Hip, Thigh, and Knee. ILIUM Acetabulum Ischium Ischial Tuberosity Pubis.
Knee-Thigh-Hip Injuries and Knee/Femur Compliance of the ...19 Thor Knee-thigh-hip Complex • To...
Transcript of Knee-Thigh-Hip Injuries and Knee/Femur Compliance of the ...19 Thor Knee-thigh-hip Complex • To...
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Knee-Thigh-Hip Injuries and Knee/Femur Compliance of the Hybrid
III, Thor-Lx, and Human Cadavers
Shashi Kuppa, NHTSAJonathan Rupp, UMTRILarry Schneider, UMTRI
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KTH Injury Scenario in Frontal CrashesKTH Injury Scenario in Frontal Crashes
Body motion
Bolster-to-knee impact force
Force applied at the knee is transmitted through the
thigh and to the hip
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Michigan CIREN Center
Mechanisms of injury Hip injuries in Frontal CrashesMechanisms of injury
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Risk of AIS 2+ Injury in Different Restraint Environments (NASS/CDS 1993-2001)
0%2%4%6%8%
10%12%14%
head
neck
thorax/ab
duppere
xlowere
x
KTHbelo
w knee
Ris
k of
AIS
2+
Inju
ries
bag+belt bag only belt only unrestr
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Annual LLI per 100 Front Seat Occupants in different Restraint Environments (NASS/CDS 1993-2001)
0123456789
10
head/fa
ce
neck
thorax/ab
duppere
xlowere
x
KTHbelo
w knee
LLI (
year
s) p
er 1
00 O
ccup
ants
belt+bag bag belt only unrestr
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Risk of KTH injuries of restrained occupants by air bag presence (NASS/CDS 1993-2001)
0.0%
0.1%
0.2%
0.3%
0.4%
0.5%
Airbag No Airbag
Ris
k of
AIS
2+
Inju
ry hip thigh knee
3-point belt restrained occupants
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Risk of KTH Injuries in air bag equipped vehicles by vehicle model year (NASS/CDS 1993-2001)
0.0%
0.2%
0.4%
0.6%
0.8%
pre93 93-96 97-01Vehicle Model Year
Ris
k of
Inju
ry
hip thigh knee
3-point belt restrained occupants
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FMVSS 208 and NCAP Test Data
02000400060008000
1000012000
87 88 89 90 91 92 93 94 95 96 97 98 99 00 01 02
Fem
ur F
orce
(N)
Model Year
FMVSS 208 (unrestrained HIII dummy in 48 km/h frontal crash)
0
20004000
6000
8000
1000012000
14000
86 87 88 89 90 91 92 93 94 95 96 97 98 99 00 01 02 03
Fem
ur F
orce
(N)
Model Year
NCAP (restrained HIII dummy in 56 km/h frontal crash
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Forc
e (k
N)
Time (ms)
0
5
10
15
20
25
0 10 20 30 40 50
Melvin 1980. SledPadded knee stop
Leung 1983. SledPadded knee stop
Powell, 1975. Rigidimpactor
Cheng, 1984. Sled1983 VW Rabbit bolster
Melvin 1976. Lightlypadded impactor
X
X
XX
X KTH fracture
FMVSS 208 compliance testresults from a 2000 Taurus
X
Loading Rates in Previous Studies
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Inertial Effects on Loading of the KTH Complex
Force
Forc
e
Distance along femur
Forc
e
t
knee
femur
hip
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0
4
8
12
16
20
0 10 20 30 40 50 60
Effect of Joint Compliances on Short- and Long-Duration Loads
Force at knee
Force at hip
Forc
e (k
N)
Time (ms)Lag from compliance of knee and hip
X
High loading rate(Melvin et al. 1976)
Low loading rate
FMVSS 208
Hip tolerance
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UMTRI Hip Tolerance TestingSchematic of test fixture
Weightedplatform Hexcel
Molded knee
interface
RamImpactsurface
Reaction force load cell (rigidly
mounted)
Pneumaticaccelerator
Applied force load cell
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Time (ms)
Forc
e (k
N)
Rate of Loading in UMTRI Knee Impact Tests
300 N/ms
Typical loading rates in FMVSS 208 tests are also less than 300 N/ms while the loading ratesin previous research were 400-3000 N/ms.
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Femur Tolerance Testing
Reaction force load
cell
Force
• Same apparatus as hip tolerance tests.
• Same specimens as those used in the hip tolerance tests with hip disarticulated and the head of femur inserted in an acetabular cupfixed to the support.
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Femur Tolerance Testing
0
0.2
0.4
0.6
0.8
1
Hip
Tol
eran
ce a
s a
%ag
e of
Fe
mur
Tol
eran
ce
Test
Femur tolerance
Relative hip
tolerance
The femur is stronger than the acetabulum (P<0.01)Hip tolerance is 72±7% of femur tolerance
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Results of impact tests• Neutral posture hip fracture tolerance is 5.7±1.4 kN• Femur fracture tolerance is 7.6 ± 1.6 kN• Femoral neck is the weakest part of the femur.• Using the displacement of the ram and the force
applied at the knee, • The stiffness of knee-thigh-hip complex is 233 N/mm• The stiffness of knee-femur complex is 370 ± 80 N/mm
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Stiffness of Human Cadaver Knee/Femur complex at loading rates seen in 30 mph frontal crashes (FMVSS208)
0
5000
10000
15000
20000
0 22Deflection (mm)
Forc
e (N
)
Up bound= 500 N/mm
low bound= 260 N/mm
Most of the knee-femur axial compliance is due to femur bending rather than the compliance at the knee joint.
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Hybrid III Knee-thigh-hip Complex• Hybrid III knee-thigh stiffness based on fixed femur skeletal
response of knee+distal femur sections by Horsch and Patrick (1976).
• Compliance of knee padding was selected such that HIII knee+distal femur response matches the Horsch-Patrick data
• Donnelly and Roberts (1987) found the Hybrid III to produce three times greater force than cadaveric subjects in whole-body knee impact tests.
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Thor Knee-thigh-hip Complex• To better match Donnelly and Roberts data, Thor has a
compliant element in the mid femur and redistributes some of the thigh mass to the flesh.
• The knee design is similar to the Hybrid III knee with similar impact response characteristics. It has rigid hemispherical knee caps intended to provide more human-like interaction with the knee bolster.
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Knee-femur compliance of Hybrid III, Thor and cadaver in molded knee interface loading at rates similar to that seen in 30 mph frontal crashes
0
5000
10000
15000
20000
0 5 10 15Deflection (mm)
Froc
e (N
)
Hybrid III (8100 N/mm)Thor (1400 N/mm)
Cadaver up bound (500 N/mm)
Initial stiffness (1800 N/mm) of HIII knee-femur is due to compression of knee padding. After about 2 mm, the HIII stiffness increases to 8100 N/mm, which reflects the rigidity of the femurand the limited compliance offered by knee padding.
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Compliance of ATDs at typical loading rates seen in FMVSS 208 frontal crashes
Thor Knee/Femur Compliance = 3 X Cadaver Knee/Femur compliance
Hybrid III Knee/Femur Compliance = 16 X Cadaver Knee/Femur Compliance
The Thor has a less stiff force deflection response than the Hybrid III dummy due to the compliant element in the Thor femur
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Biofidelity of ATDs• Biofidelity of an ATD’s knee-thigh complex depends
on knee/femur stiffness, as well as inertial contributions of the knee/femur complex and other body regions.
• In order to address mass-coupling issues, knee impacts to whole body cadavers and ATDs (free back condition) will be conducted.
• Though the Thor knee-femur stiffness is 3 times greater than that of human cadavers, its response under dynamic knee loading, such as in frontal crashes, may be similar to that of human cadavers.
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New Knee Bolster Designs
With the advent of new knee bolster designs, such as inflatablebolsters, the biofidelity of the knee-thigh-hip complex of the ATDand appropriate injury criteria will become crucial to ensure adequate protection for the KTH complex in frontal crashes.