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647
UHM 2019, VOL. 46 NO. 5 –HYPERBARIC OXYGENATION AFFECTS VASCULAR RELAXATION UHM 2019, VOL. 46 NO. 5 – EFFECTS OF HBO2 ON GRADE 2 MCL INJURY
Copyright © 2019 Undersea & Hyperbaric Medical Society, Inc.
RESEARCH ARTICLE
Eects of hyperbaric oxygen therapy on recovery acceleration in Japanese
professional or semi-professional rugby players with grade 2 medial collateral
ligament injury of the knee: A comparative non-randomized study
Kazuyoshi Yagishita, MD 1,2, Mitsuhiro Enomoto, MD 1,2, Yuji Takazawa, MD 3,
Jun Fukuda, MD 4, Hideyuki Koga, MD 5
1 Hyperbaric Medical Center, Tokyo Medical and Dental University
2 Clinical Center for Sports Medicine and Sports Dentistry, Tokyo Medical and Dental University
3 Department of Orthopaedic Surgery, Juntendo University School of Medicine
4 Department of Health and Sports, Fujisawa Shounandai Hospital
5 Department of Orthopaedic Surgery, Tokyo Medical and Dental University
CORRESPONDING AUTHOR: Kazuyoshi Yagishita – yagishita.orth@tmd.ac.jp
____________________________________________________________________________________________________________________________________________________________________
______________________________________________________________________________________________________
KEYWORDS: hyperbaric oxygen therapy; medial collateral ligament; return to play; pain reduction; recovery acceleration
Introduction: The effects of hyperbaric oxygen (HBO2)
therapy on sprains, ligament injuries, and muscle strains
have been reported in several animal studies. In a dog model
of compartment syndrome and in a rat contused skeletal
muscle injury model, the significant effects of HBO2 therapy
on the reduction of edema and muscle necrosis have been
reported. In basic research HBO2 therapy stimulated fibroblast
activity to improve the healing process. Because of this it
expected that HBO2 therapy might improve focal edema
and pain in the acute phase and accelerate the healing of
injured tissues in athletes with a medial collateral ligament
(MCL) injury of the knee. This study aimed to examine the
short-term effects of HBO2 application subjectively, and the
long-term effects of HBO2 therapy in Japanese professional
or semi-professional rugby players with grade 2 MCL injury
of the knee.
Methods: Thirty-two professional or semi-professional
rugby players with grade 2 MCL injury of the knee were
ABSTRACT
investigated. First, in the HBO2 group (n=16), HBO2 therapy
was performed during the acute phase. Visual analog scales
(VASs) immediately before and after HBO2 therapy on the
same day were compared. Next, we retrospectively evaluated
the time to return to play in the HBO2 (n=16) and non-HBO2
(n=16) groups.
Results: VAS scores for pain while walking immediately
before and after HBO2 therapy on the same day were 37.4 ± 20.1
(mean ± standard deviation) and 32.4 ± 21.8, respectively
(p<0.001). The VAS scores for pain while jogging were
50.7 ± 25.6 and 43.9 ± 25.0, respectively (p<0.001). The
time to return to play was 31.4 ± 12.2 days in the HBO2 group
and 42.1 ± 15.8 days in the non-HBO2 group, indicating a
significant difference between the groups (p<0.05).
Conclusion: HBO2 therapy may reduce pain and accelerate
the return to play in athletes with grade 2 MCL injury of the
knee in this non-randomized study. z
____________________________________________________________________________________________________________________________________________________________________
INTRODUCTION
Aer sustaining injuries during sports, athletes are usually
required – and desire – to return to competition rapidly.
In particular, high-level athletes are required to return
to play as soon as possible. erefore, safe and eective,
multidisciplinary treatments should be established. Ath-
letes prefer such therapies, as they accelerate their return
to competition.
Injury to the medial collateral ligament (MCL) of the
knee is a frequently encountered sports injury. e inci-
dence rate of MCL injury during sports activity ranges
from 0.04 to 3.1 MCL injuries per 1,000 hours of athlete
exposures (AEs) [1-3]. Moreover, the incidence rate
during rugby competitions is relatively high [1].
As with other so-tissue injuries, MCL injury under-
goes four stages of healing. ese include: hemorrhage,
648
UHM 2019, VOL. 46 NO. 5 – EFFECTS OF HBO2 ON GRADE 2 MCL INJURY
Yagishita K, Enomoto M, Takazawa Y, et al.
inammation, repair, and remodeling [4,5]. e acute
inammatory phase is characterized by edema, pain, and
a limited range of motion, which prevents aected in-
dividuals from returning to sports activities. A rapid
reduction of pain and tissue edema at the injured site
during the acute phase would accelerate the healing
potential and reduce the time to return to previous
levels of competition.
Hyperbaric oxygen (HBO2) therapy has been noted
as eective for wound healing and so tissue injury,
including crush injury and compartment syndrome [6-10].
e eects of HBO2 therapy on so tissue injuries during
sports activities, including sprains, ligament injuries,
contusions, and muscle strains, have been reported by
several basic and clinical studies [11].
In the acute phase, HBO2 therapy improves hypoxic
tissue microcirculation following a reduction in edema.
In a dog model of compartment syndrome, signicant
eects of HBO2 therapy on the reduction of edema and
muscle necrosis have been reported [11-13] In animal
research HBO2 therapy stimulated broblast activity to
improve the healing process [14], and promoted liga-
ment healing and maximum failure load aer injury in
the remodeling phase in a rat model [15-17]. Clinical-
ly, HBO2 therapy may provide short-term eects such
as reducing edema and pain in athletes with acute an-
kle sprain, as shown in a pilot study [29]. James, et al.
rst documented the quantitative eectiveness of HBO2
therapy in sports injuries. In this preliminary report the
actual days of untness compared to the estimated days
assessed by the club physiotherapist resulted in a 70%
decrease in injury time for returning to football activities
in Scotland [36].
We reasoned therefore that HBO2 therapy might help
improve focal edema and pain in the acute phase
and accelerate the healing of injured tissues in athletes
with MCL injury of the knee. However, Barata, et al.
documented a literature review that demonstrates that
although results have proven to be promising in terms
of using HBO2 as a treatment modality in sports-related
injuries, these studies have been limited due to the small
sample size, lack of blinding, and issues with ran-
domization [22]. As there have been few quantitative
evaluations of HBO2 therapy for MCL injury, HBO2
eectiveness has not been claried in detail.
is comparative non-randomized study aimed to
evaluate the clinical ecacy of HBO2 therapy in athletes
with grade 2 MCL injury of the knees. e subjects in this
study included professional or semi-professional rugby
players. e primary outcome was dened as the short-
term eects of HBO2 therapy in the HBO2 group in the
acute phase of injury in terms of subjective VAS evalu-
ation compared immediately before and aer HBO2
therapy. e secondary outcome was dened as the
long-term eects of HBO2 in terms of the time to return
to play compared between the HBO2 and non-HBO2
groups.
MATERIALS AND METHODS
is study was approved by the institutional review
board of Tokyo Medical and Dental University in 2007.
Each subject in the HBO2 group provided written in-
formed consent before participating in the study and
starting HBO2 therapy. is study was undertaken in
full accordance with the ethical standards in the
Declaration of Helsinki.
Subjects
A total of 32 professional or semi-professional rugby
players with grade 2 MCL knee injury that occurred
during sports activity and during the rugby season that
extended from June to January were investigated in
this study. All subjects belonged to the “Top League”
Japanese rugby league, which is the top category of the
Japanese Rugby Federation.
e diagnosis of grade 2 MCL injury was made via
clinical examination by the authors, who were the
team medical doctors. eir specialty was orthopedics
and sports medicine, and they possessed a keen ability to
diagnose injuries accurately.
e grade of MCL injury was judged by manual
examination as follows, and any right-le asymmetry
was considered a positive nding:
A) grade 1: negative instability in the manual valgus
stress test at full extension and at 30 degrees of knee
exion, and positive tenderness at the injured MCL
site;
B) grade 2: negative instability in the manual valgus
stress test at full extension, and positive instability
in this test at 30 degrees of exion; and
C) grade 3: positive instability in the manual valgus
stress test at full extension and at 30 degrees of exion
(Table 1).
Exclusion criteria included a past history of MCL injury
and/or other knee joint injuries including anterior cruciate
ligament injury or meniscus injury.
From 2007 to 2011 all the patients with grade 2 MCL
injury during the acute phase within six days of injury
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UHM 2019, VOL. 46 NO. 5 – EFFECTS OF HBO2 ON GRADE 2 MCL INJURY UHM 2019, VOL. 46 NO. 5 – EFFECTS OF HBO2 ON GRADE 2 MCL INJURY
Yagishita K, Enomoto M, Takazawa Y, et al.
in four teams were referred to our hospital. All the cases
were included in this study. All the cases were enrolled,
consented, and underwent treatment with HBO2 therapy
(HBO2 group, n=16). From 2001 to 2006, patients with
grade 2 MCL injury were not administered HBO2 therapy
and were determined as the non-HBO2 group (n=16).
e data in the non-HBO2 group were collected from
their team doctors or their trainers.
Hyperbaric oxygen therapy protocol
e HBO2 chamber in our hospital is a multiplace unit
capable of holding 16 patients (NHC-412-A, Nakamura
Tekko-Sho Corp., Tokyo, Japan). In this series HBO2 ther-
apy was performed using 2.8 atmospheres absolute (ATA)
(283.6 kPa) for 60 minutes. In the HBO2 group (n=16),
HBO2 application started as soon as possible, including
the same day of injury (Day 0). Each patient received a
total of ve HBO2 treatments within 10 days aer injury.
Treatment and rehabilitation protocol post injury
All subjects underwent treatment assuming that they
would be participating in a competitive match within the
same season. e treatment and rehabilitation protocols
aer injury continued to be non-surgical and included
initial rest, cryotherapy, compression, elevation, and re-
striction of weight bearing in the acute phase within
72 hours [31]. Patients were advised on early rehabilita-
tion, including early range of motion and strengthening
exercise of the quadriceps and hamstrings in a standard
fashion. Weight bearing was permitted as soon as possible
with use of a hinged knee brace when the athlete had mod-
erate or severe pain [31-33]. Finally, aer patients’ muscle
strength, proprioception, agility, and cardiopulmonary
function had recovered to levels that were comparable to
the contralateral side, the patients were permitted to re-
turn to play. e medical sta members for all teams
checked this protocol, and conrmed their treatments
according to this protocol.
Evaluation
Short-term eects of HBO2 therapy on the subjective
evaluation of pain: VAS evaluation
First, in the HBO2 group, VAS scores were used to sub-
jectively evaluate pain. ese scores were compared
immediately before and aer HBO2 therapy on the
same day, which means that we assessed dierences in
the 117-minute treatment. In the VAS evaluation, such
question items of pain at rest, pain while walking, and
pain while jogging were included. VAS scores consisted
of 100 points at full marks, with the worst condition
being 100 points and no complaint being 0 points.
Long-term eects of HBO2 therapy
on time to return to play
Second, time to return to play in the HBO2 (n=16) and
non-HBO2 (n=16) groups was compared. e day of
return to play was determined as the day the athlete
participated in a competitive match. In the non-HBO2
group the time to return to play was retrospectively in-
vestigated through the team medical records, to which
two of the authors had access as medical team doctors.
In addition, we analyzed time to return to play regard-
ing teams and eld positions in all cases (n=32). We also
analyzed time to return to play regarding teams, po-
sitions, number of HBO2 treatments and early or late
application of HBO2 in the HBO2 group (n=16).
Statistical analysis
In this study data were shown as mean ± SD. Statistical
analyses were performed using the Wilcoxon signed rank
test for the VAS evaluation, and the Mann-Whitney U
test for the evaluation of time to return to play between
the HBO2 and non-HBO2 groups, and time to return to
play regarding positions, length of HBO2 treatment time
and early or late HBO2 application. e Kruskal-Wallis
test was performed for the evaluation of time to return
to play among the teams.
All data were analyzed using SPSS version 19.0 (IBM,
Armonk, New York, U.S.). e signicance level for
statistical analysis was set at p<0.05.
RESULTS
Demographics of the subjects
HBO2 group: Mean age of subjects in the HBO2 group
was 27.2 ± 3.3 (range; 22-32) years and all were male.
Subjects in the HBO2 group belonged to these teams:
A (six patients); B (four patients); C (three patients);
or D (three patients) among 14 teams in the top Japa-
__________________________________________________________________________
Table 1. Diagnosis of the grade of MCL injury
__________________________________________________________________________
instability by
manual valgus test tenderness
at full at 30 degrees at the injured
extension of exion MCL site
______________________________________________________________________
Grade 1 (–) (–) (+)
Grade 2 (–) (+) (+)
Grade 3 (+) (+) (+)
__________________________________________________________________________
650
UHM 2019, VOL. 46 NO. 5 – EFFECTS OF HBO2 ON GRADE 2 MCL INJURY
Yagishita K, Enomoto M, Takazawa Y, et al.
nese rugby league. Rugby positions were distributed as:
11 forwards and ve backs, with the right knee aected
in 8 patients and the le knee aected in eight patients
(Table 2). e mean number of days from injury to the
rst HBO2 session was 2.2 ± 1.4 (range; 0-6) days. Five
HBO2 treatments were recommended. However, average
number of HBO2 sessions was 4.6 ± 0.7 (range; 3-5).
In total, 73 courses of HBO2 were performed in 16
patients (three treatments in two patients, four treat-
ments in three patients, ve treatments in 11 patients).
Non-HBO2 group: Mean age was 27.0 ± 2.0 (range; 24-
31) years and all were male. Subjects in the non-HBO2
group belonged to teams A (six patients) or C (10 patients).
Rugby positions were distributed as follows: six forwards
and 10 backs, with the right knee aected in eight patients
and the le knee aected in eight patients (Table 2). Two
of the authors were medical doctors from teams A and C,
respectively. ey managed the medical protocol and
records including the recovery process and time to re-
turn to play. ere were no statistical dierences in age,
body weight, or height between the HBO2 and non-HBO2
groups.
VAS evaluation in the HBO2 group
We used 58 VAS scores obtained from 13 patients for
analysis, excluding three subjects for whom there was
insucient data. e VAS scores regarding pain at rest
immediately before and aer HBO2 therapy on the same
day were: 18.8 ± 17.7 and 17.3 ± 16.4, respectively (p=0.11),
for pain while walking; 37.4 ± 20.1 and 32.4 ± 21.8, respec-
tively (p<0.001); and for pain while jogging, 50.7 ± 25.6
and 43.9 ± 25.0, respectively (p<0.001) (Figure 1).
Time to return to play between the HBO2 group
and the non-HBO2 group
All subjects were able to participate in a competitive
match aer injury within the same season. Time to
return to play was 31.4 ± 12.2 (range; 10-58) days in the
HBO2 group and 42.1 ± 15.8 (range; 18-71) days in the
non-HBO2 group (Figure 2). ere was a signicant
difference between the two groups (p<0.05).
Time to return to play regarding teams, positions,
number of HBO2 treatments, and early or late
application of HBO2
Regarding time to return to play there were no signicant
dierences among the teams, but there were statistical
dierences between positions (Table 3). Regarding the
number of HBO2 treatments, time to return to play was
21.6 ± 9.6 (range; 10-38) days in the three- or four-
treatment HBO2 group (n=5) and 35.8 ± 9.9 (range;
25-58) days in the ve-treatment HBO2 group (n=11).
ere was a signicant dierence between the groups
(p<0.05). Regarding early or late HBO2 application,
time to return to play was 27.9 ± 9.3 (range; 10-41) days
in the early HBO2 group within two days aer injury
(n=11) and 39.0 ± 13.1 (range; 23-58) days in the delayed
HBO2 group three to ve days aer injury (n=5). ere
were no significant differences between the groups.
DISCUSSION
e healing process of so tissue injury, which includes
MCL injury, is divided into the inammatory or acute,
proliferative, and remodeling phases. In the acute or
inammatory phase, focal injured so tissue is charac-
terized by tissue hypoxia microvascular dysfunction, tissue
ischemia and hypoxia, and edema [5]. HBO2 therapy
can mitigate resolve tissue hypoxia by increasing dis-
solved oxygen tension. MCL injury in the acute phase
is also characterized by edema, pain, and limited range
of motion; hence, rapid reduction of pain and tissue
edema at the injured site in the acute phase could
also accelerate the healing process and return to play.
Skyhar, et al. reported the eects of HBO2 on tissue
edema and necrosis of muscle in the dog compart-
ment model associated with hemorrhagic hypotension.
ey concluded that those ndings might be the results
of improvement of oxygenation of hypoxic tissue and
reduction of edema, which came from reductions in
serum and hematocrit leakage, resorption of extracellular
uid, and improvement in local circulation [11]. ey
mentioned that the mechanisms – i.e., hyperoxygenation
and vasoconstriction [12] – were similar to those of the
_________________________________________________________________________________________________________________________________________________________
Table 2. Patient distribution
_________________________________________________________________________________________________________________________________________________________
position aected side
n age (years) height (cm) body weight (kg) forwards (n) backs (n) right (n) le (n)
_________________________________________________________________________________________________________________________________________________________
HBO2 16 27.2 ± 3.3 (22-32) 182.l ± 9.3 97.3 ± 14.4 11 5 8 8
Non-HBO2 16 27.0 ± 2.0 (24-31) 180.5 ± 7.5 89.0 ± 10.9 6 10 8 8
_________________________________________________________________________________________________________________________________________________________
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UHM 2019, VOL. 46 NO. 5 – EFFECTS OF HBO2 ON GRADE 2 MCL INJURY UHM 2019, VOL. 46 NO. 5 – EFFECTS OF HBO2 ON GRADE 2 MCL INJURY
Yagishita K, Enomoto M, Takazawa Y, et al.
dog compartment syndrome model in the normotensive
state reported by Strauss, et al.
Using a rat contused skeletal muscle injury model
Oyaizu, et al. reported that HBO2 therapy reduced
muscle wet weight, and decreased the extracellular space
and vascular permeability, which resulted in rapid reduc-
tion of edema [30].
Regarding the eects of HBO2 therapy on ligament
healing, the results of several animal research studies have
been reported. Horn, et al. used a rat model of surgical
MCL laceration with HBO2 therapy exposure at 2.8 ATA
for 1.5 hours a day for ve days aer surgery [15]. Maxi-
mum failure load and stiness at two, four, six and
eight weeks were analyzed. e maximum failure load
and stiness at four weeks in the HBO2 group were statis-
tically greater than in the control group. Moreover, the
HBO2 group reached normal levels at four weeks. How-
ever, the HBO2 group at six weeks was not statistically
dierent from the control group, which suggested that
HBO2 therapy accelerated the return to normal ligament
level.
Mashitori, et al. created a 2-mm segment of MCL in a
rat model and applied HBO2 therapy at 2.5 ATA for two
hours a day for ve days. Maximum failure load and
type I procollagen gene expression at 14 days in the
HBO2 groups statistically increased in conjunction with
HBO2 application[16]. Ishi, et al. examined the eects
of three dierent HBO2 exposures on the healing of rat
patellar ligament injury: HBO2 exposures included 1.5
ATA for 30 minutes, 2.0 ATA for 30 minutes, and 2.0
ATA for 60 minutes once a day and for 10 sessions. Aer
two weeks, HBO2 therapy at 2.0 ATA for 60 minutes was
___________________________________________________________________________
FIGURE 1
VAS scores immediately before HBO2 and after HBO2
___________________________________________________________________________
FIGURE 2
Time to return to play in the non-HBO2 and HBO2 groups
___________________________________________________________________________ ___________________________________________________________________________
§: p<0.05
*: p<0.001
___________________________________________________________________________ ___________________________________________________________________________
____________________________________________________________________________________________________________________________________________________________
Table 3. Time to return to play regarding the teams and positions
____________________________________________________________________________________________________________________________________________________________
HBO2 non-HBO2
Team Number Forwards (n) Backs (n) subtotal Number Forwards (n) Backs (n) subtotal
____________________________________________________________________________________________________________________________________________________________
A 6 27.3±11.0 (4) 43.5±5.5 (2) 32.5±12.0 (6) 6 52.0±19.0 (2) 40.3±11.3 (4) 44.2±15.4 (6)
____________________________________________________________________________________________________________________________________________________________
B 4 25.5±2.5 (2) 26.5±3.5 (2) 26.0±3.1 (4)
____________________________________________________________________________________________________________________________________________________________
C 3 31.5±6.5 (2) 58 (1) 40.3±13.6 (3) 10 42.5±14.5 (4) 39.7±15.3 (6) 40.8±15.1 (10)
____________________________________________________________________________________________________________________________________________________________
D 3 27.3±11.0 (3) 27.3±11.0 (3)
____________________________________________________________________________________________________________________________________________________________
Total 16 27.6±26.6 (11)* 41.2±12.0 (5)* 31.4±12.2 (16) 16 45.7±16.7 (6) 39.9±13.9 (10) 42.1±15.8 (16)
____________________________________________________________________________________________________________________________________________________________
statisitical dierence between forwards and backs *: p<0.05 (average ± SD days)
652
UHM 2019, VOL. 46 NO. 5 – EFFECTS OF HBO2 ON GRADE 2 MCL INJURY
Yagishita K, Enomoto M, Takazawa Y, et al.
the most eective, resulting in enhanced extracellular
matrix deposition as measured by collagen synthesis
[17]. Possible mechanisms of action of HBO2 on ligament
injury include reduction of edema and swelling, and
promotion of broblast proliferation in the scar tissue
to produce more type I procollagen mRNA[16].
Clinical reports of the time loss due to MCL injury
had been variously documented. e time loss in grades
2 and 3 MCL injury in the U.S. Military Academy study
was reported as 29 days [2], and the Union of European
Football Association injury study reported 23 ± 23 days
of layo time in 346 MCL injuries [34]. Derscheid, et
al. reported a mean return to football within 20 days in
patients with grades 1 or 2 MCL injuries who were treated
non-operatively [35]. Regarding rugby, especially in high-
level rugby players at a professional or semi-professional
level, Dallalana, et al. reported knee injuries in the English
professional rugby union, and documented a time loss of
41 days in grade 2 MCL injury [1].
However, clinical data is scarce regarding the short- and
long-term eects of HBO2 therapy in patients with MCL
injury. Moreover, little is known regarding its eect in
accelerating recovery time. Only Soolsma reported the
eects of HBO2 therapy on functional recovery during
the fourth, h and sixth week aer injury using a double-
blind controlled study. However, this study has not been
published as an original article but only as a university
report [28].
is study is the rst clinical report regarding the short-
term eects of HBO2 therapy on subjective symptoms
and the long-term eect of HBO2 therapy on return to
play, comparing an HBO2 group with a non-HBO2 group.
Time to return to play is inuenced by many factors,
including the athletic event; eld position; circumstances
of schedule; other conventional treatment protocols,
including RICE (rest, ice, compression and elevation)
treatment at the acute phase; and post-injury rehabili-
tation protocol. In this study, in order to minimize the
eect of subject bias, all subjects were professional or
semi-professional rugby players who belonged to the
same top category of the Japanese Rugby Federation.
In this study, the VAS scores regarding pain while
walking and jogging were signicantly reduced, which
indicated an increase in the short-term eect of HBO2
therapy. e VAS scores for pain at rest were not signi-
cantly dierent between immediately before and aer
HBO2 therapy, but the VAS scores while walking and
jogging were signicantly dierent. Walking and
bending the knee joint increased the tissue pres-
sure, and this increase exacerbated the knee pain
around the MCL. HBO2 application helps reduce ede-
ma and tissue pressure and would have eects on re-
duction of VAS scores during walking and jogging.
e time to return to play in the non-HBO2 group was
42.1 days, which is consistent with the Dallalana, et al.
report on conventional treatment in professional rugby
players. us, it was considered that the control group
of non-HBO2 therapy in this study was suitable, and the
time to return to play of 31.4 days in the HBO2 group
was judged as signicantly valuable data in regard to the
long-term eects of HBO2 therapy on the acceleration of
recovery. Regarding number of HBO2 treatments, there
was a signicant dierence between the three- or four-
treatment HBO2 group and the ve-treatment HBO2
group. We speculated that the subjects in the ve-
treatment HBO2 group might include cases of greater
severity.
LIMITATIONS
We recognize several limitations of this study. First, this
was not a prospective comparative study, and it is not
possible to exclude that factors related to the interven-
tion, including a possible placebo eect, may have con-
founded the results. e number of subjects was small, and
the injury periods of the HBO2 and non-HBO2 groups
were dierent. e subjects in this study belonged to the
top-level category; however, the HBO2 group included
four teams, whereas the non-HBO2 group included only
two teams. e results showed the wide range of recovery
time, which might include mild and severe cases of
grade 2 MCL injury for the subjects in this study. In
addition, it will be necessary to examine dierences
in the eects of HBO2 therapy on injured tissue com-
pared to non-injured healthy tissue, as well as conven-
tional therapies such as RICE treatment and/or use of
orthotics.
e VAS evaluations immediately before and aer
HBO2 therapy had the possibility to show only the
eects of the 117-minute rest. e VAS scores of the
patients who had not received HBO2 and simply had
117 minutes of rest would be more appropriate as a
control. In addition, the VAS evaluation in the non-HBO2
limb would be performed hopefully for comparing the
eects of HBO2 on the healthy limb and injured limb in
the future.
HBO2 can have positive eects on MCL injuries. How-
ever, practitioners should be cautious in using HBO2
therapy for off-label sports medicine injuries.
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UHM 2019, VOL. 46 NO. 5 – EFFECTS OF HBO2 ON GRADE 2 MCL INJURY UHM 2019, VOL. 46 NO. 5 – EFFECTS OF HBO2 ON GRADE 2 MCL INJURY
CONCLUSION
We examined the eects of HBO2 therapy on professional
or semi-professional Japanese rugby players with grade 2
MCL injury that occurred during sports activities. HBO2
therapy could have a short-term eect on pain reduction
during the acute phase, and a long-term eect on acceler-
ation of recovery with a decreased time to return to play.
n
Acknowledgments
We would especially like to thank Mr. Masuhide Udono
and Mr. Masahiro Furudate for their communication of
information on athletes, and all the medical engineers of
Hyperbaric Medical Center at Tokyo Medical and Dental
University for supporting this study.
Conicts of interest and source of funding statement:
Kazuyoshi Yagishita has received scientic grant from
YMFS YAMAHA Sports Challenge Fund.
For the remaining authors none were declared.
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