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STRESS ANALYSIS OF THE RADIAL HEAD REPLACEMENT IN AN ELBOW ARTICULATION
Poster 154, Poster Session 1/Upper Extremity. 14:45-15:45, Room 103 & Alley Area
S634
STRESS ANALYSIS OF THE RADIAL HEAD REPLACEMENT IN AN ELBOW ARTICULATION P. Hlavon 1, V. Fuis1, T. Navrat1 and Z. Florian2 Centre of Mechatronics – Institute of Thermomechanics Academy of Sciences of the Czech Republic and Institute of Solid Mechanics, Mechatronics and Biomechanics, Faculty of Mechanical Engineering, Brno University of Technology. 2 Institute of Solid Mechanics, Mechatronics and Biomechanics, Faculty of Mechanical Engineering, Brno University of Technology, Brno, Czech Republic. email: [email protected], web: www.fme.vutbr.cz/en/prdetail.html?pid=2623
1
INTRODUCTION In case of a traumatological contusion of the elbow joint the bearing surfaces of the proximal end of the radius are damaged or broken off, resulting in their surgical removal. This operation does not make the elbow connection non-functional; however, it results in shortening the antebrachial bones, causing unpleasant pain in the patient’s wrist. GEOMETRICAL AND COMPUTATIONAL MODELS Upon the initiative of the medical team, efforts are invested to create such a partial joint replacement of the proximal end of the radius that would suitably replace the patient’s missing bone tissue and, at the same time, to preserve the same functionality of the radio-humeral connection. In this section, several contact tasks were solved in various parts of the computational model, see Fig.1, and for various geometry and various materials of proximal replacements. The main contact places are - the contact of the replacement and the cartilage at the humerus, for two curvatures of the bearing-on surfaces (R16, R35mm). The second one is the contact of the upper part of replacement and the rest of proximal part at the bone tissue. The third one is the area of humeral-ulnar articulation. Border conditions were selected zero movements at all the three coordinate axes and zero turns for the lower humerus part. Likewise, the same dynamic conditions were prescribed in the respective z-direction of the fixed coordinate system at the upper surfaces of the humerus´s section and zero movements in x and y directions. All tasks were solved mostly as a one-sided contact. The static load at all nodes of the selected surfaces at the radius section corresponded generally to the articular junction in physiological state. RESULTS AND DISCUSSION The best correspondence, see Table.1, for the first RHR type, to the physiological state, exhibits the proximal
replacement made of high-pressure polyethylene, the difference of which makes 0.8 %. The analysis also shows that if we increase the number of elements by about 50 %, the contact pressure in this area will decrease by about 2.7 %. Thus, it is clear that the number of elements needs not to be here increased. For the second RHR type was also achieved fair correspondence in contact pressures. There are shown two numbers for different geometrical position of radius against humerus. The value (without turning) is naturally corresponds with geometrical posture of physical state, it is at around 1MPa bigger than physiological state. More favorable value of the contact stress is achieved for slight turning of main radial axes against humerus main axes. It is because of more auspicious adjusting of contact areas between RHR and cartilages on the humerus surface. There were also analysed cases to determine how modification of contact pressures will be for changeable Joung’s modulus of used cartilage and materials of RHR’s. REFERENCES 1. HlavoĖ, P., Florian, Z., Fuis, V. (2005): Stress-deformation analysis of elbow articulation., Engineering Mechanics, pp.331-337-337, Engineering Academy of the Czech Republic. 2. HlavoĖ, P., Florian, Z., Fuis, V., Návrat, T., Janíþek P. (2006): Stress-deformation analysis of an elbow articulation with radial head replacement, World Congress on Medical Physics and Biomedical Engineering 2006, ISBN 3-540-36839-6, ISSN 1727-1983, Seoul, South Korea. ACKNOWLEDGEMENTS At present, this project is supported and solved as a part of the grant by the Czech Science Foundation 101/05/0136 Clinical Biomechanical Problems of Big Human Joints, and research project AV0Z20760514.
Table.1 Results from contact analyses Journal of Biomechanics 40(S2)
Fig.1 Computational model XXI ISB Congress, Poster Sessions, Wednesday 4 July 2007
S634
STRESS ANALYSIS OF THE RADIAL HEAD REPLACEMENT IN AN ELBOW ARTICULATION P. Hlavon 1, V. Fuis1, T. Navrat1 and Z. Florian2 Centre of Mechatronics – Institute of Thermomechanics Academy of Sciences of the Czech Republic and Institute of Solid Mechanics, Mechatronics and Biomechanics, Faculty of Mechanical Engineering, Brno University of Technology. 2 Institute of Solid Mechanics, Mechatronics and Biomechanics, Faculty of Mechanical Engineering, Brno University of Technology, Brno, Czech Republic. email: [email protected], web: www.fme.vutbr.cz/en/prdetail.html?pid=2623
1
INTRODUCTION In case of a traumatological contusion of the elbow joint the bearing surfaces of the proximal end of the radius are damaged or broken off, resulting in their surgical removal. This operation does not make the elbow connection non-functional; however, it results in shortening the antebrachial bones, causing unpleasant pain in the patient’s wrist. GEOMETRICAL AND COMPUTATIONAL MODELS Upon the initiative of the medical team, efforts are invested to create such a partial joint replacement of the proximal end of the radius that would suitably replace the patient’s missing bone tissue and, at the same time, to preserve the same functionality of the radio-humeral connection. In this section, several contact tasks were solved in various parts of the computational model, see Fig.1, and for various geometry and various materials of proximal replacements. The main contact places are - the contact of the replacement and the cartilage at the humerus, for two curvatures of the bearing-on surfaces (R16, R35mm). The second one is the contact of the upper part of replacement and the rest of proximal part at the bone tissue. The third one is the area of humeral-ulnar articulation. Border conditions were selected zero movements at all the three coordinate axes and zero turns for the lower humerus part. Likewise, the same dynamic conditions were prescribed in the respective z-direction of the fixed coordinate system at the upper surfaces of the humerus´s section and zero movements in x and y directions. All tasks were solved mostly as a one-sided contact. The static load at all nodes of the selected surfaces at the radius section corresponded generally to the articular junction in physiological state. RESULTS AND DISCUSSION The best correspondence, see Table.1, for the first RHR type, to the physiological state, exhibits the proximal
replacement made of high-pressure polyethylene, the difference of which makes 0.8 %. The analysis also shows that if we increase the number of elements by about 50 %, the contact pressure in this area will decrease by about 2.7 %. Thus, it is clear that the number of elements needs not to be here increased. For the second RHR type was also achieved fair correspondence in contact pressures. There are shown two numbers for different geometrical position of radius against humerus. The value (without turning) is naturally corresponds with geometrical posture of physical state, it is at around 1MPa bigger than physiological state. More favorable value of the contact stress is achieved for slight turning of main radial axes against humerus main axes. It is because of more auspicious adjusting of contact areas between RHR and cartilages on the humerus surface. There were also analysed cases to determine how modification of contact pressures will be for changeable Joung’s modulus of used cartilage and materials of RHR’s. REFERENCES 1. HlavoĖ, P., Florian, Z., Fuis, V. (2005): Stress-deformation analysis of elbow articulation., Engineering Mechanics, pp.331-337-337, Engineering Academy of the Czech Republic. 2. HlavoĖ, P., Florian, Z., Fuis, V., Návrat, T., Janíþek P. (2006): Stress-deformation analysis of an elbow articulation with radial head replacement, World Congress on Medical Physics and Biomedical Engineering 2006, ISBN 3-540-36839-6, ISSN 1727-1983, Seoul, South Korea. ACKNOWLEDGEMENTS At present, this project is supported and solved as a part of the grant by the Czech Science Foundation 101/05/0136 Clinical Biomechanical Problems of Big Human Joints, and research project AV0Z20760514.
Table.1 Results from contact analyses Journal of Biomechanics 40(S2)
Fig.1 Computational model XXI ISB Congress, Poster Sessions, Wednesday 4 July 2007