report on thor-lx design and performance

Report published on the EEVC web site: www.eevc.org

Report on THOR-Lx Design and Performance WG12 report March 2009

Report published on the EEVC web site: www.eevc.org

EEVC WG12 Report – Document Number 546

Report on THOR-Lx Design and Performance

March 2009

Authors P. Vezin, P. Thomas (WG21), M. van Ratingen, J. Carroll and D. Hynd

On behalf of the European Enhanced Vehicle-safety Committee (EEVC) Working Group 12

Number of Pages (including Appendices) 64

EEVC Working Group 12 Version THOR Lx Design and Performance Final

i Report published on the EEVC web site: www.eevc.or

CONTENTS

Summary 1

Part 1: Leg Injury Analysis– Patterns of Injury 3

1 Introduction 3

2 Development of leg injuries compared to other body regions 3 2.1 Injured body regions in frontal accidents 4 2.2 Distribution of AIS 2+ injuries in frontal accident 7 2.3 Distribution of AIS 3+ injuries in frontal accident 9 2.4 Injured body regions in frontal accidents with overlap less than 20% 11 2.5 Distribution of AIS 2+ injuries in frontal accident with overlap < 20% 13

3 Development of different leg injuries 14 3.1 Specific leg injuries in frontal accidents 15 3.2 Distribution of AIS 2+ lower extremity injuries in frontal accident 18 3.3 Specific leg injuries in frontal accidents with overlap less than 20% 20

4 Results and Discussion 22 4.1 Change in injury rates for each body region 22 4.2 Nature of lower extremity injuries 24

Appendix – Overview of databases used in analysis. 25

Part 2: THOR-Lx Design and Performance 27

1 Background 27

2 Design of THOR-Lx 28 2.1 Anthropometry 28 2.2 Advanced design features 28 2.3 Instrumentation 30

3 Performance of the THOR-Lx 32 3.1 Mandatory certification requirements 32 3.2 Design reference requirements 32 3.3 Biofidelity Requirements 34

3.3.1 Biofidelity requirements by NHTSA: 34 3.3.2 Biofidelity requirements by European Project FID: 40

4 Remarks 42

References 43


ii Report published on the EEVC web site: www.eevc.or

Part 3: Lower Leg Injury Criteria for use with the THOR-Lx 44

1 Introduction 44

2 THOR-Lx Dummy-specific Injury Risk Functions 45 2.1 Introduction 45 2.2 Hynd et al. (2003) 45 2.3 Rudd et al. (2004) 47

3 Human Injury Risk Functions 49 3.1 Introduction 49 3.2 Funk et al. (2001) 49 3.3 Kuppa et al. (2001a and 2001b) 51 3.4 Funk et al. (2002) 53 3.5 Funk et al. (2004) 55

4 THOR-Lx Biofidelity Assessment 56 4.1 Rudd et al. (1999) 56

5 Other Information 57 5.1 Rudd et al. (2001) 57 5.2 Shaw et al. (2002) 57 5.3 Rudd et al. (2003) 57

6 Summary 59

7 Discussion 61

8 Recommendations 62

References 63


1 Report published on the EEVC web site: www.eevc.org

Summary

Introduction The THOR (Test device for Human Occupant Restraint) frontal impact dummy was developed as the next generation in crash test dummies. Since 1995, a prototype THOR dummy and the first production dummy, known as THOR Alpha, have been produced. This dummy has been evaluated by organisations worldwide, including the FID EC project consortium in Europe.

Based on the fact that almost half of the crash injuries of the lower extremities occur below the knee and, of which, ankle and foot injuries are the most frequent and can be responsible for long-term impairment and immobility, dummy lower legs for addressing lower leg injuries in frontally-oriented impacts were needed to be used within the THOR. The more recently designed THOR-Lx Hybrid III Retrofit (called THOR-Lx/HIIIr) leg, or THOR-Lx, is the lower extremity used with this advanced anthropometric test device.

The THOR-Lx is an improvement as compared with previously existing crash test dummy technology, because it incorporates significantly improved biofidelity and expanded injury assessment capabilities. Thanks to its enhanced design and measurement capabilities, THOR-Lx offers numerous functional benefits as compared with previously existing frontal impact dummy lower legs, including detailed assessment of foot motions and ankle/foot/tibia injury potential.

With different, or improved, biofidelity over existing dummy lower extremity then, under the same loading conditions, the THOR-Lx response and transducer outputs may be different to those of the existing dummy leg, such as those currently used with Hybrid III. If the outputs are different for the same impact conditions, then existing injury assessment reference values, for use with other dummies, cannot simply be transferred for use with the THOR. Instead it is important to redefine injury criteria based on risk functions applicable to the THOR-Lx specifically - in other words, to develop dummy-specific injury risk functions.

THOR-Lx Design and Performance This report is intended to give descriptions and recommendations regarding the design, performance and use of the THOR Lx to assess lower leg injuries in frontal car crashes. To achieve these objectives, a description of the design of the new features available within the THOR Lx and its performance, including certification and biofidelity requirements, is provided in Part 2. Some of these advances include: 1) axial compliance to represent compressibility of the tibia, 2) a fully functioning ankle that allows rotation in all three directions and 3) an Achilles’ cable that provides an alternate load path in the lower leg and controls dorsiflexion.

The lower leg is instrumented with two load cells and accelerometers. The upper load cell measures Fx, Fz, Mx, and My while the lower records Fx, Fy, Fz, Mx, and My. The tibia accelerometer measures Ax and Ay while the foot accelerometer measures Ax, Ay, and Az. In addition, three rotary potentiometers are used to measure the rotation of the ankle joint about the X, Y, and Z axes. A uniaxial load cell is installed to measure the Achilles Cable tension.

The THOR-Lx performance is examined according to three kinds of requirement: i) certification requirements; ii) design reference requirements and; iii) biofidelity requirements. The design reference requirements are used as an additional functionality check of the product, and the biofidelity requirements to evaluate the “humanlike” behaviour of the THOR-Lx leg. Biofidelity requirements defined by NHTSA comprise quasi static tests to assess the biofidelity for inversion/eversion, plantarflexion, internal/external rotation and dorsiflexion. Dynamic tests were also defined for inversion/eversion and heel impact and as additional requirement, dorsiflexion.

In addition to these requirements, the FID EC project proposed two sets of tests to evaluate the biofidelity of the lower leg one is a pendulum impact to the toe. The other is a pendulum test to the heel.



Leg Injury Analysis– Patterns of Injury An accident data analysis was conducted by the EEVC WG21 on request of the WG12 in order to prioritise injuries for different body regions of belted drivers and front seat passengers, occurring in frontal accidents. This analysis is reported in the Part 1 of the document.

The analysis was performed using four European accident databases (from UK, Sweden, France and Germany). This study confirms and highlights the importance of injury quoted AIS2+of the leg compared to the others body regions. Moreover, despite differences between the databases, it is demonstrated that relative to other body regions at AIS 2+ the importance of lower extremity injuries remained effectively unchanged and they represented between 15-30% of all injured body regions for cars registered during the periods 1990-1995, 1996-2000 and since 2000 within the different data sources.

Among all the different injury patterns of the lower extremity, the analysis performed by the WG21 confirmed that the most common injuries concerned the lower leg and more specifically the skeletal parts. The higher rates of AIS2+ were found for tibia and fibula, ankle and foot. These injuries can not be evaluated correctly with the current dummy leg and the additional measurement capabilities of the THOR-Lx represents a good improvement in order to evaluate correctly the risk of lower leg injuries in frontal accidents.

Lower Leg Injury Criteria for use with the THOR-Lx The assessment of the injury risk through the use of crash test dummies is often conditioned by the characteristics of the dummy such as its anthropometry, biofidelity, repeatability and so forth that are supposed to be good. Moreover, to be useful, the physical parameters measured by the dummy part have to be related to an injury risk function and injury criteria. Injury risk functions can be either human injury risk functions or dummy-specific injury risk functions. If the biofidelity requirements for the dummy contain some uncertainty, this implies that the direct use of human injury risk functions with the dummy would be subject to the same uncertainty. The EEVC approach has therefore been to use dummy-specific injury risk functions where possible - that is, to calibrate the injury prediction measurements of the dummy. Using this dummy-specific approach, the injury risk function for the dummy is able to account for the biofidelity performance of the dummy.

Part 3 of the document reviews the published injury risk functions that have been proposed for use with the THOR-Lx advanced lower leg. The biofidelity of the THOR Lx compared with the human lower leg in similar loading conditions was also evaluated. Based on the papers reviewed, injury assessment reference values are recommended for use with the THOR-Lx. However, it should be remembered that not all of these were developed specifically for use with the THOR. As such, they may not be absolutely applicable to the prediction of injury, as they stand. Therefore, it is also recommended that work be directed towards developing THOR-Lx specific injury risk curves for all parameters that are considered as important.



Part 1: Leg Injury Analysis– Patterns of Injury

By P. Thomas (EEVC WG21) and P. Vezin (INRETS).

1 Introduction This set of data tables and graphs has been prepared by EEVC WG 21 on request of WG 12. The leg injury analysis comprises the description of the patterns of injury from:

,the UK CCIS ־

,the French Rhône Register ־

,the Swedish STRADA and ־

.the German GIDAS Databases ־

The analysis was conducted by:

,Ruth Welsh (VSRC Loughborough University) for the UK CCIS data ־

,Johan Strandroth (Swedish National Roads Authority) for Swedish data ־

Sylviane Lafont and Gilles Vallet (INRETS) for French INRETS Rhône Register data ־and,

.Dietmar Otte, Joachim Nehmzow (MHH) and Volker Eis (Ford Europe) for GIDAS data ־

The data were compiled by Pete Thomas (chairman of EEVC WG21).

Each dataset has its own opportunities and restrictions so not every table can be replicated from each source. Where similar but non-identical data is presented differences are highlighted.

The analysis is restricted to frontal impacts only and to cars with year of first registration not older than 1990 - only M1 vehicles up to 2.5t GVW1 in crashes where the most severe collision was a frontal impact between 1 and 11 O'clock force direction. Furthermore only belted frontal passengers are included.

The analysis first considers the development of lower leg injuries as compared to other injury locations (in terms of body regions). Date of manufacture is not recorded in most accident databases so date of first registration will be used. Three age ranges – 1990 – 1995, 1996 – 1999, 2000+ were defined and analysed separately.

The data from different countries are collected using different inclusion criteria so the percentages cannot be directly compared between the two groups although comparisons of the percentages within a country are valid.

2 Development of leg injuries compared to other body regions To understand the importance of lower leg injuries in frontal car crash, these injuries need first to be compared with the other injured body regions. The following tables provided a comparison of the number of leg injuries with other body regions per AIS for four different European databases. The concerned body regions are Head, Neck, Thorax, Abdomen and upper extremities. Concerning the lower extremities, the pelvis is detailed separate from the rest of the lower extremity.

In each of the tables in this section the basic unit will be a car occupant. For instance, in the Table 1.a. below there were 1060 belted front occupants in the CCIS data in cars in the selected registration years. 682 of these sustained no head injury while 237 sustained an AIS 1 head injury. There were 49 casualties for whom the injury status of their head was not known. 1 M1: Carriage of Passengers with a minimum of 4 wheels and up to 9 occupants. With a Gross Vehicle Weight less than 2.5t



As explained in the introduction the data from the different country can not be merged due to the differences in collection and analyses (see Appendix). Consequently the results are given for each of the four databases. Moreover, the data from each of the three age ranges are given in separate tables: Table 1.a for car registered in the period 1990-1995, Table 1.b for the period 1996-1999 and Table 1.c for car registered since 2000.

In each table, the AIS of the lower extremity are the highest value across both legs. A discussion and analysis of the results are given in section 4.1

2.1 Injured body regions in frontal accidents

Table 1.a. Injured body regions in frontal accidents with cars registered between 1990 and 1995

AIS LevelLocation of injury 0 1 2 3 4 5 6 9 (Unknown) Total number

UK CCIS Head 682 237 47 18 13 10 4 49 1060 Neck 647 350 8 6 0 0 3 46 1060 Thorax 504 367 70 25 35 8 3 48 1060 Abdomen 730 233 38 9 4 0 0 46 1060 Pelvis 966 8 27 11 2 0 0 46 1060 Lower Extremities 571 324 60 59 0 0 0 46 1060 Upper Extremities 623 272 88 31 0 0 0 46 1060 Unknown 985 27 0 1 0 0 0 47 1060

Sweden STRADA Head 130 146 67 40 34 15 13 4 449 Neck 331 105 8 3 0 1 1 0 449 Thorax 94 121 42 73 57 49 12 1 449 Abdomen 345 29 43 18 13 1 0 0 449 Pelvis 447 0 0 2 0 0 0 0 449 Lower Extremities 168 105 78 98 0 0 0 0 449 Upper Extremities 292 76 47 34 0 0 0 0 449 Unknown

France INRETS Rhône Register

Head 499 60 73 11 17 1 9 0 670 Neck 590 79 1 0 0 0 0 0 670 Thorax 405 166 47 21 15 8 8 0 670 Abdomen 605 35 18 7 4 1 0 0 670 Pelvis 662 0 0 6 2 0 0 0 670 Lower Extremities 367 181 71 50 1 0 0 0 670 Upper Extremities 460 120 60 30 0 0 0 0 670 Unknown 618 51 0 0 0 0 1 0 670

Germany GIDAS Head 520 184 62 7 5 3 5 21 807 Neck 501 273 10 3 0 1 3 16 807 Thorax 395 320 46 9 14 6 3 14 807 Abdomen 736 37 10 5 2 0 0 17 807 Pelvis 748 33 7 2 1 1 0 15 807 Lower Extremities 530 202 34 27 0 0 0 14 807 Upper Extremities 577 173 35 10 0 0 0 12 807 Unknown



Table 1.b. Number of injuries in frontal accidents with cars registered between 1996 – 1999

AIS Level Location of injury 0 1 2 3 4 5 6 9 (Unknown) Total number



France INRETS Rhône Register





Table 1.c. Number of injuries in frontal accidents with cars registered 2000 onwards AIS Level Location of injury 0 1 2 3 4 5 6 9 (Unknown) Total number



France INRETS Rhône Register Head 230 24 21 0 5 3 2 0 285 Neck 258 26 0 0 0 1 0 0 285 Thorax 190 63 11 12 7 1 1 0 285 Abdomen 258 18 3 4 2 0 0 0 285 Pelvis 277 0 0 7 1 0 0 0 285 Lower Extremities 175 68 21 21 0 0 0 0 285 Upper Extremities 191 55 21 18 0 0 0 0 285 Unknown 256 29 0 0 0 0 0 0 285




2.2 Distribution of AIS 2+ injuries in frontal accident

The following graphs show the distribution per body segment of the rate of AIS2+ injuries sustained by a belted front occupant. For example, there were 1011 head injuries in the CCIS data in cars registered between 1990-1995 and of which 92 were quoted ≥ 2 (The unknown injuries were not counted). Consequently, the rate of AIS2+ is 92/1011 = 9.10%. The data from each European database are presented separately. In each figure a comparison of the three group of car registration date are given. UK CCIS, Swedish Strada, French Rhône Register and German GIDAS data are plotted in Figure 2.1 to 2.4 respectively.

UK CCIS Data

1,7%

3,9%

11,7%

11,7%

6,3%

1,7%

12,9%

4,1%

2,5%

11,1%

11,0%

3,9%

1,4%

11,4%

4,2%

2,0%

10,8%

5,0%

9,1%

13,9%

9,8%

0%

2%

4%

6%

8%

10%

12%

14%

16%

Head Neck Thorax Abdomen Pelvis LowerExtremities

UpperExtremities

Rate of A

IS2+

injury

1990‐19951996‐20002000+

Figure 2.1: Distribution of AIS 2+ injuries in frontal accident for three different range of registration

(1990-1995; 1996-2000; >2000) - UK CCIS database

Swedish STRADA Data

2,9%

0,4%

39,2%

18,0%

28,7%

7,8%

48,8%

21,0%

1,2%

35,3%

20,9%

22,7%

5,1%

35,6%

10,8%

0,7%

14,6%

52,0%

38,0%

16,7% 20,5%

0%

10%

20%

30%

40%

50%

60%


UpperExtremities

Rate of A

IS2+

injury

1990‐19951996‐20002000+


(1990-1995; 1996-2000; >2000) - Swedish STRADA database



French INRETS Rhône Register Data

0,1% 1,2%

18,2%

13,4%

11,0%

0,3%

15,6%

5,6%

2,0%

19,2%

13,8%

10,9%

0,4%

11,2%

3,2%

2,8%

13,7%

14,8%16,6%

4,5%

14,7%

0%

5%

10%

15%

20%

25%


UpperExtremities

Rate of A

IS2+

injury

1990‐19951996‐20002000+


(1990-1995; 1996-2000; >2000) - French Rhône Register database

German GIDAS Data

2,1%

1,4%

7,7%

5,7%

8,0%

2,0%

7,7%

0,5% 1,0%

5,2%

3,2%

7,3%

0,5%

5,2%

0,5%

0,5%

5,2%

9,8%10

,4%

2,2%

3,6%

0%

2%

4%

6%

8%

10%

12%


UpperExtremities

Rate of A

IS2+

injury

1990‐19951996‐20002000+


(1990-1995; 1996-2000; >2000) - German GIDAS database



2.3 Distribution of AIS 3+ injuries in frontal accident The following figures were plotted using the same methodology than for the distribution of AIS 2+ injuries in frontal accident but for the injuries rated ≥3. In each figure a comparison of the three group of car registration date are given. The data from each European database are presented separately. UK CCIS, Swedish Strada, French Rhône Register and German GIDAS data are plotted in Figure 2.5 to 2.8 respectively.

UK CCIS Data

0,9% 1,

3%

5,8%

3,1%3,3%

0,7%

6,3%

1,2%

0,7%

4,9%

2,3%

1,9%

0,4%

5,6%

1,2%

0,9%

2,3%

1,3%

4,5%

7,0%

5,9%

0%

1%

2%

3%

4%

5%

6%

7%

8%


UpperExtremities

Rate of A

IS3+

injury

1990‐19951996‐20002000+


(1990-1995; 1996-2000; >2000) - UK CCIS database

Swedish STRADA Data

1,1%

0,4%

21,8%

7,6%

17,7%

1,2%

39,1%

12,5%

1,2%

21,3%

10,9%

12,9%

2,7%

28,0%

3,4%

0,7%

4,6%

42,6%

22,9%

7,1%

11,2%

0%

5%

10%

15%

20%

25%

30%

35%

40%

45%


UpperExtremities

Rate of A

IS3+

injury

1990‐19951996‐20002000+


(1990-1995; 1996-2000; >2000) - Swedish STRADA database




0,0%

1,2%

7,6%

4,5%

3,6%

0,3%

7,7%

2,0%

2,0%

6,9%

5,4%

3,5%

0,4%

7,4%

2,1%

2,8%

6,3%

7,8%

5,7%

1,8%

7,4%

0%

1%

2%

3%

4%

5%

6%

7%

8%

9%


UpperExtremities

Rate of A

IS3+

injury

1990‐19951996‐20002000+


(1990-1995; 1996-2000; >2000) - French Rhône Register database

German GIDAS Data

0,9%

0,5%

3,4%

1,3%1,

5%

0,7%

2,5%

0,5%

0,2%

3,0%

0,0%

1,6%

0,5%

2,1%

0,0%

0,0%

1,6%

4,0%

2,5%

0,9%

1,6%

0%

1%

1%

2%

2%

3%

3%

4%

4%

5%


UpperExtremities

Rate of A

IS3+

injury

1990‐19951996‐20002000+


(1990-1995; 1996-2000; >2000) - German GIDAS database



2.4 Injured body regions in frontal accidents with overlap less than 20%

The Table 1-d to 1.f contain the same information as described in section 2.1 but the data are provided only for accident with an overlap of less than 20%. But for this accident condition the data are only available for UK CCIS and Germany GIDAS databases. In each table, the AIS of the lower extremity are the highest value across both legs. A discussion and analysis of the results are given in section 4.1

Table 1.d.: Number of injuries in frontal accidents with cars registered between 1990 and 1995 and overlap less than 20%.




Table 1.e. Number of injuries in frontal accidents with cars registered between 1996 - 1999 and overlap less than 20%


UK CCIS





Table 1.f. Number of injuries in frontal accidents with cars registered between 2000 onwards and overlap less than 20%.






2.5 Distribution of AIS 2+ injuries in frontal accident with overlap < 20%

The following figures were plotted using the same methodology than for the distribution of AIS 2+ injuries in frontal accident but frontal accident with overlap < 20%. The data from each European database are presented separately. UK CCIS and German GIDAS data are plotted in Figure 2.9 and 2.10. In each figure a comparison of the three group of car registration date are given.

UK CCIS Data

0,0%

0,0%

3,1%

4,7%5,2%

2,6%

5,9%

2,6%

1,3%

10,5% 11,1%

5,4%

1,4%

7,4%

0,7%

3,4%

4,7%

1,6%

9,4%

4,7%

5,4%

0%

2%

4%

6%

8%

10%

12%


UpperExtremities

Rate of A

IS2+

injury

1990‐19951996‐20002000+

Figure 2.9: Distribution of AIS 2+ injuries in frontal accident with overlap lass than 20% for three

different range of registration (1990-1995; 1996-2000; >2000) - UK CCIS database

German GIDAS Data

3,3%

0,7%

2,6% 3,

3%

4,6%

1,1%

4,5%

2,3%

1,1%

4,5%

0,0%

11,1%

0,0%

8,3%

2,8%

2,8%

11,1%

3,9%

5,3%

2,0%

5,6%

0%

2%

4%

6%

8%

10%

12%


UpperExtremities

Rate of A

IS2+

injury

1990‐19951996‐20002000+

Figure 2.10: Distribution of AIS 2+ injuries in frontal accident with overlap lass than 20% for three

different range of registration (1990-1995; 1996-2000; >2000) - German GIDAS database



3 Development of different leg injuries The analysis of the accident data examines in a second step the development of the different lower leg injuries in detail. The following Tables 2.a to 2.c provided a comparison of the number of different type of injuries from AIS 0 to AIS 4 for four different databases. The different types of injuries concerned either bone or soft tissues including ligament injuries. The concerned lower extremity parts are Upper leg, Knee, Lower leg, Ankle joint and Foot.

Again the analysis has been done for all AIS levels separately. Analysis with respect to AIS 2+ will reduce the number of leg injuries too much because they are generally not rated higher than AIS 4. The table shall show the injury locations on the leg with the highest overall share.

The units within the following tables will be injuries so for example if a casualty has a right patella fracture, a right tibia fracture and a fractured left femur there will be three entries in the table. The distribution of AIS 2+ lower extremity injuries were plotted in different figures in section 3.2 and 3.4. A discussion and analysis of the results are given in section 4.2.

As explained in the previous section the data from the different country can not be merged due to the differences in collection and analyses (see Appendix). Consequently the results are given for each of the four databases. Moreover, the data from each of the three age ranges are given in separate tables: Table 2.a for car registered in the period 1990-1995, Table 2.b for the period 1996-1999 and Table 2.c for car registered since 2000.

In each table, the AIS of the lower extremity are the highest value across both legs.



3.1 Specific leg injuries in frontal accidents

Table 2.a. Number of specific leg injuries in frontal accidents with cars registered between 1990 and 1995

AIS Level Location of injury 1 2 3 4 Total number

UK CCIS

Upper leg ‐ non‐skeletal 0 1 0 0 1 Upper leg ‐ skeletal 0 35 77 2 114 Knee ‐ surface tissues 0 0 0 0 0 Knee ‐ skeletal (including ends of femur/tibia) 0 30 2 0 32 Knee ‐ ligaments 0 4 0 0 4 Lower leg ‐ non‐skeletal 0 0 0 0 0 Lower leg ‐ skeletal 2 56 13 0 71 Ankle joint ‐ skeletal and ligamentous 14 42 2 0 58 Foot ‐ skeletal 1 14 0 0 15 Others 894 6 0 0 900 Total number 911 188 94 2 1195

Sweden STRADA Upper leg ‐ non‐skeletal 4 1 0 0 5 Upper leg ‐ skeletal 7 1 33 0 41 Knee ‐ surface tissues 25 0 0 0 25 Knee ‐ skeletal (including ends of femur/tibia) 31 13 17 0 61 Knee ‐ ligaments 0 4 0 0 4 Lower leg ‐ non‐skeletal 11 4 5 0 20 Lower leg ‐ skeletal 12 25 37 0 74 Ankle joint ‐ skeletal and ligamentous 1 11 3 0 15 Foot ‐ skeletal 5 14 0 0 19 Others 9 5 3 0 17 Total number 105 78 98 0 281

France INRETS Rhône Register Upper leg ‐ non‐skeletal 20 7 0 0 27 Upper leg ‐ skeletal 9 1 49 1 60 Knee ‐ surface tissues 1 0 0 0 1 Knee ‐ skeletal (including ends of femur/tibia) 96 29 0 0 125 Knee ‐ ligaments 5 4 1 0 10 Lower leg ‐ non‐skeletal 0 0 0 0 0 Lower leg ‐ skeletal 1 20 16 0 37 Ankle joint ‐ skeletal and ligamentous 23 17 1 0 41 Foot ‐ skeletal 10 32 0 0 42 Others 94 12 5 0 111 Total number 259 122 72 1 454

Germany GIDAS Upper leg ‐ non‐skeletal 12 0 2 0 14 Upper leg ‐ skeletal 0 1 21 0 22 Knee ‐ surface tissues 133 1 0 0 134 Knee ‐ skeletal (including ends of femur/tibia) 1 7 2 0 10 Knee ‐ ligaments 0 3 0 0 3 Lower leg ‐ non‐skeletal 46 0 0 0 46 Lower leg ‐ skeletal 1 7 5 0 13 Ankle joint ‐ skeletal and ligamentous 7 11 0 0 18 Foot ‐ skeletal 2 18 0 0 20 Others 67 8 2 0 77 Total number 269 56 32 0 357



Table 2.b. Number of specific leg injuries in frontal accidents with cars registered between 1996 and 1999


UK CCIS Upper leg ‐ non‐skeletal 0 0 0 0 0 Upper leg ‐ skeletal 1 43 93 2 139 Knee – surface tissues 0 0 0 0 0 Knee ‐ skeletal (including ends of femur/tibia) 3 60 17 0 80 Knee ‐ ligaments 0 6 0 0 6 Lower leg ‐ non‐skeletal 0 0 0 0 0 Lower leg ‐ skeletal 3 35 12 0 50 Ankle joint ‐ skeletal and ligamentous 16 74 0 0 90 Foot – skeletal 27 57 0 0 84 Others 1556 13 1 0 1570 Total number 1606 288 123 2 2019

Sweden STRADA Upper leg ‐ non‐skeletal 2 0 0 0 2 Upper leg ‐ skeletal 6 1 20 0 27 Knee – surface tissues 20 0 0 0 20 Knee ‐ skeletal (including ends of femur/tibia) 23 7 8 0 38 Knee ‐ ligaments 0 0 0 0 0 Lower leg ‐ non‐skeletal 14 2 2 0 18 Lower leg ‐ skeletal 16 13 24 0 53 Ankle joint ‐ skeletal and ligamentous 0 4 0 0 4 Foot – skeletal 7 7 0 0 14 Others 9 2 1 0 12 Total number 97 36 55 0 188

France INRETS Rhône Register Upper leg ‐ non‐skeletal 9 2 0 0 11 Upper leg ‐ skeletal 1 0 25 0 26 Knee – surface tissues 1 0 0 0 1 Knee ‐ skeletal (including ends of femur/tibia) 39 12 0 0 51 Knee ‐ ligaments 2 5 0 0 7 Lower leg ‐ non‐skeletal 0 0 0 0 0 Lower leg ‐ skeletal 0 12 9 0 21 Ankle joint ‐ skeletal and ligamentous 5 21 0 0 26 Foot – skeletal 6 18 0 0 24 Others 46 3 2 0 51 Total number 109 73 36 0 218

Germany GIDAS Upper leg ‐ non‐skeletal 3 0 0 0 3 Upper leg ‐ skeletal 0 0 10 0 10 Knee – surface tissues 77 1 0 0 78 Knee ‐ skeletal (including ends of femur/tibia) 0 3 0 0 3 Knee ‐ ligaments 0 0 1 0 1 Lower leg ‐ non‐skeletal 18 0 0 0 18 Lower leg ‐ skeletal 0 5 1 0 6 Ankle joint ‐ skeletal and ligamentous 2 4 1 0 7 Foot – skeletal 0 5 0 0 5 Others 24 1 1 0 26 Total number 124 19 14 0 157



Table 2.c. Number of specific leg injuries in frontal accidents with cars registered from 2000 and newer


UK CCIS Upper leg ‐ non‐skeletal 0 0 0 0 0 Upper leg ‐ skeletal 2 23 70 1 96 Knee – surface tissues 0 0 0 0 0 Knee ‐ skeletal (including ends of femur/tibia) 3 29 11 0 43 Knee ‐ ligaments 0 6 0 0 6 Lower leg ‐ non‐skeletal 1 22 12 0 35 Lower leg ‐ skeletal 1 30 15 0 46 Ankle joint ‐ skeletal and ligamentous 19 41 2 0 62 Foot – skeletal 23 26 0 0 49 Others 804 6 1 1 812 Total number 853 183 111 2 1149

Sweden STRADA Upper leg ‐ non‐skeletal 2 0 0 0 2 Upper leg ‐ skeletal 3 1 15 0 19 Knee – surface tissues 11 0 0 0 11 Knee ‐ skeletal (including ends of femur/tibia) 19 5 6 0 30 Knee ‐ ligaments 0 3 0 0 3 Lower leg ‐ non‐skeletal 11 1 6 0 18 Lower leg ‐ skeletal 24 9 16 0 49 Ankle joint ‐ skeletal and ligamentous 1 9 2 0 12 Foot – skeletal 3 10 0 0 13 Others 4 0 1 0 5 Total number 78 38 46 0 162

France INRETS Rhône Register Upper leg ‐ non‐skeletal 7 2 1 0 10 Upper leg ‐ skeletal 2 0 20 1 23 Knee – surface tissues 0 0 0 0 0 Knee ‐ skeletal (including ends of femur/tibia) 30 8 1 0 39 Knee ‐ ligaments 2 3 0 0 5 Lower leg ‐ non‐skeletal 0 0 12 0 12 Lower leg ‐ skeletal 0 13 0 0 13 Ankle joint ‐ skeletal and ligamentous 13 5 0 0 18 Foot – skeletal 1 8 0 0 9 Others 40 6 0 46 Total number 95 45 34 1 175

Germany GIDAS Upper leg ‐ non‐skeletal 1 0 0 0 1 Upper leg ‐ skeletal 0 0 3 0 3 Knee – surface tissues 32 0 0 0 32 Knee ‐ skeletal (including ends of femur/tibia) 0 1 0 0 1 Knee ‐ ligaments 0 1 0 0 1 Lower leg ‐ non‐skeletal 9 1 0 0 10 Lower leg ‐ skeletal 0 2 2 0 4 Ankle joint ‐ skeletal and ligamentous 3 1 1 0 5 Foot – skeletal 0 2 0 0 2 Others 7 1 0 0 8 Total number 52 9 6 0 67



3.2 Distribution of AIS 2+ lower extremity injuries in frontal accident

The following graphs show the percentage of the type of injury with respect to the other AIS2+ injuries. For example, there were 114 upper leg – skeletal injuries in the CCIS data in cars registered between 1990-1995 among 284 injuries quoted ≥ 2. Consequently, the rate of injuries AIS2+ is 114/284 = 40.14%. In each figure a comparison of the three group of car registration date are given but the data from each European database are presented separately. UK CCIS, Swedish Strada, French Rhône Register and German GIDAS data are plotted in Figure 3.1 to 3.4 respectively. The results are analysed and discussed in section 4.2.

UK CCIS Data

40,1%

1,4%

0,0%

24,3%

15,5%

4,9%

2,1%

0,0%

33,4%

0,0%

18,6%

1,5%

0,0%

11,4%

17,9%

13,8%

3,4%

0,0%

31,8%

0,0%

13,5%

2,0%

15,2%

14,5%

8,8%

2,7%

0,0%0,4%

11,3%

11,5%

0%

5%

10%

15%

20%

25%

30%

35%

40%

45%

Upper leg ‐ non‐skeletal

Upper leg ‐ skeletal

Knee ‐ surface tissues

Knee ‐ skeletal

Knee ‐ ligaments

Lower leg ‐ non‐skeletal

Lower leg ‐ skeletal

Ankle joint ‐ skeletal and ligamentous

Foot ‐ skeletal

Others

Rate of A

IS2+

injury

1990‐19951996‐20002000+

Figure 3.1: Distribution of AIS 2+ lower extremity injuries in frontal accident for three different range of

registration (1990-1995; 1996-2000; >2000) - UK CCIS database

Swedish STRADA Data

19,3%

2,3%

5,1%

35,2%

8,0%

8,0%

4,5%

0,0%

23,1%

0,0%

16,5%

0,0%

4,4%

40,7%

4,4%

7,7%

3,3%

0,0%

19,0%

0,0%

13,1%

3,6%

29,8%

13,1%

11,9%

1,2%

17,0%

0,6%

0,0%

8,3%

0%

5%

10%

15%

20%

25%

30%

35%

40%

45%




Knee ‐ skeletal

Knee ‐ ligaments




Foot ‐ skeletal

Others

Rate of A

IS2+

injury

1990‐19951996‐20002000+


registration (1990-1995; 1996-2000; >2000) – Swedish STRADA database




26,2%

2,6%

0,0%

18,5%

9,2%

16,4%

8,7%

1,8%

22,9%

0,0%

11,0%

4,6%

0,0%

19,3%

19,3%

16,5%

4,6%

3,8%

26,3%

0,0%

11,3%

3,8%

16,3%

6,3%

10,0%

7,5%

14,9%

3,6%

0,0%

15,0%

0%

5%

10%

15%

20%

25%

30%




Knee ‐ skeletal

Knee ‐ ligaments




Foot ‐ skeletal

Others

Rate of A

IS2+

injury

1990‐19951996‐20002000+


registration (1990-1995; 1996-2000; >2000) – French Rhône Register database

German GIDAS Data

25,0%

3,4%

0,0%

13,6%

12,5%

20,5%

11,4%

0,0%

30,3%

3,0%

9,1%

3,0%

0,0%

18,2%

15,2%

15,2%

6,1%

0,0%

20,0%

0,0%

6,7%

6,7%

26,7%

13,3%

13,3%

6,7%

10,2%

2,3%

1,1%

6,7%

0%

5%

10%

15%

20%

25%

30%

35%




Knee ‐ skeletal

Knee ‐ ligaments




Foot ‐ skeletal

Others

Rate of A

IS2+

injury

1990‐19951996‐20002000+


registration (1990-1995; 1996-2000; >2000) – German GIDAS database



3.3 Specific leg injuries in frontal accidents with overlap less than 20% The following figures were plotted using the same methodology than for the distribution of AIS 2+ lower extremity injuries in frontal accident but frontal accident with overlap < 20%. The data from each European database are presented separately. Only UK CCIS and German GIDAS data are available. Due to the very low number of cases the figures are not presented. . The results are analysed and discussed in section 4.2.

Table 2.d. Number of specific leg injuries in frontal accidents with cars registered between 1990 and 1995 and overlap less than 20%.


UK CCIS Upper leg ‐ non‐skeletal 0 0 0 0 0 Upper leg – skeletal 0 0 1 0 1 Knee ‐ surface tissues 0 0 0 0 0 Knee ‐ skeletal (including ends of femur/tibia) 0 0 0 0 0 Knee – ligaments 0 0 0 0 0 Lower leg ‐ non‐skeletal 0 0 0 0 0 Lower leg – skeletal 0 2 0 0 2 Ankle joint ‐ skeletal and ligamentous 0 0 0 0 0 Foot – skeletal 0 0 0 0 0 Others 50 0 0 0 50 Total number 50 2 1 0 53

Germany GIDAS Upper leg ‐ non‐skeletal 1 0 0 0 1 Upper leg – skeletal 0 0 1 0 1 Knee ‐ surface tissues 22 0 0 0 22 Knee ‐ skeletal (including ends of femur/tibia) 0 1 0 0 1 Knee – ligaments 0 0 0 0 0 Lower leg ‐ non‐skeletal 8 0 0 0 8 Lower leg – skeletal 0 0 0 0 0 Ankle joint ‐ skeletal and ligamentous 1 1 0 0 2 Foot – skeletal 0 0 0 0 0 Others 13 1 0 0 14 Total number 45 3 1 0 49

Table 2.e. Number of specific leg injuries in frontal accidents with cars manufactured between 1996 and 1999 and overlap less than 20%







Table 2.f. Number of specific leg injuries in frontal accidents with cars registered from 2000 and overlap less than 20%






4 Results and Discussion

4.1 Change in injury rates for each body region

The results from the different databases showed some similarities, at AIS 2+ levels, head and thorax injury rates reduced substantially over the time period. The UK CCIS data showed a general decrease in the rates of AIS 2+ injuries across the three groups of manufacturing years for all body regions. Head injury rates reduced 9.1% to 3.9% while thorax injury rates reduced from 13.9% to 11.4%. AIS 2+ lower extremity injury rates also reduced from 11.7% to 9.8%. Over the same time period AIS 2+ pelvis injury rates decreased from 3.9% to 2.0 %. The Swedish Strada data showed some similarities to the UK data, at AIS 2+ levels, head and thorax injury rates reduced substantially from 38.0% to 22.7% and from 52.0% down to 35.6% respectively. AIS 2+ pelvis injury rates remained very low over the time period. The GIDAS data showed the same reductions over the three periods, the head, thorax, pelvis and lower extremity injuries were reduced from 10.4%, 9.8%, 1.4% and 7.7% down to 7.3%, 5.2%, 0.5% and 3.6% respectively. The French injury data gathered within the Rhône Register showed similar patterns to that of other countries but less pronounced and continuous with reduction in AIS 2+ injury rates to the head and thorax and lower extremity but with a marginal increase in the second period compared to the older cars. Moreover, the rate of pelvis injuries, although very low, showed an increase from 1.2% up to 2.8%.

At AIS 3+ level head and thorax injury rates also declined with a more or less pronounced decrease according to the database. For instance, the decrease for the thorax was more important in UK and Germany than in France where only a small variation is observed. The rate of pelvis injuries was very low for all databases and over the three periods. Only the French data showed an increase in the rate of AIS3+ pelvis injury from 1.2% up to 2.8%. Concerning the lower extremity injuries, the trends were not so obvious. For UK and French data, lower extremity injury rates were roughly the same for the post-2000 vehicles as they were in the pre-1996 cars. Meanwhile the same rate decreased for Swedish and German data.

The Swedish STRADA and French Rhône Register data did not included an estimate of overlap; this was only available within the UK and German data. The GIDAS data showed increases in AIS 2+ injury rates to all body regions except the neck over the three periods, lower extremity injuries increased from 2.6% to 5.6%. The UK data showed large variation over the period. Leg injuries represent 3.4%, 10.5% and 5.4 % for the period 1990-1195, 1996-2000 and 2000+, respectively. It should be note that leg injuries were rarely sustained in low overlap crashes. In the most recent cars there were only 8 AIS 2+ lower extremity injured people with overlap <20% out of a total of 163 occupants for CCIS data and only 2 out of a total of 37 car occupants for GIDAS data and, consequently, these results are sensitive to low number variation. Due to the very small sample AIS 3+ results can not be analysed. It should be not that, there were highly significant differences between the Swedish injury patterns and other databases, primarily as a result of differences in sampling methods but possibly also deriving from differences in the car fleet and on-road use between the different environments.

The lower extremity injuries were the third most frequent injury for both AIS 2+ and 3+ levels. Only the GIDAS and STRADA data showed reductions in lower extremity injuries over the three periods, this was observed at both AIS 2+ and AIS 3+ levels. UK CCIS and French Rhône Register showed variation of AIS 3+ that remained globally constant over the period.

Relative to other body regions at AIS 2+ the importance of lower extremity injuries remained effectively unchanged and they represented between 21-23% of all injured body regions in all three periods within the UK data. It represented between 26-28.4% in France, between 16-20% in Germany and 18-23% within STRADA data. The following graphs show the distribution of AIS2+ injuries per body region. The rate for a body region (i.e. lower extremity) are determined by divided the number of AIS2+ injuries for this specific body region by the total number of AIS2+ injuries for all the body regions.



UK CCIS Data

2,9%

6,9%

20,6%

20,6%

12,6%

3,4%

26,0%

8,3%

5,1%

22,4%

22,3%

8,9%

3,3%

26,1%

9,7%

4,6%

24,8%

8,8%

15,9%

24,4%

22,6%

0%

5%

10%

15%

20%

25%

30%


UpperExtremities

Rate of AIS2+

injury

1990‐19951996‐20002000+

Swedish STRADA Data

1,7%

0,3%

23,5%

10,8%

17,3%

4,8%

29,9%

12,8%

0,7%

21,6%

12,8%

20,6%

4,7%

32,4%

9,8%

0,7%

13,3%

31,1%

22,6%

10,0%

18,6%

0%

5%

10%

15%

20%

25%

30%

35%


UpperExtremities

Rate of A

IS2+

injury

1990‐19951996‐20002000+


0,2% 1,7%

26,5%

19,5%

16,3%

0,4%

23,1%

8,3%

3,0%

28,4%

20,5%

19,1%

0,6%

19,8%

5,6%

4,9%

24,1%

21,5%24

,1%

6,5%

25,9%

0%

5%

10%

15%

20%

25%

30%


UpperExtremities

Rate of A

IS2+

injury

1990‐19951996‐20002000+

German GIDAS Data

5,5%

3,5%

19,6%

14,5%

28,8%

7,2%

27,9%

1,8% 3,6%

18,9%

11,7%

31,8%

2,3%

22,7%

2,3%

2,3%

22,7%25,1%

26,4%

5,5%

15,9%

0%

5%

10%

15%

20%

25%

30%

35%


UpperExtremities

Rate of A

IS2+

injury

1990‐19951996‐20002000+

Figure 4.1: Rate of AIS2+ lower leg injuries compared with other body regions

for 4 European databases (UK CCIS, Swedish STRADA, French Rhône Register and German GIDAS)



4.2 Nature of lower extremity injuries

The nature of the lower extremity showed some variation across each age range of cars although there were differences of note between the different databases.

In the Swedish data tibia and fibula fractures were the most common, representing 30-40% of all AIS 2+ lower extremity injuries. Other frequent injury locations were the femur, and knee, each typically representing 15%-20% of all lower extremity injuries.

The UK, French and German data showed femur fractures as the most common AIS 2+ injury, varying between 36% and 40% of all lower extremity AIS 2+ injuries for UK and between 20 and 30% for French and German data.

The other common injuries were the patella, tibia and fibula, ankle joint and foot all sustained AIS 2+ injuries at around 15%. In all data, ankle and foot injuries represented a significant contribution to the lower extremities injuries that were mainly bone injuries (i.e. fractures).

The German data showed an increase in tibia/fibula fractures from 14% to 27% and UK, French and Swedish data showed large variations without trends of decrease in the same type of fractures. The German data showed a decrease in femur and foot fractures over the period, although they remained relatively common, while the others sources of data did not significant trend of reduction and the rate of these injuries were relatively high.

In summary, tibia and fibula fractures, injuries of the ankle and foot as well, are identified as significant injuries in frontal car accident.



Appendix – Overview of databases used in analysis. This section provides brief details of the databases used in this analysis.

CCIS – UK Co-operative Crash Injury Study The objective of the Cooperative Crash Injury Study (CCIS) is to investigate and correlate car crash data, with a view to increasing the understanding of human injury mechanisms, and the effectiveness of car secondary safety systems. This is achieved by obtaining detailed data on vehicle damage and occupant injuries from a representative statistical sample of the National road accidents. The study provides the mechanism to monitor in-depth crash performance of car structures, occupant protection systems and the benefits of countermeasures now becoming available. CCIS is a collaborative project. The UK Department for Transport, several motor vehicle manufacturers and a vehicle component supplier jointly fund the programme of research.

CCIS examines accident damaged cars in which the occupants have been injured. Medical information from occupants is collected and collated against the vehicle damage. Vehicle examinations include an assessment of the performance of the vehicle structure and whether it was a factor in any resulting occupant injury. This information is then made anonymous and entered into a database. The CCIS database employs sampling criteria based upon vehicle age and injury outcome. To be included, the accident must have involved a passenger car less than 7 years old in which an occupant was injured. Additionally the car must have been towed away from the accident scene.

CCIS is a statistically significant sample of accidents within the UK. Investigations are carried out for around 80% of serious and fatal and 10-15% of slight accidents occurring in selected geographical regions. Currently, information on approximately 1300 vehicles is gathered each year for inclusion into the database. It is not currently possible to weight the CCIS data in order to address the sampling bias towards serious injury.

CCIS continues to evolve; the information it gathers is regularly reviewed to allow new technologies entering the market to be included into the database. This data has been analysed by VSRC.

STRADA - Swedish Traffic Accident Data Acquisition STRADA is a National information system concerning injuries and accidents within the Swedish road transport system. In the first instance data is collected from the police. This is later enhanced where possible with records from the hospitals in order to provide a more comprehensive picture of the nature of the injuries received.

The police accident reports contain information about the accident such as the geographic area, time, place, speed limit, weather and road conditions and also include sketches where the positions of those involved are marked, before and after the accident. The reports contain information relating to all involved vehicles and all injured persons. This is the basis of the STRADA database.

Where possible the STRADA data is enhanced with reports from the medical care which contain information about the injuries and circumstances of the accident. Injuries are then coded according to the AIS coding scheme.

Analysis using the STRADA database may be done for a number of purposes. It is possible to make a selection on a certain kind of accident and if the injured person was a driver or a passenger. It is also possible to search for the location of the accident, or where treatment was received. The results of the search can be presented on a map or in statistical reports. STRADA works with GIS-related presentation which creates new possibilities to analyse for example the accident situation within a certain geographical area such as a district, next to a school or a bus-stop.

In-depth analysis is carried out on that part of the STRADA data that contains medical reports and hence the injuries are coded according the AIS coding scheme. This data has been analysed by SRA.



French Injury Data – Rhône Register The Rhône Département has a population of 1.6 million. Since 1995 casualties caused by road traffic accidents occurred in the Département have been recorded on a continuous basis in a register that is recognized by the National Registers Committee. The criterion for inclusion on the register is not place of residence but the location of the accident.

Data collection involves all 282 of the healthcare structures which administer care to road traffic casualties in the Rhône Département: Fire and emergency services, emergency medical service (SAMU), mobile emergency units (SMUR), emergency, treatment of shock, resuscitation, forensic medicine, surgery, rehabilitation and convalescence units who fill in a datasheet for each casualty.

The recorded health events are death or injury (at least one injury as defined by the Abbreviated Injury Scale (AIS), during a road traffic accident involving at least one moving vehicle (including roller skates and skateboards). Pedestrian falls are thus excluded. The datasheets from the different sources are combined under the same identifier when data is entered into the database. The cross-checking, coding, checking and data entry is performed rigorously and efficiently to achieve optimum data quality: 122,498 datasheets were processed between 1997 and 2006. The injury descriptions are produced by combining the medical data from different medical departments.

In order to obtain the figures here, we linked medical data from the Rhône Register and accident and vehicle data from the electronic form of police reports. The database now includes 10 years of reported accidents in the Rhône Département. This data has been analysed by INRETS –UMRESTTE Laboratory.

In-depth Accident Data - GIDAS GIDAS is a joint project of the Federal Highway Research Institute (BASt) of Germany and the German Association for Research in Automobile Technology (FAT). It started in 1999 in the two research areas Dresden and Hanover. About 2,000 accidents are recorded each year. The teams consisting of technical and medical students investigate the data at the accident scene and the hospitals.

Each case is then encoded in the database with about 3,000 variables. The database contains detailed information about:

- the environment (meteorological influences, street condition, traffic control);

- the vehicles (deformations, technical characteristics, safety measures);

- the persons (first aid measures, therapy, rehabilitation) and;

- the injuries (severity, description, causation).

On the basis of the full-scale sketch of the accident scene and the vehicle deformations every accident is reconstructed.

Due to the fact that the research areas represent the average German topography very well and that the accidents are investigated by a statistical sampling plan, the statistics are representative for Germany.



Part 2: THOR-Lx Design and Performance

by M Van Ratingen (FTSS) and P. Vezin (INRETS),

1 Background This Part provides an overview of the background of the THOR-Lx/HIIIr leg, the design and the performance of the leg.

Part of the scope of the THOR (Test device for Human Occupant Restraint) project, a test device for whole-body trauma assessment in a variety of occupant restraint environments, supported actively by the National Highway Traffic Safety Administration (NHTSA), included the development of an advanced lower extremity THOR-Lx. The lower extremity used in the Hybrid III dummy does not provide the desired range of motion or joint torque characteristics required to meet the new standards proposed by NHTSA in 1998. In addition, the Hybrid III lower leg was only instrumented in the tibia section, and the assessment of injury to the foot and ankle was not possible. In the automobile environment, the interest in the evaluation of lower extremity injuries has recently increased. With the widespread use of seat belts and airbags, more people are surviving the major chest and head trauma only to experience a long recovery period in rehabilitating lower leg injuries.

In 1994, the NHTSA Vehicle Research and Test Center (VRTC), together with Applied Safety Technology Corporation (ASTC), began development of the ALEX (Advanced Lower Extremity) which would be used on the advanced frontal dummy. GESAC pursued in 1997 the development under NHTSA direction resulting in the THOR-Lx leg. Both designs (the ALEX and the THOR-Lx leg) have been tested and refined during the next year.

Based on the results GESAC and ASTC (now Denton ATD, Inc.) have combined their efforts and designed a lower extremity which can be retrofitted to the Hybrid III 50% male dummy. This lower extremity has been released as the THOR-Lx/HIIIr unit, which incorporates aspects from both designs. Figure 1.1 shows a picture of the completed THOR-Lx/HIIIr unit assembly.

Figure 1.1: Complete THOR-Lx/HIIIr leg with the flesh removed (left) and fully assembled (right)



2 Design of THOR-Lx THOR-Lx is an improvement over previous anthropometric lower extremities, especially the Hybrid III leg, because it is more biofidelic and has additional instrumentation. The design of the THOR-Lx/HIIIr is based on recent biomechanical data which include the guidelines for the basic geometric dimensions of the lower extremity, location of the ankle and subtalar joints and inertial properties of the leg and foot (Crandall et al, 1996).

2.1 Anthropometry

The anthropometry, i.e. geometrical and inertial dimensions, for the THOR-Lx/HIIIr (SAE THOR workshop 2007) is given in the following Table 2.1

Table 2.1: THOR-Lx/HIIIr anthropometry compared with Hybrid III and human

Dimension [cm]

Thigh circumference (max.) 57.3

Thigh length (H point to Knee) 42.7

Leg circumference (max.) 36.8

Leg length ‐

Mass [Kg]

Thigh Mass 7.6

Leg Mass 3.4

Foot Mass 0.94

CG & Moment of Inertia

Thigh CG Z (from knee) [cm] 19.8

Leg CG Z (from ankle) [cm] 20.0

Thigh Iyy [kg‐cm²] 1 600

Leg Iyy [kg‐cm²] 400

The thigh mass and the inertia values of the THOR-Lx/HIIIr are possible anthropometry issues that are under examination by the THOR SAE Working Group.

2.2 Advanced design features

The design of the leg (Figure 2.1) includes:

• An axial compliant element (Figure 2.2) to represent compressibility of the tibia for biofidelic axial load response;

• a spring damper Achilles tendon to simulate passive resistance of musculature to dorsiflexion and to produce the desired ankle motion and torque characteristics (Figure 2.3);

• a fully functioning ankle (Figure 2.4) that allows rotation in all three directions thanks to separate location of dorsiflexion and inversion/eversion joint centres of rotation represented by the ankle and the subtalar joints, and continuous torque angle joint characteristics (Shams, 1999). The rotation of the ankle joint about the z-axis (internal and external rotation) has been redesigned to provide a joint torque characteristic which is similar to measured human data.

• soft stop elements were used to provide human-like stiffness at the extremes of motion (Figure 2.5). The design of the bumper has been recently updated to reach the large cross section at 40 degrees of rotation.



Figure 2.1: THOR-Lx/HIIIr Schematic Diagram with Key Elements

Figure 2.2: Design of the : THOR-Lx/HIIIr with axial compliant element

Figure 2.3: Design of spring damper Achilles tendon

Figure 2.4: Design of Ankle

Neutral Rotated

Figure 2.5: Design of the soft stop elements



Moreover, the knee, tibia and foot skins were redesigned to be lighter weight and to integrate with the hardware. This new design consists of:

• Molded knee covers (Figure 2.6); • Standard Hybrid-III knee housing; • Modified Hybrid-III flesh; • Optional: the Hybrid-III ball bearing knee slider assembly; • Foot and ankle segments (Figure 2.7).

a)

b)

Figure 2.6: Design of knee a) Molded knee covers. b) Ball bearing slider positioning for the right knee

assembly (outside view/inside view)

Figure 2.7: Design of the foot

2.3 Instrumentation

An important feature of the THOR-Lx/HIIIr leg is the surplus of measurement capabilities compared to the standard frontal dummy leg. The upper tibia load cell is a four channel unit, while the lower one provides five channel capabilities. Three rotary potentiometers were used to measure the rotation of the individual ankle joints, thereby providing complete kinematic data. A pair of uniaxial accelerometers on the tibia shaft provides the acceleration in the X and Y axes to allow the transformation of the measured tibia moment to the calculated ankle moment. Finally, a single triaxial accelerometer unit on the foot was included to enable correlation with prior foot/ankle injury tolerance studies. In short, the THOR-Lx leg includes the following instrumentation (Figure 2.8):

• Upper tibia forces and moments (Fx, Fz, Mx, My); • Lower tibia forces and moments (Fx, Fy, Fz, Mx, My); • Tibia accelerations at mid-shaft (Ax, Ay optional); • Foot angular displacement about 3-axes; • Mid-foot accelerations (3-axis, optional); • Achilles tension tension (uniaxial) (optional); • Knee Shear Displacement.



Figure 2.8: Overview of the instrumentation of the THOR-Lx



3 Performance of the THOR-Lx The THOR-Lx performance is examined according to:

A) The mandatory certification requirements; B) The design reference requirements and; C) The biofidelity requirements.

The design reference requirements are used as an additional functionality check of the product, and the biofidelity requirements to evaluate the “humanlike” behaviour of the THOR-Lx leg.

3.1 Mandatory certification requirements

The performance of the THOR-Lx leg with regard to the certification requirements is evaluated by the performance of two kind of separate dynamic tests evaluating the range of motion and the resistance of the ankle joint soft stops by applying inversion and eversion motion to the ankle (one test for inversion, one for eversion). The impact velocity is 2.0 ± 0.1 ms-1 for each test.

Also dynamic test is performed one to evaluate the dynamic dorsiflexion behaviour and the Achilles tendon contribution. The anatomical area of impact is the ball of the foot; the impact velocity is 5.0 ± 0.1 ms-1.

Finally, a dynamic test is performed to examine the tibia axial compliance with a pendulum impact to the heel of the foot. The impact velocity is 4.0 ± 0.1 ms-1.

In Table 3.1 an overview is provided of the certification requirements.

Table 3.1: THOR-Lx/HIIIr mandatory certification requirements.

Dynamic Impact Test Criteria Requirement

Inversion/Eversion Peak lower tibia compressive Force Peak angle resistive Moment Peak angle Rotation

552 – 675 N 36.3 – 44.4 N.m 30.3°– 37.0°

Ball of foot Peak lower tibia compressive Force Peak angle resistive Moment Peak angle Rotation

2956 – 3613 N 77.1 – 94.2 N.m 32.7°– 39.9°

Heel of foot Peak lower tibia compressive Force 2738 – 3346 N

3.2 Design reference requirements

In addition to the certification tests, design reference guidelines have been established. Quasi-static tests are defined to examine the range of motion and the resistance of the ankle joint soft stops in:

• Dorsiflexion with the Achilles tendon, • Dorsiflexion without the Achilles tendon, and • Plantar flexion.

A dynamic impact tests to the ball of the foot is performed to examine the ankle motion response at low dorsiflexion angles.

A dynamic impact test to the heel of the foot (sole/tibial compression) is performed to examine the behaviour of the tibia compliant bushing assembly, therefore the impulse loss in the dynamic heel impact can be determined.

An overview of the design reference requirements is provided in Table 3.2.



Table 3.2: Design reference guidelines for the THOR-Lx/HIIr.

Quasi‐static Tests Torque (N.m) Angle (°)

Dorsiflexion with Achilles tendon 40 92

16.3 – 19.9 33.4 – 40.8

Dorsiflexion without Achilles tension 10 37

16.6 – 20.2 33.5 – 40.9

Plantarflexion 3 17

28.2 – 34.4 44.0 – 53.8

Dynamic impact to ball foot Tests

Lower tibia My peak between ‐15 ‐0 74.1 – 90.5 N.m

Lower tibia My peak between 0 ‐ 15 71.3 – 87.1 N.m

Dynamic impact to heel foot Tests

Impulse Loss 2.71 – 87.1 N.s

In addition to the above mentioned requirements an additional requirement has been defined to for the dynamic inversion/eversion functionality of the THOR-Lx leg based on the data of Sokol-Jaffredo et al. (2000). The contribution of the fibula and the angle between the forefoot and heel is defined as a requirement.

Table 3.3: Static and dynamic inversion and inversion minima and maxima

Quasi‐static Tests Torque (N.m) Angle (°)

Dorsiflexion with Achilles tendon 40 92

16.3 – 19.9 33.4 – 40.8

Dorsiflexion without Achilles tension 10 37

16.6 – 20.2 33.5 – 40.9

Plantarflexion 3 17

28.2 – 34.4 44.0 – 53.8



3.3 Biofidelity Requirements

In addition to the mandatory certification and design requirements, biofidelity requirements have been defined for the THOR-Lx leg. NHTSA has defined the following biofidelity requirements for the THOR-Lx and within the European project FID also requirements have been defined.

3.3.1 Biofidelity requirements by NHTSA:

Biofidelity requirements have been defined for the following conditions by NHTSA: 1) dynamic heel impact; 2) dynamic dorsiflexion; 3) quasi-static inversion/eversion; 4) quasi-static plantarflexion; 5) quasi-static internal/external rotation; 6) quasi-static dorsiflexion and as additional requirement; 7) dynamic inversion/eversion.

3.3.1.1 Dynamic heel impact

The requirement is based on the tests conducted at the Medical College of Wisconsin (Kuppa et al., 1998). The biomechanical response is defined by the peak impact force vs. impact energy for two impact speeds: 2 m/s and 5.6 m/s (Figure 3.1).

Figure 3.1: Dynamic heel impact biofidelity response requirement



3.3.1.2 Dynamic dorsiflexion

The requirement is based on the cadaver data conducted at Renault (Crandall et al., 1996; Portier et al., 1997). Only the data during the loading were considered. A requirement was defined for the moment vs. angle relationship (Figure 3.2). The force and moment are measured at distal tibia and the moment is computed through the ankle cross-section and at ankle only.

a)

b)

Figure 3.2: Dynamic dorsiflexion biofidelity response requirement a) for total ankle section, b) at ankle only



3.3.1.3 Quasi-static inversion/eversion

For the quasi-static condition the requirement is based on the data of Petit et al. (1996) and consists of a moment versus angle relationship obtained when the foot in inversion (Figure 3.3). For the quasi-static eversion the requirement consists of a angle versus moment relationship based on the data of Crandall et al., (1996) and Petit et al. (1996) (Figure 3.4). The results of both labs were identical and therefore a single moment-angle curve can be derived from both sets of data.

Figure 3.3: Quasi-static inversion biofidelity response requirement

Figure 3.4: Quasi-static eversion biofidelity response requirement



3.3.1.4 Quasi-static plantarflexion

The proposed requirement, angle vs. moment relationship is based on the data obtained by Parentau and Viano (1996); however an initial fat response up to 25 degrees has been included. (Figure 3.5).

Figure 3.5: Quasi-static plantarflexion biofidelity requirement

3.3.1.5 Quasi-static internal/external response

The quasi-static response in internal and external rotation is derived from tests performed by Siegler et al. (1988). This response is not defined as a requirement however should be used as a guide to provide a smooth response when the foot is rotated about the z-axis (Figure 3.6).

Figure 3.6: Quasi-static internal/external rotation biofidelity requirement



3.3.1.6 Quasi-static Dorsiflexion

This requirement is based on the volunteer response with the knee flexed at 90 degrees (Crandall et al., 1996) and defined as an angle-moment relationship (Figure 3.7). The first graph shows the response for the complete ankle section, including the effect of the Achilles, while the second graph shows the response only of the ankle joint.

a)

b) Figure 3.7: Quasi-static dorsiflexion biofidelity requirement

a) with Achilles ; b) for ankle only, without Achilles



3.3.1.7 Dynamic inversion/eversion

This is an additional requirement. The requirement is based on the data of Sokol-Jaffredo et al. (2000). The contribution of the fibula was defined and the angle between the forefoot and the heel was determined (Figure 3.8). The SAE harmonization Working Group decided (2008) to include these inversion/eversion dynamic loading conditions as a biofidelic requirement for the THOR-Lx.

Figure 3.8: Additional requirement dynamic inversion/eversion biofidelity response.



3.3.2 Biofidelity requirements by European Project FID:

Within the FID Project, two tests have been proposed to evaluate the biofidelity of the lower leg (van Don et al., 2003) based on the corridors provided by Wheeler et al., (2000). One is a pendulum impact to the toe, impact speed 6 m/s. The other is a pendulum test to the heel, impact speed 4 m/s. For the toe impact condition the requirements have been defined for the following variables: the pendulum acceleration versus time; the tibial force versus time and the bending moment versus time.

Figure 3.9: Pendulum Acceleration versus Time (Toe Impact)

Figure 3.10: Tibial Force versus Time (Toe Impact)

-25

-20

-15

-10

-5

0

5

10

15

0 10 20 30 40

Time (ms)

Ben

ding

Mom

ent M

y (N

.m)

Figure 3.11: Bending moment versus time (toe impact)



For the heel impact condition requirements have been defined for the following variables: pendulum acceleration versus time and tibial force versus time.

Figure 3.12: Pendulum Acceleration versus Time (Heel Impact)

Figure 3.13: Tibial Force versus Time (Heel Impact)



4 Remarks In addition to the description of the design and of the performance requirements of the existing THOR-Lx, some activities are on going to improve the lower leg of the THOR dummy. There are some questions that are under investigation by the SAE harmonization group. Without entering in too many details, the following questions need to be solved in short terms:

a. Anthropometry Review and document the existing anthropometry of the Lx Legs indicating the source of ־

the Lx Leg anthropometry and the accuracy. .Consider replacing the Lx foot with a molded shoe (similar to WorldSID) ־

b. Biofidelity Review the biofidelity studies and design specifications that support the Lx Leg biofidelity ־

and document the sources and accuracy of the existing Lx Leg. This should include the muscle tensing assumptions (especially for dorsiflexion) and the geometric compensation adjustments made for ankle forces and moments.

Verify the range of motion for ankle dorsiflexion, inversion and eversion, both statically ־and dynamically, and review and document the IARVs for these motions.

.Incorporate OSU tibia subluxation response into knee slider and revise IARV as necessary ־

c. Instrumentation .Improve the durability of the ankle angular displacement pots ־

d. Hardware Improve the heel and sole of the foot flesh which tears easily and frequently (note that ־

replacing the foot with a molded shoe will eliminate this problem). Modify the ankle design to improve the durability of the rostas and the bumpers as well as ־

the repeatability and reproducibility. .Modify the tibia axial compression “sticking” of the load cell ־ Modify the Achilles tendon design to reduce friction in the cable and improve the setting of ־

the initial foot plantar flexion angle. Study the complexity of the Lx Leg design and simplify it to the extent possible ־ Study the certification procedures of the Lx Leg and improve/simplify them to the extent ־

possible.

For a longer term some additional issues need to be addressed: a. Anthropometry Quantify tibia curvature and consider incorporating curvature into the Lx Leg design ־

b. Biofidelity Quantify the effect of tibia curvature on leg response and consider incorporating curvature ־

into the Lx Leg design



References 1 Crandall, J., Portier, L., Petit., Hall, G., Bass, C., Klopp, G., Hurwitz, S., Pilkey, W.,

Trosseille, X., Tarriere, C., and Laussau, JP. (1996) Biomechanical response and physical properties of the leg, foot and ankle. Proceedings of the 40th Stapp Car Crash Conference. 4-6 November 1996, Albuquerque, New Mexico (SAE technical paper 962424, pp 173-192): Society of Automotive Engineers, Inc. (SAE), 400 Commonwealth Drive, Warrendale, PA 15096-001, U.S.A.

2 Kuppa, S., Klopp, G., Crandall, J. Hall, G., Yoganandan, N., Pintar, F., Eppinger, R., Sun, E., Khaewpong, N., and Kleinberger, M. (1998) Axial impact characteristics of dummy and cadaver lower limbs. Proceedings of the 16th International Technical Conference on the Enhanced Safety of Vehicles. Vol. 2, pp 1608-1617. May 31- June 4, Windsor, Ontario, Canada: National Highway Traffic Safety Administration (NHTSA), US Department of Transportation (available on the NHTSA internet site, www.nhtsa.dot.gov).

3 Paranteau, C., and Viano D. (1995) A new method to determine the biomechanical properties of human and dummy joints. Proceedings of the 1995 International IRCOBI Conference on the Biomechanics of Impact. September 13-15, 1995, Brunnen, Switzerland: International Research Council on the Biomechanics of Impact.

4 Petit., P., Portier, L., Foret-Bruno,JY., Trosseille, X., Parenteau, C., Coltat, JC., Tarrière, C., and Lassau, JP. (1996) Quasi-static characterization of the human foot-ankle joints in simulated tensed state and updated accidentological data. International IRCOBI Conference on the Biomechanics of Impact. September 11-13, 1996, Dublin, Ireland: International Research Council on the Biomechanics of Impact.

5 SAE THOR workshop (2007) 20-21 April, Detroit MI.

6 Siegler, S., Chen, J., and Schneck, CD. (1988) The three-dimensional kinematics and flexibility Characteristics of the human ankle and subtalar joints- Part I: Kinematics. Journal of Biomechanical Engineering, Transactions of the ASME, Vol. 110(4): pp. 364-373.

7 Sokol-Jaffredo, A., Potier, P., Robin, S., and LeCoz, JY. (2000) Cadaver lower limb dynamic response in inversion-eversion. Proceedings of the 2000 International IRCOBI Conference on the Biomechanics of Impact. September 20-22, 2000, Montpellier, France: International Research Council on the Biomechanics of Impact.

8 van Don, B., van Ratingen, M., Bermond, F., Masson, C., Vezin, P., Hynd, D., Owen, C., Martinez, L., Knack, S., and Schaeffer, R., on behalf of EEVC WG12 (2003) Biofidelity impact response requirements for an advanced mid-sized male crash test dummy. Proceedings of the 18th International Technical Conference on the Enhanced Safety of Vehicles. May 19-22, 2003, Kyoto, Japan. Paper No. 76. National Highway Traffic Safety Administration (NHTSA), US Department of Transportation (available on the NHTSA internet site, www.nhtsa.dot.gov).

9 Wheeler, LK., Owen, C., Roberts, A., Lowne, RW., Manning, PA., Wallace, WA. (2000) Biofidelity of Dummy Legs for Use in Legislative Car Crash Testing. Vehicle Safety 2000, IMechE. Conference Transactions 2000, London, UK, pp. 183-198.



Part 3: Lower Leg Injury Criteria for use with the THOR-Lx

by D Hynd and J A Carroll (TRL Limited)

1 Introduction The assessment of the ability of a vehicle to protect its occupants is regulated through the use of crash test dummies and impactors that are designed to represent the human being protected. A lot of effort is put in to the development of a dummy or impactor to ensure that its anthropometry, biofidelity, repeatability and so forth are good. However, as the biofidelity of dummy parts is rarely a perfect match to the defined biofidelity targets and the targets themselves are usually based on a small amount of data, there is always some uncertainty regarding the biofidelity performance of the dummy. The final requirement for a dummy part or impactor is an injury risk function, which allows parameters measured with the dummy or impactor to be related to a risk of injury in the human. Injury risk functions can be either human injury risk functions or dummy-specific injury risk functions. If the biofidelity requirements for the dummy contain some uncertainty, this implies that the direct use of human injury risk functions with the dummy would be subject to the same uncertainty. The EEVC approach has therefore been to use dummy-specific injury risk functions where possible - that is, to calibrate the injury prediction measurements of the dummy - usually by using one of the following methods:

• Performing matching PMHS and dummy tests. In this case, it is important that the lab-based test conditions are representative of those under which the human is injured and in which the dummy will be used.

• Performing accident reconstructions with the dummy or impactor. In this case, it is important that the loading conditions in the accident are well understood and accurately replicated.

Using this dummy-specific approach, the injury risk function for the dummy is able to account for the biofidelity performance of the dummy.

This Part reviews the published injury risk functions that have been proposed for use with the THOR-Lx advanced lower leg.



2 THOR-Lx Dummy-specific Injury Risk Functions

2.1 Introduction

Only two references for THOR-Lx dummy-specific injury risk functions have been identified from the literature: Hynd et al. (2003) and Rudd et al. (2004). Hynd et al. developed a risk function for foot and ankle injuries versus axial force (Fz) in the lower tibial load cell of the THOR-Lx. This study focused on injuries with long-term consequences for the injured occupant, such as long recovery time, impairment or disability, not on a particular AIS level. The test sample was elderly, with a mean age of 76 years.

The Rudd et al. study developed THOR-Lx dummy-specific injury risk functions for ankle dorsiflexion angle. Unusually, this injury risk function was not developed by repeating post mortem human subject (PMHS) tests with a dummy part and comparing injury in the PMHS with dummy measurements. Rather, they developed a human injury risk function and transformed it to the THOR-Lx by comparing the human and dummy moment-angle relationships under the same loading conditions. This was in contrast to the study by Kuppa et al. (2001b - see Section 3) that used the human injury risk functions directly with the THOR-Lx (with no transformation or scaling) on the basis that they considered the biofidelity of the THOR-Lx to be good. Rudd et al. found that the moment-angle response of the human and THOR-Lx in their tests was very similar until 35° of dorsiflexion, but that the THOR-Lx was markedly stiffer than the human at greater dorsiflexion angles. The injury risk curve as a function of moment was considered to be the same for the THOR-Lx and the PMHS.

2.2 Hynd et al. (2003)

Hynd et al. (2003) performed sled-based impact tests with fourteen fresh-frozen PMHS to investigate the tolerance of the foot and ankle to axial loading. The goal of these tests was to understand how the dummy part behaves in the same loading conditions that a living human would experience in a front impact, and thereby develops a dummy-specific injury risk function. The sled pulse was based on a number of frontal offset car crash tests with mid-size saloon cars. A fairly constant 20 g pulse was established for 25 ms before a much higher intrusion pulse was administered resulting in a force of up to 10 kN, for a period of 10 ms. To provide tests at injury and non-injury levels, the severity of the tests was varied by altering the severity of the footwell intrusion part of the pulse.

The PMHS specimens were mounted to the sled above the knee, with the foot resting on a foot-plate and brake pedal representation. A knee brace and Achilles tendon tension were used to replicate knee and ankle extension moments found in emergency braking, giving a pedal force of approximately 870 N. This matched the pedal force from emergency braking volunteer trials in the TRL driving simulator.

The injuries were not grouped by AIS level, but by the likely long-term consequences: those injuries with long recovery times or a likelihood of disability or impairment were classified as serious injuries; those injuries with minor consequences were grouped with the non-injury tests. Serious injuries included calcaneus fracture, talar neck fracture and pilon fracture. Most of the injuries generated in the study were calcaneus fractures, although other hard and soft tissue injuries were recorded.

Each test severity was then replicated with the THOR-Lx. The external loading conditions (sled deceleration and foot-plate intrusion pulse) were identical to those used in the PMHS tests. No knee brace or active Achilles tension was used, as the dummy part does not have active musculature when used in a car crash test. However, the passive dorsiflexion resistance provided by the THOR-Lx Achilles tension was used (this is intended to give the correct dorsiflexion response with passive resistance, not the dorsiflexion response that would be found with the Achilles tension required in emergency braking). In this way, the test results provide a transform between the living human leg (or a close surrogate) in a heavy braking condition and the passive dummy part that would be used in a full-scale vehicle test.



The dummy does not have the muscle tone of the living human in pre-impact bracing and has no means of representing such muscle tone in a full-scale vehicle test. Comparing the unmodified dummy part with the PMHS plus internal muscle tone representation gives a transfer function between the living human (or our best attempt at a surrogate for the living human) and the dummy as it will be used in full-scale vehicle testing. Alternatively, the unbraced occupant can be represented by an injury risk function for an unbraced THOR-Lx (see below)

A probit analysis of the mean THOR-Lx measurements at each test severity compared with ankle and foot injuries in PMHS tests at the same severity was performed. Only upper and lower tibial axial force yielded statistically significant relationships with injury. A 50 % risk of serious ankle or foot injury was shown to coincide with a THOR-Lx lower tibial axial force of 4.3 kN (see Figure 2.1).

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

0 1 2 3 4 5 6 7 8 9 10

THOR-Lx Lower Tibia Axial Force Fz (kN)

Prob

abili

ty

Probability of serious ankle injury

95% confidence limits

Figure 2.1: Probit probability of serious foot or ankle injury for the THOR-Lx lower tibia Fz

(Hynd et al., 2003)

Figure 2.2 shows a comparison of the THOR-Lx lower tibia force (Fz) with and without knee restraint at the highest impact severity tested. At lower severities, the difference was smaller, but even at the highest severity the peak force was only 1 kN higher with knee restraint. This data indicates that the injury risk function for a THOR-Lx with knee restraint should be at most 1 kN greater than shown in Figure 2.1, and probably less - i.e. a 50% risk of injury at 5.3 kN, rather than 4.3 kN as shown in the figure.

A 50% risk of injury at 4.3 kN could be used with an unbraced THOR to estimate the risk for an occupant that is bracing, but this may overestimate the risk for an unbraced occupant. A 50% risk of injury at 5.3 kN could be used (as measured in the dummy, with no active knee extension), but this may underestimate the risk to occupants who are bracing (e.g. braking). Ideally, the dummy should better represent either the braced or unbraced occupant, depending on which group is considered the priority for injury prevention.

THOR-Lx Lower Tibia Force (Fz) with and without Knee Restraint at High Severity (200 mm Honeycomb)

-8

-7

-6

-5

-4

-3

-2

-1

0

1

-10 0 10 20 30 40 50 60 70 80 90 100

Time (ms)

Forc

e (k

N)

Without knee restraint

With knee restraint

Figure 2.2: Comparison of THOR-Lx lower tibia force (Fz) with and without knee restraint

at high impact severity



2.3 Rudd et al. (2004)

Biomechanical impact tests were performed by Rudd et al. (2004) on PMHS and dummy lower extremities in order to investigate the ankle dorsiflexion response and injury outcome from brake pedal loading on the forefoot. A test fixture was constructed such that a simplified pedal load was applied to the forefoot in a manner similar to that used by Portier et al. (1997).

A univariate Weibull model was used by Rudd et al. to produce an injury risk function for the mass-scaled ankle joint moment. A similar univariate Weibull model was created for the prediction of injury risk based on the dorsiflexion angle. Figure 2.3 shows the Weibull-based fracture injury risk together with the data points for eighteen tests and 95th percentile confidence intervals. The injury assessment reference values from these curves are shown in Table 2.1.

Rudd et al. then produced further models based on their data combined with that from Portier et al. (1997), using non-mass-scaled moments. The resulting moment risk function indicated a 58 Nm ankle moment corresponding to a 25 % risk of injury and 78 Nm for a 50 % risk. The angle criterion developed from the combined dataset was slightly less conservative than the Rudd et al. data alone: a 25 % risk of injury occurred at 44° instead of 42°.

Rudd et al. discuss the applicability of these values to the THOR-Lx. They say that the THOR-Lx moment-angle response becomes much stiffer than the PMHS above 35°, see Figure 2.4. To develop dorsiflexion injury assessment reference values for use with the THOR-Lx, Rudd et al. chose the curves from their data alone, as they were more conservative than the combined data values. They then mapped the THOR-Lx moment-angle stiffness into the curves to produce transformed curves, see Figure 2.5. The reference values from these are shown in Table 2.2.

Figure 2.3: Weibull-based fracture injury risk as a function of dorsiflexion angle (Rudd et al., 2004)

Table 2.1: Injury assessment reference values from parametric models (Rudd et al., 2004)

Injury 25 % risk 50 % risk

Moment 59 Nm 85 Nm

Angle 42° 51°



Figure 2.4: Thor-Lx and cadaver moment-angle relationships.

The 25% and 50% risk points are also shown (Rudd et al., 2004).

Figure 2.5: Original and transformed ankle rotation-based risk curves from survival analysis

with Weibull distribution (Rudd et al., 2004)

Table 2.2: Dorsiflexion injury assessment reference values for use with THOR-Lx (Rudd et al., 2004)

Injury 25 % risk 50 % risk

Moment 59 Nm 85 Nm

Angle 36° 40°



3 Human Injury Risk Functions

3.1 Introduction

The following information has been obtained from a review of the available recent literature. Unlike the two papers considered in Section 2, the injury criteria in this Section are not specific to the THOR-Lx, being relevant to human injury thresholds instead. However, each source could be considered as a basis for developing THOR-Lx dummy-specific injury risk functions. This would require repeating the tests with the THOR-Lx instead of the PMHS specimens. The injury risk function could then be re-drawn in terms of the dummy measurement values.

3.2 Funk et al. (2001)

Funk et al. (2001) constructed a test apparatus to deliver dynamic axial impact loads to the plantar surface of the foot of a PMHS specimen. During impact, peak footplate velocity was approximately 5 m.s-1. PMHS specimens were sectioned above the knee at mid-femur, preserving the functional anatomy of the knee joint and leg musculature. Leg specimens were placed horizontally in the test rig with the foot neutrally positioned on the footplate and the knee flexed 90° and constrained in an adjustable block. In approximately half of the tests, active triceps surae muscle tension was simulated by applying tension to the Achilles tendon, of either 1.7 kN or 2.6 kN.

Injuries included 14 calcaneus, one pilon, six talus, three medial and three lateral malleolus, two fibular, and five tibial plateau fractures in the 15 specimens without Achilles tension. In the group with Achilles tension, there were 11 calcaneus, six pilon, three talus, one medial and five lateral malleolus, and seven tibial plateau fractures out of 15 specimens. Altogether there were six artifactual fractures of the tibia associated with the inserted tibial load cell. A further 14 specimens received no foot or ankle injury (either no injury, tibial plateau injury only or artifactual mid-tibia injury only), but these were not included in the statistical analysis. The dominance of calcaneus fractures was similar to that found in the Hynd et al. (2003) data.

A multivariate Weibull model using age, gender, body mass, and peak Achilles force as predictor variables was found to best represent the peak unscaled axial tibia force data. Two sets of injury curves are shown in the paper. Firstly, injury risk functions for the American fifth percentile female and 50th percentile male at two different ages (45 and 65 years) assuming no Achilles tension, are shown (see Figure 3.1). Also, Funk et al. show injury risk functions for a 65 year-old American 50th percentile male at varying levels of Achilles tension, from 0 to 3 kN (Figure 3.2).

To develop THOR-Lx specific injury risk functions using the data produced by the work of Funk et al. would require reproduction of the test conditions. This should not be too difficult as the test apparatus is well documented in the paper. However, in addition to conducting comparative tests with the THOR-Lx, it may also be necessary to conduct PMHS tests at non-injurious levels. This may be a more demanding requirement than testing with the THOR-Lx in terms of financial, time, and specimen preparation aspects.

It should be noted that only the 30 injured specimens (including six with artifactual fracture concomitant with other foot and ankle fractures) were included in the statistical analysis and these were treated as uncensored, or exact, data within the Weibull analysis. A further 14 specimens received either no injury (four specimens), artifactual fracture only (eight specimens), tibial plateau fracture only (one specimen), or data acquisition error (one specimen). There are therefore another 12 tests that did not result in injury (censored data - including the no injury and artifactual fractures) that could be included if a different statistical analysis method was used. However, if the statistical method using the non-injury data does not take account of the censoring of the data, then the analysis may be less powerful than that undertaken by Funk et al., even though slightly more specimens are included. This is because there is more information available when the exact force of fracture is known than if it is not known.



In the discussion, Funk et al. produce a table showing injury assessment reference values, Table 3.1. These values were estimated using no Achilles tension because neither the Hybrid III nor the THOR-Lx is equipped with active musculature. Although the THOR-Lx does simulate passive muscle tension acting through the Achilles tendon, the amount of passive muscle tension is negligible when the ankle is in the neutral position, which was the ankle orientation studied by Funk et al.

Hynd et al. (2003, Section 2) comment that none of the previously reported injury risk results are directly comparable with their work. However, as described above, Funk et al. (2001) also develop axial tibia force injury risk functions. Funk et al. showed that their 50 % risk of injury could vary by as much as 2 kN for the 45 year old and 65 year old values. Extending this concept it might be considered that the tibial tolerance of the older specimens used by Hynd et al. (mean of 76 years old) should be less than that of the 65 year olds. Assuming that the degradation of bone is roughly linear from 45 to 75 years old, then the axial tibia force, associated with a 50 % risk of injury, could be at least 1 kN less at 75 than at 65.

Figure 3.1: Injury risk functions for the

American 5th percentile female and American 50th percentile male at two different ages

assuming no Achilles tension (Funk et al., 2001)

Figure 3.2: Injury risk functions for a

65 year-old American 50th percentile male at varying levels of Achilles tension

(Funk et al., 2001)

Table 3.1: Matrix on injury assessment reference values for blunt axial impact loading of the foot/ankle complex assuming no Achilles tension (Funk et al., 2001)

Dummy type Age (years) 30 % risk 50 % risk

5th percentile female 45 4.4 kN 5.0 kN

65 3.2 kN 3.7 kN

50th percentile male 45 7.3 kN 8.3 kN

65 5.3 kN 6.1 kN

However, in addition, Funk et al. evaluates the effect of Achilles tension. They report Achilles tension (from 0 to 3 kN) accounting for 2 kN of variation in the 50 % injury risk axial tibia force values. Hynd et al. used 500 N of Achilles tension and force generated through knee bracing, with their specimens. Therefore, if the percentage contribution from Achilles tension is added to the Funk et al. injury risk value (for a 65 year old with no Achilles tension), and the contribution from increasing age subtracted, the force for 50% risk of injury is 5.4 kN (for a 75 year old with 500 N of Achilles tendon tension), which is 25% greater than the 4.3 kN predicted by Hynd et al., but very close to the 5.3 kN found for a bracing THOR-Lx (see Section 2.2).



This may be because the Hynd et al. value is specific to the THOR-Lx, not the human as reported in Funk et al., or because of differences in the PMHS samples or test conditions used. Also, the Funk et al. curve is for risk of fracture, whereas the Hynd et al. curve is for serious injury, which included the more serious foot and ankle fractures, particularly calcaneus, pilon and talar neck fractures. Moreover, given the confidence limits on the Hynd et al. data (none are given for the Funk et al. data), it is unlikely that the force thresholds from the two studies are significantly different.

Work conducted within the EC FID project (Hynd and Carroll, 2003) assessed the biofidelity of the THOR-Lx in a set-up similar to that used by Funk et al. In both experimental set-ups, the leg was mounted horizontally with a rigid support or fixture at the knee. The impact force was administered to the plantar surface of the foot. However, in the Funk et al. tests the force was applied over the whole of the foot rather than being directed at either the ball of the foot or the heel, as was the case in the Hynd and Carroll tests. Despite this, the Hynd and Carroll results are thought to provide useful information on the biofidelity of the THOR-Lx tibia axial force measurements in a similar test scenario.

Hynd and Carroll reported that for impact tests directed at the ball of foot at impact speeds of 4 and 6 m.s-1, the peak tibia axial force values were within a corridor defined from comparative PMHS tests. For the heel tests at 4 m.s-1, the THOR-Lx peak axial force values were slightly lower than those of the PMHS. Therefore one might expect the THOR-Lx to very slightly underestimate the tibia axial force in test conditions such as those used by Funk et al. By itself, this would not be expected to account for the thirty percent difference between the values obtained by Funk et al. and those from Hynd et al.

3.3 Kuppa et al. (2001a and 2001b)

Kuppa et al. (2001b) examined NASS/CDS data files for the years 1993-1999 to determine the risk of injury to different body regions for outboard front seat occupants in air bag equipped vehicles involved in frontal crashes. In the paper, Kuppa et al. present lower extremity injury criteria, based on existing published data.

The impact tests by Banglmaier et al. (1999) were further analysed by Kuppa et al. using logistic regression to develop injury risk curves for tibial plateau and condyle fractures. According to the risk curve that was developed, 5.6 kN and 7 kN of proximal tibia axial force respectively correspond to 25 % and 50 % probabilities of AIS 2+ tibial condyle and plateau fractures, see Figure 3.3. These tests could be reproduced with the THOR-Lx relatively easily to determine THOR-Lx specific injury risk values.

For the tibia, axial force and moment critical values (Fc and Mc) are suggested to be 12 kN and 240 Nm, respectively. Revised Tibia Index values are proposed at 0.91 and 1.16, apparently corresponding to 25 % and 50 % probabilities of AIS 2+ leg shaft injuries.

For an injury criterion for calcaneus, talus, ankle and midfoot fractures, Kuppa et al. base their values on the combined dataset published by Yoganandan et al. (1996), which was developed using data from the Medical College of Wisconsin, Wayne State University and Calspan. Logistic regression analysis was used to produce a risk of AIS 2+ injury versus lower tibia axial force. Kuppa et al. found that lower tibia axial force values of 5.2 kN and 6.8 kN corresponded to 25 % and 50 % probabilities of AIS 2+ calcaneal, talar, ankle or midfoot fractures, respectively, see Figure 3.4. The Yoganadan tests are simple pendulum impacts similar to those in the dummy certification procedure and could therefore be repeated easily with the THOR-Lx, if this has not already happened.



Figure 3.3: Risk of AIS 2+ tibial plateau or

condyle injury as a function of upper tibia axial force (Kuppa et al., 2001b)

Figure 3.4: Probability of AIS 2+ calcaneus,

talus, ankle, and midfoot fractures as a function of lower tibia axial force (Kuppa et al., 2001b)

To develop an ankle joint dorsiflexion injury criterion, further analysis of the data reported by Portier et al. (1997) was conducted by Kuppa et al. using logistic regression. They found that an ankle joint moment of 50 Nm and 60 Nm, due to dorsiflexion, respectively correspond to 25 % and 50 % probabilities of AIS 2+ ankle and malleolar injuries, see Figure 3.5. This procedure was repeated at the time with a Hybrid III and therefore there should be no reason why a THOR-Lx (fitted to a Hybrid III or THOR dummy) could not be evaluated also. To ensure accurate reproduction of the test conditions, it may be advisable for the original test apparatus of Portier et al. to be used. This data set has been updated with new data and injury risk functions for dorsiflexion angle and ankle moment have been developed by Rudd et al. (2004) (see Section 2.3). The Rudd injury risk functions account for the poor biofidelity of the THOR-Lx at dorsiflexion angles greater than 35° and should be used in preference to the Kuppa functions.

Based on quasi-static data from Paranteau et al. (1998), Kuppa et al. presented that they considered the average subtalar failure moment in inversion and eversion to be the same and equal to 40 Nm with a standard deviation of 10 Nm. They constructed a preliminary inversion or eversion risk of injury curve as a cumulative normal distribution based on these values. Using this curve, Kuppa et al. found that 33 Nm and 40 Nm of inversion or eversion at the subtalar joint respectively corresponded to 25 % and 50 % probabilities of AIS 2+ malleolar and ligamentous injuries, see Figure 3.6. If this data is to be used, it is recommended that the dynamic inversion and eversion stiffness of the human and THOR-Lx are compared and the risk curve in Figure 3.6 is adjusted using the method of Rudd et al. (2004) discussed in Section 2.3. However, dynamic inversion or eversion data would be preferred.

Figure 3.5: Probability of AIS 2+ malleolar and ligamentous injuries as a function of ankle joint

moment due to dorsiflexion (Kuppa et al., 2001b)

x

Figure 3.6: Probability of AIS 2+ malleolar and ligamentous injuries as a function of subtalar

joint moment due to inversion/eversion (Kuppa et al., 2001b)



Kuppa et al. (2001a) assessed the THOR-Lx, fitted to a Hybrid III, in four frontal impact crash tests. These tests were full-scale vehicle tests impacting an EU deformable barrier with a 40 % overlap. The relative risk of injury was assessed using the limits at 25 % probability of AIS 2+ injury proposed by Kuppa et al. (2001b). These tests were paired with equal tests again using a Hybrid III dummy, but with the Denton leg fitted instead of the THOR-Lx. In the Denton leg tests, the risk of injury was assessed using the injury threshold values proposed for the Denton leg.

Due to the small size of the sample used to develop the inversion and eversion moments by Kuppa et al. (2001b), the 50 % probability of injury was used for this parameter. It was reported that the THOR-Lx was designed to produce an ankle moment of 60 Nm at 35° dorsiflexion and a subtalar moment of 40 Nm at 35° inversion or eversion. Therefore, Kuppa et al. used 35° of dorsiflexion or inversion or eversion while assessing foot and ankle injury using the THOR-Lx.

The THOR-Lx, with its ankle rotation measurements, predicted a higher incidence of foot and ankle injuries than leg shaft or tibial plateau fractures. This matched well with the accident data presented in the paper. The Denton leg predicted leg shaft fractures in one vehicle test, but did not exceed its foot and ankle injury limits in any of the four vehicle crash tests. Kuppa et al. associated these differences in injury prediction between the Denton leg and the THOR-Lx with the differences in their design, instrumentation and associated injury limits.

3.4 Funk et al. (2002)

Funk et al. (2002) tried to model empirically the effects of axial preloading and dorsiflexion on the injury tolerance of the human ankle/subtalar joint in dynamic inversion and eversion. Eleven male and six female PMHS lower leg specimens were obtained, aged 40 to 75 years.

Moments about the inversion-eversion axis of the foot were applied dynamically through the subtalar joint centre. The proximal tibia was mounted to the test apparatus in three different ways to simulate three different loading conditions: neutral flexion and no axial preload; neutral flexion and 2 kN axial preload; 30° dorsiflexion and 2 kN preload.

In general, the test conditions are explained well in the paper and the tests appear to be easily reproducible. However, as the experimental apparatus incorporates honeycomb pieces, it is suggested that Funk et al. be asked directly about the test set-up before the feasibility of reproducing these tests with a THOR-Lx is determined.

The injury tolerance of the ankle/subtalar joint was characterised using the method of survival analysis. Weibull models were used to draw injury risk curves for subtalar joint angles and moments. These are reproduced in Figure 3.7 and Figure 3.8. The points extrapolated from these curves are shown in Table 3.2 and Table 3.3.

In the discussion to the paper, Funk et al. advise that, for a crash test dummy, basing an injury criterion on angle has several practical advantages, provided that the dummy reproduces the subtalar joint moment that a human would experience at a given inversion or eversion angle. These advantages are that an angle criterion is much simpler than a moment criterion and also, the subtalar moment is strongly dependent on rotation direction, level of axial preload, and gender.



Figure 3.7: Injury risk as a function of subtalar joint moment for different rotation directions (eversion and inversion), levels of axial preload (0 kN to 3 kN), and genders (female and male) (Funk et al., 2002)

Figure 3.8: Injury risk as a function of inversion/eversion angle

for different levels of axial preload (Funk et al., 2002)

Table 3.2: Injury assessment reference values in terms of subtalar joint moment (Funk et al., 2002)

Direction Axial load Gender 25 % risk 50 % risk

Inversion

None Male 24 Nm 31 Nm

Female 18 Nm 23 Nm

2 kN Male 58 Nm 75 Nm

Female 43 Nm 56 Nm

Eversion

None Male 45 Nm 58 Nm

Female 34 Nm 43 Nm

2 kN Male 110 Nm 142 Nm

Female 82 Nm 106 Nm



Table 3.3: Injury assessment reference values in terms of inversion/eversion angle of the calcaneus with respect to the tibia (Funk et al., 2002)

Axial load 25 % risk 50 % risk

0 kN 28° 33°

1 kN 31° 37°

2 kN 34° 41°

3 kN 38° 45°

3.5 Funk et al. (2004)

The Tibia Index (TI) addresses combined axial compression and bending experienced at the midshaft of the leg. The critical force and moment values used to calculate the TI were based on quasistatic biomechanical tests. Funk et al. (2004) state that the TI is based on a combined stress analysis of a beam, with the TI predicting injury based on loading experienced by the tibia at its centroid in the transverse plane. They comment that it is important to note that the internal moment experienced at the centroid of the bone is not necessarily the same as a moment applied externally through the ankle and knee joints or by a transverse force applied to the leg. A substantial moment in the midshaft of the tibia can be induced by pure axial loading, simply due to the curvature of the bone.

Another factor identified by Funk et al. that affects tibial loading in a human is the presence of the fibula. Dummy legs do not incorporate a fibula; they measure the load sustained by the entire leg. However, the TI is based on the injury tolerance of isolated tibiae.

Funk et al. report on quasistatic leg compression tests, performed on five PMHS leg specimens. Each specimen was implanted with both a six-axis tibial and fibular load cell. The percentage of the overall axial load borne by the fibula ranged from -8 % to 19 %. In most specimens, the fibula experienced the greatest compressive load when the ankle was everted and the least compressive load (sometimes tension) when the ankle was inverted. Funk et al. found that the fibula bears an average of 6 % of the leg load when the ankle is neutrally orientated.

Funk et al. also used computed tomography to characterise tibial curvature of the leg specimens.

Within the paper, Funk et al. present a reformulation of the TI to express it in terms of an externally applied moment. This reformulated TI contains expressions including a term for the eccentricity of the tibia. While the THOR-Lx is perfectly straight, the Hybrid III leg and human tibia are curved, although to different degrees. Therefore the injury boundaries imposed by the TI (of critical force and moment) will be different for the human, Hybrid III leg, and THOR-Lx.

In the discussion, Funk et al. comment on the Revised Tibia Index, as proposed by Kuppa et al. (2001b). They discuss the proposed reduction of the critical values in an attempt to more accurately model the behaviour of the whole tibia. The comment by Funk et al. is that the critical values in the TI are not intended to represent whole tibia behaviour and therefore the proposed Kuppa et al. revisions are inappropriate.



4 THOR-Lx Biofidelity Assessment

4.1 Rudd et al. (1999)

Rudd et al. (1999, updated and revised in Rudd et al. 2000) reported on the biofidelity and response characteristics of the THOR-Lx prototype dummy lower extremity. They had performed several types of test on the THOR-Lx, including quasi-static ankle joint moment-angle determinations and dynamic dorsiflexion tests, and simulated toepan impacts (Rudd et al., 2000 only). The THOR-Lx results were compared with PMHS, the Hybrid III dummy lower extremity and volunteer responses, where possible. Rudd et al. concluded that their results indicated that the THOR-Lx is an improvement over the Hybrid III dummy lower extremity. They report that design features that had limited the biofidelity of the Hybrid III lower extremity had been improved, and the THOR-Lx provided a more realistic representation of the human lower limb suitable for crash testing.



5 Other Information

5.1 Rudd et al. (2001)

In evaluating the lower limb injury mitigation capabilities of an inflatable carpet system for use in frontal impacts, Rudd et al. conducted sled tests using the THOR-Lx. To interpret their results, in terms of injury risk, Rudd et al. made the assumption that the response from the THOR-Lx is biofidelic. On this assumption they apply injury limits from human data in the literature.

The tibia axial load tolerance of 5.3 kN is, apparently, the lowest value in the range of fracture forces found in the literature. This is taken from the reference value for a 65 year old, predicted by the survivor function introduced by Funk et al. (2001). The Tibia Index threshold value of 1 is used by Rudd et al. as well as a dorsiflexion angle of 30° (Portier et al., 1997).

5.2 Shaw et al. (2002)

The paper by Shaw et al., summarises a series of sled tests performed by the University of Virginia to evaluate the THOR-Lx (Hybrid III retrofit, HIIIr) compared with Hybrid III lower extremities, when fitted to a Hybrid III dummy. Three crash conditions were used in the tests representing two different full vehicle pulses. These were chosen to determine if introduction of the THOR-Lx/HIIIr legs would affect critical NCAP test results, such as head and chest acceleration. Two of the three conditions included the use of an intruding toepan, with either translation only or translation and rotation.

The occupant restraint systems and test hardware reportedly performed consistently throughout the test series. The coefficients of variation for most of the dummy response parameters were less than 10 %. Mean head and chest accelerations varied by up to 2 g from tests with the THOR-Lx to tests with the Hybrid III lower extremities and chest deflection varied by up to 2 mm. Therefore, the test-to-test repeatability of the dummy responses was reported as being generally acceptable for all of the test conditions for both legs. The greatest variability was recorded for the right femur axial loads, which were well below the Injury Assessment Reference Value of 10 kN. This was explained by Shaw et al. to be due to a glancing blow the right knee made with the knee bolster. More substantial knee bolster contact, as seen in the left femur response, produced less variability. Shaw et al. concluded that although very small response differences were recorded, the study identified no substantial differences that were attributable to leg type.

5.3 Rudd et al. (2003)

The paper by Rudd et al. presents results from sled tests performed to evaluate the THOR-Lx Hybrid III retrofit in relation to the Hybrid III leg. The design of the tests was to allow evaluation of repeatability, durability and response comparison. These tests were the same as those reported by Shaw et al. (2002).

Both sets of dummy lower extremities were subject to an identical series of severe sled tests without any reported equipment failures. This was in despite of ankle rotations being near to or reaching their limits in the two or the three test conditions with toepan intrusion.

In the tests with intrusion, Rudd et al. commented on differences between the distal axial tibia force recorded by the Hybrid III and THOR-Lx. The THOR-Lx had a higher initial peak response than the Hybrid III which was attributed to the force being applied more in line with the THOR-Lx tibia load cell than that in the Hybrid III leg. After this initial inertial response, and during dorsiflexion of the foot, the THOR-Lx distal tibia force again showed differences from the Hybrid III. This later difference, with higher forces in the THOR-Lx, was reported as being due to several kN of axial load acting on the tibia as a result of the Achilles tendon substitute. As there is no Achilles substitute in the Hybrid III leg, then this force was not present in the Hybrid III.



To account for this force, Rudd et al. include in their conclusions, the suggestion that the THOR-Lx be modified to measure Achilles tendon force.

Again, in the tests with intrusion, Rudd et al. noticed and commented on the differences in ankle design between the Hybrid III and the THOR-Lx, more than in the tests with no intrusion. For the Hybrid III, increasing the ankle rotation by a few degrees near the limits causes very large increases in ankle moment due to the discontinuous joint stop design. In the THOR-Lx, the contribution of the internal and external joint stops results in more gradual increase in moment at the limits. This was thought by Rudd et al. to be more human-like.

In assessing the injury predictions made by the THOR-Lx, Rudd et al. used the Injury Assessment Reference Values (IARVs) introduced by Kuppa et al. (2001b). Even with these lower values, lower than are used with the Hybrid III, the THOR-Lx gave a more conservative assessment of injury risk. Despite this, Rudd et al. concluded that the Kuppa et al. (2001b) IARVs provided meaningful interpretation of the THOR-Lx instrument measurements.



6 Summary Only two papers from the literature have identified injury risk functions specifically for use with the THOR-Lx: these are summarised in Table 6.1. Other injury risk values, for use with 50th percentile human males, are shown in Table 6.2 :

Table 6.1: THOR-Lx specific injury risk thresholds

Measurement parameter

Injury risk Source

25 % 50 %

Axial tibia force (75 year old)

3.3 kN 4.3 kN Hynd et al., 20032


4.3 kN 5.3 kN Modified from Hynd et al., 20033

Ankle moment (dorsiflexion)

59 Nm (THOR-Lx and PMHS

risk functions are supposed to be the same)

85 Nm (THOR-Lx and PMHS

risk functions are supposed to be the same)

Rudd et al., 2004

Ankle angle (dorsiflexion)

36° 40° Rudd et al., 2004

2 This injury risk curve is an attempt to define the risk of injury in bracing conditions on a THOR-Lx used without bracing. 3 This injury risk curve defines the tolerance of a bracing subject and should be used on a bracing THOR-Lx.



Table 6.2: Injury assessment reference values for use with a 50th percentile male human

Measurement parameter Injury risk

Source 25 % 50 %

Axial tibia force 7.3 kN (45 year old)

7.3 kN (45 year old)

Funk et al., 2001

Axial tibia force 5.3 kN (65 year old)

5.3 kN (65 year old)

Funk et al., 2001

Axial tibia force (distal)

5.2 kN 6.8 kN Kuppa et al., 2001b

Axial tibia force (proximal)

5.6 kN 7 kN Kuppa et al., 2001b

Tibia Index 0.91 1.16 Kuppa et al., 2001b

Tibia Index 1 ‐

Rudd et al., 2001, Funk et al., 2004

Ankle moment (dorsiflexion) 50 Nm 60 Nm Kuppa et al., 2001b

Ankle moment (inversion/eversion)

33 Nm 40 Nm Kuppa et al., 2001b

Ankle moment (inversion) 24 Nm (no axial load)

31 Nm (no axial load)

Funk et al., 2002

Ankle moment (inversion) 58 Nm (2 kN axial load)

75 Nm (2 kN axial load)

Funk et al., 2002

Ankle moment (eversion)



Funk et al., 2002


110 Nm (2 kN axial load)

142 Nm (2 kN axial load) Funk et al., 2002

Ankle angle (dorsiflexion) ‐ 35° Kuppa et al., 2001a

Ankle angle (dorsiflexion) 30° Rudd et al., 2001

Ankle angle (inversion/eversion)

‐ 35° Kuppa et al., 2001a


28° (no axial load)

33° (no axial load)

Funk et al., 2002


38° (3 kN axial load)

45° (3 kN axial load)

Funk et al., 2002



7 Discussion Where THOR-Lx dummy-specific injury risk functions are available, it is suggested that these be adopted for use with the THOR-Lx.

In the case of the axial tibia load, Hynd et al. (2003) developed an injury criterion for the lower (distal) tibia. The THOR-Lx has a compliant element in the midshaft of the lower leg. An effect of this feature is that for axial forces applied to the distal end of the THOR-Lx, the upper (proximal) tibia load cell has a smaller force acting on it than the lower tibia. The injury criterion from Hynd et al. is smaller than that proposed for the proximal tibia by Kuppa et al. (2001b). Therefore, it is suggested that until a THOR-Lx specific proximal load cell injury risk function is developed, then the Kuppa et al. value is not necessary.

From the Hynd et al. study, a 50% risk of injury at 4.3 kN could be used to estimate the risk for an occupant that is bracing, but this may overestimate the risk for an unbraced occupant. A 50% risk of injury at 5.3 kN could be used occupants who are bracing (e.g. braking). Ideally, the dummy should better represent either the braced or unbraced occupant, depending on which group is considered the priority for injury prevention. See footnote on page 18 for more information.

In the Kuppa et al. study (Yoganandan configuration), an injury risk function is determined for PMHS. It would be better if some THOR-Lx leg tests were performed in order to recommend a threshold specific to the dummy. As the biofidelity requirements for the THOR-Lx include the Yoganandan configuration (GESAC, 2005) it is supposed that the dummy test results should be available somewhere. If so, it is recommended that an injury risk curve relevant for the THOR-Lx is constructed with these data.

As suggested by Funk et al. (2004), the Tibia Index threshold should be kept at 1 until different material property data or understanding becomes evident. However, it may be worth investigating whether the TI is redundant if an axial tibia force criterion is set at 4.3 kN. That is, whether the TI can exceed 1 before the axial load of 4.3 kN is exceeded (see Funk et al.).

For ankle moment inversion and eversion criteria, the decision has to be made whether preference lies with the values presented by Kuppa et al. (2001b) or with those from Funk et al. (2002). The data used by Kuppa correspond to quasi-static tests, while the data from Funk correspond to dynamic tests. Therefore, it would be more appropriate to choose the results from dynamic tests, for injury risk curves. For eversion tolerance, moment as well as angle are available from Funk study. Therefore, it would be more consistent to use the same study to provide both curves.

The Funk et al. values incorporate variability due to the axial load applied. The THOR-Lx will have some Achilles tension in its standard set-up and this will result in some preloading of the lower leg. When Hynd et al. were setting the levels of axial pre-loading in their experimental work, to replicate typical loads associated with pre-impact bracing, they used about 500 N for the simulated Achilles tension in the PMHS. If the THOR-Lx Achilles tension is assumed to be equivalent to about 500 N in a human bracing before an impact, then this force can be taken into account using the ranges provided by Funk et al. The injury risk functions for inversion may then be expected to be very similar to those presented by Kuppa et al. It would be necessary to confirm that the biofidelity of the THOR-Lx in this loading condition was adequate before adopting this approach.

For eversion, however, the values from Funk et al. are much greater. It seems more likely than not, and is suspected to be more correct from a biomechanical basis, that the moment necessary to cause an injury in inversion will be different to that in eversion. To take this difference into account, the injury risk function from the Funk et al. should be employed. Using the same process and assumed Achilles tension of 500 N, then the corresponding injury risk function gives 61 Nm and 79 Nm, for a 25 % or 50 % risk of injury, respectively. Again, the biofidelity of the THOR-Lx in this loading condition should be confirmed before adopting this approach. As for the Hynd et al. injury risk function, estimates of risk for braced and unbraced occupants are given in this report. The THOR-Lx is not equipped with active musculature. It is Unknown whether the dummy would behave similarly or not with or without muscle activation. Therefore tolerances in braced conditions are to be considered with caution.



8 Recommendations Based on the papers reviewed for Sections 2 and 3 the injury assessment reference values shown in Table 8.1 are recommended for use with the THOR-Lx. However, it should be remembered that not all of these were developed specifically for use with the THOR. As such, they may not be absolutely applicable to the prediction of injury, as they stand. Therefore, it is also recommended that work be directed towards developing THOR-Lx specific injury risk curves for all parameters that are considered as important. This table should be updated when dummy specific injury criteria become available.

Table 8.1: Injury assessment reference values recommended to be used with the THOR-Lx

Measurement parameter

Injury risk THOR-Lx specific Reference

25 % 50 %


Braced (500 N) 4.3 kN 5.3 kN Yes

(unbraced THOR dummy) Modified from

Hynd et al., 2003


Braced (500 N) 3.3 kN 4.3 kN Yes

(unbraced THOR dummy) Hynd et al., 2003

Ankle moment (dorsiflexion) 59 Nm 85 Nm Same as PMHS Rudd et al., 2004

Ankle angle (dorsiflexion) 36° 40° Yes Rudd et al., 2004

Tibia Index 1 - No Rudd et al., 2001

Rudd et al., 2004

Ankle moment (inversion) 24 Nm 31 Nm No Funk et al., 2002

Ankle moment (inversion)

Braced (500 N) 32.5 Nm 42 Nm No Modified from

Funk et al., 2002

Ankle moment (eversion) 45 Nm 58 Nm No Funk et al., 2002


Braced (500 N) 61 Nm 79 Nm No Modified from

Funk et al., 2002

Ankle angle (inversion/eversion) 28° 33° No Funk et al., 2002


Braced (500 N) 29.5° 35° No Modified from

Funk et al., 2002



References 1. Banglmaier R F, Dvoracek-Driksna D, Oniang’o T E and Haut R C (1999). Axial

compressive load response of the 90° flexed human tibiofemoral joint. Proceedings of the 43rd Stapp Car Crash Conference. 25-27 October 1999, San Diego, California (SAE technical paper 99SC08): Society of Automotive Engineers, Inc. (SAE), 400 Commonwealth Drive, Warrendale, PA 15096-001, U.S.A.

2. Funk J R, Crandall J R, Tourret L J, MacMahon C B, Bass C R, Khaewpong N and Eppinger R H (2001). The effect of active muscle tension on the axial injury tolerance of the human foot/ankle complex. Proceedings of the 17th International Technical Conference on the Enhanced Safety of Vehicles. 4-7 June 2001, Amsterdam, the Netherlands: National Highway Traffic Safety Administration (NHTSA), US Department of Transportation (available on the NHTSA internet site www.nhtsa.dot.gov).

3. Funk J R, Srinivasan S C M, Crandall J R, Khaewpong N, Eppinger R H, Jaffredo A S, Potier P and Petit P Y (2002). The effects of axial preload and dorsiflexion on the tolerance of the ankle/subtalar joint to dynamic inversion and eversion. Stapp car crash journal, vol. 46. Proceedings of the 46th Stapp Car Crash Conference. 11-13 November 2002, Pointe Verdra Beach, Florida (SAE technical paper 2002-22-0013): ): Society of Automotive Engineers, Inc. (SAE), 400 Commonwealth Drive, Warrendale, PA 15096-001, U.S.A.

4. Funk J R, Rudd R W, Kerrigan J R and Crandall J R (2004). The effect of tibial curvature and fibular loading on the tibia index. Traffic Injury Prevention, 2004 (5) 164-172.

5. GESAC (2005). Biomechanical response requirements of the THOR NHTSA Advanced Frontal Dummy (Revision 2005.1). GESAC-05-03. Boonsboro, MD, USA: GESAC Inc. March, 2005.

6. Hynd D and Carroll J A (2003). Tibia and foot biofidelity of the THOR-Lx. Unpublished Project Report (PR/SE/832/2003): TRL, Crowthorne, UK.

7. Hynd D, Willis C, Roberts A, Lowne R, Hopcroft R, Manning P and Wallace W A (2003). The development of an injury criteria for axial loading to the THOR-Lx based on PMHS testing. Proceedings of the 18th International Technical Conference on the Enhanced Safety of Vehicles. 19-22 May 2003, Nagoya, Japan: National Highway Traffic Safety Administration (NHTSA), US Department of Transportation (available on the NHTSA internet site, www.nhtsa.dot.gov).

8. Kuppa S, Haffner M, Eppinger R and Sanders J (2001a). Lower extremity reponse and trauma assessment using the THOR-Lx/HIIIr and the Denton leg in frontal offset vehicle crashes. Proceedings of the 17th International Technical Conference on the Enhanced Safety of Vehicles. 4-7 June 2001, Amsterdam, the Netherlands: National Highway Traffic Safety Administration (NHTSA), US Department of Transportation (available on the NHTSA internet site www.nhtsa.dot.gov).

9. Kuppa S, Wang J, Haffner M and Eppinger R (2001b). Lower extremity and associated injury criteria. Proceedings of the 17th International Technical Conference on the Enhanced Safety of Vehicles. 4-7 June 2001, Amsterdam, the Netherlands: National Highway Traffic Safety Administration (NHTSA), US Department of Transportation (available on the NHTSA internet site, www.nhtsa.dot.gov).

10. Parenteau C, Viano D and Petit P (1998). Biomechanical properties of human cadaveric ankle-subtalar joints in quasi-static loading. Journal of Biomechanical Engineering 120(1). 105-111.

11. Portier L, Petit P, Dômont A, Trosseile X, Le Coz J-Y, Tarrière and Lassau J-P (1997). Dynamic biomechanical dorsiflexion responses and tolerances of the ankle joint complex. Proceedings of the 41st Stapp Car Crash Conference. 13-14 November 1997, Orlando, Florida (SAE technical paper 973330): Society of Automotive Engineers, Inc. (SAE), 400 Commonwealth Drive, Warrendale, PA 15096-001, U.S.A.



12. Rudd R, Crandall J and Butcher J (1999). Biofidelity evaluation of dynamic and static response characteristics of the THOR-Lx dummy lower extremity. Proceedings of the 1999 International IRCOBI Conference on the Biomechanics of Impact. 23-24 September 1999, Sitges, Spain: International Research Council on the Biomechanics of Impact.

13. Rudd R, Crandall J and Butcher J (2000). Biofidelity evaluation of dynamic and static response characteristics of the THOR-Lx dummy lower extremity. International Journal of Crashworthiness, 5 (2) 127-139.

14. Rudd R W, Crandall J R, Hjerpe E and Håland Y (2001). Evaluation of lower limb injury mitigation from inflatable carpet in sled tests with intrusion using the THOR-Lx. Proceedings of the 17th International Technical Conference on the Enhanced Safety of Vehicles. 4-7 June 2001, Amsterdam, The Netherlands: National Highway Traffic Safety Administration (NHTSA), US Department of Transportation (available on the NHTSA internet site, www.nhtsa.dot.gov).

15. Rudd R W, Crandall J R and Shaw G (2003). Response of the THOR-Lx and Hybrid III lower extremities in frontal sled tests. Reprinted from Biomechanics (SP-1784), SAE World Congress. 3-6 March 2003, Detroit, Michigan (SAE technical paper 2003-01-0161): Society of Automotive Engineers, Inc. (SAE), 400 Commonwealth Drive, Warrendale, PA 15096-001, U.S.A.

16. Rudd R, Crandall J, Millington S, Hurwitz S and Höglund N (2004). Injury tolerance and response of the ankle joint in dynamic dorsiflexion. Stapp car crash journal, vol. 48. Proceedings of the 48th Stapp Car Crash Conference. 1-3 November 2004, Nashville Tennessee (SAE technical paper 2004-22-0001): Society of Automotive Engineers, Inc. (SAE), 400 Commonwealth Drive, Warrendale, PA 15096-001, U.S.A.

17. Shaw G, Rudd R W, Crandall J R and Luo F (2002). Comparative evaluation of dummy response with THOR-Lx/HIIIr and Hybrid III lower extremities. Reprinted from Impact Biomechanics (SP-1665), SAE World Congress. 4-7 March 2002, Detroit, Michigan (SAE technical paper 2002-01-0016): Society of Automotive Engineers, Inc. (SAE), 400 Commonwealth Drive, Warrendale, PA 15096-001, U.S.A.

18. Yoganandan N, Pintar F A, Boynton M, Begeman P, Prasad P, Kuppa S M, Morgan R M and Eppinger R H (1996). Dynamic axial tolerance of the human foot-ankle complex. Proceedings of the 40th Stapp Car Crash Conference. 4-6 November 1996, Albuquerque, New Mexico (SAE technical paper 962426): Society of Automotive Engineers, Inc. (SAE), 400 Commonwealth Drive, Warrendale, PA 15096-001, U.S.A.

report on thor-lx design and performance

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