Description

The research theme, it was a part of a large subject of study, which attracts the knowledge from different fields (anatomy, surgical techniques, orthopaedics, mechanics, bio-mechanisms, computer science, technical graphics, computer aided design). The subject of this study 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.
The elbow is an important joint from the human skeleton and it is composed of bones, ligaments, tendons and cartilages. From such reason, scientifically studies are very difficult to realize because the elbow is one of the most complex joint in the human body, almost they are made in a statically system.
First, to understand the problems, which appear in this joint, it is very important to know the anatomy of the elbow and the way in which the components are working together to realize a normal functionality.

SOLUTION

To obtain the bone cross sections was used a PHILIPS AURA CT tomograph installed in the Emergency Hospital of Craiova and the three bone components (Figure 1).
To obtain the tomographies of the three bone components (humerus, cubitus and radius) were used two scanning schemes presented in Figure 2. First, was completed a complete scanning operation for 5 mm distances having the results 147 images. After that, had been obtaining cross section images at the distance of 1.25 mm for the ends of the bones and the elbow joint area.

The elbow is one of the most complex joint from the human body, but this paper proves the mechanical studies can be made starting from anatomical knowledges. The behavior of the virtual elbow can give the important informations which can be used in the fields of robotics, medicine sciences and medical robotics. Also, on the virtual elbow joint can be attached virtual prosthetic elements for virtual post-surgery simulations.
The obtained models were completed with the mass properties and the virtual bones had in that moment the same inertial characteristics as the real bones.

To have the possibility to report the next 3D model to a fixed coordinate system and to respect a correct rep Were obtained 10 images folders and, after a strict selection, were used only 4, one for each bone component including the upper and lower areas and the joint area.
To have the possibility to report the next 3D model to a fixed coordinate system and to respect a correct representation scale, the studied bones were scanned with a plastic bar having known dimensions (Figure 3).
In Figure 4 were presented two important images of the humerus in the upper area.
The obtained images were re-drawn in AutoCAD over the real tomographies and the drawing were imported in SolidWorks (a parametrical CAD software), section by section, in parallel planes. The sketches made for humerus bone were presented in Figure 5, also two details for the upper and lower areas.
Solidworks permits to obtain a solid by “unifying” the sections drawn in parallel planes. The shape which solidyfing the these sections was the Loft Shape and it define the solid starting with the sections and a Guide Curve defined automatically by the software. In Figure 6 was presented the definition scheme for the humerus bone. In the same way and using the Loft shape was defined the virtual models for the cubitus and radius bones (Figure 7).
For the preparation of the model for the kinematic analysis the bone components were loaded in the SolidWorks module assembly of program. This module allows to define the motion constraints (the type axle-axle, flat-plane, distance a.s.o.) and the definition of the bio-mechanical system in terms of D.O.F.
First, it was used the Mate command for the correct displacement of the three components. For the study of the kinematic and dynamic analysis the mechanical system has been exported as ACIS (SAT) file. The VisualNastran is the program that allows the study of kinematics and it is based on forces occurring in the mechanical system and allows finite element analysis for the various components.
In the first stage, the mechanical system looks like in the Figure 8.

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