PhD Fekete - SZIE version - 2.2 - Szent István Egyetem

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Results 4.<strong>2.2</strong>. Discussion and interpretation of the results Let us first look at the magnitude and the pattern of the sliding-rolling ratio of the different prostheses and then at the tibiofemoral contact forces. The calculation of the sliding-rolling is considered on both sides of the condyles (lateral and medial) and involves the slip in every direction (spatial). In the case of the SZIU prototype model (Figure 4.6), both of the lateral and medial sides start from a positive sliding-rolling ratio of 0.2. The functions gradually increase with occasional irregularities to 0.42 at the medial side and 0.38 at the lateral side. The irregularity during the motion is originated to the contact of the complex geometries. These mapped geometries are numerically approximated curves, thus their smoothness is also a factor that can cause less smooth functions. In Figure 4.16, an approximated prosthesis curve is visible from the sagittal view. The original analytical curve is represented with continuous line, the tangents with dotted lines, and the numerical curve with a dashed line. Figure 4.16. Approximated prosthesis curve As the two bodies establish a contact and they start moving along these curves, the sharp approximating lines (Figure 4.16 a-b) may cause small jumps, skips on the bodies, which appear mainly on the sliding-rolling functions. If we neglect these irregularities, the increment shows closely linear growth. With regard to the kinetics, namely the tibiofemoral force (Figure 4.7), between the condyles, the evolution of the force can be described as closely linearly increasing, with a maximum of 4.5-8.5 times of the BW. The Biotech TP and the TP P/S models (Figure 4.8 and Figure 4.10) are from the same manufacturer. They have quite similar characteristics both in their kinematics and their kinetics. In both cases the sliding-rolling evolution is quite smooth along the complete segment (0˚ to 120˚) compared to the SZIU model which is more hectic. However the tibiofemoral force of the TP model (Figure 4.9) is half times lower compared to the TP P/S force (Figure 4.11). The sliding-rolling curves regarding the TP and TP P/S start approximately from 0.3. From 40- 60˚ of flexion angle, the TP and TP P/S functions begin to increase until they reach the maximum sliding-rolling ratio, 0.7 in the case of the TP model and 0.725 in case of the TP P/S on both medial and lateral side. The BioMet Oxford model (Figure 4.12) has lower sliding attribute, since between 20-60˚ of flexion angle it only reaches the value of 0.2-0.22. It has also the feature of closely linear growth, with minor irregularities, on both sides. – 132 –
Results Among the tested prostheses, this replacement provided the lowest peak sliding-rolling value, namely 0.56. As for the kinetics, the tibiofemoral force (Figure 4.13) has the same magnitude as the BioTech TP P/S (Figure 4.11). While the evolutions of the sliding-rolling functions are somewhat similar regarding the SZIU, Biotech TP- TP P/S or BioMet Oxford models, the DePuy prosthesis (Figure 4.14) follows a completely different pattern. The curve is practically constant, with less than 5% of periodic deviation. The maximum value of the curve is registered at 23˚ of flexion angle at the medial side where it reaches for a short interval the value of one, which means complete sliding. After that the function decreases to an average 0.75. The tibiofemoral force (Figure 4.15) is similar to the BioMet Oxford model (Figure 4.13). If we compare the magnitude of the lateral and medial sliding-rolling ratio, a slightly higher percentage of sliding can always be credited to the medial compartment. This difference is quite visible for the DePuy or SZIU prosthesis while it is less obvious concerning the Biotech or BioMet models. This difference was also confirmed by the study of Wilson et al. [Wilson et al., 1998]: from 0˚ to 5˚ of flexion angle the sliding-rolling ratio at the medial side was significantly higher (approximately 1.5-2 times) compared to the lateral side, between 5˚ and 10˚ was about 1-0.5 times and from 20˚ of flexion angle the difference stays in the range of 5-8%. Since in general the sliding-rolling ratio is slightly (5-8%) higher on the medial side, the medial results were taken as reference functions. By fitting a third-order function on each medial sliding-rolling curve, and summarizing them in one graph, the following results were obtained (Figure 4.17): χ [-] 1 Sliding-rolling ratios of different prostheses 0.8 0.6 0.4 0.2 Flexion angle [°] 0 20 40 60 80 100 120 BioMet BioTech TP BioTech TP P/S SZIU DePuy Figure 4.17. Summarized sliding-rolling ratios of the prostheses – 133 –
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SZENT ISTVÁN UNIVERSITY KINETICS A
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CONTENTS NOMENCLATURE AND ABBREVIAT
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NOMENCLATURE AND ABBREVIATIONS F pf
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ψ : Angle between the quadriceps t
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v CTt : Tangential velocity compone
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Introduction 1. INTRODUCTION AND OB
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1.3. Aims of the PhD thesis Introdu
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Literature review 2. LITERATURE REV
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Literature review Figure 2.3. The f
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Literature review Figure 2.6. Patel
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Literature review Figure 2.8. Compo
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Literature review The knee carries
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Literature review For this reason,
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Literature review Figure 2.12. Thre
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Literature review As a short overvi
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Literature review Moment arm 60 [mm
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Literature review I. They demonstra
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Literature review The presented mod
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Literature review ε angle [˚] 100
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Literature review Fpf/Fq [-] 1.2 1
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Literature review β angle [˚] Mal
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Literature review Figure 2.35. Mech
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Literature review Moment arm 60 [mm
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Literature review Let us follow the
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Literature review Finally, the pate
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Literature review Figure 2.43. Tota
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Literature review One great advanta
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Literature review Implant wear is t
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2.3.2. General numerical models Lit
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a) The tibia plateau is a flat surf
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Literature review From their calcul
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Literature review Although a simila
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Literature review Slide/Roll [-] 1
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Literature review Figure 2.62. Mult
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Materials and Methods 3.1. Methodol
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Materials and Methods For the sake
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Materials and Methods 9 th QUESTION
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Materials and Methods 3.3. New anal
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Materials and Methods 3.3.3. Free-b
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Materials and Methods Figure 3.6. F
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Materials and Methods By the introd
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Materials and Methods 3.4. Experime
Page 85 and 86: Materials and Methods Figure 3.7. C
Page 87 and 88: Materials and Methods All of the pa
Page 89 and 90: Materials and Methods 3.4.5. Measur
Page 91 and 92: x c Materials and Methods ∑ Fi
Page 93 and 94: Materials and Methods Probability D
Page 95 and 96: Materials and Methods Figure 3.18.
Page 97 and 98: Materials and Methods By doing so,
Page 99 and 100: 3.4.7.2. Steps of the approach Mate
Page 101 and 102: Materials and Methods All the funct
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Page 105 and 106: Materials and Methods If the center
Page 107 and 108: Materials and Methods By the use of
Page 109 and 110: Materials and Methods Thus, one pri
Page 111 and 112: Materials and Methods I. The patter
Page 113 and 114: 3.6.3. Geometrical models Materials
Page 115 and 116: Materials and Methods − − −
Page 117 and 118: 3.6.4.3. Contact [MSC.ADAMS] Materi
Page 119 and 120: Materials and Methods Besides the k
Page 121 and 122: Materials and Methods By multiplyin
Page 123 and 124: Results 4. RESULTS 4.1. Results reg
Page 125 and 126: Results This closely equal percenta
Page 127 and 128: Results Fpf/BW [-] 8 Fekete et al.
Page 129 and 130: Results In reality, human subjects
Page 131 and 132: Results 4.2. Results regarding the
Page 133 and 134: Results 0.8 Χ [-] 1 Sliding-rollin
Page 135: Results Χ [-] 1 Sliding-rolling ra
Page 139 and 140: Results χ [-] 1 Averaged sliding-r
Page 141 and 142: Results Χ [-] 1 Sliding-rolling ra
Page 143 and 144: 4.3. New scientific results Results
Page 145 and 146: Results 3 rd Thesis: Based on the m
Page 147 and 148: Conclusions and Suggestions 5. CONC
Page 149 and 150: Conclusions and Suggestions Suggest
Page 151 and 152: Summary 6. SUMMARY In this doctoral
Page 153 and 154: Appendix APPENDIX A1. Bibliography
Page 155 and 156: Appendix [31] Csizmadia B. M., Nán
Page 157 and 158: Appendix [61] Gill H. S., O’Conno
Page 159 and 160: Appendix [93] Klebanov B. M., Barla
Page 161 and 162: Appendix [123] Nägerl H., Frosch K
Page 163 and 164: Appendix [154] Reuben J. D., McDona
Page 165 and 166: Appendix [187] Wahrenberg H., Lindb
Page 167 and 168: Appendix 6. Fekete G., Kátai L.: M
Page 169 and 170: Appendix Figure 3. Setting Stitchin
Page 171 and 172: Appendix Fpf/Fq [-] 1.2 h = 6 mm h
Page 173 and 174: Appendix η1 angle [˚] 6 Hirokawa
Page 175 and 176: Appendix Figure 13. Mechanical mode
Page 177 and 178: Appendix Ψ angle [˚] 10 Van Eijde
Page 179 and 180: Appendix Figure 19. Mechanical mode
Page 181 and 182: Appendix - 177 -
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PhD Fekete - SZIE version - 2.2 - Szent István Egyetem

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