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Biomechanics II (thorax and lower extremity)
Chest Tolerance and Standards
Epidemiology
Incidence of Injury to Each Torso Part
Torso Frontal Side
Part Impact impact
Sternum 14% 4%
Heart 10% 13%
Ribs 50% 63%
Aorta 9% 17%
Thoracic Spine 4% 8%
Other chest 39% 47%
Spleen 7% 23%
Liver 25% 34%
Other Abdomen 18% 31%
Thorax: Basic anatomy
From: Huelke D. F. “The anatomy of the human chest”
Injury mechanisms
• Compression of the thorax -> rib fractures, lung injuries
– Single rib fractures -> AIS 1 or 2 – 2 – 3 rib fracture -> AIS 2 or 3 – rib multiple fractures may lead to life
threatening complications -> flail chest – lung injuries
» pneumothorax » hemothorax » lung contusion + flail chest -> pneumonia -> ††
• shock waves (viscous loading within the thorax cavity) -> lung injuries
• inertia loading -> rupture of aorta
Common thoracic injuries
Rib fractures are most common
⁻ Fracture were observed in 93.5% of severely injured belted drives
Other injuries are:
₋ Sternal fractures
₋ Liver lacerations
₋ Clavicular fracture
₋ Separation of the sternoclavicular joint
Thoracic Injury mechanism
• The various injury types appear to be dependent on the rate of loading because of the viscoelastic nature of the tissues involved
• For automotive crashes, both deformation and rate of loading play a role in injury causation – Low Speed Crush Injuries (For impact speeds below 3
meters per second (m/s)) -injury mechanism is compression of the organs
– High Speed Impact Injuries -transmission of a pressure wave through the chest wall by a high-speed blunt projectile or by a blast wave
Abdominal Injury Mechanisms
• For automotive injuries, dual dependency on compression and velocity
• Solid organs appear to be more at risk than the hollow organs
• Belt-induced injuries to both the hollow and solid organs have been seen in the field
• Lower abdominal organs could only be injured severely by the lap-belt in association with submarining of the occupant
Thoracic Injury Mechanisms Rib fractures
Lung Injuries – haemo- or pneumo-thorax
Injuries to heart and arteries – 1
Upward motion of heart
Injuries to heart and arteries - 2
Force from below to above on the right side can result in aortic tear just beyond left sub-clavian artery
Injury to the heart and arteries: Neck Hyperextension and chest compression
Lung collapse and mediastinal shift due to haemo or pheumo – thorax
⁻ Belt restraint produce fractures along a path near regions of loading under the belt (distribution around rib 6
⁻ Airbag restraints without belts produce fractures at anterolateral rib locations
Kent et al. STAPP 2001
From Huelke D. F. “The anatomy of the human chest”
Biomechanical response
Thoracic biomechanical response studies – Volunteers – Cadavers – Animals (rabbits, dogs, monkeys, pigs)
Types of cadaver thorax tests – Impactor test – Drop test – Sled test – Full scale crash test
Biomechanical Response – Technique Method developed to improve chest deflection
measurements (12 accelerometers on the test subject)
Force-deflection plots for quasi-static loading
Frontal impact – biomechanical response • Frontal loading
– Static loading ≠ dynamic loading
– Plateau influenced by impactor velocity
– High hysteris
based on: Lobdell T. E. “Impact response of the human thorax”
from: Kroell, C. K.: “Thoracic response to blunt frontal loading”
Techniques to Determine Thoracic
Deflection
Accelerometer locations Direction
the most lateral point on the 4th right and left rib.
From left to right along the normal direction of the body.
the most lateral point on the 8th right and left rib.
Parallel with the body in a forward direction.
At the top of the sternum Forward direction.
At the lowest part of the sternum Forward direction.
1st thoracic vertebra Three-axial; head -fot, left-right, forward-backward shoulders
12th thoracic vertebra Three-axial; head -fot, left-right, forward-backward shoulders
Mechanical Response of the Thorax
• Dynamic data were obtained by Nahum et al and Kroell et al using a 152-mm (6-inch) impactor, weighing 227 N (51 lb) or 191 N (43 lb) shown in figure.
• Response corridors for impact speeds of 4.9 m/s (11 mph) and 7.2 m/s (16 mph)
• The static stiffness of an unembalmed thorax was found to vary from 6.3 to 10.9 kN/m (36 to 62 lb/in
Adjusted force-skeletal deflection curves
Frontal Thoracic Response to flat impactors
Mechanical Response of thorax
• Patrick performed a courageous study on himself in 1970, using a 10-kg (22 lb) pendulum
• Impact velocities ranged from 2.4 to 4.6 m/s (8 to 15 ft/s)
• Generally cadaveric data needs to be increased to simulate a tensed living human, – Patrick’s data agree better
with the unadjusted cadaveric data
Plateau force versus impactor velocity
Initial stiffness of the load-deflection response of the chest
Response to Belt Loading
• Belt loading stiffness at the sternum ranged from 17.5 to 26.3 kN/m (100 to 150 lb/in) while disc loading ranged from 8.8 to 17.5 kN/m (50 to 100 lb/in)
• Tests on pigs show, – Thoracic force-deflection curves exhibited an initial low
stiffness region with a concave-upward stiffening behavior up to about 25 to 50 mm (1 to 2 in) of deflection.
– followed by a high stiffness response up a maximum deflection of 100 to 150 mm (4 to 6 in)
– dead animals had a low stiffness of 35.7 kN/m (204 lb/in) and a high stiffness of 115.7 kN/m (661 lb/in)
– stiffness of living pigs was slightly over half the value of dead pigs
Side Impact Thoracic Response
• Flat impactor test results:
– initial dynamic stiffness ranged from 273.6 to 437.8 kN/m (1563 to 2500 lb/in) at 6.1 m/s (20 ft/s)
– At the higher velocity, the values were 437.8 and 790.0 kN/m (2500 to 4500 lb/in)
• Drop test:
– Dynamic stiffness of the thorax was in a range from 96.8 to 255 kN/m (553 to 1457 lb/in).
Pendulum impacts conducted by Viano et al
Force-deflection and force-time response for chest impacts--Raw Data
Force-deflection and force-time response for chest impacts--Normalized
Stiffness values were not computed but the suggested corridors had an initial stiffness of 100 to 140 kN/m.
Mechanical Response of the Abdomen
• Mechanical response data from impacts to the abdomen, particularly frontal impact data, are somewhat sparse
• As for lower abdominal response to belt loading, the only data available were taken from porcine subjects by Miller.
• Rouhana et al scaled the data to the human level using the equal stress/equal velocity method
Lower abdominal frontal impact stiffness
Lower abdominal response to dynamic belt loading
Tolerance of the Abdomen
• The large number of abdominal organs and the difference in structure and strength between solid and hollow organs render the study of tolerance rather difficult.
• An additional difficulty is the effect of obesity, age and disease, such as cirrhosis of the liver, and the presence of material in the hollow organs, such as partially digested food in the intestines and a fetus in a uterus
Tolerance of the Abdomen to Frontal Impact
Author (ref)
Tolerance Injury Severity
Organ Remarks
Melvin et al [137]
p = 310 kPa AIS 4-5 Liver Exposed, perfused, N =17 Rhesus monkey, fixed back, V=2.5m/s
Lau and Viano [128, 129]
F=0.24 kN AIS > 3 Liver Rabbits, N=26, Compression 16%, fixed back
Horsch et al [140]
V*C =0.72 AIS > 3 Liver Steering wheel impact, N = 17, V = 32 km/h
Miller [86] F = 3.76 kN AIS > 4 Lower Abdomen
25% prob. of injury, Swine, N=25, Lap belt load
Miller [86] C = 48.3% AIS > 4 Lower Abdomen
25% probability of injury, Swine, N= 25, Lap belt load
Miller [86] Fmax*Cmax = 2.0 kN
AIS > 4 Lower Abdomen
25% probability of injury, Swine, N= 25, Lap belt load
Upper pelvis Response
• Pendulum impact data obtained b are shown in Figure
• On the left are force-deflection curves with initial stiffnesses of 100, 75 and 128.6 kN/m for the three impact velocities of 4.3, 6.7 and 9.5 m/s respectively.
• Force-time response curves are shown on the right of Figure
• When these force-time histories are compared with normalized data obtained from cadaveric drop tests onto rigid armrests, distinct differences are obvious
Mechanical Response of the Pelvis - Frontal
• Cadaver was suspended in a restraint harness and one knee was impacted
• Both the linear and angular acceleration of the pelvis were measured but the angular acceleration about the spinal (z-) axis was not always predominant for this off-axis impact
• Mechanical impedance, as an analytical tool and resonance was estimated to occur between 180 and 280 Hertz had large scatter of data
Lateral Impact Response of the Pelvis
• The impact speeds ranged from 21 to 44.6 km/h (13.0 to 27.7 mph).
• Each cadaver sustained multiple (2 to 5) impacts that were administered at increasing velocities until fracture occurred
• Force-deflection curves for the 33.8 km/h impacts shown in figure
Force-deflection response of the pelvis
Tolerance of the Pelvis in frontal impact
• Patrick et al. results for advance aged subjects – Range of loads for pelvic fracture was 6.2 to 11.8 kN (1400
to 2650 lb)
– Hip and/or pelvic fractures resulted from combined knee loads of 8.9 to 25.6 kN (2000 to 5760 lb)
• Although no definitive tolerance level has been established for the pelvis for frontal impact, one can deduce that the 10-kN femoral load limit in FMVSS 208 adequately protects the pelvis
• The three-point belt is not likely to cause injury to the sacroiliac joint, even in the absence of an airbag
Tolerance of the Pelvis to Lateral Impact
Caesari et al. – For males, the force at fracture, at the level of the 3-ms clip,
ranged from 4.9 to 11.9 kN (1000 to 2900 lb). – The corresponding range for females was 4.4 to 8.2 kN (1000
to1840 lb). – The average force for an AIS 2 or 3 pelvic injury was 8.6 kN
(1930 lb) for males and 5.6 kN (1260 lb) for females
• Proposed tolerance force at the level of the 3-ms clip – 10 kN (2250 lb) for a 75-kg person. – 4.6kN (1030 lb) for a 5th-percentile female
• Two more measures for pelvic injury are the acceleration and the displacement.
• With absence of data, 10kN force is best tolerance
Injury criteria & tolerances
1: Chest deflection due to compression mechanism
• Compression Criterion (CC): maximum chest compression is much better indicator of injury severity than acceleration or force!
⁻ frontal, blunt impact, quasi static: Vimp< 3 m/s
⁻ use normalized chest deflection: 35% deflection -> AIS 3
Injury criteria & tolerances
2: Acceleration and force due to compression mechanism & inertial loading
• Single acceleration: <60 g at CG when t < 3 ms (specified in United States regulations FMVSS 208), limited validation
• Chest severity index (SI): 1000 (not used, bad validation)
• Force on the sternum: 3.3 kN =>minor injuries) • Distributed load shoulder + chest: 8.0 kN
=> resulted in only minor injuries, compare F=60 g (acc criterion ) * 30 kg (chest mass) = 18 kN
• Thoracic Trauma Index (TTI) – “+” mass, age – “-” pure statistical function
Severity Index (SI)
SI was introduced by Gadd, 1996
a= acceleration (g)
2.5=weighting factor based on the slope of the tolerance curve t=time (sec)
(bad validation)
2.5SI a dt
Thoracic Trauma Index (TTI)
• TTI = 1.4 * AGE + 0.5 * (RIBY + T12Y) * MASS / Mstd
Where:
TTI = Thoracic Trauma Index (dimension: g) AGE = age of the subject in years RIBY = maximum absolute value of lateral acceleration in g’s of the 4th and 8th rib on struck side after signal filtering T12Y = maximum absolute value of lateral acceleration in g’s of 12th thoracic vertebra after signal filtering MASS = test subject mass in kg Mstd = standard reference mass of 75 kg
• TTI(d) = 0.5 * (RIBY + T12Y) Where: TTI(d) = definition of the TTI used for 50th percentile dummies
Used as criterion in side impact in USA
Injury criteria & tolerances
3: Viscous criterion due to compression mechanism & viscous response
See: SAE J211
• Viscous Criterion (VC) is a time function formed by the product of the velocity of deformation: V(t) and the instantaneous compression function: C(t)
V(t) is calculated by differentiation of the deformation, and C(t) is calculated in relation to initial torso thickness (D)
• valid if 3 m/s < Vimpact < 30 m/s
( ) ( )( )* ( ) *
d D t D tVC V t C t
dt D
VC: ranges of validity
• Less compression produce similar injury
levels when impact velocity is increased!
based on Lau I.V., Viano, D. C. “The Viscous Criterion: Bases and Applications of an Injury Severity Index for Soft Tissues”
Viscous response
• Serious injury to soft tissue and organs occurs at the time of peak viscous response, well before maximum deflection
• The maximum chest compression is needed to protect against crushing injuries, which may occur during slow or static deformation of the chest and abdomen
VC criterion
• The tolerance level for a 25% probability of severe injury (AIS 4+) was found to be VCmax = 1 m/s
• VC has been criticized that it is a measure of the energy stored in the thorax and not the energy dissipated
• It has also been hypothized that varied loading conditions by different restraints need a more restraint specific injury criterion
Combined Thoracic Index (CTI) - 1
A max = Maximum chest acceleration (g) A int = X-axis intercept (dummy specific), 85 g’s for 50% HIII D max = Maximum chest deflection (mm) D int = Y-axis intercept (dummy) specific, 102 mm for 50% HIII
max max
int int
A DCTI
A D
Thorax – Crash Safety Legislation
Frontal Collision EU (96/79/EG) Thorax Compression Criterion (ThCC): 50 mm Soft Tissue Criterion (VC): 1.0 m/s Side Collision EU (96/27/EG) RDC (Rib Deflection): 42 mm Soft tissue criterion (VC): 1.0 m/s
Frontal Collision USA (FMVSS 208) 50% HII Chest acceleration: 60 g Thorax compression: 63 mm 5% HII Chest acceleration: 60 g Thorax compression: 52 mm Side Collision USA (FMVSS 214) Thoracic Trauma Index (TTI): 85 g (4 – door) 90 g (2 – door)
Injury Mechanisms of the Thoraco-Lumbar Spine
• If the injury involves the spinal cord, paraplegia can result • Mechanism of injury for these wedge fractures is a
combined compressive and bending load • Two load paths down the spine to transmit vertical (axial)
compression generated by inertial loading, depending on the orientation of the lumbar spine – The two load paths are the discs and the articular facets that
transmit compressive load by bottoming the tips the inferior facets onto the laminar of vertebra below
• Disc rupture is a slow degenerative process • An extremely violent single loading event causes the
nucleus pulposus to extrude from the side of the disc
Lower extremity - bones
Anatomy of the knee
Movement Directions
• Flexion
• Extension
• Adduction
• Abduction
• Rotation
Movement of the ankle joint
Physiological movement of joints of extremities
Kapandji [1970], White and Panjabi [1978], Frankel and Nordin [1980]
Physiological feature
Motion range of joints (degree)
Shoulder Elbow Hip Knee *Ankle- subtalar
Flexion 180 145-160 90-145 20-30 Extension 45-50 0 20-30 30-50 Abduction 140 0 45 30-40 Adduction 30-45 0 30 25-35 Lateral rotation 80 90 30 Medial rotation 95 85 60 Inversion 15-20 Eversion 15-Oct Axial rotation
* The motion of the ankle is combined with that of the subtalar joint.
Pelvic Injury Mechanisms
• Common injuries to the pelvis in frontal impacts result from severe knee loading into the dash
• Separation of the pelvis from the sacrum at the sacroiliac joint can occur if the knee is wedged between the front seat back and the dash
• In side impacts, the most frequent injury in this case is pubic rami fractures followed by acetabular fractures
Injury mechanisms to lower extremity in frontal impacts
Injury mechanisms of the knee joint in pedestrian accidents
Damage mechanism of knee joint
Kajzer et al. 1997
Knee Joint Injuries
• Frequently injured in motor vehicle crashes when it comes into contact with the instrument panel or dash
• Dashboard which slopes down and away from the occupant, ensures that PCL s preserved
Ankle Joint Injuries
• In offset impacts, footwell intrusion can place the foot in dorsiflexion as well as in inversion or eversion
• Pylon fractures appear to be due to the simultaneous application of a large brake pedal load through the mid-foot in concert with the application of a large calf muscle force
Pelvis: injury mechanisms
Frontal impact Lateral impact
Posterior hip dislocation
Fracture - dislocation
Intrapelvic (femur neck, trochanter) fracture- dislocations and fractured pelvis
Fractures of the ankle and direction of forces
Moment-angle characteristics of the hip joint
Mechanical Response of the Knee and Femur
• This was a rigid 5-kg (11-lb) pendulum impact against the knee of a seated cadaver that did not have a back support.
• The drop height was 0.225 m (8.9 in).
• Other forms of response data include peak femur acceleration as a function of peak knee impact force and mean peak knee impact force as a function of pendulum mass.
Knee femur impact response
Mechanical Response of the Knee and Femur
• For the knee, studies have been conducted to quantify the force-deflection characteristics associated with the human knee being forced into energy-absorbing or crushable materials
• Nyquist tested a cross-section of volunteers utilizing Styrofoam of known crush characteristics
• To prevent soft tissue injuries to the knee in the automotive environment, Viano obtained the stiffness the knee joint for static posterior tibia subluxation relative to the femur.
• The linear range of the stiffness values from the five cadaver specimens tested had an average of 149 kN/m (850 lb/in)
Mechanical Response of the Tibia
• The bones were tested in 3-point bending, 11 of them in the antero-posterior (AP) direction and 9 in the latero-medial (LM) direction
• The dynamic load was provided by a 32-kg (70.6-lb) linear impactor at speeds between 2.1 and 6.9 m/s (6.9 to 22.6 ft/s)
• From the known bending moment, the tensile stress to failure was computed
• The response curve for AP loading had an average stiffness of 282 ± 92 kN/m (1610 ± 525 lb/in) when the impact force was plotted against deflection
• The LM response was bi-linear. – initial stiffness was 105 ± 36 kN/m (600 ± 206 lb/in) and – final stiffness prior to fracture was 265 ± 70 kN/m (1513 ± 400 lb/in). – The difference in stiffness is obviously due to the contribution from
the fibula which is stronger in the AP direction
Mechanical Response of the Ankle
Ankle Response in Dorsiflexion Ankle Response in Inversion/Eversion
Because of the variability in the data, the response curves for dorsiflexion of the ankle are ill-defined
The only dynamic data obtained by Begeman et al for inversion/eversion The data provided by Crandall et al were for quasi-static tests
Femur strength Femur strength.
Male Female
Torque (N = m) 175 136
Range 141-222 78-207
Bending (kN) 3.92 2.58
Range 3.43-4.66 2.26-3.33
Average maximum moment (N = m)
310 180
Long axis compression (kN) 7.72 7.11 Range 6.85-8.56 5.63-8.56 From Messerer, as reported in Naham and Melvin
Tibia and fibula strength
Tibia strength
Male Female
Torque (N = m) 89 56
Range 63-110 47-63
Bending (kN) 3.36 2.24
Range 2.30-4.90 1.86-2.65
Average maximum moment (N = m)
207 124
Long axis compression (kN) 10.36 7.49
Range 7.05-16.39 4.89-10.37
Fibula strength.
Male Female
Torque (N = m) 9 10
Range 6-12 8-16
Bending (kN) 0.44 0.3
Range 0.35-0.54 0.21-0.39
Average maximum moment (N = m)
27 17
Long axis compression (kN) 0.6 0.48
Range 0.24-0.88 0.20-0.83
From Messer, as reported in Naham and Melvin.
Pelvis impact response - tolerances
• Vertical loading – 3.7 kN dynamic -> bilateral dislocation of the sacroiliac joint – 3.5 kN static -> similar kind of injury (Fasola et al. 1955)
• Frontal loading – 2.7 kN at the pubis -> fracture of the pubic rami (Fasolaet et al. 1955) – 8.9 – 25.6 kN at the knee -> hip/pelvic fractures (Melvin et al. 1980) – 37 kN noted -> not fractures (Nusholtz 1982)
• Lateral loading – Fracture force: 4.9 – 11.9 kN for males, 4.4 – 8.2 kN for females (Ramet,
Cesari 1979 – 1983) – Average force for AIS 2-3: 8.6 kN for males, 5.6 kN for females – Impact Force = 193.85 Wc – 4710.6, Wc – body weight -> for 50th
percentile male: 9.8 kN – even study from UMTRI and University of Heidelberg
Force-deflection response of pelvis
Lateral impact to greater trochanter, pendulum diameter 150 mm, mass 23.4 kg, speed 16.2-33.8 km/h. Peak pelvis acceleration and pelvic deformation not reliable measures. Ratio of pelvic deformation to pelvic width correlate with pubic rami fracture: 25% probability of fracture at 27% pelvic compression
Viano et al. 1989
Pelvic Fracture Risk Curve
Impact force of 8.9 kN – 20% risk of pelvic fracture
Impact force of 9.8 kN – 50% risk of pelvic fracture
Tolerance levels of upper and lower leg
• Femur force EEVC WG 10 ≤ 4 kN 4.23 kN 5.28 kN 7.1 – 7.7 kN (static axial compression) 11.6 kN (dynamic axial compression)
• Femur bending moment EEVC WG 10 ≤ 220 Nm 310 Nm (males static)
• Tibia acceleration EEVC WG 10 ≤ 150 Fractures 170 – 270 g (average 222 g) No fractures 185 – 243 g (average 202 g) 124 – 207 Nm (static bending moment) 280 – 320 Nm (dynamic bending moment)
Tolerance levels of the knee
• Shearing EEVC WG 10 ≤ 6mm at 4 kN
12 mm (no preload, quasistatic)
16-28 mm (preload, dynamic)
2.4-2.9 kN shearing force
400-500 Nm bending moment
• Bending EEVC WG 10 ≤ 150
110 (dynamic) – 190 (quasistatic, no preload)
15-160 (preload dynamic)
Levels of knee force and moment in various studies
Setup of four-point knee bending test
Bhalla’s results compared with response os FLEX-PLI and TRL-PLI
• Konosu and Tanahashi 2003
Femur Injury Criterion (FIC)
F (kN) =23.14 – 0.71 T (ms), for T<20 ms
F (kN) = 8.9 kN, for T>=20 ms
where:
F is the axial compressive force
T is the primary load pulse duration.
Tibia injury criterion Tibia Index (TI)
TI=(M/Mc) + (F/Fc) < 1.0 and Fmax <8 kN
where:
Mc=225 Nm and Fc=35.9 kN
Basis: Static bending tests of tibia (Yamada)
Bone properties:
ultimate compressive stress = 210 Mpa
ultimate tensile stress = 150 Mpa
Tolerance levels of the ankle joint
• Ankle moment (quasi –static)
– 33 Nm in dorsiflexion
– 40 Nm in plantarflexion
– 34 Nm in inversion
– 48 Nm in eversion
• Ankle bending angle
– 34 deg. In inversion (quasi –static)
– 32 deg. in eversion (quasi –static)
Tolerance of the Femur
• Dynamic data available for three decades
• Femur Injury Criterion F (kN) = 23.24 – 0.72 T (ms), for T < 20 ms
F (kN) = 8.90 for T ≥ 20 ms
– 12 kN (2700 lb) may not be exceeded
– 10 kN (2250 lb) may not be exceeded for durations of less than 3 ms
– 7 kN (1575 lb) may not be exceeded for durations of less than 10 ms
Authors Test Type Peak Load Range (kN)
Fracture Type
Percent Fractured
Padding Thick-ness
Duration Range (ms)
Patrick et al (64)
Sled 4.2-17.1 Condyl-ar
25 Rigid/Thin
>30
Patrick et al [92]
Sled 8.8 None 0 36 mm 30
Brun-Cassan et al [143]
Sled 3.7-11.4 None 0 25 mm Unknown
Powell et al [150, 151]
Pendulum 11 Shaft/Neck
13 None 10-20
Powell et al [150, 151]
Pendulum 7.1-10.4 Condyl-ar
33 None 10-20
Melvin et al [152]
Pendulum 18.8 average
Condyl-ar
29 None <10
Melvin et al [152]
Pendulum 16.2-22.7 None 71 None <10
Melvin et al [152]
Pendulum 13.6-28.5 Condyl-ar
18 25 mm 22 max
Melvin et al [152]
Pendulum 19.7 Shaft 20 50 mm <10.7
Melvin et al [152]
Pendulum 14.7 None 40 50 mm <10.7
Stalnaker et al [155]
Pendulum 13.4-28.5 Shaft/ Neck and
Condyl-ar
100 None Unknown
Stalnaker et al [155]
Pendulum 15.7 average
Condyl-ar
33 25 mm Unknown
Stalnaker et al [155]
Pendulum 5.3-14.0 None 60 50 mm Unknown
Tolerance of the Patella
• Tolerance implies the minimum load needed to damage a bone or a piece of tissue.
• Any load above this minimum will also cause damage. • Thus, there is no assurance that the forces measured in
those knee impacts are close to the tolerance value or have well exceeded this limit
• The problem is further complicated by the fact that the forces generated by padded impacts are borne by both the patella and the condylar surfaces around it.
• Hence rigid body impacts alone can be considered. – Minimum fracture loads - 2.5 to 3.1 kN (560 to 700 lb) – Average failure load ranged from 4.6 to 5.9 kN (1030 to 1320 lb).
Tolerance of the Knee
• Two issues with knee injury in automotive crash
– Damage to the posterior cruciate ligament (PCL) from impacts to the tibia just below the knee
– Post-traumatic osteoarthritis in the patellofemoral joint, which can result from knee impact with the instrument panel
• Padding in instrument panel should have crush strength of 0.69 to 1.35 MPa (100 to 200 psi)
Tolerance of the Tibia
Tolerance data for tibial bending impacts
Gender Direction
of Loading
Number of Data Points
Bending Moment
(N.m)
Total Reaction Load (kN)
Mean S. D. Mean S. D.
Males and
Females
AP and LM 21 308 79 4.83 1.23
AP only 11 300 77 4.6 1.37
LM only 10 317 84 4.86 1.27
Males Only
AP and LM 16 317 88 4.8 1.45
AP only 8 304 90 4.57 1.59
LM only 8 330 89 5.03 1.37
Females Only
AP and LM 5 278 30 4.48 0.61
AP only 3 288 37 4.7 0.74
LM only 2 264 14 4.16 0.22
ACKNOWLEDGEMENTS
• Material in the presentations is adapted from different sources including presentations made in the annual TRIPP safety course, material available on the www, LS Dyna manual as well as other published material.
• We also acknowledge the support from Ratnakar Marathe in preparing some of the contents.
