Dragos POPA, George GHERGHINA, Marin TUDOR, Daniela TARNITA
A 3D GRAPHICAL MODELLING METHOD FOR HUMAN FEMUR BONE
Abstract: The paper presents a method of study and the steps to obtain a virtual bone. For that purpose
was used a CAD parametric software which permits to define models with a high degree of difficulty. The
obtained model attached to other bones will be study using finite elements method and will be prepared
for kinematics and dynamic simulation.
Key words: human knee, geometric definition, mechanical characteristics, geometrical model, dynamic
simulation.
1. INTRODUCTION
In this moment the human kind passes an important
step of an industrial development. A main component of
that evolution consists in the informational world
community, which gets by Internet the global tendencies.
So, the researchers from the entire world can cooperate
on the great study projects because the distances are
shorter and the borders disappeared. The concurrential
component is very important because it is recepted like
an evolving factor to elaborate the new technologies.
Having these reasons, the studies or technologies cannot
be realized by one-field researchers. So, in the world,
appear a new many-field orientation, which permits the
development of the border fields with multi-national
teams, which cooperate to elaborate new technologies
and methods for informational community [1].
The research theme consists of a large subject of
study, which attracts the knowledge from different fields
(anatomy, surgical techniques, orthopedy, mechanics,
bio-mechanisms, computer science, technical graphics,
computer aided design). The subject of this paper permits
the cooperation between many researchers which activate
in different fields and which have the capacity to develop
informational methods and technologies to solve difficult
problems given by the complexity of the scientifically
target [1].
Fig. 1 The main components of the human knee [2].
The main bones of the knee are:
- The Femur – the longest bone of the body;
- Tibia – the longest bone of the leg;
- Patella – the smallest bone of the leg;
- Fibula (Figure 2).
2. THE STUDY OF THE ANATOMICAL
ELEMENTS OF THE KNEE JOINT
The knee joint is an important joint from the human
locomotion system and it is composed of bones,
ligaments, tendons and cartilages. From such reason,
scientifically studies are very difficult to realize because
the knee is the most complex joint in the human body,
almost they are made in a statically system [2].
To understand the problems which appear in this
joint, it is very important to know the anatomy of the
knee and the way in which the components are working
together to realize a normal functionality [2].
The knee has ligaments, tendons, bones and cartilages
like the main components (Figure 1).
Fig. 2 The bone components of the knee joint [2].
To elaborate the 3D virtual model for the knee joint
were studied four of the main components such as:
femur, tibia, fibula and patella. First, for these bones
were made pictures from different angles and these were
measured (Figure 3 and 4). Also, were determined the
masses for each component (Table 1).
DECEMBER 2006  VOLUME 1  NUMBER 2 JIDEG 37
A 3D Graphical Modelling Method for Human Femur Bone
using the command Insert/Reference Geometry/Plane
(Figure 5).
It was defined a first section sketched in plane 40
which was presented in Figure 6.
Fig. 3 The real components of the knee joint.
The masses of the bone components.
No.
1.
2.
3.
Name
Femur
Tibia
Fibula
Table 1
Mass [kg]
0.455
0.310
0.060
To obtain the pictures was used a Spycam 100 digital
camera having the storing capacity of 20 photos. Also,
the bones were supposed over sheets of paper with lines
drawn from 10 to 10 millimeters. In Figure 4 was
presented two pictures of femur bone.
Fig. 6 The first section for defining the base shape.
In the same way, in planes 190, 300 and 420 were
defined the sections presented in Figure 7.
Fig. 4 Two images of the real femur.
3. THE OBTAINING METHOD OF THE 3D
MODEL OF THE FEMUR
To obtain the 3D model was used SolidWorks – a
CAD software of third generation. Using the
measurement made on real bone component and after the
identification of the simple shapes it was starting the
modeling operation [3].
Fig. 7 Three section defined in three different planes.
Using the command Insert/Base/Loft the defined
sections were united in a single shape presented in Figure
8.
Fig. 5 The initial five reference planes.
Initially, were defined the five reference plane (the
planes 0, 40, 190, 300 and 420) in which were made
measurements for corespondent planes on real model
38 DECEMBER 2006  VOLUME 1  NUMBER 2 JIDEG
Fig. 8 The base shape of the virtual femur bone.
A 3D Graphical Modelling Method for Human Femur Bone
Using a sketch drawn in an axial plane and the
command Insert/Boss/Revolve it was defined the shape
presented in Figure 9.
At the two extruded shape it were attached two Dome
shapes and after that all the features were filleted (Figure
13).
Fig. 13 The Dome shape applied on the other side of the plane.
Fig. 9 The first additional revolving feature.
At that feature it was attached a secondary shape
using Dome command (Figure 10.).
In an inclined plane with 120 degrees it was drawn
the sketch presented in Figure 14.
Fig. 10 The Dome feature applied on a plane surface.
Using the command Insert/Boss/Extrude applied
twice were obtained the features presented in Figure 11.
Fig. 14 The sketch drawn in inclined plane.
Using the command Boss-Revolve applied to the
precedent sketch it was obtained the feature presented in
Figure 15.
Fig. 11 The extruded features.
In a medial plane was defined the sketch and using a
Loft feature it was obtained the shape presented in Figure
12.
Fig. 12 The feature Loft defined in a middle plane.
Fig. 15 The Boss-Revolve feature.
Using the command Insert/Features/Fillet and the
radius of de 3 mm was obtained the feature from Figure
16.
Fig. 16 The fillet of de 3 mm obtained on precedent feature.
DECEMBER 2006  VOLUME 1  NUMBER 2 JIDEG 39
A 3D Graphical Modelling Method for Human Femur Bone
Using the precedent plane it was drawn the sketch
from Figure 17.
Using the Fillet command applied for different edges
and surfaces was obtained the final model of the femur
bone (Figure 21).
Fig. 17 The sketch from the precedent plane.
That sketch was extruded using a middle plane
obtaining the feature from Figure 18.
Fig. 21 The virtual model of the femur bone.
4. CONCLUSION
Fig. 18 The inclined extruded feature obtained using a middle
plane.
Using the two free surfaces it was defined the Loft
feature shown in Figure 19.
The obtained model was completed with the mass
properties and the virtual femur had in that moment the
same inertial characteristics. So, using the command
Tools/Mass Properties was obtained a mass of 455.46
grams and a medium density of the 0.00056 grams/mm3.
The virtual femur was prepared for any finite
elements analysis or for kinematical and dynamical
simulation.
5. REFERENCES
Fig. 19 The Loft feature applied on two surfaces.
In that stage, the virtual bone had the shape presented
in Figure 20.
[1] Gherghina, G., Popa, D., Calbureanu, M., Tudor, M.
(2000). Grafica asistata de calculator - doua
modalitati de abordare, Pub. University of Craiova.
[2] Tarnita D.N., Tarnita D., Grecu D., Niculescu D.,
Didu S. (2002). Considerations on the complications
appeared in cases of menisci ruptures operated
through arthroscopy, The 4th Central European
Orthopaedic Congress, Dubrovnik, June 2002.
[3] Solidworks 98 Plus –User’s Guide.
Authors:
Eng. 'UDJRú 323$, Ph.D., lecturer, The University of
Craiova, e-mail: [email protected];
Eng. George GHERGHINA, Ph.D., professor, The
University of Craiova, e-mail: [email protected];
Eng. Marin TUDOR, Ph.D., lecturer, The University of
Craiova, e-mail: [email protected];
Eng. Daniela TARNITA, Ph.D., professor, The
University of Craiova, e-mail: [email protected].
Fig. 20 The initial model of the virtual femur.
40 DECEMBER 2006  VOLUME 1  NUMBER 2 JIDEG