PhD Fekete - SZIE version - 2.2 - Szent István Egyetem

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Introduction 1. Except kicking, jogging or jumping the highest forces appear in the knee joint under squatting movement, 2. Under squatting movement, almost the complete flexion angle (0˚ to 120-130˚) is used while during gait, running or other activities, it is limited to its one-third, onefourth of the complete range, 3. While patients with total knee replacements can carry out e.g. gait fairly well, kneeling or squatting often means difficulty due to the imperfection of the implants. These are the main reasons why this study deals exclusively with squatting. The kinetic description of squatting is limited to the so-called standard squat in the literature, where the torso is restrained to carry out only vertical motion, which means that practically the centre of gravity does not change its position during the squat. This simplification has been widely used and so far, only a few authors pointed out, that the moving centre of gravity might have a significant effect on the kinetics of the knee joint. On the grounds of this hypothesis, it will be demonstrated in this thesis how significantly the movement of the centre of gravity alters the knee kinetics under squatting movement. This new movement will be titled as non-standard squat. Nevertheless, there are also questions in the kinematics of the knee that studies have not yet dealt with, for example the sliding-rolling ratio in the active functional arc, which expands from 20˚ to 120˚ of flexion angle. The sliding-rolling ratio is not only interesting in case of spur, helical or other gear connections, but in any engineering systems where components have to withstand long-term varying loading conditions and wear. Human knee prostheses are such elements, and for this reason, tribological tests are carried out on them before the actual production. Naturally, to obtain reliable results, experiments have to be carried out with realistic kinetic and kinematic boundary conditions. Due to the multiple studies about the kinetics of the knee joint under different movements, the loading issue is well-known and fundamentally researched. Problems rise, when certain parameters, such as the sliding-rolling parameter has to be set for a test. Regarding its ratio, only rough estimations are available in the literature, and that is related to the beginning of the motion between 0˚ to 20-30˚ of flexion angle. These results claim that in this initial segment, rolling is dominant, while above these certain angles sliding is primer. So far, sliding-rolling results related to 0-30˚ segment have been widely applied throughout tribological experiments, although if this ratio is underestimated, the actual wear will be much higher than the expected. For this reason, another fundamental aim of this thesis is to answer the question of the applicable sliding-rolling ratio in the functional arc of the knee joint (20-120˚ of flexion angle). – 8 –
1.3. Aims of the <strong>PhD</strong> thesis Introduction In this doctoral thesis, two main questions are set as primary goals. The first question is related to a significant everyday motion, the non-standard squatting, and its kinetics. What is the difference between the standard and non-standard squatting? In case of standard squatting, the horizontal displacement of the center of gravity is neglected during the movement (it is supposed to be fixed in one point). However, this parameter is considered in the non-standard squat and its position depends on the flexion angle. So far, only the standard squat has been substantially investigated, which lacks this significant parameter. For this reason, the choice fell on the non-standard squat since the horizontal movement of the centre of gravity, or in other words the forward movement of the trunk, may considerably alter the kinetics of this type of movement. The forward-backward movement of the trunk as a factor, has been recognized and mentioned in earlier studies, but it was always left out of consideration. A new analytical-kinetical model that involves this parameter answers the question of how the forward movement of the trunk may affect the patellofemoral forces. By having involved the effect of moving center of gravity (movement of the trunk) into the model, the patellofemoral force, the tibiofemoral force, the patellar tendon force and the quadriceps force can be derived in case of standard and non-standard squatting alike. The output of this question serves more as a fundamental understanding of the knee joint, where the results can be used as initial conditions, related specifically to the loading conditions in the replacement design. The second question deals with a more practical-orientated issue, namely the sliding-rolling ratio. This ratio actually defines the relative motion between the condyles of the femur and the tibia. For this reason, it is in a close interrelation with wear and therefore it has an essential effect on the lifetime and the survivorship of the knee implants. The foregoing phenomenon has also a fundamental side. Only a limited number of studies (analytical, numerical, and experimental) have dealt comprehensively with the question of sliding-rolling, and exclusively only but one study investigated this phenomenon on both lateral and medial sides of prostheses geometries. Preliminary results have already been published, for example in the beginning of the motion up to 20-30˚ of flexion angle the relative motion is dominantly rolling, while above these angles sliding is prevailing. As for an output, this phenomenon is substantially essential in the tribological tests on actual prostheses. The presence of sliding-rolling produces different wear phenomenon on the connecting surfaces and for this reason a proper ratio has to be applied during these experiments. So far, these preliminary results were normative for tribological tests regardless of the applied domain (20-30˚ of flexion angle or above). Considering that a ratio, which is applicable for lower angles, would also be appropriate at higher angles is most certainly incorrect. For this reason, the ratio has to be investigated between 20˚ and 120˚ of flexion angle in order to provide valid results for experimental tests. The result of the second question is a multibody model, which can predict the sliding-rolling ratio of different prostheses. By the summary of these models, a general range about the ratio is appointed. – 9 –
Page 1 and 2: SZENT ISTVÁN UNIVERSITY KINETICS A
Page 3 and 4: CONTENTS NOMENCLATURE AND ABBREVIAT
Page 5 and 6: NOMENCLATURE AND ABBREVIATIONS F pf
Page 7 and 8: ψ : Angle between the quadriceps t
Page 9 and 10: v CTt : Tangential velocity compone
Page 11: Introduction 1. INTRODUCTION AND OB
Page 15 and 16: Literature review 2. LITERATURE REV
Page 17 and 18: Literature review Figure 2.3. The f
Page 19 and 20: Literature review Figure 2.6. Patel
Page 21 and 22: Literature review Figure 2.8. Compo
Page 23 and 24: Literature review The knee carries
Page 25 and 26: Literature review For this reason,
Page 27 and 28: Literature review Figure 2.12. Thre
Page 29 and 30: Literature review As a short overvi
Page 31 and 32: Literature review Moment arm 60 [mm
Page 33 and 34: Literature review I. They demonstra
Page 35 and 36: Literature review The presented mod
Page 37 and 38: Literature review ε angle [˚] 100
Page 39 and 40: Literature review Fpf/Fq [-] 1.2 1
Page 41 and 42: Literature review β angle [˚] Mal
Page 43 and 44: Literature review Figure 2.35. Mech
Page 45 and 46: Literature review Moment arm 60 [mm
Page 47 and 48: Literature review Let us follow the
Page 49 and 50: Literature review Finally, the pate
Page 51 and 52: Literature review Figure 2.43. Tota
Page 53 and 54: Literature review One great advanta
Page 55 and 56: Literature review Implant wear is t
Page 57 and 58: 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
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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
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Materials and Methods Figure 3.7. C
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Materials and Methods All of the pa
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Materials and Methods 3.4.5. Measur
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x c Materials and Methods ∑ Fi
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Materials and Methods Probability D
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Materials and Methods Figure 3.18.
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Materials and Methods By doing so,
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3.4.7.2. Steps of the approach Mate
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Materials and Methods All the funct
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Materials and Methods β [º] 40 20
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Materials and Methods If the center
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Materials and Methods By the use of
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Materials and Methods Thus, one pri
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Materials and Methods I. The patter
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3.6.3. Geometrical models Materials
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Materials and Methods − − −
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3.6.4.3. Contact [MSC.ADAMS] Materi
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Materials and Methods Besides the k
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Materials and Methods By multiplyin
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Results 4. RESULTS 4.1. Results reg
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Results This closely equal percenta
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Results Fpf/BW [-] 8 Fekete et al.
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Results In reality, human subjects
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Results 4.2. Results regarding the
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Results 0.8 Χ [-] 1 Sliding-rollin
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Results Χ [-] 1 Sliding-rolling ra
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Results Among the tested prostheses
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Results χ [-] 1 Averaged sliding-r
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Results Χ [-] 1 Sliding-rolling ra
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4.3. New scientific results Results
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Results 3 rd Thesis: Based on the m
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Conclusions and Suggestions 5. CONC
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Conclusions and Suggestions Suggest
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Summary 6. SUMMARY In this doctoral
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Appendix APPENDIX A1. Bibliography
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Appendix [31] Csizmadia B. M., Nán
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Appendix [61] Gill H. S., O’Conno
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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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