Use of Hybrid Assistive Limb (HAL®) for a postoperative patient with cerebral palsy: a case report
Mataki et al. BMC Res Notes
® Use of Hybrid Assistive Limb (HAL ) for a postoperative patient with cerebral palsy: a case report
Yuki Mataki 2
Hiroshi Kamada 0
Hirotaka Mutsuzaki 1
Yukiyo Shimizu 6
Ryoko Takeuchi 2
Masafumi Mizukami 5
Kenichi Yoshikawa 4
Kazushi Takahashi 4
Mayumi Matsuda 4
Nobuaki Iwasaki 1
Hiroaki Kawamoto 3 7
Yasuyoshi Wadano 1
Yoshiyuki Sankai 3 7
Masashi Yamazaki 0 7
0 Department of Orthopaedic Surgery, University of Tsukuba , 1-1-1 Tennoudai, Tsukuba, Ibaraki 305-8575 , Japan
1 Department of Rehabilitation Medicine, University of Tsukuba Hospital , 2-1-1 Amakubo, Tsukuba, Ibaraki 305-8576 , Japan
2 Department of Orthopaedic Surgery, Ibaraki Prefectural University of Health Sciences Hospital , 4773 Ami, Inashiki-gun, Ibaraki 300-0331 , Japan
3 Information and Systems, Faculty of Engineering, University of Tsukuba , Tsukuba , Japan
4 Department of Physical Therapy, Ibaraki Prefectural University of Health Sciences Hospital , 4733 Ami, Inashiki-gun, Ibaraki 300-0331 , Japan
5 Department of Physical Therapy, School of Health Sciences, Ibaraki Prefectural University of Health Sciences , 4669-2 Ami, Inashiki-gun, Ibaraki 300-0394 , Japan
6 Center for Medical Sciences, Ibaraki Prefectural University of Health Sciences , 4669-2 Ami, Inashiki-gun, Ibaraki 300-0394 , Japan
7 Cybernic Research Center, University of Tsukuba , Tsukuba , Japan
Background: The Hybrid Assistive Limb (HAL®) is an exoskeleton wearable robot suit that assists in voluntary control of knee and hip joint motion. There have been several studies on HAL intervention effects in stroke, spinal cord injury, and cerebral palsy. However, no study has investigated HAL intervention for patients with cerebral palsy after surgery. Case presentation: We report a case of using HAL in a postoperative patient with cerebral palsy. A 15-year-old boy was diagnosed with spastic diplegia cerebral palsy Gross Motor Function Classification System level IV, with knee flection contracture, equinus foot, and paralysis of the right upper extremity with adduction contracture. He underwent tendon lengthening of the bilateral hamstrings and Achilles tendons. Although the flexion contractures of the bilateral knees and equinus foot improved, muscle strength decreased after the soft tissue surgery. HAL intervention was performed twice during postoperative months 10 and 11. Walking speed, stride, and cadence were increased after HAL intervention. Post HAL intervention, extension angles of the knee in stance phase and hip in the pre-swing phase were improved. In the gait cycle, the proportion of terminal stance in the stance and swing phase was increased. Conclusions: Hybrid Assistive Limb intervention for postoperative patients with cerebral palsy whose muscle strength decreases can enhance improvement in walking ability. Further studies are needed to examine the safety and potential application of HAL in this setting.
Hybrid Assistive Limb (HAL); Cerebral palsy; Operation
The Hybrid Assistive Limb (HAL®) is a wearable robot
suit that assists in voluntary control of knee and hip
joint motion [
]. The HAL detects the bioelectric
signals generated by patients’ muscle activities and/or
force-pressure signals caused by patients’ weight shifts.
The bioelectric signals are detected from the hip
extensor muscle, hip flexion muscle, knee extensor muscle,
and knee flexion muscle by applying electrodes.
Electrodes are often applied to the gluteus, rectus femoris,
quadriceps femoris, and hamstrings. Power units on the
hip and knee joints on both sides consist of angular
sensors and actuators, and the control system consists of
cybernic voluntary control (CVC) and cybernic
autonomous control (CAC) subsystems (Fig. 1). HAL® differs
from other robots in that it provides motion according
to the wearer’s voluntary drive. Other robots use
autonomously generated predefined motion for users.
Hybrid Assistive Limb intervention improved
walking ability and balance in chronic stroke patients [
Kawamoto et al. [
] reported that walking speed, stride,
and cadence in the 10 m-walk test and Berg balance
scale increased in chronic stroke patients. In the acute
stroke phase, HAL intervention may improve outcomes
in selected patients [
]. Moreover, there have been
several studies of HAL intervention effects in chronic
spinal cord injury (SCI) [
]. Recently, some authors
have reported the use of HAL in the acute phase or
early postoperative period following SCI [
intervention for acute and postoperative SCI patients
enhances improvement in walking ability. The
arrangement of the interactive feedback through HAL is
postulated to efficiently excite the remaining corticospinal
tract in the injured brain and spinal nerves and enhance
the effects of physical therapy. Additionally, the cycle of
voluntary movement from afferent signals in the brain
is postulated to heighten the excitability of the existing
intracortical network and promote the formation of new
Cerebral palsy is associated with abnormal generation
of bioelectrical signals in the lower limbs associated with
brain damage. Patients with spastic cerebral palsy who
could not walk alone gained gait ability by wearing HAL;
therefore, Taketomi et al. [
] indicated that HAL is
an effective method for walking and stair ascent
assistance for cerebral palsy patients. However, no report of
HAL intervention has been described in a patient with
cerebral palsy after surgery. We report a case of HAL
intervention in a patient with cerebral palsy after
tendon lengthening surgery of the bilateral hamstrings and
Achilles tendons. In this study, although the flexion
contracture of the bilateral knees and equinus foot improved,
the muscle strength of bilateral knee flexion and ankle
dorsiflexion decreased after tendon lengthening of the
bilateral hamstrings and Achilles tendons. Improvement
of joint range after surgery did not immediately lead to
improvement in walking ability. HAL intervention with a
CVC system can potentially improve walking ability due
to enhanced range of movement, muscle strength, and
feedback within the neurological system throughout the
gait cycle. Patients with cerebral palsy and abnormal gait
may be able to learn a more normal walking pattern with
A 15-year-old boy was diagnosed with spastic
diplegia cerebral palsy, Gross Motor Function Classification
System level IV, knee flexion contracture, equinus foot,
and paralysis of right upper extremity with adduction
contracture. His height was 160.0 cm and his weight
was 50.2 kg. He underwent tendon fractional release
of the bilateral tendons of the semitendinosus muscle,
semimembranosus muscle, and biceps femoris
muscle. Achilles tendon lengthening was performed on the
right equinus foot using Vulpius elongation. His lower
limbs were fixed with above knee plaster splints in the
knee extended position and intermediate ankle position
2 weeks after surgery, and he subsequently used short leg
braces. Preoperative passive range of joint motion
values were as follows: right knee 35–130/left knee 20–130,
ankle dorsiflexion with knee extension (DKE) 15/15, and
ankle dorsiflexion with knee flexion (DKF) 35/35. At 6
postoperative months, range of joint motion was right
knee 15–130/left knee 10–130, DKE 15/10, and DKF
25/20. Knee extension range and DKF improved
postoperatively. Preoperative manual muscle testing showed
the following: knee extension 3/3, knee flexion 4/4, ankle
dorsiflexion 1/1, and ankle plantar flexion 1/1. Before
surgery, he had begun crawling in the house. Before HAL
intervention, he could not move with crawling because
of postoperative muscle weakness. It was thought that
muscle weakness was due to disuse muscle atrophy after
Hybrid Assistive Limb intervention was administered
twice during postoperative months 10 and 11 in an
outpatient department. Normal outpatient physical therapy
was carried out in combination. The patient used the
HAL for clinical study type S size (target 145–165 cm).
A walking device (All-in-One Walking Trainer;
Healthcare Lifting Specialist, Denmark) with a harness was used
for safety, and the HAL intervention consisted of
walking with the assistance of two physical therapists
(Additional files 1 and 2). The HAL intervention session lasted
60 min, including rests (10 min) and time for attachment/
detachment (20 min). The HAL suit has a hybrid control
system comprising the CVC and CAC. The CVC mode of
the HAL suit can support the patient’s voluntary motion
by providing assistive torque to each joint according
to voluntary muscle activity. This study used the CVC
mode, which allows the operator to adjust the degree of
physical support to the patient’s comfort and gradually
reduce support as training progresses. Functional
ambulation was assessed with the 10 m-walk test without
wearing HAL and video analysis preoperatively and pre- and
post- each HAL intervention (Additional files 3 and 4).
We analyzed one gait cycle of the patient with Dartfish.
Walking speed, stride, and cadence in the 10 m-walk test
were analyzed. We took a walking video from the sagittal
plane and analyzed the video in slow motion, pausing the
image to measure the joint angle using the Dartfish Team
Pro ver5.5. The angle of the hip, knee, ankle, and trunk in
walking and in the gait cycle was analyzed using video.
Video images were played back frame by frame, and the
phase at the beginning of each gait cycle was confirmed.
One gait cycle is defined as the movement starting from
initial contact on one side till the next initial contact on
the same side. The beginning of the loading response
phase is defined as the initial contact, the beginning of
mid stance is defined as opposite side toe off, the
beginning of terminal stance is defined as heel off, the
beginning of pre swing is defined as opposite side initial
contact, the beginning of initial swing is defined as toe
off, the beginning of the mid swing is defined as
intersection of the feet, and the beginning of the terminal stance
is defined as the vertical lower leg.
In the 10 m-walk test, the patient used ankle foot
orthosis preoperatively, and did not use orthosis pre- and
post-HAL intervention. He used the walker as a walking
Table 1 shows the results of the 10 m-walk test. Speed,
stride, and cadence for walking were almost the same
preoperatively and pre-HAL intervention. Post-first HAL
intervention, speed, stride, and cadence were increased
compared to pre-HAL intervention. This was maintained
until the next HAL intervention and further improved
after the second HAL intervention. HAL intervention
increased walking speed from 21.7 to 32.1 m/min, stride
from 0.40 to 0.47 m, and cadence from 54.23 to 68.9
Ankle angle during walking showed little change
because he wore a short leg brace while walking
preoperatively. Pre-HAL intervention, the dorsiflexion angle was
large in the terminal stance and pre-swing, the plantar
flexion angle was large in the initial swing, and there was
a large difference between the right and left ankle angle
(Fig. 2a, b). Post-HAL intervention, range of movement
of the ankle joint became more narrow, left-right
symmetry increased (Fig. 2a, b), and extension angles of the
knee in the stance phase increased (Fig. 2c, d). Excessive
dorsiflexion and plantar flexion of the ankle joint
disappeared due to extension of the angle of the knee (Fig. 2a,
b). His extension angle of the hip did not increase and
the trunk was leaning forward (Fig. 2e, f ). Flexion of the
upper limbs was strong due to spastic diplegia; therefore,
he walked with the head bent forward. Because of the
anteversion position, his hip joint did not show extension
in walking (Fig. 2g). Although the horizontal plane and
the hip joint were examined, extension of the hip angle in
the pre-swing phase was increased (Fig. 2h, i). In the gait
cycle, asymmetry between the left and right was
prominent preoperatively (Fig. 3). Comparing pre- and
postHAL, the proportion of terminal stance in the stance
phase and swing phase was increased. Since the length of
stride was expanded due to increased extension angles of
the knee and hip, the ratio of terminal stance and
terminal swing increased (Fig. 3).
After HAL intervention, he was able to crawl and
gained the ability to move within his house, similar to
his status before operation. There was no adverse event
such as fall or fractures during the HAL intervention. The
patient was able to walk easily while wearing HAL, and
he actively participated in HAL intervention.
Discussions and conclusions
Before the operation, a crouching gait was prominent,
with noticeable flexion contracture of the knee. Although
the extension angle of the knee expanded postoperatively,
the crouching gait remained. The crouching gait
improved due to the expanded extension angle of the
knee in the stance phase after the HAL intervention.
With increased extension angles of the knee and hip in
the stance phase, the speed, length of stride for walking,
and cadence markedly increased. Based on these
findings, we report that the combination of HAL
intervention and surgery with improvement of contractures of
the knee and ankle can enhance improvement in walking
ability for the patient with cerebral palsy. Improvement
in walking ability leads to improved lower limb
function, improved standing ability, and reduced need for
After the first HAL intervention, speed, length of stride
for walking, and cadence increased on the 10 m-walk test
in the pre-second HAL intervention. We considered this
a sustained effect of the first intervention. Post-second
HAL intervention, the speed, length of stride for
walking, and cadence increased more than before the second
intervention. The result of this intervention suggested
that the effect is potentially persistent and the effect is
increased with repeated HAL interventions. Thus, it is
necessary to consider the frequency and timing of HAL
On video gait analysis using Dartfish, it is possible to
determine the gait cycle accurately [
] and to
measure the joint angle based on the timing of the gait cycle.
Three-dimensional gait analysis is necessary for more
accurate joint angle measurement.
Cerebral palsy is the most frequent motor disability
of childhood, with a neonatal prevalence of
approximately 2 per 1000 live births [
]. Robot rehabilitation
for cerebral palsy has been described in several papers
]. After a 3-week trial of robotic-assisted
treadmill therapy, patients with bilateral spastic cerebral palsy
showed improvements in the functional tasks of
standing and walking [
]. Retraining gait using the driven
gait orthosis improved gait speed and the Gross Motor
Function Measure score [
]. Repeated active movement
aligns with the motor learning theory currently popular
in physical treatment as a means of inducing neuroplastic
changes in the brain [
]. Robot intervention for
physical treatment is considered to be effective in improving
walking ability for patients with cerebral palsy.
Hybrid Assistive Limb intervention may be a new
treatment option in patients with cerebral palsy after soft
tissue surgery. To obtain a treatment effect, it is necessary
to investigate the indications and limitations of HAL
intervention, and to determine an effective protocol
using HAL intervention. Borggraefe et al. [
for 12 sessions of robot intervention (4 sessions/week).
Meyer et al.  aimed for 20 sessions of robot
intervention (2–5 sessions/week). The currently reported case
includes less frequent training than previous reports. In
children and young people, the effect of this intervention
may be obtained with less frequent application.
These robots provide autonomous motion to patients
based on the desired kinematic trajectory of the lower
limb joints or the end effector, mimicking the walking
motion of an able-bodied person. HAL interactively
provides motion according to the wearer’s voluntary drive
In this case, although the flexion contractures of the
bilateral knees and equinus foot improved, the muscle
strength with bilateral knee flexion and ankle
dorsiflexion was decreased following tendon lengthening of the
bilateral hamstrings and Achilles tendons. HAL
intervention can be an effective tool for improvement in range of
movement and muscle strength after soft tissue
operations by providing assistance with the power units of
the HAL hip and knee joints. HAL intervention may be
applied in patients with cerebral palsy who undergo soft
tissue operations for improvement in joint contractures
and decreased muscle strength.
After myotomy, tenotomy, or the lengthening of
tendon or muscle, muscles cannot perform sufficiently,
and the alignment of the legs is altered. HAL can assist
the muscle and provide walking training to improve
towards a more normal gait.
Voluntary drive and normalized motion assistance
provided by the external device form the foundation
for a proprioceptive feedback loop for patients with
cerebral palsy. HAL intervention produces neural
activity and repeated execution of specific tasks. The HAL
intervention promotes learning and leads to a state of
appropriate proprioceptive feedback. We were able to
carry out the HAL intervention for cerebral palsy in a
postoperative patient safely and effectively.
After soft tissue surgery for cerebral palsy, although
flexion contractures of the bilateral knees and
equinus foot improved, muscle strength of bilateral knee
flexion and dorsiflexion temporarily decreased in our
patient. In this case, using HAL intervention, the
extension angle of the knee and hip in the stance phase was
expanded and the walking speed, length of stride, and
cadence increased. Use of the HAL intervention in a
postoperative patient with cerebral palsy can enhance
improvement in walking ability.
We will increase the use of HAL for patients with
spastic cerebral palsy. Patients with cerebral palsy may
have thin legs, in which case it is necessary to adjust the
size of the cuff and belt for the lower limbs, because the
size of the cuff and belt is large. Meyer uses Lokomat
for patients with Guillain–Barre syndrome and
athetoid-type cerebral palsy. We will consider using HAL
for patients with other types of cerebral palsy. Further
studies are needed to examine the safety and potential
applications of this technique.
Additional file 1. Image of Hybrid Assistive Limb (HAL®) intervention for
Additional file 2. Video of Hybrid Assistive Limb (HAL®) intervention for
Additional file 3. Image of Gait pre and post Hybrid Assistive Limb
(HAL®) intervention for cerebral palsy.
Additional file 4. Video of gait pre and post Hybrid Assistive Limb (HAL®)
intervention for cerebral palsy.
CAC: cybernic autonomous control; CVC: cybernic voluntary control; DKE:
dorsiflexion with knee extension; DKF: dorsiflexion with knee flexion; HAL: Hybrid
Assistive Limb; SCI: spinal cord injury.
YM, HK1, HM, MM1, NI, HK2, YW, YS1 and MY conceived the study and
participated in its coordination; YM analyzed the data and drafted the manuscript.
YS2, RT, KY, KT, KM and MM2 were involved in patient examination. HK1
corresponding to Hiroshi Kamada, HK2 corresponding to Hiroaki Kawamoto,
MM1 corresponding to Masafumi Mizukami, MM2 corresponding to Mayumi
Matsuda, YS1 corresponding to Yukiyo Shimizu, and YS2 corresponding to
Yoshiyuki Sankai. All authors read and approved the final manuscript.
HK reports personal fees from null, outside the submitted work. HK reports
personal fees from CYBERDYNE. INC, outside the submitted work. YS2 reports
grants from Japan Science and Technology Agency (JST), grants from grants‐
in‐aid for academic-industrial collaboration, outside the submitted work; and
CEO of CYBERDYNE Inc. (*Note: YS2 does not have the patent to the work.
University of Tsukuba has the patent (patent title: 装着式動作補助装置、装
術の発明)) and the royalty is paid to University from CYBERDYNE Inc. and a
part of the royalty is paid to YS2 according to the National University rules. YS2
corresponding to Yoshiyuki Sankai.
Availability of data and materials
All data generated or analyzed during this study are included in this published
article [and its additional files].
Consent for publication
The patient and parents provided written consent for publication of this case
report and associated images and video.
Ethics approval and consent to participate
Before participating in the walking exercise using HAL, the patient and the
family provided written informed consent, and the study was approved by
the Ethics Committee of the Ibaraki Prefectural University of Health Sciences
This study was supported by the Industrial Disease Clinical Research Grants of
the Ministry of Health Labour and Welfare, Japan (Grant No. 14060101-01).
Springer Nature remains neutral with regard to jurisdictional claims in
published maps and institutional affiliations.
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