in infants also show similar kinematic variables as walking. Our previous research and meta-analysis have shown preterm infants with WMD, unlike their full-term peers, continue to maintain a highly synchronized kicking pattern at 5 months, especially between hip and knee joints and between hip and ankle joints.1 That is, when preterm infants with WMD try to flex their hip joint, their knee and ankle joints also flex – this pattern is similar to the common walking pattern in children with cerebral palsy (i.e., crouch gait). Consequently, how to train preterm infants with WMD to ‘break up’ this synchronized kicking pattern in their early age is important such that preterm infants with WMD can advance their motor development, just like their healthy full-term peers.

In prior research, we have used a mobile reinforcement paradigm to successfully train a group of full-term infants to use their non-preferred kicking patterns, the combination of desynchronized hip-knee kicking pattern, in order to receive a mobile reinforcement.2 However, a study by Sargent, et al3 showed preterm infants, unlike their full-term peers, had difficulties in producing the de-synchronized hip-knee kicking pattern, even though they did learn the contingency between their movement and mobile reinforcement. One possible explanation is that these preterm infants may not have sufficient muscle strength and are not aware of how to use their legs effectively. Therefore, it is important to have a smart exoskeleton to assist preterm infants with WMD to learn how to kick de-synchronized between joints, especially between hip and knee joints.

Currently, to our knowledge, only one research team from Harvard Engineering is developing a device to assist in infant’s kicking4. However, their device only assists in hip adduction, abduction, flexion, and knee flexion. It does not help train infants with WMD to de-synchronize their joint movements. 

The goal of this project is to design a lightweight, safe, and sturdy lower-extremity exoskeleton that can assist preterm infants with WMD (age between 3-10 months old) to learn de-synchronized kicking patterns with a mobile reinforcement. This kicking exoskeleton device can provide assistance at the beginning to mold infants kicking in the selected de-synchronized pattern, and then decrease the required assistance or even provide resistance to train the infant’s muscle strength. This kicking exoskeleton should also be able to be programmed to train different kicking patterns and to link with the mobile reinforcement to provide extra motivation/learning.

References:

1. Chen, Y., Fetters, L. (2002). A comparison of the leg coordination patterns of preterm and fullterm infants: A meta-analysis. Formosan Journal of Physical Therapy, 27(6), 303-313.
2. Chen, Y., Fetters, L., Saltzman, E.L., & Holt, K.G. (2002). Making the mobile move: Constraining from task and environment. Infant Behavior and Development, 25(2): 195-220.
3. Sargent, B., Kubo, M., & Fetters, L. (2018). Infant discovery learning and lower extremity coordination: Influence of prematurity. Physical and Occupational Therapy in Pediatrics, 38(2):210-225.
4. Subramanyam K., Rogers E., Kulesza M., et al. (2015). Soft wearable orthotic device for assisting kicking motion in developmentally delayed infants. Journal of Medical Devices.

https://biodesign.seas.harvard.edu/files/biodesignlab/files/2015_subramanyam_-_dmd_-_soft_wearable_orthotic_device_for_assisting_kicking_motion_in_developmentally_delayed_infants.pdf