The application of kinematics to reproduce patellar cartilage and determine the compression thereof during specific movements.

Kruger, Anria (2017-03)

Thesis (MEng)--Stellenbosch University, 2017.

Thesis

ENGLISH ABSTRACT: The aim of this study is to investigate the biomechanics of the patellofemoral joint in an in-vitro model. The project has three objectives: Firstly, a process needs to be designed that is able to estimate the geometry of the patellofemoral joint cartilage. Secondly, cartilage compression as a result of the investigated movements are determined. Finally, the associated stresses are estimated. The outcome of the objectives will provide information on the degree of cartilage deformation during different functional tasks. The geometry of the patellar cartilage was estimated through the use of kinematics, the bones from the CT scans of the patella and femur, and the MRI scans of the uncompressed patellofemoral cartilage. This process included reproducing the kinematic models of two knees for a passive and squat motion and then using the results to estimate the patellar cartilage. It was found that the process was able to estimate the geometry of the patellar cartilage through the application of the kinematics and the uncompressed cartilage produced by the MRI scans. It was noted that the cartilage geometry differed between motions and between investigated knees in terms of thickness, but in general conformed to the geometry of patellar cartilage. The deformation and compression of the patellofemoral cartilage was also determined by comparing the resulting estimated cartilage with the uncompressed cartilage segmented from the MRI scans. The main finding was that compression of the cartilage does result from the application of the investigated movements and that there was a definitive difference between the passive and squat movements. Finally, the stresses as a result of the different compressions on the cartilage were investigated through FEA. The main findings was that the squat movement consistently resulted in larger stresses than the passive movement and that the stresses recorded on the patellar osseous-cartilage surface interface also produced larger stresses than the stresses found on the cartilage surface. It was concluded that the designed process was able to determine the geometry of the patellar cartilage by using kinematics and the CT scans of the knee with little input from the MRI scans. Furthermore, through using kinematics, the compression of the cartilage due to these movements could be determined. It was concluded that the squat movement consistently produced larger compressions and stresses than the passive movement. This leads to the conclusion that it would be more appropriate to use the passive compression to modify and improve patellar replacements since it results in less compression and smaller stresses on the patella. Therefore, the replacement can still be modified to improve the geometry and account for some compression in the replacement, but not modified too much through the use of the squat movement to cause excessively larger stresses in the knee.

AFRIKAANSE OPSOMMING: Die doel van hierdie studie is om die biomeganika van die patellofemorale gewrig te ondersoek in 'n in-vitro model. Die projek het drie hoof doelwitte: Eerstens, moet 'n proses ontwerp word wat in staat is om die geometrie van die patellofemorale kraakbeen te skat. Tweedens word die kraakbeen kompressie as gevolg van die ondersoekte bewegings ook bepaal. Ten slotte, sal die verwante spannings ook bepaal word. Die uitslag van die doelwitte sal dus inligting voorsien oor die mate van kraakbeen vervorming tydens verskillende funksionele take. Die geometrie van die knieskyf kraakbeen is beraam deur die gebruik van kinematika, die bene gekry vanaf die CT-skanderings van die patella en femur, en die MRI-skanderings van die nie-saamgeperste patellofemorale kraakbeen. Hierdie proses sluit in die reproduksie van die kinematiese modelle van twee knieë vir 'n passiewe en hurk beweging waarvandaan die knieskyf kraakbeen dan geskat word. Daar is bevind dat die proses die geometrie van die knieskyf kraakbeen kon skat deur die toepassing van die kinematika en die nie-saamgeperste kraakbeen van die MRI-skanderings. Daar is opgemerk dat die kraakbeen geometrie verskil het tussen bewegings en tussen ondersoekte knieë in terme van dikte, maar in die algemeen voldoen het aan die geometrie van knieskyf kraakbeen. Die vervorming en kompressie van die patellofemorale kraakbeen is ook bepaal deur die geskatte kraakbeen met die nie-saamgeperste kraakbeen te vergelyk. Die belangrikste bevinding was dat daar wel kompressie is van die kraakbeen as gevolg van die toepassing van die ondersoekte bewegings en dat daar 'n definitiewe verskil tussen die passiewe en hurk bewegings is. Ten slotte, die spannings as gevolg van die verskillende drukke op die kraakbeen was ondersoek deur EEA. Die belangrikste bevinding was dat die hurk beweging deurlopend gelei het tot groter spannings as die passiewe beweging en dat die spannings op die knieskyf ossaal-kraakbeen oppervlak koppelvlak tot groter spannings gelei het as die spannings op die kraakbeen oppervlak. Daar is tot die gevolgtrekking gekom dat die ontwerpte proses wel in staat was om die geometrie van die knieskyf kraakbeen te bepaal deur gebruik te maak van kinematika en die CT-skanderings van die knie met min insette van die MRI-skanderings. Verder deur gebruik te maak van kinematika, was die kompressie van die kraakbeen van die gevolglike bewegings bepaal. Daar is tot die gevolgtrekking gekom dat die hurk beweging deurlopend groter kompressies en spannings veroorsaak het as die passiewe beweging. Dit lei tot die gevolgtrekking dat dit meer gepaslik sal wees om die passiewe kompressie te gebruik om knieskyf vervangings te verbeter aangesien dit lei tot minder kompressie en kleiner spannings op die patella. Sodoende kan die vervanging steeds aangepas word om die geometrie te verbeter en van die kompressie in rekening te neem om die vervanging te verbeter, maar nie so veel te verander deur die gebruik van die hurk beweging as om onnodige oormatig groter spannings in die knie te veroorsaak nie.

Please refer to this item in SUNScholar by using the following persistent URL: http://hdl.handle.net/10019.1/101162
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