International Journal ofEnvironmental Researchand Public Health

Case Report

Seated Virtual Reality-Guided Exercise Improved Gait in a
Postoperative Hallux Valgus Case
Masami Nakamoto 1,2, *, Akihiro Kakuda 1,2 , Toshinori Miyashita 1 , Takashi Kitagawa 3 , Masashi Kitano 1,3 ,Masahiko Hara 1,4 and Shintarou Kudo 1,2,3
1

2

3

4

*



Citation: Nakamoto, M.; Kakuda, A.;
Miyashita, T.; Kitagawa, T.; Kitano,M.; Hara, M.; Kudo, S. Seated Virtual
Reality-Guided Exercise Improved
Gait in a Postoperative Hallux Valgus
Case. Int. J. Environ. Res. Public Health2021, 18, 13267. https://doi.org/
10.3390/ijerph182413267
Academic Editor: Paul B. Tchounwou

Inclusive Medical Science Research Institute, Morinomiya University of Medical Sciences, 1-26-16, Nanko-kita,
Suminoe-ku, Osaka 559-8611, Japan; kakuda@morinomiya-u.ac.jp (A.K.); miyashita.osaka@gmail.com (T.M.);
2021dms001@s.morinomiya-u.ac.jp (M.K.); hara@medivr.jp (M.H.); kudo@morinomiya-u.ac.jp (S.K.)
Department of Physical Therapy, Morinomiya University of Medical Sciences, 1-26-16, Nanko-kita,
Suminoe-ku, Osaka 559-8611, Japan
Graduate School of Health Science, Morinomiya University of Medical Sciences, 1-26-16, Nanko-kita,
Suminoe-ku, Osaka 559-8611, Japan; 2020mhs003@s.morinomiya-u.ac.jp
mediVR, Inc., 106-2-3-8, Terauchi, Toyonaka-shi, Osaka 561-0872, Japan
Correspondence: nakamoto@morinomiya-u.ac.jp; Tel.: +81-6-6616-6911

Abstract: Virtual reality (VR)-guided exercise therapy using mediVR KAGURA has been reported to
improve gait function by extending the arm to spatial targets while sitting. We aimed to investigate
toe and trunk–pelvic function and plantar sensation during gait in a postoperative patient withhallux valgus. A 60-year-old woman, whose foot deformities had improved 6 months earlier,participated in the study. The exercise therapy interventions were performed twice weekly for
15 min. This study used an A-B-A design: 1-week pre-phase, 3-week intervention phase, and 2-weekpost-phase. The plantar pressure distribution and thoracic and pelvic displacements during gaitwere recorded at the end of each phase. The tactile pressure thresholds of the foot were determined
before and after each exercise. The maximum force and impulse under the hallux increased after
the intervention. The sensory threshold of the hallux was reduced. The amplitude of the thoracic
and pelvic displacement was shortened in lateral and extended in the vertical and progressional
directions after the intervention. We found that a 3-week VR-guided exercise improved toe function,
plantar sensation, and postural adjustment of the trunk and pelvis during gait in a patient who had
undergone surgery for hallux valgus, and the effects continued for 2 weeks.
Keywords: single-case study; ABA experimental design; virtual reality; hallux valgus; seatedrehabilitation

Received: 4 November 2021
Accepted: 14 December 2021
Published: 16 December 2021

1. Introduction
Publisher’s Note: MDPI stays neutral
with regard to jurisdictional claims inpublished maps and institutional affiliations.

Copyright: © 2021 by the authors.
Licensee MDPI, Basel, Switzerland.
This article is an open access article
distributed under the terms andconditions of the Creative Commons
Attribution (CC BY) license (https://creativecommons.org/licenses/by/

Deformities of the hallux valgus cause chronic pain. This pain disrupts gait, affects
the whole body, and reduces the quality of life [1,2]. Conservative treatment for hallux
valgus includes exercise therapies, such as strengthening of the hallux abductor, orthotic
therapy, and medication. If the pain does not improve with these treatments, surgery is
indicated [3]. However, in cases of hallux valgus after correcting the alignment by surgery,gait problems often persist and cause recurrent deformity and pain [4,5]. It is necessary
to improve gait in conjunction with local conservative treatment and surgery. In addition,
rehabilitation for hallux valgus is often provided at an outpatient clinic, and the effects ofexercise therapy on gait should last for several weeks. However, there are a few reports on
effective exercise therapy for gait in patients with hallux valgus [6].
mediVR KAGURA® (mediVR, Inc., Osaka, Japan) has been reported to improve walking ability without increasing lower limb muscle strength [7,8]; however, the mechanism
remains unclear. Exercise therapy with the use of virtual reality (VR) requires quick arm
movements extending to spatial targets. This reaching motion has been shown to improve4.0/).

Int. J. Environ. Res. Public Health 2021, 18, 13267. https://doi.org/10.3390/ijerph182413267

https://www.mdpi.com/journal/ijerph

Int. J. Environ. Res. Public Health 2021, 18, x FOR PEER REVIEW

2 of 9arm movements extending to spatial targets. This reaching motion has been shown to im2 of 9
prove the movement strategy of the trunk [9] and upper limb function [10]. We hypothesized that the load on the pelvis and lower limbs with trunk movement could improve
gait function. Therefore, in this study, we investigated the effects of VR-guided sitting
the movement
strategyof the trunk[9] andduring
uppergait
limbinfunction[10]. We hypothesizedthatexerciseon toe andtrunk–pelvic
functiona postoperative
patient with halthevalgus.
load on the pelvis and lower limbs with trunk movement could improve gait function.
lux
Therefore, in this study, we investigated the effects of VR-guided sitting exercise on toe
trunk–pelvic
function during gait in a postoperative patient with hallux valgus.
2.andMaterials
and Methods

Int. J. Environ. Res. Public Health 2021, 18, 13267

2.1.
Participantand Methods
2. Materials
60-year-old woman participated in this study. Her height and weight were 156.5
2.1. A
Participant
cm and58.0 kg, respectively.
At the time
participation,
6 months
passedA 60-year-old
woman participated
inof
this
study. Her heightand hadweightweresince
156.5bicm
lateralsurgery
for hallux valgus,
and thehallux valgus6 angles
on theright
andand 58.0
kg, respectively.
At the timeof participation,monthswere
had 7.3°
passedsincebilateral
14.8°
on theShevalgus,
had been
byvalgus
the hallux
valgusshethewasin her◦ onsurgery
for left.
halluxandbothered
the hallux
angleswere since
7.3◦ onright
and50s,14.8and
had
been
using
commerciallyavailable
wide
shoes
and
a
nighttimetoeseparator
splinttothe left. She had been bothered by the hallux valgus since she was in her 50s, and had been
reduce
the
pain,
which
interfered
with
her
daily
life.
Subsequently,
shevisitedahospitalusing commercially available wide shoes and a nighttime toe separator splint to reduce theforthewhichfirst timeand immediately
underwent
surgery asshe
indicated,months before
pain,interferedwith her daily
life. Subsequently,
visited a6 hospitalfor the ourfirstintervention.
Shewashospitalized
for
three
weeks,
postoperatively,
andunderwent
time and immediately underwent surgery as indicated, 6 months before our intervention.
standard
exercise therapy
for weeks,
hallux postoperatively,
valgus, range ofand
motionexercises,
and exercise
muscleShe was hospitalized
for threeunderwent
standard
strengthening
training
for
the
feet.
She
was
independent
in
her
daily
life
and
returnedtherapy for hallux valgus, range of motion exercises, and muscle strengthening training toforwork
afterShe
being
from
thedaily
hospital.
There
were nointerventhe feet.
wasdischarged
independentin herlife andreturned
to otherwork therapeutic
after being discharged
tions
thehospital.
last 5 months.
she still
experienced
pain and unsteadinessduringfrominthe
There However,were no othertherapeuticinterventionsin the last 5 months.
gait.
The levelof painat the timeofandintervention
in this
study
was
5 on
theofNumerical
However,she still
experienced
pain
unsteadinessduring
gait.
The
level
pain at the
Rating(NRS). in this study was 5 on the Numerical Rating Scale (NRS).
time ofScaleintervention
This
Thisstudy
studywaswasapproved
approvedby
bythe
theResearch
ResearchEthics
EthicsReview
ReviewCommittee
Committeeof
ofMorinomiya
Morinomiya
UniversityofMedicalSciences(reference
number:2020-006).
The
purposeofUniversity of Medical Sciences (reference number: 2020-006). The purpose ofthis
thisstudy
study
waswasexplained
explainedto
toher,
her,andandconsent
consentwas
wasobtained
obtainedbefore
before thethe study
study waswas conducted.
conducted.
2.2.Experimental
ExperimentalDesign
Design2.2.
Thisstudy
studywaswasa singlecase,
an A-B-A
design:1 beforeweek before
intervention
Thisa singlecase,
withwith
an A-B-A
design:1 weekintervention
phase
phase
(A1),
3-weekintervention
phase
(B),
and
2
weeks
after
the
intervention
phase
(A2)
(A1), 3-week intervention phase (B), and 2 weeks after the intervention phase (A2)
(Figure(Figure1). Each VR-guided
exercisewas
sessionwas performed
fortwice
15 min,twice
a week(six
1).
Each VR-guided
exercise session
performed
for 15 min,a week(six
sessions
in total). data
Kinematic
gait wererecorded
thephase,end ofandeachinsessions
total). Kinematicduringdata
gait during
were recordedat theend of ateachthephase,senand thresholdthe sensoryofthresholdtheidentified
sole was identified
beforeeach exercisesory
the sole ofwasbefore andafter andeachafter
exercisesession. session.
These
These
measurements
were
conducted
duringtheworkdaytominimize
disruption
todailymeasurements were conducted during the workday to minimize disruption to daily life.
life.

Figure 1. Experimental design. A1 phase, 1 week before intervention; B phase, 3-week intervention
Figure 1. Experimental design. A1 phase, 1 week before intervention; B phase, 3-week intervention(twice-a-week exercise); A2 phase, 2 weeks after the intervention. Kinematic data during gait are(twice-a-week exercise); A2 phase, 2 weeks after the intervention. Kinematic data during gait arerecordedatatthe
theendendofofeach
eachphase,
phase,and
andthethesensory
sensorytest
testisisconductedconductedbefore
beforeandandafteraftereach
eachexercise
exerciserecordedsession.
session.

2.3. Intervention
2.3. Intervention
The VR-guided exercise was performed while sitting in a chair with a backrest, wearThe VR-guided exercise was performed while sitting in a chair with a backrest, wearing a head-mounted display, and holding a controller with both hands (Figure 2). The
ing a head-mounted display, and holding a controller with both hands (Figure 2). The
participant was instructed to, as quickly as possible, catch red or blue falling objects or red
participant was instructed to, as quickly as possible, catch red or blue falling objects oror blue fixed targets in a three-dimensional virtual space, with her right or left controller,
respectively. The red objects and targets were presented in the right space only, and the blue
ones were presented in the left space only to prevent her from moving across the midline.
The objects and targets were presented straight ahead and diagonally 45◦ ahead on each

Int. J. Environ. Res. Public Health 2021, 18, x FOR PEER REVIEW

3 of 9red or blue fixed targets in a three-dimensional virtual space, with her right or left conInt. J. Environ. Res. Public Health 2021, troller,
18, 13267 respectively. The red objects and targets were presented in the right space 3only,of 9and the blue ones were presented in the left space only to prevent her from moving acrossthe midline. The objects and targets were presented straight ahead and diagonally 45°
ahead on each side and at three distances in each direction (at stretched arm length, 90%sideand at three
distanceseach
direction(at stretchedarmoflength,
90% ofThemaximumof maximum
reachlength, inand
halfway
between),for a total
12 locations.
first exreach
length,andhalfway
between),
for
a
total
of
12
locations.
The
first
exerciseprogramercise program was configured manually by a skilled therapist to ensure that physicalwasconfigured
manuallybyThea skilled
therapist was
to ensure
thatthephysical
activity
was fully
activity
was fully
induced.
same programused for
subsequent
exercisesesinduced.
The
same
program
was
used
for
the
subsequent
exercisesessions.
sions.

Figure2.2.Images
Imagesof
ofthe
themediVR
mediVRKAGURA-guided
KAGURA-guidedexercise.
exercise.
Figure2.4.
2.4. Measurements
Measurements®
StaticStaticandanddynamic
dynamicplantar
plantarpressurepressuredata
datawere
wererecorded
recordedusing
usingaaFootscan
Footscan®pressurepressure
plate
12 mm
mm withwith 4096
plate(RSscan(RSscanInternational,International,Olen,
Olen,Belgium;
Belgium;578
578××418
418×× 12
4096 resistive
resistive sensors,
sensors,2 ), which
aa datafrequency ofof 300300Hz,
Hz,andanda apressurepressurerange
range
1–127
N/cm
2), whichdata acquisitionacquisition frequency
ofof
1–127
N/cm
was
was
connected
a computer.
The participant
was asked
to stand
60 walks andatwalkatconnected
to a tocomputer.
The participant
was asked
to standfor 60 fors anda comafortablecomfortable
the whichplate, waswhich
was locatedat theofcentera 10-m path.
walking
speed speed
on theonplate,
locatedat the centera 10-mofwalking
The
path.
The
recordingofdynamic
plantarpressure
wasterminatedifthepatient
recording of dynamic plantar pressure was terminated if the patient stepped on stepped
the plateon
thetimes
platewiththreeher
times
with
right
data wereanalyzedusingFootscan
the Scientific® softthreerightfoot.herThe
datafoot.
wereTheanalyzedusing
the ScientificFootscan® software (RSscan International, Olen, Belgium). Footprint impressions in theware (RSscan International, Olen, Belgium). Footprint impressions in the standing posistanding position were obtained, and arch width, which was defined as the length of ation were obtained, and arch width, which was defined as the length of a perpendicularperpendicular line drawn from the mid-point of the medial border in the arch area to theline drawn from the mid-point of the medial border in the arch area to the mid-foot [11],mid-foot [11], was measured using a ruler. The maximum force and impulse of the vertical
was measured using a ruler. The maximum force and impulse of the vertical force comforce component at the hallux and first metatarsal zones were calculated, and the averageponent at the hallux and first metatarsal zones were calculated, and the average value ofvalue of the three gait cycles was obtained.
the three gait cycles was obtained.
During the gait cycle, thoracic and pelvic displacements were recorded using two small
During the gait cycle, thoracic and pelvic displacements were recorded using two
sensors with built-in acceleration and angular velocity sensors (MVP-WS2-S, MicroStone
small sensors with built-in acceleration and angular velocity sensors (MVP-WS2-S, MiCorp., Nagano, Japan), which were connected to a computer. Each sensor was fixed
croStone Corp., Nagano, Japan), which were connected to a computer. Each sensor was
to her back at the seventh thoracic and first sacral vertebrae. The vertical, lateral, andfixed to her back at the seventh thoracic and first sacral vertebrae. The vertical, lateral, andprogressional amplitudes of the thoracic and pelvic displacements were calculated fromprogressional
amplitudesof thepelvicthe
displacements
wereoncalculatedfromtheobtained data,
excludingthe thoracic
gait cycleandwhereinpatient stepped
the platform.
the stride-to-stride
obtained data, excluding
the gait
cycle
whereinthe patient
stepped on the platform.
The
time variability
(STV)
was
also calculated[12].
The Tactile
stride-to-stride
time
variability
(STV)
was
also
calculated[12].
pressure thresholds of the planter under the hallux and first metatarsal headpressure
thresholds of the planter
under the (Sakai
hallux Medical
and firstCo.,
metatarsal
head
were Tactile
identified
using Semmes–Weinsteinmonofilaments
Ltd., Tokyo,
wereidentified
using
Semmes–Weinsteinmonofilaments(Sakai
MedicalCo.,
Ltd.,
Tokyo,
Japan), which consisted of 20 filaments of 0.008–300 g. Pressure was applied for approximately 1.5 s until a bend at a right angle was obtained [13]. The force of the filament withthree accurate responses was adopted as the threshold for the site.
3. Results
Arch widths measured from static pressure distribution were 28 mm, 32 mm, and
30 mm in A1, B, and A2 periods, respectively (Figure 3): the NRS for pain was 5, 4, and 5,
respectively.

Progressional
First sacral vertebra
Vertical
LateralInt. J. Environ. Res. Public Health 2021, 18, 13267
Progressional
Stride-to-stride time variability

mm

10

31

26

mm
mm
mm
%

20
47
17
15.5

40
41
35
3.8

31
47
24
3.2

4 of 9FigureFigure3.
3. Representations
Representationsof
ofarcharchwidth
widthfromfromthetheright
rightfootprint
footprintupon
uponstanding
standingin
ineacheachperiod.
period.

The results of the kinematic parameters in gait for A1, B, and A2 are shown in Table 1.
The maximum force and impulse of the hallux zone during gait increased from A1 to B andA2 (Figure 4). The impulse of the first metatarsal zone decreased from A1 to A2 (Figure 4).
The amplitudes of the thoracic and pelvic displacement in the vertical and progressional
directions were extended, as were those of thoracic displacement in the lateral direction
from A1 to B and A2 (Figure 5). In the frontal plane, the trajectory of these displacementschanged into a figure-of-eight (middle row of Figure 5), and the STV decreased from A1
to B and A2 (Table 1). The tactile pressure threshold of the hallux was 8 g in A1 and was
lowered to 0.4 g by the third exercise session (Figure 6). There was no significant change inthe first metatarsal head, and the threshold was in the range of 60–100 g (Figure 7).
Table 1. Serial changes in kinematic parameters during gait.
Kinematic Parameter
Plantar pressure
Maximum force
HalluxFirst metatarsal
ImpulseHalluxFirst metatarsal
Amplitudes of the thoracic and pelvic displacement
Seventh thoracic vertebra
Vertical
LateralProgressional
First sacral vertebra
Vertical
LateralProgressional
Stride-to-stride time variability

A1

B

A2

N
N

39.6
183.2

±
±

3.3
42.5

57.7
202.0

±
±

20.1
21.5

68.3
183.6

±
±

25.7
17.2

N·s
N·s

7.5
74.6

±
±

1.3
32.3

14.6
77.8

±
±

6.9
10.1

12.7
54.4

±
±

5.3
4.3

mm
mm
mm

14
76
10

40
50
31

30
63
26

mm
mm
mm
%

20
47
17
15.5

40
41
35
3.8

31
47
24
3.2

Int. J. Environ. Res. Public Health 2021, 18, x FOR PEER REVIEW
Int. J. Environ. Res. Public Health 2021, 18, x FOR PEER REVIEW
Int. J. Environ. Res. Public Health 2021, 18, 13267

5 of 95 of 95 of 9Figure4.4.Waveform
Waveformobtained
obtainedby
byadding
addingandandaveraging
averagingthe
theverticalverticalforce
forcecomponent
componentofofthree
threegait
gait
FigureFigure 4. Waveform obtained by adding and averaging the vertical force component of three gait
cyclesunder
underthethehallux
halluxandandfirst
firstmetatarsal.
metatarsal.
cyclescycles under the hallux and first metatarsal.

Figure 5. The trajectory of the thoracic and pelvic displacements in the sagittal, frontal, and horizontal
Figure 5. The trajectory of the thoracic and pelvic displacements in the sagittal, frontal, and horiFigure
trajectoryphases.
of the thoracic and pelvic displacements in the sagittal, frontal, and horiplanes 5.
at Thethe A1–B–A2
zontal planes at the A1–B–A2 phases.
zontal planes at the A1–B–A2 phases.

Int. J. Environ. Res. Public Health 2021, 18, x FOR PEER REVIEW
Int. J. Environ. Res. Public Health 2021, 18, x FOR PEER REVIEW
Int. J. Environ. Res. Public Health 2021, 18, 13267

6 of 9Figure 6. Tactile pressure sensitivity threshold in the right hallux. The vertical axis is logar
Figure 6. Tactile pressure sensitivity threshold in the right hallux. The vertical axis is logarithmic.

Figure 6. Tactile pressure sensitivity threshold in the right hallux. The vertical axis is logar

Figure 7. Tactile pressure sensitivity threshold in the right first metatarsal head. The vertical axis is
Figure7. Tactile pressure sensitivity threshold in the right first metatarsal head. The vertic
logarithmic.
logarithmic.
Figure7. Tactile pressure sensitivity threshold in the right first metatarsal head. The vertic
4. Discussion
logarithmic.

Six months after surgery for hallux valgus, improvements in the load on the hallux
4. Discussion
and the thoracic and pelvic movements, and stride variability during gait and sensation ofSix months after surgery for hallux valgus, improvements in the load on the4.
theDiscussion
hallux, were observed following VR-guided exercise for 3 weeks; despite this, there
andthoracic and pelvic
movements,and stride thevariability
duringgait and se
were thenoin deformity
pain. Furthermore,
effects were
Sixsignificant
months changes
after surgery
for orhalluxvalgus, improvements
inmaintained
the load on theofthehallux, were observed following VR-guided exercise for 3 weeks; despite thafter
2 weeks.
and Galica
the thoracic
and pelvic
movements,
andonstride
variability
duringhallux
gait and se
et al. [14] foundthat theinmaximum
forceorthe halluxof patients with
were no significant
changes
deformity
pain.
Furthermore,
the effects werofthehallux,were
observed
followingVR-guided
exercisefor3
weeks;
despite thi
valgus (66.2 ± 10.5 years, 74.5 ± 16.3 kg) was 64.9 ± 41.7 N, which was significantly
tainedafter 2 weeks.
lower thanthat in healthyelderly people(64.3 ± 9.7oryears,
80.9± 17.9 kg, 78.4 the± 39.7N). werwere
no significant
changesin deformity
pain.
Furthermore,
effects
Galicaetcaseal. (58.0[14] kg),
found
that
the maximum
force
on
the
halluxofpatients withIn
thepresentthemaximum
force
of
the
hallux
was
39.6
±
3.3
N
beforetained after 2 weeks.
valgus(66.2 ± 10.5
years,
74.5 ± low,
16.3 kg) was± 41.7 N,
which
was significantl
the intervention,which
extremely
if the 64.9
difference
weightis considered.
Galica et al.
[14] isfoundthat the evenmaximum
force oninthe
halluxof patients with
However,the intervention,
maximum
to 57.7± 20.1which
thanthatafterin healthyelderly thepeople(64.3 force± 9.7increased
years, 80.9
± 17.9kg,N,78.4± 39.7 N
valgus(66.2 ± 10.5
years,
74.5±of16.3kg) was64.9 hallux± 41.7valgus,
N, which
was significantl
wasapproximately
the
same
as
that
the
elderly
without
considering
thepresent case (58.0 kg), the maximum force of the hallux was 39.6 ± 3.3 N before ththanthat ininweight.
healthyInelderly(64.3 ±force
9.7 years,
80.9metatarsal± 17.9 kg,
78.4was± 39.7 N)
difference
contrast,people
the maximum
on the firsthead
vention,which
is extremely
low,even if thedifferencein weight
is considered.
Ho
183.2 ± 42.5
in thekg),
present
which washigherthanthat inwas
the 39.6
study±bypresent
caseN(58.0
the case,
maximum
forceof thehallux3.3Galica
N before th
after
the
intervention,themaximumforce
increased
to
57.7
±
20.1
N,
which
was
a
et al. (123.4± 63.0isN)extremely[14]. Although
theevenmaximumon the firstmetatarsal
vention,which
low,
if theforce
differencein weight
is remained
considered. Hohigh, thethe
impulse2 weeks
after thewithout
intervention.
These
resultsconsideringsuggest that toe
matelysamedecreased
as that of
the elderly
halluxvalgus,the diffe
after
theduringintervention,
the maximum
force increased
to 57.7the± 20.1N,
which was afunctiongait
was
improvedbytheintervention.
Furthermore,tactilepressure
weight. In contrast, the maximum force on the first metatarsal head was 183.2 ± 4
matelytheas thatthe elderly
halluxconsidering
the differ
thresholdof samethe hallux
wasof
reducedby the without
third session
and valgus,
maintained
thereafter. In
thepresent
case, whichwashigherthanthat in the
study
by Galica
et al. (123.4 ±cases of hallux
valgus, thesensory
impairmentof on
the thefootfirst
is oftencaused byhead
compression
weight.
In contrast,
maximum
force
metatarsal
was 183.2 ± 42[14].
Althoughthecutaneous
maximum
force
on
the
first metatarsal
remainedhigh,
the impofthedorsomedial
nerve
due
to
deformityofthemetatarsal
head
and/orthe present case, which was higher than that in the study by Galica etal. (123.4 ±creased2 weeks
after theintervention.
These
resultssuggestthat
toesensory
function dur
injury of thedorsomedial
cutaneousnerve after
surgery[15]. The
mediantactile[14]. Although the maximum force on the first metatarsal remained high, the impu
thresholds
ofthehallux
and
the
first
metatarsal
headinJapanese
healthyyoung
peoplewas improved by the intervention. Furthermore, the tactile pressure threshold of
creased 2 weeks after the intervention. These results suggest that toe function dur
lux was reduced by the third session and maintained thereafter. In cases of hallux
was improved by the intervention. Furthermore, the tactile pressure threshold ofsensory impairment of the foot is often caused by compression of the dorsomedi
lux was reduced by the third session and maintained thereafter. In cases of hallux
neous nerve due to deformity of the metatarsal head and/or injury of the dorso
sensory impairment of the foot is often caused by compression of the dorsomedi

Int. J. Environ. Res. Public Health 2021, 18, 13267

7 of 9are 0.4 and 0.7 g, respectively [16], and both are 2.0 g in diabetic patients without apparent
peripheral neuropathy [17]. In this case, the deformity was corrected by surgery; however,
the threshold was 8 g before the intervention. After the intervention, the threshold was
reduced to 0.4 g, which is the same level as that of young people. It is unlikely thatstructural changes, such as repair of damaged nerves or an increase in receptors, occurredin a short time. In fact, the first metatarsal head, which is the surgical site, had a very highthreshold and showed no change in the period. The threshold was probably neurologicallylowered because of increased sensory stimulation of the hallux during gait in daily life.
The trunk and pelvis move in the vertical, lateral, and progressional directions during
normal gait (gait analysis, second edition) [18]. In the present case, the lateral movementin the trunk was significant, and the vertical and progressional movements in the trunk
and pelvis were insignificant before the intervention. After the intervention, the former
became shorter, and the latter became larger. It has been reported that the amplitudes
of vertical, lateral, and progressive displacements in the thoracic vertebrae are 25–95,
20–60, and 5–30 mm [19], and those in the pelvis are approximately 40, 45, and 26 mm [20],respectively, in elderly people. After the intervention, the amplitudes were almost withinthese ranges, and the trajectory of the trunk and pelvis changed to form a normal figureof-eight [21]. The movements required in this study included trunk flexion and rotationand pelvic forward tilt in the sitting position within 90% of the maximum effort. Thus, theexercise was not designed to increase the range of motion of the trunk or pelvis. Supposedly,
the changes during gait were observed due to improvements in the postural adjustment of
the trunk and pelvis.
STV is an index of fluctuation in gait; a two-fold difference was observed in themeasured STV values between those with a history of falls and those without a historyof falls [22]. In elderly people without an apparent disease, STV has been reported toincrease due to a decline in motor function and psychogenic factors such as anxiety during
fall [12]. It has been reported that the mean STV was 3.6 ± 1.8 (1.6–10.4%) in people aged
80–89 years [12] and 2.10 ± 0.94 % in people aged 65–69 years [23]. The STV, in this case,was 15.5%, showing a markedly greater variability than the typical value in the elderly.
After 3 weeks of intervention, her STV was 3.8%, which is close to the standard values for
elderly people. We could not identify the factors that caused the significant decrease in
STV, since this study did not measure lower limb muscle strength or conduct any in-depth
interviews about pain, self-efficacy, and anxiety. However, it is possible that because theintervention used was not expected to improve knee extension muscle strength [7], theneurological motor function may have improved, resulting in a significant decrease in STV.
This study suggests that the improvement in walking abilities reported in previous
studies using mediVR KAGURA [7,8] is related to the changes in toe function, plantar
sensation, and postural adjustment of the trunk and pelvis. As mentioned above, theexercise used in this study is more likely to have improved gait function by influencing
sensorimotor function rather than by structural changes, such as increasing range of motion
or muscle strength, which would otherwise have been the main purpose in general exercise
therapy for hallux valgus [24]. In addition, the spatial target reaching exercise while sitting
has mainly aimed to train upper limb function [9,10] or trunk function [25], and a few
reports have examined the effects on gait using kinematic data. Furthermore, this exercise
is not commonly prescribed to improve gait in hallux valgus cases. Therefore, whether
the results observed in this study could also be obtained by performing the exercise by
therapists would need to be compared in further studies.
On the contrary, the effects of VR therapy on deformity or pain were not observed inthis study. Footwear and orthosis reduced hallux valgus-induced pain [26] and prevented
severe deformity [27]. The interventions in this study focused on improving gait function
rather than reducing pain or deformity. Therefore, VR therapy in this study should be
combined with treatment for pain and prevention of severe deformity.
This study has some limitations. In this study, there was neither improvement nor
enhancement of the hallux valgus throughout the intervention period. However, in feetInt. J. Environ. Res. Public Health 2021, 18, 13267

8 of 9with persistent hallux valgus, incorrect active use of the toes could exacerbate the deformity [4,5]. Thus, the risk of deterioration, as measured by hallux valgus angle and archheight, [24] should have been better documented while conducting interventional studies
for such cases with hallux valgus. Additionally, there was an inability to load the hallux
and abnormal thoracic and pelvic movements during gait, which improved after the intervention. In this exercise, loading of the pelvis and lower limbs, which is necessary duringgait, is repeated while sitting. This may have activated the center of gravity shift andplantar sensation during gait and subsequently improved sensorimotor function. However,these mechanisms cannot be clarified because we did not record neurological data, such as
electromyography of the trunk and lower limbs, during exercise therapy and gait. Hence,these issues should be examined in detail in further studies.
5. Conclusions
This study found that a 3-week VR-guided exercise improved toe function, plantar
sensation, and postural adjustment of the trunk and pelvis during gait in a patient who had
undergone surgery for hallux valgus, and the effects continued for 2 weeks. It is necessary
to examine whether this effect is evident in all cases of hallux valgus. In the future,
the VR-guided exercise in this study may be investigated for application in preventive
and therapeutic approaches for hallux valgus before surgery and in early treatment after
surgery.
Author Contributions: Conceptualization, M.N., A.K., and S.K.; methodology, M.N., A.K., M.K.,
M.H., and S.K.; software, M.H.; validation, M.N., A.K., and S.K.; formal analysis, M.N., A.K., T.M.,
and T.K.; investigation, M.N. and A.K.; resources, S.K.; data curation, M.N. and A.K.; writing—original draft preparation, M.N.; writing—review and editing, S.K.; visualization, M.N. and A.K.;
supervision, S.K.; project administration, S.K.; funding acquisition, M.N. All authors have read andagreed to the published version of the manuscript.
Funding: This work was funded by JSPS KAKENHI Grant Number JP21K17503.
Institutional Review Board Statement: This study was approved by the Research Ethics Review
Committee of Morinomiya University of Medical Sciences (reference number: 2020-006).
Informed Consent Statement: Informed consent was obtained from the subject involved in the
study.
Conflicts of Interest: Masahiko Hara is the chief executive officer and stockholder of mediVR, Inc.,a company that holds several patents on VR-guided, dual-task rehabilitation. However, this casereport did not receive any specific grant from the company. The other authors declare no conflict ofinterest associated with this manuscript.

References
1.
2.
3.
4.
5.
6.
7.
8.
9.

O’Leary, C.B.; Cahill, C.R.; Robinson, A.W.; Barnes, M.J.; Hong, J. A Systematic Review: The Effects of Podiatrical Deviations on
Nonspecific Chronic Low Back Pain. J. Back Musculoskelet. Rehabil. 2013, 26, 117–123. [CrossRef] [PubMed]
Koken, M.; Guclu, B. The Effect of Hallux Valgus Surgery on Quality of Life. J. Am. Podiatr. Med. Assoc. 2020, 110, 1–4. [CrossRef][PubMed]Hecht, P.J.; Lin, T.J. Hallux Valgus. Med. Clin. N. Am. 2014, 98, 227–232. [CrossRef]
Ford, L.A.; Hamilton, G.A. Procedure Selection for Hallux Valgus. Clin. Podiatr. Med. Surg. 2009, 26, 395–407. [CrossRef][PubMed]Duan, X.; Kadakia, A.R. Salvage of Recurrence After Failed Surgical Treatment of Hallux Valgus. Arch. Orthop. Trauma. Surg.
2012, 132, 477–485. [CrossRef]
Hawson, S.T. Physical Therapy Post-Hallux Abducto Valgus Correction. Clin. Podiatr. Med. Surg. 2014, 31, 309–322. [CrossRef]
Omon, K.; Hara, M.; Ishikawa, H. Virtual Reality-Guided, Dual-Task, Body Trunk Balance Training in the Sitting Position
Improved Walking Ability Without Improving Leg Strength. Prog. Rehabil. Med. 2019, 4, 20190011. [CrossRef] [PubMed]
Takimoto, K.; Omon, K.; Murakawa, Y.; Ishikawa, H. Case of Cerebellar Ataxia Successfully Treated by Virtual Reality-Guided
Rehabilitation. BMJ Case Rep. 2021, 14, e242287. [CrossRef]
Morikawa, T.; Katoh, H. Spinal Kyphotic Alignment Changes Spinal Movement Strategy During Lateral Reaching Motion While
in a Sitting Position. J. Phys. Ther. Sci. 2020, 32, 48–51. [CrossRef]

Int. J. Environ. Res. Public Health 2021, 18, 13267

10.
11.
12.

13.
14.
15.
16.
17.
18.
19.
20.
21.
22.
23.
24.
25.
26.
27.

9 of 9Kim, C.Y.; Lee, J.S.; Lee, J.H.; Kim, Y.G.; Shin, A.R.; Shim, Y.H.; Ha, H.K. Effect of Spatial Target Reaching Training Based on Visual
Biofeedback on the Upper Extremity Function of Hemiplegic Stroke Patients. J. Phys. Ther. Sci. 2015, 27, 1091–1096. [CrossRef]
Leung, A.K.; Cheng, J.C.; Zhang, M.; Fan, Y.; Dong, X. Contact Force Ratio: A New Parameter to Assess Foot Arch Function.
Prosthet. Orthot. Int. 2004, 28, 167–174. [CrossRef]
Hausdorff, J.M.; Nelson, M.E.; Kaliton, D.; Layne, J.E.; Bernstein, M.J.; Nuernberger, A.; Singh, M.A. Etiology and Modification ofGait Instability in Older Adults: A Randomized Controlled Trial of Exercise. J. Appl. Physiol. 2001, 90, 2117–2129. [CrossRef][PubMed]Bell-Krotoski, J. Advances in Sensibility Evaluation. Hand Clin. 1991, 7, 527–546. [CrossRef]
Galica, A.M.; Hagedorn, T.J.; Dufour, A.B.; Riskowski, J.L.; Hillstrom, H.J.; Casey, V.A.; Hannan, M.T. Hallux Valgus and Plantar
Pressure Loading: The Framingham Foot Study. J. Foot Ankle Res. 2013, 6, 42. [CrossRef]
Herron, M.L.; Kar, S.; Beard, D.; Binfield, P. Sensory Dysfunction in the Great Toe in Hallux Valgus. J. Bone Jt. Surg. Br. 2004, 86,
54–57. [CrossRef]
Kimoto, Y.; Hasegawa, M.; Kanai, S. Relationship Between the Sense of Touch and Plantar Pressure for the Entire Sole of the Foot.
J. Phys. Ther. Pract. Res. 2011, 20, 85–89. (In Japanese)
Kimura, K.; Endo, Y. Age-Related Changes in the Tactile Pressure Sensitivity Threshold in the Sole of the Foot in Diabetic Patients.
J. Phys. Ther. Sci. 2018, 30, 917–920. [CrossRef]
Perry, J.; Burnfield, J. Gait Analysis: Normal and Pathological Function, 2nd ed.; Slack Inc.: Philadelphia, PA, USA, 2010; pp. 121–127.
Thorstensson, A.; Nilsson, J.; Carlson, H.; Zomlefer, M.R. Trunk Movements in Human Locomotion. Acta. Physiol. Scand. 1984,
121, 9–22. [CrossRef] [PubMed]
Waters, R.L.; Morris, J.; Perry, J. Translational Motion of the Head and Trunk During Normal Walking. J. Biomech. 1973, 6, 167–172.
[CrossRef]
Gard, S.A.; Knox, E.H.; Childress, D.S. Two-Dimensional Representation of Three-Dimensional Pelvic Motion During Human
Walking: An Example of How Projections Can Be Misleading. J. Biomech. 1996, 29, 1387–1391. [CrossRef]
Hausdorff, J.M.; Edelberg, H.K.; Mitchell, S.L.; Goldberger, A.L.; Wei, J.Y. Increased Gait Unsteadiness in Community-dwelling
Elderly Fallers. Arch. Phys. Med. Rehabil. 1997, 78, 278–283. [CrossRef]
Doi, T.; Makizako, H.; Tsutsumimoto, K. Gait Variables from Trunk Acceleration and Fall Among Community-Dwelling Older
Adults. J. Jpn. Phys. Ther. Assoc. 2016, 43, 75–81. (In Japanese)
Park, C.H.; Chang, M.C. Forefoot disorders and conservative treatment. Yeungnam Univ. J. Med. 2019, 36, 92–98. [CrossRef]
Santamaria, V.; Rachwani, J.; Manselle, W.; Saavedra, S.L.; Woollacott, M. The Impact of Segmental Trunk Support on Posture andReaching While Sitting in Healthy Adults. J. Mot. Behav. 2018, 50, 51–64. [CrossRef] [PubMed]
Ying, J.; Xu, Y.; István, B.; Ren, F. Adjusted Indirect and Mixed Comparisons of Conservative Treatments for Hallux Valgus: A
Systematic Review and Network Meta-Analysis. Int. J. Environ. Res. Public. Health. 2021, 18, 3841. [CrossRef] [PubMed]
Budiman-Mak, E.; Conrad, K.J.; Roach, K.E.; Moore, J.W.; Lertratanakul, Y.; Koch, A.E.; Skosey, J.L.; Froelich, C.; Joyce-Clark, N.
Can Foot Orthoses Prevent Hallux Valgus Deformity in Rheumatoid Arthritis? A Randomized Clinical Trial. J. Clin. Rheumatol.
1995, 1, 313–322. [CrossRef] [PubMed]