A six degrees of freedom arthrometer for examination of knee joint laxity
Translated title
Et artrometer med seks frihedsgrader til undersøgelse af slaphed i knæleddet
Authors
Bech, Mathias Niels Blicher ; Nielsen, Morten Hauge ; Bak, Philip Valentin
Term
4. semester
Education
Publication year
2017
Submitted on
2017-06-07
Pages
75
Abstract
Knæledsløshed (løshed i leddet) kan give instabilitet og er forbundet med øget risiko for knæskader. Skader øger sandsynligheden for senere tilstande som slidgigt. De nuværende målemetoder har begrænsninger, herunder ikke-kvantiable vurderinger og fokus på kun én bevægelsesretning. Formålet med denne afhandling var at udvikle et arthrometer med seks frihedsgrader til at understøtte undersøgelse af statisk knæløshed. Metoder: Arthrometeret består af en top- og bundplatform forbundet med seks lineære aktuatorer for at give den nødvendige bevægelighed. Længde og størrelse blev simuleret i AnyBody Modeling System, og topplatformens holdbarhed blev vurderet med en finitte element-analyse (FEM) i SolidWorks. En forenklet motion capture-test blev udført for at verificere arthrometerets bevægelsesområde (ROM) i forhold til de højeste løshedsværdier rapporteret i litteraturen. ROM blev testet ved manuelt at placere arthrometeret i yderstillinger under tre forskellige undersøgelser: antero–posteriør (AP) translation, varus–valgus (VV) rotation og intern–extern (IE) rotation. Resultater: Maksimal AP-translation, VV-rotation og IE-rotation var henholdsvis 383,41 mm, 18,97° og 90,17°. Diskussion: Det præsenterede arthrometer har potentiale til at belaste enkelte ledbånd i knæet og dermed understøtte undersøgelse af statisk knæløshed. Derudover giver det mulighed for at kombinere bevægelser og kræfter i flere planer.
Knee joint laxity (looseness of the joint) can cause instability and is linked to a higher risk of knee injuries. Such injuries increase the likelihood of later conditions like osteoarthritis. Current measurement methods have limitations, including non-quantifiable assessments and focusing on only one direction of movement. This thesis aimed to develop an arthrometer with six degrees of freedom to support examination of static knee joint laxity. Methods: The arthrometer has a top and bottom platform connected by six linear actuators to provide the required mobility. Length and size were simulated in the AnyBody Modeling System, and the durability of the top platform was evaluated using finite element analysis (FEA) in SolidWorks. A simplified motion capture test was performed to verify the device’s range of motion (ROM) against the highest laxity values reported in the literature. ROM was tested by manually positioning the arthrometer at end positions during three examinations: anterior–posterior (AP) translation, varus–valgus (VV) rotation, and internal–external (IE) rotation. Results: Maximum AP translation, VV rotation, and IE rotation were 383.41 mm, 18.97°, and 90.17°, respectively. Discussion: The arthrometer presented has the potential to stress individual knee ligaments and thus assist in examining static knee joint laxity. It also makes it possible to combine movements and forces across multiple planes.
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