PhD Fekete - SZIE version - 2.2 - Szent István Egyetem

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Materials and Methods 8 th QUESTION: Should the slip ratio or other quantity be used to define the slidingrolling phenomenon? ANSWER: In the literature, several types of slip ratios, sliding-rolling ratios, etc, appear. Many of these sources refer to a so-called slip ratio defined by O’Connor et al. [O’Connor et al., 1996]: Where α = ∫ R ⋅dα s s m Slip ratio = (3.39) 2 2 s m and s = ( R − r ) α 1 α f ∫ 1 – 106 – ⋅ dα f icr (3.40) α R is the radius of the curvature; r icr is the radius from the ICR (instantaneous center of rotation) location and α is the flexion angle. s m is the displacement between successive convex points on the convex femoral surface and s f is the displacement between successive convex points on the flat tibial surface. The slip ratio is defined as follows: the slip ratio of one represents pure rolling, and a slip-ratio of infinity represents pure slip while intermediate values represent combination of roll and slip together. This definition does not make the phenomenon easily understandable, or gives a well-defined ratio, since between one and infinity the difference is infinite. Another ratio has to be introduced, which can describe this local motion preferably as a percentage. For this reason, a new ratio will be introduced which can describe the sliding-rolling phenomenon as a percentage. 9 th QUESTION: Should real bone structure geometry be examined or prosthesis geometry? ANSWER: The condyles are covered by meniscus, which fulfil several purposes: on the one hand, it stabilizes the knee that no severe lateral or medial slip would occur, and on the other hand, it disperses the load on the surface. In order to model real human bone geometry, the meniscus system should be modelled as well, which highly complicates the work. It is more advisable to work with current prosthesis geometries, where no meniscus modelling is included. Therefore, prosthesis geometries are used in the numerical-kinematical model. 10 th QUESTION: Between what angles should the sliding-rolling ratio be examined? By summarizing the findings of the experimental and mathematical (numerical) literature, in case of experimental testing of prosthesis materials the sliding-rolling ratios are widely applied between 0.3-0.46 [Hollman et al., 2002, Van Citters et al., 2007] but only in the range of 0˚ to 30˚ flexion angle due to the firm belief that in the beginning of the motion, rolling is dominant. This assumption has been proven correct, although at higher flexion angles, presumably, the sliding-rolling ratio changes significantly [Nägerl et al., 2008, Reinholz et al., 1998], but the results related to the sliding-rolling ratio above 30˚ of flexion angle are rather limited. Since the pattern of the sliding-rolling phenomenon has not been thoroughly investigated in full extension, the aims are the followings:
Materials and Methods I. The pattern and magnitude of the sliding-rolling ratio have to be determined between 20- 120˚ of flexion angle on several prosthesis geometries. This segment is considered as the fundamental active arc (Figure 2.10), which is totally under muscular control and involves most of our daily activities [Freeman, 2001]. a. The arc between zero and 20˚, where the so-called “screw home mechanism” happens, is a great interest for anatomist although it may have a little importance in the daily living activities [Haines, 1941] as being only used in such activities as one-legged stance [Smith, 1956] or normal stance. b. The arc between 120˚ and 160˚ is not considered due to two reasons: there is no increment in the patellofemoral forces above 120˚ of flexion angle, and it only appears in the Asian cultures as an everyday activity, thus it has smaller relevance [Thambyah, 2008]. II. The change of the sliding-rolling ratio has to be investigated, as a function of different commercial and prototype prostheses. This should help to find the lower and upper limit of the sliding-rolling ratio between the condyles. III. The possible effect of the lateral and medial collateral ligaments on the sliding-rolling ratio should be examined. It is unknown how much influence has the ligaments on the local kinematics, therefore as a first step, an investigation will be carried out by involving them into the multibody system. GENERAL COMMENTS By summarizing the above-mentioned conclusions, a new multibody model will be constructed which includes three important, but earlier neglected factors: valid three-dimensional geometry, friction between the condyles and as a modelling experiment, collateral ligaments. The modelling of the condylar geometries will be based on four commercial prostheses and one prototype prosthesis. The spring constants and damping constant of the ligaments will be obtained from the literature. In addition, a new definition will be introduced to characterize simply and precisely the slidingrolling phenomenon in contrast to the earlier applied, less obvious and descriptive slip ratio. The examined motion throughout this part of the thesis is the standard squat. For the same reason as it was in the case of the analytical-kinetical model, we chose to investigate the squatting for the following facts: under this movement the patellofemoral and tibiofemoral forces in the knee reach extremity, squatting is a daily used motion, and it has great clinical importance as a rehabilitation exercise. – 107 –
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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
Page 59 and 60: a) The tibia plateau is a flat surf
Page 61 and 62: Literature review From their calcul
Page 63 and 64: Literature review Although a simila
Page 65 and 66: Literature review Slide/Roll [-] 1
Page 67 and 68: Literature review Figure 2.62. Mult
Page 69 and 70: Materials and Methods 3.1. Methodol
Page 71 and 72: Materials and Methods For the sake
Page 73 and 74: Materials and Methods 9 th QUESTION
Page 75 and 76: Materials and Methods 3.3. New anal
Page 77 and 78: Materials and Methods 3.3.3. Free-b
Page 79 and 80: Materials and Methods Figure 3.6. F
Page 81 and 82: Materials and Methods By the introd
Page 83 and 84: 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
Page 103 and 104: Materials and Methods β [º] 40 20
Page 105 and 106: Materials and Methods If the center
Page 107 and 108: Materials and Methods By the use of
Page 109: Materials and Methods Thus, one pri
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 and 136: Results Χ [-] 1 Sliding-rolling ra
Page 137 and 138: Results Among the tested prostheses
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
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Appendix [123] Nägerl H., Frosch K
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Appendix [154] Reuben J. D., McDona
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Appendix [187] Wahrenberg H., Lindb
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Appendix 6. Fekete G., Kátai L.: M
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Appendix Figure 3. Setting Stitchin
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Appendix Fpf/Fq [-] 1.2 h = 6 mm h
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Appendix η1 angle [˚] 6 Hirokawa
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Appendix Figure 13. Mechanical mode
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Appendix Ψ angle [˚] 10 Van Eijde
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Appendix Figure 19. Mechanical mode
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Appendix - 177 -
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PhD Fekete - SZIE version - 2.2 - Szent István Egyetem

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