KNEE JOINT INJURY MECHANISMS AND INJURY CRITERIA IN FULL ²SCALE TESTS ACCORDING TO IMPACT POSITION

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1 KNEE JOINT INJURY MECHANISMS AND INJURY CRITERIA IN FULL ²SCALE TESTS ACCORDING TO IMPACT POSITION ARNOUX P.J. 1, THOLLON L. 1, BEHR M. 1, BRUNET C. 1 CESARI D. 2 1 Laboratoire de Biomécanique Appliquée, UMRT 24 Faculté de Médecine - INRETS, Université de la Méditerranée, Marseille, France. 2 INRETS, Scientific direction, Bron, France. ABSTRACT In pedestrian safety research, the definition of an injury criterion for the knee joint should provide issues to future regulation procedures. Also, do the existing injury criteria (based on knee lateral shearing levels and flexion levels for sub-segment testing) remain efficient for full scale tests? Is the impact location on the leg influencing injury mechanisms and injury criteria assumptions? Lastly, what are the potential consequences of these differences to the pelvis component during the first phase of impact? The LLMS lower limb model coupled to a hybrid 3 was used to investigate these questions. This work was based on pedestrian full scale experiments performed in the Laboratory and a sensitivity analysis regarding various impact positions. The results obtained for this car geometry showed that injury mechanisms (i. e. the proportion of shearing and lateral flexion) for the knee joint and the pelvis are directly related to the impact position. Lastly they lead to improve existing injury criteria by adding combination of two injury modes. Keywords: PEDESTRIANS, INJURY CRITERIA, KNEES, LEGS, FINITE ELEMENT METHOD IN PEDESTRIAN CAR ACCIDENT a large field of research is devoted to the development of vehicle safety countermeasures directed towards the response of the human knee joint. A large portion of this research concerns the experimental investigation of human body behaviour through cadaver experiments, the design and validation of human lower limb models or mechanical surrogates. All these works try to investigate injury mechanisms, injury criteria by correlation to trauma situation and consequently car safety efficiency. From an experimental point of view, during a pedestrian impact, knee injuries could result from a combination of lateral shearing and bending of the knee (Kajzer 199 and 1993, Teresinski 21, Bose 24). Pure shearing induces collateral tibial and anterior cruciate ligaments failure while a primarily bending mainly induces medial collateral ligament failure. More recently, Bose (24) performed 3- point bending tests on isolated knee joints in order to obtain a combination of shearing and bending effects, and confirmed injuries to medial collateral and anterior cruciate ligaments. It can be noted that knee injuries are not restricted to the injuries described above. Tibia fractures (especially with at the tibial eminence in contact with the intercondylar notch at impact), posterior cruciate ligament injuries, fibula and femur fractures can also be observed. From all these studies, it appears that the main challenge for improving leg protection should focus on knee ligament damage and failure minimization. This challenge should not be managed separately as what s happened on the hip joint components. With various car designs, lower limb behaviour can differs according to the shape of the car and the impacts position and modify knee joint loadings and the induced kinematics. In the specific field of numerical simulation, multibody mathematical models were used in order to provide an overall insight to the kinematics involved in pedestrian impact loading (Yang et al., 1994, Wismans et al., 198, Serre et al. 25). In order to provide an accurate investigation of trauma chronology during the impact, finite elements model has been design since the past 1 years. The first models, designed by Bermond (1994) and Yang (1996) were dedicated to pedestrian loading cases especially sub segment tests performed by Kajzer (199 & 1993). The more recent lower limb FE IRCOBI Conference Madrid (Spain), September

2 models (Schuster et al. (2), Arnoux et al. (22) and Beillas (21), Chawla et al. (24)) focused on an accurate description of anatomical components that are involved in joint mechanics or are injured during trauma situations. In these models, material properties were obtained from individual tissue testing and try to integrate damage and failure of deformable bone and soft tissue structures. These models are then validated against sub-segment and full scale post mortem human subject (PMHS) in various loading configuration in order to evaluate mechanical behaviour of the whole structure. Besides validating for overall impact response some of the more advanced models, as they can record data not available experimentally, are capable of predicting injury mechanisms and thus help define injury tolerances (Takahashi et al. (23), Nagasaka et al., (23), Chawla et al. (24), Arnoux et al. 25). In Nagasaka pedestrian lower limb model, injuries are based on the height and angle of the impact to include a wide range of vehicle geometry and impact configuration. Based on similar objectives of understanding lower limb injury mechanisms and estimating injury thresholds we have evaluated the ultimate bending angle and shear displacement threshold for ligament failure to be 15-2 and 13-15mm respectively on the base of available sub segment tests (Arnoux et al. 25) and Bose et al. (26)). The LLMS model used for the study was developed by Arnoux et al. (21) and Beillas et al. (21). An accurate geometric model of a 5 th % adult male was reconstructed using MRI measurements. The total number of elements was close to 35, with characteristic length chosen to obtain initial time step ranging from.8 to 1 s. Material properties for each tissue component were determined from previously published PMHS studies. To validate the material response of the model, validation was performed at three levels: isolated tissue tests, sub-segment tests and finally entire lower limb tests (Table 1) Table 1 : Validation tests performed on LLMS model Validation Tests Soft Tissue Tensile Tests Anterior Cruciate Ligament Posterior Cruciate Ligament Medial collateral Ligament Lateral collateral Ligament Patellar Tendon Long Bone Tests Femur Bending (3-points) Tibial Lateral-Medial Bending Tibial Antero-posterior Bending Sub-Segment Loading Patellar impact on flexed knee Parameters Stress, Force Force Force Tibia impact on flexed knee Force Anterior posterior flexed knee Quasi-static leg compression Quasi-static tibia/fibula comp. Ankle Inversion/Eversion/dorsiflexion Moment Rotation Three point knee bending Moment Rotation Four point knee bending Moment Rotation Whole Lower Limb tests Pedestrian lateral bending Force, Rotation Pedestrian lateral shearing Force Frontal Sled test Force The present study aims at investigate these injury mechanisms regarding real full scale pedestrian crash situations. In particular, for a defined car model, the question is related to the influence of impact position on injury mechanisms and injury criteria definition on the knee joint. Additionally the possible consequences at the hip joint level regarding kinematics and transmitted loads were investigated. To achieve this, the injury prediction capability of LLMS-hybrid III were investigated regarding a real pedestrian experimental tests performed in the laboratory. The injury mechanisms evaluation was based on certain model parameters (e.g. local strain in soft tissues, Von Mises stress in bones, internal energy) which cannot be measured in experimental tests. In particular, by assuming that ligaments failure is related to strain level, the knee joint injury threshold is based on the relationship between admissible strain levels in the ligaments and overall knee joint kinematics such as lateral flexion and shearing, torsion effects. 32 IRCOBI Conference Madrid (Spain), September 26

3 INJURY MECHANISMS & CRITERIA EVALUATION IN PEDESTRIAN IMPACTS THE LLMS MODEL FOR PEDESTRIAN used for this work was coupled to an Hybrid III 5 percentile rigid dummy model in order to take into account the effects of the whole human body kinematics during the test. The details of LLMS model (from design to validation) were not reported in this paper as they were already largely published (Arnoux 21, 24, 25, Beillas 21). The coupling consisted in adding a part of the pelvis bone to the initial pelvis rigid body component. The initial geometry of a hybrid pelvis was modified in order to ensure repositioning of the model up to the standing position (cf. figure 1.). The upper proximal femur to the head of femur was considered as a rigid body. The hip joint was then defined using a mathematical joint at the centre of the femoral head. Rotations at the hip joint were defined using torque versus angle user functions in a local skew system (cf. figure 1). Fig. 1 Overview of LLMS Hybrid 3 coupling on the pelvis segment The model reference pedestrian impact test was relevant with experimental tests performed in the context of a French APPA ( Amélioration de la protection des piétons lors de collisions avec des automobiles ) PREDIT ( Programme de Recherche et d inovation dans les transports terrestres ) project. It consists in putting the model (5 percentile one as for experiment) in standing position in front of a Euroncap supermini (segment B) class finite element car model. The car model was then put in braking conditions (pitching angle ~ 2 ) with an initial velocity of 1.88ms -1 and, according to the acceleration recorded during experiments; we postulated a constant deceleration of 5.58 ms -2. As it was performed during experiment, the pedestrian model and more particularly the impacted leg was set into a light flexion at the same height of the knee joint in front of the car bumper (figure 2). The analysis performed in this work focus only on lower limb behaviour for the first phase of the pedestrian impact until first injuries appears on the leg (figure 2) Fig. 2 Illustration of LLMS Hybrid 3 kinematics in the first phase of the impact and Von Mises curve on bones components IRCOBI Conference Madrid (Spain), September

4 THE INJURY MECHANISMS EVALUATION was based on same methodology as in previous work (Arnoux et al., 24).Although the material definition of the FE knee model did not include failure behaviour, however specific parameters like ligament strain bone stress were recorded in balance to joint kinematics to estimate failure and injury mechanisms timings. To measure ligament strain in the model, several uni-axial low stiffness springs (length approximately equal to twice element dimension) were assembled in series along the main axis of each ligament and pasted to ligament structure. During post processing individual spring extension was recorded and computed to provide strain level by comparison to initial length of each spring. Then the global strain for each ligament (computed as the mean strain level along the ligament) was used to illustrate strain levels in the ligament. In the present work, the failure threshold values (Table 2) were compared to the global strain level. The maximum curve of local strain level was obtained by defining the curve of maximum of local strain. It was used as an additional indication to the structure strain field (homogenous for lateral ligaments whereas strong dispersions appeared for cruciates). High local strain level could be understood as additional information to determine the failure risk and location. In previous studies (Arnoux et al. 24, 25), injury criteria were obtained through numerical investigation on sub segment tests. Once the model is assumed to be validated, the next step of this approach was to record not experimentally available data such as ligament strain level. Assuming that ultimate strain is a failure criteria for ligament, the injury criteria previously investigated was based on the relationship between knee ligaments strain level and knee joint kinematics. This previous work led to postulate on an injury criteria in pure shearing (13-15mm) and in pure lateral flexion (15-2 ). Table 2: Tissue failure threshold values used for predicting model failure (Arnoux et al., 25) Failure Threshold Values Ligaments Collateral MCL, LCL 28% Cruciate ACL, PCL 22% Bones Ultimate Stress Femur 125 MPa Tibia Metaphysis 13MPa Epiphysis 11MPa Patella 125MPa Fibula Head 125MPa Diaphysis 1MPa For this test, the collateral medial ligament and posterior cruciate ligament were both injured in the first phase of the impact with an approximated time for failure at around 9-1ms (figure 3). A complementary analysis of strain distribution along the ligaments showed very high strain level at ligament insertion which let us to postulate on a potential failure at ligament insertions Max level in S3-PED2B,6,5,4,3,2 *, LCP-Max-strain LCA-Max-strain LLE-Max-strain LLI-Max-strain Total level in S3-PED2B,4,35,3,25,2,15,1, LCP-Total-strain LCA-Total-strain LLE-Total-strain LLI-Total-strain Fig. 3 knee ligaments (maximum and total) strain level in the first phase of the impact From von Mises distribution, damage and failure on bones occurs on the proximal fibula due to the contact with the bumper (figure 4). No femur or tibia failure was reported, but Von Mises distribution 322 IRCOBI Conference Madrid (Spain), September 26

5 was located on distal femur metaphysic and proximal tibia metaphysis with maximum amplitude around 1-12MPa. With the analysis of rotation and lateral shearing of the knee, we observed lateral rotation effects (around ) but a very small lateral shearing (lower than 5 mm) (figure 5). An additional significant translation along the limb axes was observed and reached 1mm. Note that in this case, torsion effects (reaching 5 at the first injury time) were observed. This phenomenon also observed for sub segment was described as a natural safety countermeasure for ligaments recruitment in the knee joint Fig. 4 Von Mises stress distribution (MPa) on tibia fibula with failure location on fibular component Knee rotations in C3-PED2B Knee shearing in C3-PED2B Rotation ( ) Lateral rotation Frontal rotation Leg torsion Displacement (mm) Shear_X Shear_Y Shear_Z Fig. 5 Knee joint rotations and shearing level (Y for lateral shearing). In previous work, the knee joint injury criteria were postulated on the bases of Kajzer and Bose experimental tests. The results obtained with real car impact show that the ligaments injury seems to be related to the combination of the two classical lateral shearing and flexion, and a new one (regarding numerical simulation) which is the stretching on the knee joint along the leg axes. The shearing and lateral flexion levels obtained are below already defined injury thresholds. These results lead us to assume that the injury criteria should be improved by defining a relation between shearing, bending (and also by stretching effects). INFLUENCE OF IMPACT POSITION Due to knee joint mechanics, the impact position in pedestrian is assumed to be determinant to the injury mechanisms observed and consequently the definition or relevance of injury criteria. In order to investigate quantitatively this situation, several numerical simulations were performed with various realistic impact position from the medial femur, femur metaphysic, distal femur metaphysic, centred on knee joint, and lastly on proximal tibia metaphysic. This position were obtained through a vertical positioning of the car model. For these various situation, the same methodology as described in IRCOBI Conference Madrid (Spain), September

6 previous section was applied in order to evaluate injury mechanisms. FOR THE UPPER FEMUR IMPACT, the front car bumper was set to the 2/3 inferior of the femur (figure 6) which is 165mm above the reference impact position. The conditions of the impact car velocity and deceleration are the same as those described in previous section. In the beginning of the shocks (for the first 12ms), ligaments strain level recorded on lateral were largely below injury threshold with strain level below 18%. For cruciate ligaments, maximum local strain curve show an inhomogeneous strain field with a tibial ligament insertion highly recruited (it reach the ultimate threshold) due to shearing effects. At the end of the first phase, after bone failure (see below), the knee joint structure is highly recruited with and LCA potential failure. Knee joint kinematics showed differences with the reference test. Whereas stretching effects (Shear Z) were constant, the shearing effects were dominant in the first 1ms with level below the 13mm criteria value defined in previous works. On the opposite, once bone failure occurred, the shearing effects decrease and lateral flexion reach 2 at the time of anterior cruciate ligament potential failure. Regarding Von Mises Stress curve, if stress concentration seems to be located on the same area as for previous tests, due to front car shape, the femur is recruited as a three point flexion in the opposite directions as in the reference test. This loading leads to bone failure at time closed to 11ms Fig. 6 Four steps of lower limb kinematics and Von Mises stress iso curves on bones for the pedestrian upper femur impact. In the upper femur impact test, the knee joint kinematics seems to be a combination of dominant lateral shearing coupled with lateral flexion until the bone failure which is first injury mechanisms observed. Once bone failure occurred, the knee joint exhibit a dominant lateral flexion leading to ligaments injury with amplitude of 2 which is relevant to previous criteria. Max level in C3-PED2E,5,45,4,35,3,25,2,15,1, LCP-Max-strain LLE-Max-strain LCA-Max-strain LLI-Max-strain Total level in C3-PED2E,35,3,25,2,15,1, LCP-Total-strain LCA-Total-strain LLE-Total-strain LLI-Total-strain 324 IRCOBI Conference Madrid (Spain), September 26

7 Rotation ( ) Knee rotations in C3-PED2E Lateral rotation Frontal rotation Leg torsion Displacement (mm) Knee shearing in C3-PED2E Shear_X Shear_Y Shear_Z Fig. 7 Upper femur impact : Knee ligaments maximum and total strain level, Joint kinematics with Shear Y for anterior posterior degree of freedoms, Shear Y for lateral shearing, Shear Z for stretching effects on the leg FOR DISTAL FEMUR IMPACT, the front car bumper was set in front of the femur distal metaphysic which is 95mm above the reference impact position. Impact conditions are same as described in previous tests. The strain curves analysis on ligaments indicates a potential failure of the medial collateral ligament and posterior cruciate ligament (for time ranged from 12 to 14ms). Regarding knee joint kinematics (figure 8 & 9), this potential failure was obtained for of coupled lateral flexion (~12 to 16 ) and lateral shearing effect (~11 to 13mm). This result showed that combination of the two mechanisms leading to ligament failure. Note that front car shape, in particular the lower bumper is simultaneously in contact with lower tibia during the injury mechanisms which could limit the lateral flexion level. For femur and tibia bones, the Von Mises curves showed same location with flexion effects on femur metaphysic which lead to same failure situation as for the upper femur impact at 2ms (later than ligaments injuries) Fig. 8 Three steps of lower limb kinematics and Von Mises stress iso curves on bones for the pedestrian distal femur impact.,9,8,7,6,5,4,3,2,1 Max level in C3-PED2C LCP-Max-strain LLE-Max-strain * LCA-Max-strain LLI-Max-strain Total level in C3-PED2C,5,45,4,35,3,25,2,15,1, LCP-Total-strain LLE-Total-strain LCA-Total-strain LLI-Total-strain IRCOBI Conference Madrid (Spain), September

8 Knee rotations in C3-PED2C Knee shearing in C3-PED2C Rotation ( ) Lateral rotation Frontal rotation Leg torsion Displacement (mm) Shear_X Shear_Y Shear_Z Fig. 9 Distal femur impact : Knee ligaments maximum and total strain level, Joint kinematics with Shear Y for anterior posterior degree of freedoms, Shear Y for lateral shearing, Shear Z for stretching effects on the leg FOR KNEE JOINT IMPACT, the impact occurs on the middle of the knee joint (3mm above reference impact tests) with both primary contact with tibia and femur bones and with same conditions as previous tests (figure 1 & 11). Regarding strain level distribution, the posterior cruciate ligament and medial collateral ligament seems to be injured in the first 7 to 9 ms and then anterior cruciate ligaments. The maximum local strain recorded confirmed these assumptions. The knee joint kinematics is similar to the previous test with a combination of lateral flexion (8-1 ), lateral shearing (1-11mm) and also stretching effects. The front car shape, in particular the lower bumper, is simultaneously in contact with lower tibia during the injury mechanisms which could limit the lateral flexion amplitude. This result indicates that injury criteria should be here a combination between shearing and lateral flexion. Regarding bone structures, Von Mises curves reach values closed to failure limits but didn t fail. Max level in C3-PED2F 1,9,8,7,6,5,4,3,2, LCP-Max-strain LLE-Max-strain LCA-Max-strain LLI-Max-strain Total level in C3-PED2F,9,8,7,6,5,4,3,2, LCP-Total-strain LLE-Total-strain LCA-Total-strain LLI-Total-strain Rotation ( ) Knee rotations in C3-PED2F Lateral rotation Frontal rotation Leg torsion Displacement (mm) Knee shearing in C3-PED2F Shear_X Shear_Y Shear_Z Fig. 1 Knee joint impact : Knee ligaments maximum and total strain level, Joint kinematics with Shear Y for anterior posterior degree of freedoms, Shear Y for lateral shearing, Shear Z for stretching effects on the leg 326 IRCOBI Conference Madrid (Spain), September 26

9 Fig. 11 Three steps of lower limb kinematics and Von Mises stress iso curves on bones for the pedestrian knee joint impact. FOR METAPHYSIS TIBIA IMPACT, the contact with front car occurred on the proximal tibia metaphysic (figure 12) 45mm below reference impact position. The knee ligaments failure was postulated firstly for the two cruciate ligaments at 8ms and then for the medial collateral ligament closed to 1ms. Regarding knee joint kinematics (figure 12 & 13), lateral flexion effects is closed to 5 whereas lateral shearing is dominant and reaches the failure criteria of 13mm. Von Mises stress curves showed that bone structure were highly constraints with failure after ligaments injuries. This failure was observed on the 1/3 of tibia bone and seems to be induced by tibia lateral flexion Fig. 12 Three steps of lower limb kinematics and Von Mises stress iso curves on bones for the pedestrian metaphysic tibia impact. Max level in C3-PED2D 1,9,8,7,6,5,4,3,2, LCP-Max-strain LLE-Max-strain LCA-Max-strain LLI-Max-strain Total level in C3-PED2D,6,5,4,3,2, LCP-Total-strain LCA-Total-strain LLE-Total-strain LLI-Total-strain IRCOBI Conference Madrid (Spain), September

10 Knee rotations in C3-PED2D Knee shearing in C3-PED2D Rotation ( ) Lateral rotation Frontal rotation Leg torsion Displacement (mm) Shear_X Shear_Y Shear_Z Fig. 13 Metaphysis tibia impact : Knee ligaments maximum and total strain level, Joint kinematics with Shear Y for anterior posterior degree of freedoms, Shear Y for lateral shearing, Shear Z for stretching effects on the leg DISCUSSION CONCLUSION The Lower Limb Model for Safety has been designed to describe multiple loading configurations. Once the model is assumed to be well validated, it can be used for predicting injury response for a much wider range of loading parameters. The degree of uncertainty associated with identifying injury events is reduced by defining injury thresholds based on specific parameters like ligament strain and bone stress which can also related to joint kinematics. In previous works (Arnoux et al. 24, Bose et al. 26), we had investigated the definition of a knee joint injury criteria for pedestrian impacts on the base of Kajzer and Bose-Kerrigan previous works (Kajzer et al. 199, 1993, Bose 24, Kerrigan 23). The first criteria, 13mm in lateral shearing and 18 in lateral flexion, was efficient for pure shearing or lateral flexion but was not really studied for the combination of the two mechanisms. For full scale pedestrian simulations, we observed that the two mechanisms occurred simultaneously with various amplitudes according to the impact location (table 3). Table 3: Injury mechanisms synthesis; The numbering (from 1 to 3) in colon was add in order to describe the first mechanisms. The injury criteria column let to complete the injury criteria definition Impact location Injury mechanisms Joint injuries Injury criteria Bones injuries Tibia Prox Shearing dominant 1. The two cruciates 13 mm 3. Tibia 2. Medial collateral ligament Knee Joint Shearing : 1-11mm Flexion : Stretching 1. Posterior cruciate ligament 2. Medial collateral ligament 1 & 1mm Femur Distal Metaphysis Flexion: Shearing : 11-13mm Upper Femur 1. Medial collateral 2. Posterior cruciate ligament 1. Shearing dominant 2. Flexion dominant 3. Medial collateral ligament 2 14 & 11mm 3. Femur 1. Femur From these results, as impact occurred on leg, the shearing is dominant with a 13mm lateral shearing injury criteria. If impact occurs on knee joint, there is a combination of lateral shearing and flexion. On the opposite, an impact located on femur induces a dominant shearing with an associated minor lateral flexion. Consequently, we can improve injury criteria by adding the coupled 14 lateral flexion and 11mm of shearing in the definition of knee joint injury criteria. Notes these results are directly related to the front car geometry studied in this work which induce a limitation of lateral flexion effects for impact on knee joint. In a next step, they should be confirmed for various front car geometries. Moreover, the knee gets impacted with structures of different stiffness (due to various positions). This point need to be also investigated in order to evaluate the potential influence of the local car component stiffness on knee joint injury mechanisms. Regarding the injury risk for knee joint, more the impact location was high, more the ligaments 328 IRCOBI Conference Madrid (Spain), September 26

11 injuries occurred later. On the contrary this trend increases the bone failure risk with a three point failure mode for the femur. Hence, if high impact location seems to minimize (or add delay) on knee joint loading and its potential injury. The consequences for hip joint and consequently pelvis seem to follow the same trends i. e. increase of transmitted force and kinematics with height of impact location. This point should be carefully investigated in further works. Then, regarding safety regulation directive, the future choices for knee joint impact location should be linked to those for pelvis impact. If the impact location is centred on knee joint or on tibia, we can assume that needs to investigate pelvis behaviour regarding first impact phase are minor. On the contrary, for impact occurring on femur component or upper, it could be essential to investigate pelvis behaviour. The results obtained in this work show that stretching effects occurred during some tests which leads to increase strain levels on ligaments (especially with cruciates ones). It is therefore difficult to conclude on the relevance of these effects. Passive and Active muscle contribution is also expected to affect the knee joint stability in emergency pedestrian-car impact situations and its implementation to numerical models such as this should be investigated (only passive behaviour of the muscle groups is described). The further tests will be performed on model version including active or passive muscle behaviour (Behr et al. 26). The LLMS model presents also limitations in terms of descriptions of mechanical properties of biological tissues. More particularly, the damage and unsymmetrical behaviour laws were not included in the model at this stage, which limits the model validity to the first ligament failure. These first results have to be improved with further developments, including damage and failure properties. The questions of model sensitivity need to be further investigated (through mesh influence, ligaments and bone ultimate thresholds and also main mechanical parameters such as Young modulus). Current work in progress will lead to improve model definition and will let to confirm and to describe more accurately, mechanisms investigated in this work. Acknowledgment We would like to acknowledge the technical staff of the laboratory which were in charge of experiments essential to the validation and evaluation of the numerical model. We would also acknowledge Mecalog for their close collaboration as co-designer of the lower limb model. Lastly we would like to acknowledge all partners of the PREDIT APPA project (Mecalog, Faurecia, INRETS MA, INRETS UMRETTE, UTAC and LAB PSA- Renault) for their contribution especially providing the numerical model of the car front. References Arnoux P.J. Modélisation des ligaments des members porteurs, PhD dissertation, PhD Thesis, Université de la Méditerranée, Marseille, France, 2. Arnoux P.J., Kang H.S., Kayvantash K., Brunet C., Cavallero C., Beillas P., Yang H., The Radioss Lower Limb Model for safety: application to lateral impacts, International Radioss user Conference. Sophia June 21 Arnoux P.J., Cesari D., Behr M., Thollon L., Brunet C., Pedestrian lower limb injury criteria evaluation a finite element approach, Traffic Injury Prevention journal, Vol. 6, N 3, 25,pp Behr M., Arnoux P.J., Serre T., Thollon L., Brunet C., Tonic Finite Element Model of the Lower Limb., Journal of Biomechanical Engineering, 26 Apr;128(2): Beillas P., Begeman P. C., Yang K. H., King A. I., Arnoux P. J., Kang H. S., Kayvantash K., Brunet C., Cavallero C., Prasad P., Lower Limb: Advanced FE Model and New Experimental Data, Stapp Car Crash Journal, Vol. 45, 21, pp Bermond F., Ramet M., Bouquet R., Cesari D., A finite element model of the pedestrian leg in lateral impact, 14 th ESV, IRCOBI Conference Madrid (Spain), September

12 Bose D., Bhalla K., Rooij L., Millington S., Studley A., Crandall J., Response of the Knee joint to the pedestrian impact loading environment, SAE World Congress, paper , 24 Bose D., Arnoux P.J., Cardot J., Brunet C., Evaluation of knee injury threshold in pedestrian car crash loading using numerical approach, International Journal of Crashworthiness, to be published 26 Chawla A., Mukherjee S., Mohan D. and Parihar A., Validation of lower extremity model in THUMS, Proceedings of the IRCOBI conference, 24. Teresinski G., Madro R., Pelvis and hip injuries as a reconstructive factors in car-to-pedestrian accidents, Forensic Science International 124, 21, pp Kajzer J., Cavallero C., Bonnoit J., Morjane A., Ghanouchi S., Response of the knee joint in lateral impact: Effect of bending moment. Proc. IRCOBI, 1993, pp Kajzer J., Cavallero C., Bonnoit J., Morjane A., Ghanouchi S., Response of the knee joint in lateral impact: Effect of shearing loads. Proc. IRCOBY, 199, pp Kerrigan J. R., Bhalla K. S., Madeley N. J., Funk J. R., Bose D., Crandall J. R., Experiments for Establishing Pedestrian-Impact Lower Limb Injury Criteria, SAE Paper , 23. Nagasaka, K., Mizuno, K., Tanaka, E., Yamamoto, S., Iwamoto, M., Miki, K. and Kajzer, J. Finite Element Analysis of Knee Injury Risks in Car-to-Pedestrian Impacts. Traffic Injury Prevention, Vol. 4, 23, pp Nyquist G.W., Cheng R., El-Bohy A.R., King A.I.. Tibia bending : strength and response, 29 th Stapp Car Crash Conference Proc., n , 1985, pp Schuster P. J., Chou C. C., Prasad P., Development and Validation of a Pedestrian Lower Limb Non- Linear 3-D Finite Element Model, Stapp Car Crash Journal, Vol. 44, 2-1-SC21, 2 Serre T., Perrin C., Bohn M., Llari M., Cavallero C., Detailed investigations and reconstructions of real accidents involving vulnerable road users, 1 st international conference on ESAR 24, pp , 24 Takahashi Y., Kikuchi, Y., Mori, F., and Konosu, A., Advanced FE Lower Limb Model for Pedestrians. 18 th International Conference on the Enhanced Safety of Vehicles, 23 Wismans, J., Veldpaus, F., Janssen, J., Huson, A., and Struben, P., A three-dimensional mathematical model of the knee joint, Journal of Biomechanics, 198, pp Yang, J.K., and Kajzer, J., Mathematical model of the pedestrian lower extremity, International Conference on the Enhanced Safety of Vehicles, Yang J.K., Wittek A., Kajzer J., Finite element model of the human lower extremity skeleton system in a lateral impact, IRCOBI, IRCOBI Conference Madrid (Spain), September 26