Use of ankle support orthoses to
prevent lateral ankle sprains in
military personnel
Ted Croy
Al Strickler
Jose Mattos
Anna Sedney
Ankle injuries in military personnel
• Military service: intensive physical training
– Initial Entry Training
– Cadet training
– Airborne Training
• Physical demands
– Running, sports, obstacles, carrying equipment, landing from
parachuting jumps
– High rates of ankle injuries
• Ankle injuries reduce performance, individual readiness,
unit readiness
– Stretching/tearing of ligaments
– Compromised joint stability
• Military health concern
Military Ankle Injury Background
• US Military Academy (West Point): longitudinal study of 104
ankle sprains. Gerber et al. 1998
– 6wks 95% returned to full function and 100% by 6mos
– 40% had persistent symptoms
• 8 year retrospective cohort study on lateral ankle sprains
–
–
–
–
–
active duty US military Cameron et al. J Athl Train, 2010
Ankle sprain incidence rate 34.95 per 1000 person years.
Defense Medical Surveillance System
IR is 5 times higher than studies reported in civilian population
Females are 21% more likely to sustain ankle sprain than males
• $16 million spent in treatment of ankle sprain related
injuries alone in military servicemembers. Gregg S. 2008
Ankle Injury Background
• US Army Center for Health Promotion and
Preventive Medicine
– Recommended use of prophylactic ankle braces for
unit level sports
• “Wear semirigid ankle braces for high-risk activities
(recommended).” Bullock et al. 2009
– Mandatory for certain military parachuting missions
• Lateral ankle sprains in sports are the main cause
of post-traumatic ankle osteoarthritis and are
associated with ligament instability. Valderrabano et al.
AJSM, 2005
Prophylactic Ankle Bracing
• Ankle brace use reduced lateral ankle sprains
in military parachutist trainees. Amoroso, J Trauma, 1998
– Non-brace wearers RR 6.9 versus brace wearers
• Soldiers are authorized to wear lace-up ankle
braces while in military physical training
uniform.
• SECDEF is authorized to institute injury
prevention measures as a means to improve
military health readiness
• Paratrooper use of lateral
ankle braces prior to
airborne mission.
Amoroso, Parachute Injury Brace Injury
Surveillance, 2005
ASO ankle support
• Nylon, laceup ankle
supportive orthosis that is
worn over the sock and
inside the athletic
shoe/cleat
• It is unknown if the use of
this brace reduces the
incidence rate of ankle
sprains in soldiers engaged
in “high-risk” activities.
Purpose
• Conduct RCT
• Randomized to company (n=100 per
company)
• Issue braces
• Measure new cases of lateral ankle sprain
• Compare
Intervention
• Mandatory brace use for all “high-risk” activity
during Initial Entry Training
– Running
– Competitive team sports: soccer, basketball,
football
– Obstacle course
– Rifle range
• Monitor reports of ankle injuries at Troop Aid
Stations
Objective
• Our Objective is to test the hypothesis, using
RCT, that an ankle orthotic will significantly
reduce the risk of first time ankle injury
among military trainees when engaged in high
risk activities.
• Hypothesis testing:
– Null (H0): Cexposed=Cunexposed
– Alternative (H1): Cexposed≠Cunexposed
Methods Overview
•
•
•
•
•
1. Randomize
2. Issue braces and train in use
3. Measurements over 1 year
4. Comparisons
5. Analyze
Methods Overview
Randomize
Training
Companies
FY2012
Brace
No Brace
Begin Initial
Entry training
Entry Physical
Receive Brace
Issue and
Training
(+) Lateral Ankle
Sprain
(-) Lateral Ankle
Sprain
No Brace Issue
(+) Lateral Ankle
Sprain
(-) Lateral Ankle
Sprain
Randomization
•
•
•
•
Company (n=100 per company)
A new company enters each week.
Each company trains for 8 weeks.
Prospective random assignment of each
company to brace (treatment) or no brace
(control).
• Partial Blinding
Brace Use
• Mandatory training
• Mandatory brace use for all “high-risk” activity
during Initial Entry Training
– Running
– Competitive team sports: soccer, basketball,
football
– Obstacle course
– Rifle range
Measurements
• Monitor total time that recruits are participating in high risk
activities (person-days [PD’s])
• By 8 week company training time.
• Monitor reports of ankle injuries at Troop Aid Stations
• Record values for total PD’s at risk and first time ankle
injuries in each group
• Prospectively identify covariates to be accounted for:
• Stratify and use multivariate analysis
• Age
• Sex
• Race
• Time of year
Comparisons
Wore brace
No brace
Total
Ankle injuries
a
b
M
Time at risk
T1
T0
T
Cexp
Cunex
• Combined data
• Crude Incidence rates
• Absolute Rate differences with CI’s (0)
• Incidence rate ratios with CI’s (1)
Analysis
• Attributable risk (AR): the absolute reduction in the risk of first ankle
injury in military recruits wearing a brace that can be attributed to
wearing a brace.
– AR=Cunexp-Cexp
• Population attributable risk (PAR): the absolute reduction in the risk of
ankle injury in the military recruits that can be attributed to the wearing a
brace.
– PAR=Cpop-Cexp
• Attributable risk percent (AR%): the percentage reduction in the risk of the
first ankle injury in military recruits wearing a brace attributed to wearing
a brace.
– AR%=(Cunexp-Cexp)/Cunexp*100
• Population attributable risk percent (PAR%): the percentage reduction in
the risk of first ankle injury in the military recruits attributed to wearing an
brace.
– PAR%=(Cpop-Cexp)/Cpop*100
Analysis
• Final hypothesis testing:
Wore brace
No brace
Total
Ankle injuries
a
b
M
Time at risk
T1
T0
T
Cexp
Cunex
• Determine p-value and compare to our set
significance level of p=0.05
Analysis: Other Concerns
• Other side effects
– Assess at medical visits and when necessary
• Cost benefit analysis
• Subjective feedback analysis
Traditional Limitations to RCTs
•
•
•
•
•
•
20
loss to follow-up
non-compliance
non-blinding
ethical
feasibility
cost
• blinding impossible
• possible reporting bias
21
Bias
• confounding
– randomization
– base-wide enrollment
• selection bias
– base-wide enrollment
– subjects have baseline physical fitness
• information bias
– most likely possible source of bias
22
Limitations
• sources of bias
– randomization by company, not individual
– global differences in training regimen
23
• large number of healthy prescreened subjects
being randomized should overcome many
possible sources of bias
24
• will have to follow possible increase in other
injuries - side effects of or caused by braces
• identify first vs recurrent ankle injuries
25
• homogenous test population
– results may apply to military but may not
generalize outside
26
Personnel
• Recruit Battalion Commanders
• Troop Aid Station physician assistants, medics,
providers
• Drill Instructors: train on fit/use of ASOs.
• Trainees: train on fit/use
Resources and Time-Frame
• We approximate new cohorts of 100 soldiers
every week
• Our budget will allow for 5,000 braces
– Approximately $20 per brace = $100,000
• Study will last approximately one year, or until
we use all 5,000 braces
Human Subject Issues
• Military personnel are a special population
• Injury prevention interventions are appropriate
and authorized
– Including helmets, uniforms, AND medical
experiments
• Still requires Army Medical Department IRB
approval
– In addition to commanding general approval and
medical post at site
– The difference is that the standards of what is
allowable are different than at an academic center,
etc.
Human Subject Issues
• Medical Exception
– Even though soldiers are consented to participate
by higher authorities there are still extenuating
circumstances
– If a soldier has a medical contraindication to use a
brace and is randomized to a “brace” group, then
the soldier will not be forced to wear one
– If a solider already has a medical necessity to wear
a brace and is randomized to a “non-brace” group,
then the soldier may keep the brace
Summary
• Are ankle orthoses effective at reducing the
risk of first ankle injuries in military recruits?
• If YES, we can move forward with integrating
their use during military high risk activities.
• At this point, we would work with military
officials and help with policy
recommendations to implement the
intervention.
References
• M Schmidt, S Sulsky, and P Amoroso,
“Effectiveness of an outside-the-boot ankle
brace in reducing parachuting related ankle
injuries,” Injury Prevention 11, no. 3 (June
2005): 163-168.
• http://www.mmbrace.com/medspecbraces/a
nklebraces/aso-ankle-support1.htm
• http://en.wikipedia.org/wiki/Incidence_%28e
pidemiology%29