Improvement of Human Body Damage Evaluation Method by Computer Simulation- Verification of Infant Bone Properties Compared with Actual Experiment Tomotaka Matsubara1, Yasumi Ito1, Tatsuya Fukuoka2, Ryuichi Yamada1,Yoshiyuki Kagiyama1 andTetsuya Nemoto2
1．University of Yamanshi, 2． National Center for Geriatrics and Gerontology
E-mail : yasumii@yamanashi.ac.jp, g18tm026@yamanashi.ac.jp

II. Basic comparison between
experiment and analysis

actual experiment
20mm

20mm

20mm

60°

90°

30°

3.1mm

3.1mm

•As the result, in fracture risk evaluation using FEA, sufficient simulation
accuracy could be confirmed even with infant bones. And, in order to further
improve the accuracy, it is necessary to review the conventional properties ofanalysis.

Compression part
Without soft tissue• To estimate the intention of murder in case of injuries suchas child abuse and to prove negligence, reproduce infantbone in simulation is effective. Also, it is necessary toverify infant bone properties compared with actual
experiment and improve the accuracy.

Number of solids
ROI volume ratio [%]Child abuse
LoadStep1.
Accuracy verification(Keyak's formula)

Step1.
compareBonemodelFE analysis

Actual experiment

Step2. change the 3D-bone model property

oror
Keyak's formulaetc.
Minamisawa's formula

Carter's formula

Materials

Force tester

Mesh size [mm]Sample material

3.1mm

FE analysis
3D-models property

Introduction

Compression part

 Compression part
Fracture loads of the materials
changes depending on theapplied tool. In this research weadopted 30°, 60° and 90°.
 Materials
We adopted the porcine's tail asa young animal bone that iseasy to obtain.

Step2.
For high accuracy(Keyak's, Carter's, Minamisawa's, Keller's formula)Finite Element Analysis for Fracture
Software: MECHANICAL FINDER ver. 10.0 Extended Edition• It is an integrated system of (1)-(3).
(1)Reading DICOM data obtained by CT imaging to model creation(2)analysis execution (3)result display function• 3D-model based on DICOM data, it is possible to reflect the bone shape andbone density of each analysis object.

 Fracture definition
A point at which the broken
number of solids rapidly
increases is defined as afracture load.

141951，22814，13631，34248，20731，29341
100.033900ρ2.20（ρ≤0.27g/cm-3）5307ρ2.20+469
Young’s module [MPa]（0.27<ρ<0.6g/cm-3）
10200ρ2.01（0.6g/cm-3≤ρ）
Poisson ratio
0.4
Critical stress [N]σ = 0.8εYield criterion
Drucker - Prager
Crushing strain[μ]
10000

92N

196N

104N

101N

25000

F=182N

20000
15000
10000
5000
F=92N
0050

100

150
Load [N]

200

250

300

0

Relationship between load and broken number of solids (Keyak's formula)

Bone
model

50

100

150
Load [N]

200

250

300

Relationship between load and broken number of solids (Carter's formula)
190N

6N

3D-model25000

Fracture definition

Results & Discussion
 Results
Figure A showed experiment results for each tool. Angle30°: 92 N (n =3), angle60°: 124 N (n =4), angle90°: 183 N (n = 2). In the 4 trials, theresults of observing the fracture load clearly were summarized. The result
by FE is 151 N. In addition, the average of the result of angle60° and theresult of angle90° is 143 N.
 Discussion
Except for angle30° when sharp fractures occurred, the results ofexperiments and FEs are almost match (figure B). However, Even if weinclude angle30° different fracture forms, we have to make it moreaccurate. In order to be highly accurate in various cases, it is necessary tochange material properties of bone. Although Keyak's formula was usedin the analysis, it is attempted to verify Carter's formula, Minamisawa's
formula and Keller's formula which have been devised so far.

20000
15000
10000

F=3N

②5000
0050

100

150
Load [N]200250193N

199N

Relationship between load and broken number of solids (Minamisawa's formula) Results
The above figure show the fracture load (F : fracture load). The averagefracture load in Keyak's formula is 190 N (182N, 198N), in Carter's formula
is 97 N (92N, 102N), in Minamisawa's formula is 3N (3N, 2N), in Keller's
formula is 190N. To be accurate, a fracture load is a starting fracture load.
In this analysis, accurate the starting fracture load was investigated byobserving the appearance of stress distribution with broken number ofsolids. Also, the number of data is one in Keller's formula.

B. Average (60°and90°) and FE

18000
16000
14000
12000
10000
8000
6000
4000
2000
0202N

F=190N0300 Discussion
Taking into account the behavior of various bone fractures, there were noformula that could accurately simulate young bone. However, the formulaof Carter was the most similar to the young bone in this study. The fractureload is 97N in Carter's formula and it is 139N in the experiment, so there isa difference of about 40N. Since there is a difference between theexperimental value and the analytical value, we have to attempt bring it
closer. Therefore, in order to accurately simulate the young bone, it isnecessary to (1) use another formula, (2) develop a formula that fits theexperiment value, (3) increase the number of analyzes, and so on.
A. Each fracture load (experiment)

95N

Fracture load

CT-image

Dimensional
X-ray CT

193N

20000
18000
16000
14000
12000
10000
8000
6000
4000
2000
0

Load

3D-modelAutomatically calculation
dynamics parameterfrom CT data.

185N

3N

3D model creation flow using MECHANICAL FINDER

Micro-CT Analysis object
HA Phantom

182N

Broken number of solids

In this study, we conducted a comparison between experiment and analysis, inorder to verification of infant bone properties compared with actual experiment.
newborn porcine bones as infant bone was used for the experiment.
Furthermore, we changed the physical properties of the bone in the analysis
and made a developmental comparison.

Broken number of solids•

The Baltimore Convention Center
1 W. Pratt Street,Baltimore, MD 21201-2499• The following graphs show fracture loads by analysis. Two samples that can accurately compare experimental values and FE values in the same model
were used. One sample is shown below. In this study, we observed not only numerical values but also the appearance of 3D - model.
• Also, fracture loads are 86 N and 191 N, which is 139 N on average in actual experiment. This value is compared with the below.

Materials & Conditions

Abstract

February 18-23, 2019III. Developmental comparison between experiment and analysis

Broken number of solids

I. Introduction and using Analysis
SoftwareBroken number of solids

UNIVERSITYOF
YAMANASHI

AMERICAN ACADEMY OF
FORENSIC SCIENCES

50

100

150
Load [N]200250300

Relationship between load and broken number of solids (Keller's formula)Conclusions②• The formula of Carter was the most similar to the young bone in this study.
The fracture load is 97N in Carter's formula and it is 139N in the experiment.
• It is necessary to develop a formula that fits the experiment value.

Acknowledgments
This work was supported by JSPS KAKENHI Grant Number JP16H03134“Elucidation of mechanism for wound occurrence in robot mounting part, anddevelopment of safety test apparatus”, and by the Japan Food Machinery
Manufacturers’ Association “Study on force and finger bone damage” .

References
1) Joyce H Keyak, Stephen A Rossi, Kimberly A Jones, Harry B Skinner.: Prediction of femoral fracture loadusing automated finite element modeling, Journal of Biomechanics, 31-2, (1998), 125–133.
2) Dennis R. Carter, Greg H. Schwab & Dan M. Spengler. : Tensile Fracture of Cancellous Bone, Acta
Orthopaedica Scandinavica, 51:1-6, (1980), 733-741.
3) Minamisawa I. :A biomechanical study on the senile intracapsular fracture of the femoral neck speculation
concerning the fracture lines and etiological factors, Nihon Seikeigeka Gakkai Zasshi, 55-2, (1981) , 167-81.
4) Tony S. Keller. :Predicting the compressive mechanical behavior of bone, Journal of Biomechanics, 27-9,(1994), 1159-68