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Preventive Knee Braces 2003 |
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Preventive Knee Braces
2003
Basis for Current Recommendations
Basis for AAOS Position Statement
John Albright, MD
Valgus Contact in Football
Frequent Injuries: MCL + ACL
Anderson, ATC
Prevents valgus
Restricts AP
displ
The Anderson Knee
Stabler
Physician & Sports
Medicine, 1979
AAOS 1987
Preventive Knee Braces
•
Not proven
effective
•
May contribute
to injury
“Need Studies…”
•
Biomechanical
•
Functional
performance
•
Epidemiological
Biomechanical
Studies
•
Cadavers
•
Surrogate models
“Surrogate”
Knee Model Studies
Iowa Model #1
•
Poly lig. blanks
•
Thigh cuff
Iowa Model #1
•
Poly lig. blanks
•
Thigh cuff foam
•
Matched cadaver
values
–
knee stiffness
–
failure load
Relative Strain
Attenuation
MCL length
unbraced
vs
braced
Iowa Model #1
Relative Strain
McDavid 14%
DonJoy
23%
AmPro 25%
Anderson
30%
Iowa Model #1
Relative Strain
McDavid 14%
DonJoy 23%
AmPro 25%
Anderson 30%
Lenox Hill
46%
Utah Model #2
ACL Protection ?
•
Higher loads
•
High speed photo
•
Muscle forces
•
Weight bearing
Utah Model #2
Can we build a better brace?
•
Hinge effect
•
Thigh linkage
length
•
Upright
thickness
•
Breadth
•
Length
•
Cuff size
Utah Model #2
Optimized Decision Study
•
Hinge effect
•
Thigh linkage
length
•
Upright
thickness
•
Breadth
•
Length
•
Cuff size
Utah Results
•
for MCL
–
DonJoy
–
Anderson
•
for ACL
–
DonJoy
•
avoid
brace-joint contact
–
longest
–
stiffest
Utah Model #2
Conclusions
•
ACL > MCL
•
Stiffer braces
better
•
Better braces:
cuffs
Iowa Model #2
Can we build a better brace?
Iowa Model #2
Conclusions
•
Upright
thickness
•
Customize to fit
Vermont Model
“…previous models lacked…”
•
MCL fiber
orientation
•
Geometry all
ligaments
•
Soft tissue
compliance
Vermont Model
In vitro study of
PKBs
Cadaver ctr
Foam sleeve
Force trans
•
Muscle tension
•
Weight bearing
•
Knee brace
medial
Biomechanics
Testing PKBs
Summary
•
MCL
–
Some rel strain relief
–
knees straight
•
ACL
–
uncertain
–
Need improved thigh fixation
“Need Studies…”
•
Biomechanical
•
Functional
performance
•
Epidemiological
Brace Performance
Tests
Intramuscular Pressure
•
Resting
pressure (0.002)
•
Muscle
relaxation pressure (0.001)
•
Premature
fatigue
PKB Performance
Tests
Braced Leg Muscle Function
Torque
output 12 - 30%
related to
speed
Extension
velocity 20%
Blood
lactate 41%
On Field Brace
Performance
Rotation +
add/abd
Strength or
speed no effects
–
experienced
–
stronger
–
larger wearers
–
better braces
Will Brace Migrate?
Parameters tested
Dash Speed
Migration
PKB’s
•
Hard to keep up
•
May decrease
speed and endurance
•
Best performance
in worst braces
Brace Suspension
•
Customized fit
•
Velcro patches
•
Panty girdles
Velcro & “Panty
hose”
“Need Studies…”
•
Biomechanical
•
Functional
performance
•
Epidemiological
West Point Study
PKB Efficacy in
Football
DonJoy
“Protector Knee Guard”
•
Off-the-shelf
•
2 hinges + 1
upright
•
Straps + Taped
•
24% relative
strain protection (Iowa study)
West Point Study
•
1396 cadets
•
Random selection
•
Inspected -
taped daily
•
Converse
multi-cleated shoes
•
Grass fields
West Point Study
•
Examined within
1 hour
•
Ex 2 / 3 MD’s
•
ACL’s scoped
•
KT-1000
Knee Sprain Rate
All Players
•
Control 3.4
/ 1000exp
•
Braced
1.5/ 1000exp
Knee Sprain Rate
Defensive players
•
All injuries
•
MCL sprains
Knee Sprain
Severity
(Fischer exact probability 0.81)
“trend only”
•
ACL partial
tears
•
MCL mild sprains
Ankle Sprain Rate
All players
No knee brace
effect
Prophylactic
Bracing:
Big 10 Surveillance Study
Virgin Knee Study
John Albright, M.D.
John Powell, Ph.D., ATC
Big 10 Sports Medicine Committee
“MCL Sprain”
•
Tenderness
•
Pain on valgus
stress
•
+/- laxity
Pilot Study
•
Nobody wore
brace all the time!
•
Braces
“necessary evil”
Brace worn when concern for injury greater than for speed
Brace wear preference varies with perception of danger
•
Need daily
record: “brace” - ”no brace”
•
Need to compare
players at similar risk
Comparison of studies
Recorded Knee
Injuries
•
182 Total
•
100 MCL’s
Severity
(MCL Sprains)
•
Mild
78
•
Moderate 14
•
Severe 8
Unbraced Knee
Injury Rates Vary
•
Session
•
String
•
Position
String is 2nd
most important factor
Position is 3rd
most important factor
Brace Wear
Preferences
Practices
•
Non player
linemen
–
2 x injury rate
–
Braces most frequent (85%)
Given all else equal,
IS THE PKB EFFECTIVE?
Brace is 4th
most important factor
Compare Similar
Group
•
Session
•
Position
•
String
•
Brace wear
Statistical
Analysis
(Avoid Selection Bias)
•
Risk is not
equal for all
•
Repartition data
base
•
Multivariate
analysis
Conclusion
(MCL Sprains)
•
Most influential
facts are “session”, “string”, and “position”
•
All else equal,
braces tend to protect
•
Greatest for
linebackers & tight ends
Big 10 Study
Are PKB’s in use 10 years later?
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8 of 10 teams
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Line & LB-TE
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Close game -
“off”
•
MCL sprain -
“on”
PKB’s
(Epidemiology study summary)
•
Do not put ankle
at risk
•
Add 20-40%
strain relief
•
Studies suggest
effectiveness
•
Benefit position
dependent
Parental Advice for
“Virgin Knees”
•
Yes
–If lineman
–If linebacker
–If tight end
Parental Advice
After MCL Sprain
Mild………..PKB
Moderate……Functional
Previous Severe
Sprain
•
Cast molded
brace best
•
40 - 60%
stronger
•
Unloader
braces???
Future Brace
Improvements ?
•
Contour braces
on site
•
Friction free
polycentric joints
•
Decompress
attachment system
–
Part of uniform?
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