Total knee arthroplasty is a widely used and relatively successful procedure, designed to relieve pain and restore function to patients suffering from osteoarthritis. However, satisfaction following the procedure is low. One of the primary sources of pain and a cause of functional limitations following knee arthroplasty is the patellofemoral joint. Reasons for pain in the patellofemoral joint are not well understood but adverse patellofemoral biomechanics are thought to contribute. Many in vitro methods exist for the investigation of patellofemoral joint biomechanics but there is no consistent standard protocol. It is therefore difficult to draw any general conclusions regarding the effect of specific design or alignment factors on the biomechanics of the patellofemoral joint. The present study aimed to improve current understanding of factors contributing to patellofemoral complications. A knee simulator, which was based on the Oxford Knee Rig and included synthetic models for a number of soft tissue and bony structures, was developed. The simulator was demonstrated to provide a simplified but physiologically relevant model of the human knee, which allowed effective assessment of patellofemoral joint biomechanics under physiological loads. The system eliminated the need for cadaveric tissue and therefore demonstrated reduced variability, enabling the efficient assessment of a number of potentially influencing factors. A number of investigations were carried out using the simulator to assess the effect of patella component design and position, and femoral component alignment on patellofemoral biomechanics using the Scorpio NRG system. The results of these studies indicate the benefit of medialisation of the apex of the patella component and warn against excessive femoral component sagittal plane malalignment. However, in general they indicated the relatively forgiving nature of the Scorpio system to malalignment and highlighted that irrespective of alignment and patella component design, pressures in excess of material limits are frequently achieved in deep flexion.

Perioperative hypothermia (PH) is body temperature < 36°C and may occur in total knee arthroplasty (TKA) surgery. Planned hypothermia is necessary in a select number of surgical procedures but inadvertent hypothermia has deleterious consequences. TKA is a painful procedure and PH may enhance or diminish the effect of opioids and TKA pain – its effect is unclear. A new treatment for PH is a forced-air warming gown. A randomized control trial of 30 TKA patients compared the standard treatment of warm cotton blankets to a forced-air warming gown. Patients treated with the warming gown had higher temperatures (p < 0.001), used less opioid (p = 0.05) and had more satisfaction (p = 0.004) than the standard blanket group. This study suggests that warming gowns may be an effective alternative to averting PH and advocates for more research to explore the relationship between PH and its effect on pain and opioids.

Perioperative hypothermia (PH) is body temperature < 36°C and may occur in total knee arthroplasty (TKA) surgery. Planned hypothermia is necessary in a select number of surgical procedures but inadvertent hypothermia has deleterious consequences. TKA is a painful procedure and PH may enhance or diminish the effect of opioids and TKA pain – its effect is unclear. A new treatment for PH is a forced-air warming gown. A randomized control trial of 30 TKA patients compared the standard treatment of warm cotton blankets to a forced-air warming gown. Patients treated with the warming gown had higher temperatures (p < 0.001), used less opioid (p = 0.05) and had more satisfaction (p = 0.004) than the standard blanket group. This study suggests that warming gowns may be an effective alternative to averting PH and advocates for more research to explore the relationship between PH and its effect on pain and opioids.

Bakgrund: Trikompartmentell knäartroplastik (TKA) är en vanlig behandlingsmetod vid artros. Vid bildtagning finns rekommendationer författade av Svensk Ortopedisk Förening. Dessa täcker inte knäledsrotation på en frontalbild. Syftet var att ta reda på skillnader mellan röntgensjuksköterskors och radiologers rutiner att godkänna/underkänna knäfrontalbilder med TKA ifall knät projicerats roterat. Metod: Genom en enkät bestående av två till fyra frågor om fem frontalbilder på knän med TKA som elva röntgensjuksköterskor och nio radiologer fick svara på samlades materialet in. Bilderna visade fem olika knän som i denna studie respektive bedömdes som rak, lite utåtroterad, mycketutåtroterad, lite inåtroterad samt mycket inåtroterad. Frågorna var: godkänd/underkänd bild, betyg på bild och ifall de ansett att bilden varit betydande roterad eller om något annat gjort att den inte blivit godkänd. Resultat: Om de svarande skulle godkänna bilden: Bild 1: 0 % av röntgensjuksköterskorna, 67 % av radiologerna. Bild 2: 91 % av röntgensjuksköterskorna, 100 % av radiolgerna. Bild 3: 45 % av röntgensjuksköterskorna, 67 % av radiologerna. Bild 4: 45 % av röntgensjuksköterskorna, 100 % avradiologerna. Bild 5: 18 % av röntgensjuksköterskorna, 100 % av radiologerna. Konklusion: Radiologerna hade större tolerans gentemot rotation av knäled med inopererad TKA jämfört med röntgensjuksköterskorna. Detta innebär att röntgensjuksköterskorna skulle ta om bildersom radiologer hade godkänt, vilket leder till onödig extra stråldos till patienter. Det var för litet urval för att dra någon slutsats, men om resultatet gäller nationellt bör tydliga rekommendationer författas gällande rotation vid bildtagning av frontalbilder på knäleder med inopererad TKA.

Total knee arthroscopy is one of the most performed and most successful orthopedic surgeries, with nearly a million procedures performed in 2020 in the United States alone. Due to changing patient demographics, the use of cementless fixation for implant stability is becoming more prevalent amongst recipients. Cementless implants rely on the surface morphology of a porous coating to bond implant to bone; the quality of this bond is dependent on an interference fit and the roughness, or coefficient of friction, between implant and bone. Stress shielding is a comparison of the properties in implanted bone to natural bone; it is a commonly used measurable when using a finite element model to optimize implant design. The purpose of this study is to investigate how different coating types (coefficients of friction) and the location of their application affect the stress shielding response in the tibia. A finite element model was constructed to investigate the impact of these variables. The results concluded that the stress distribution in an implanted tibia is dependent on the coefficient of friction applied at the tip of the stem. Lower friction coefficients applied to the stem tip resulted in higher compressive stresses, and higher friction coefficients resulted in lower compressive stresses. Thus, lower friction coefficients provided more favorable stress shielding responses, however, at the expense of stress concentrations of greater magnitude.

<p>Titel: Fonders förvaltningsavgifter vs avkastning – Lönar det sig att betala lite mer eller är det bara dumdristigt?</p><p>Seminariedatum: 2008-06-04</p><p>Ämne/kurs: Magisteruppsats/ D-nivå</p><p>Författare: Anna Asplund och Malin Elfving</p><p>Handledare: Stig Westerdahl</p><p>Nyckelord: Fonder, Förvaltningsavgifter, TKA, Avkastning</p><p>Syfte: Syftet med studien är att undersöka om det föreligger ett samband mellan fonders förvaltningsavgifter och dess avkastning samt om avkastningen och förvaltningsavgifterna skiljer sig mellan olika fondtyper.</p><p>Metod: Studien bygger på en deduktiv forskningsansats eftersom vi utgår från befintliga begrepp och teorier. Då vi ville undersöka en stor population har vi använt oss av en kvantitativ forskningsstrategi. Studien grundar sig på åren 2004-2007. För att bestämma ett samband mellan de två variablerna förvaltningsavgift och avkastning har vi använt oss av regressionsanalyser. För att undersöka om avkastningen och förvaltningsavgifterna skiljer sig åt mellan de olika fondtyperna har vi använt oss av medelvärdesanalyser.</p><p>Empiri: Vi har hämtat data gällande förvaltningsavgifter och avkastning på de fonder som ingår i urvalet från Morningstar som är en oberoende utgivare av fondinformation.</p><p>Slutsatser: Studiens resultat visar att ett samband mellan fondernas avkastning och dess förvaltningsavgift (TKA) endast kan fastställas år 2005, då ett negativt samband föreligger. Detta år visar indikationer på att det finns skillnader i resultaten och att det inte beror på slumpen. De resterande åren kan resultaten dels bero på slumpen samt har de en dålig förklaringsgrad vilket innebär att resultaten i studien ej kan skildra verkligheten. Räntefonderna är den fondtyp som har den lägsta genomsnittliga avkastningen under den undersökta perioden, aktiefonderna har den högsta. Räntefonderna har även den lägsta genomsnittliga TKA medan den fondtyp som i denna studie har den högsta genomsnittliga TKA är fond-i-fonder.</p> / <p>Title: Mutual funds; administration fees vs. proceeds – Is it profitable to pay a bit more or is it just foolish?</p><p>Seminar date: 2008-06-04</p><p>Course: Master Thesis/D-level</p><p>Authors: Anna Asplund and Malin Elfving</p><p>Advisor: Stig Westerdahl</p><p>Keywords: Mutual funds, Administration fees, TKA, Proceed</p><p>Purpose: The purpose of the study is to investigate if there is a connection between the administration fees of mutual funds and their proceeds. The study aims to examine different kinds of funds which invests in different kinds of markets and if there are differences between these funds.</p><p>Methodology: The study is founded on a deductive research effort since we take our starting-point in existing terminology and theories. Since we wanted to examine a large population we used a quantitative research strategy. In order to determine a connection between the two variables; administration fee and proceed we have used regression-analysis.</p><p>Empirical foundation: We have collected data concerning administration fees and proceed on the funds in the selection from Morningstar, which is an independent publisher of mutual fund information</p><p>Conclusion: It is only for the year of 2005 the study shows a possible negative connection between the administration fees of mutual funds and their proceeds. For the unit trusts a possible connection cannot be established for any of the examined years.</p>

Titel: Fonders förvaltningsavgifter vs avkastning – Lönar det sig att betala lite mer eller är det bara dumdristigt? Seminariedatum: 2008-06-04 Ämne/kurs: Magisteruppsats/ D-nivå Författare: Anna Asplund och Malin Elfving Handledare: Stig Westerdahl Nyckelord: Fonder, Förvaltningsavgifter, TKA, Avkastning Syfte: Syftet med studien är att undersöka om det föreligger ett samband mellan fonders förvaltningsavgifter och dess avkastning samt om avkastningen och förvaltningsavgifterna skiljer sig mellan olika fondtyper. Metod: Studien bygger på en deduktiv forskningsansats eftersom vi utgår från befintliga begrepp och teorier. Då vi ville undersöka en stor population har vi använt oss av en kvantitativ forskningsstrategi. Studien grundar sig på åren 2004-2007. För att bestämma ett samband mellan de två variablerna förvaltningsavgift och avkastning har vi använt oss av regressionsanalyser. För att undersöka om avkastningen och förvaltningsavgifterna skiljer sig åt mellan de olika fondtyperna har vi använt oss av medelvärdesanalyser. Empiri: Vi har hämtat data gällande förvaltningsavgifter och avkastning på de fonder som ingår i urvalet från Morningstar som är en oberoende utgivare av fondinformation. Slutsatser: Studiens resultat visar att ett samband mellan fondernas avkastning och dess förvaltningsavgift (TKA) endast kan fastställas år 2005, då ett negativt samband föreligger. Detta år visar indikationer på att det finns skillnader i resultaten och att det inte beror på slumpen. De resterande åren kan resultaten dels bero på slumpen samt har de en dålig förklaringsgrad vilket innebär att resultaten i studien ej kan skildra verkligheten. Räntefonderna är den fondtyp som har den lägsta genomsnittliga avkastningen under den undersökta perioden, aktiefonderna har den högsta. Räntefonderna har även den lägsta genomsnittliga TKA medan den fondtyp som i denna studie har den högsta genomsnittliga TKA är fond-i-fonder. / Title: Mutual funds; administration fees vs. proceeds – Is it profitable to pay a bit more or is it just foolish? Seminar date: 2008-06-04 Course: Master Thesis/D-level Authors: Anna Asplund and Malin Elfving Advisor: Stig Westerdahl Keywords: Mutual funds, Administration fees, TKA, Proceed Purpose: The purpose of the study is to investigate if there is a connection between the administration fees of mutual funds and their proceeds. The study aims to examine different kinds of funds which invests in different kinds of markets and if there are differences between these funds. Methodology: The study is founded on a deductive research effort since we take our starting-point in existing terminology and theories. Since we wanted to examine a large population we used a quantitative research strategy. In order to determine a connection between the two variables; administration fee and proceed we have used regression-analysis. Empirical foundation: We have collected data concerning administration fees and proceed on the funds in the selection from Morningstar, which is an independent publisher of mutual fund information Conclusion: It is only for the year of 2005 the study shows a possible negative connection between the administration fees of mutual funds and their proceeds. For the unit trusts a possible connection cannot be established for any of the examined years.

Introduction: Studies show that Total Knee Arthroplasty (TKA) is successful for the majority of patients however some continue to experience some functional limitations and anecdotal evidence indicates that stiffness is a common complaint. Some studies have suggested an association between stiffness and functional limitations however there has been no previous work which has attempted to objectively quantify knee joint stiffness following TKA. The purpose of this study was to pilot and evaluate a method for the quantitative evaluation in joint stiffness in replaced knees, OA knees and healthy controls and to explore whether there is an association between stiffness and functional limitations post-TKA surgery. Methods: The first part of the study created a biomechanical model of knee stiffness and built a system from which stiffness could be calculated. A torque transducer was used to measure the resistance as the knee was flexed and extended passively and an electrogoniometer concurrently measured the angular displacement. Stiffness was calculated from the slope of the line relating the passive resistive torque and displacement. The torque and joint angle at which stiffness was seen to increase greatly was also noted. The system was bench tested and found to be reliable and valid. Further tests on 6 volunteers found stiffness calculations to have acceptable intra-day reliability. The second part was conducted on three groups: those with end-stage knee OA (n = 8); those who were 1 year post-TKA (n = 15) and age matched healthy controls (n = 12). Knee range of motion was recorded and participants then completed the WOMAC, the SF-12 and a Visual Analogue Score for stiffness as well as indicating words to describe their stiffness. Four performance based tests – the Timed Up and Go (TUG), the stair ascent/descent, the 13m walk and a quadriceps strength test were also undertaken. Finally, passive stiffness at the affected knee was measured. Results: 100% of OA, 80% of TKA and 58% of controls reported some stiffness at the knee. The OA group reported significantly higher stiffness than the OA or TKA groups. There was no difference in self-reported stiffness between the TKA and control groups. Of the total number of words used to describe stiffness, 52% related to difficulty with movement, 35% were pain related and 13% related to sensations. No significantly differences were found between groups in the objective stiffness measures. Significant differences were found however in threshold flexion stiffness angles between groups. When this angle was normalised, differences between groups were not significant. No significant differences were found between groups in the threshold stiffness torque. Greater self-reported stiffness was found to be associated with worse self-reported function. A higher flexion stiffness threshold angle was associated with slower timed tests of function but also with better quadriceps muscle strength. Conclusions: The results support anecdotal reports that perceived stiffness is a common complaint following TKA but there was no evidence to show that patients with TKA have greater stiffness than a control group. There was however evidence to show that patients’ were unable to distinguish between sensations of stiffness and other factors such as pain. Self-perceived increased stiffness was associated with worse functional performance. Greater stiffness however was not necessarily negative. Stiffness increases earlier in flexion range were associated with better functional performance. These results suggest that an ideal threshold range for stiffness may exist; above which negative perceptions of the knee result in worse function but below which, knee laxity and instability may also result in worse function.

Knee joint kinematics is the result of a complex roto-translation movementcharacteristic of the tibio-femoral (TF) and patello-femoral (PF) articulations.This movement depends on the shape of the femur, the tibial plateau andthe patella. Moreover, it depends also on the morphological and mechanicalproperties of the soft tissues of the knee joint. In fact, the knee is characterizedby an extrinsic stability due to the active constraints (muscles and tendons)and passive soft tissues (menisci, retinaculum and ligaments) that surround it.As a result, knee kinematics and kinetics are different in each human being, andsometimes, even in the same person, with the right knee behaving differentlycompared to the left one.The ideal total knee arthroplasty TKA, used to correct pathologies that couldaffect the knee joint, should enable the restoration of the patient’s functionalknee kinematics and kinetics, so that the patient does not normally notice theTKA implant.Nowadays, TKA surgery is a well-established procedure and surgeons maychoose from among the broad range of TKA solutions available on the marketto meet the patient’s request. Prostheses may differ because of shape, materials,and mechanical constraints of their components. Consequently, the restorationof the knee joint biomechanics is limited by the degrees of freedom guaranteedby the adopted design solution.Despite the success of TKAs, pain and limited motor skills are reportedto still affect the clinical outcomes and not all patients are shown to be happyafter a TKA.Current complaints regarding post-TKA surgery might be related to the absenceof a proven tool that enables predicting patient-specific outcomes based ondifferent TKA solutions and providing guidelines to surgeons. In fact, surgicalpre-planning is usually based on a patient’s evaluation that the clinician canmake also based on medical images, and clinical experience. Data reported inthe literature can help in guiding the surgeon to a final decision regarding thebest subject-specific solution.Numerical methods, able to simulate knee biomechanics for various configurations,can be fundamental for the development of the appropriate reliableand effective tools to support clinically-tailored responses to a question.In particular, they can be used for subject-specific analyses on the intact kneeand for supporting the surgical pre-planning phase by comparing the effect ofdifferent solutions.When developing a subject-specific knee model, different kinds of datainputsare needed, such as the knee shapes and alignment information, softtissuesbehavior and boundary conditions describing the investigated motortasks. Often, most of this requested data are unlikely to be available (e.g.subject-specific soft-tissues material properties). Consequently, it is a commonoperating procedure to integrate literature data with subject-specific informationin order to develop knee models for collecting personalized outputsthat could be used to address research and clinical questions.However, up to now, the resulting effect of different generalized sources, asa mix of subject-specific and literature data, still needs to be evaluated for itsimpact on personalized outputs concerning knee behaviour.Furthermore, clinical questions are often focused on specific requests thatpartially use features of more complex knee models that could require too muchtime to be efficiently incorporated into daily clinical evaluations.For these reasons, the principal aims of this research have been to assess,first, the impact of differently derived generalized sources on the developmentof an intact subject-specific knee model or after a TKA; second,to provide guidelines to identify efficient clinically-tailored data sourcesused in and for knee modeling.To accomplish these tasks, a numerical knee model of an intact knee wasdeveloped based on both subject-specific and literature data sources. Theinfluence of different approaches to deal with a subject’s information, such asthe reconstruction of the knee geometries from different imaging sources, hasiiibeen evaluated. Moreover, a sensitivity analysis was performed to understandthe potential changes on kinetics and kinematics outcomes due to differentlyderived literature inputs, such as models and the properties that characterizethe joint materials and ligaments description. The outputs collected after finiteelement analyses were analyzed and compared with already published experimentaloutcomes for the same analyzed specimen and replicated boundaryconditions.Additionally, the effects on knee joint contact forces and kinematics afterTKA surgery and due to the mis-alignment of implant components or misidentificationsof ligament insertions were evaluated in another sensitivityanalysis performed with a rigid body analysis for four different TKA designsimplanted in a subject-specific knee model. As for the intact knee model, theanalyzed configurations were compared against already published experimentaloutputs or literature data replicating similar boundary conditions.Moreover, several dedicated knee models were developed to address specificclinical questions, such as the lack of biomechanical explanations for certainbehaviours of TKA designs.Once compared to already published experimental or literature data, the resultsof the developed models agree.The main results from the numerical simulations performed show that, changingthe values of some of the parameters used as inputs, the knee model kinematicsis less influenced than the contact forces and stresses outputs.In particular, in developing an intact knee model, the main effecting parameteris the material properties selection for the knee cartilage layers. Among theconfigurations analyzed using subject-specific knee models with TKAs, theposition of the tibial component and the height of the patellar buttonare the most effecting inputs.Exploring the different chapters of this research thesis, several specific resultsare shown regarding each main step followed in developing a knee numericalmodel. For example, new approaches based on MRIs have been suggested andtested proving that they are suitable for collecting subject-specific informationregarding geometrical shapes and landmark definitions. Moreover, a newgraphical method was proposed resulting more effective and immediate thanconventional representations in reporting huge amount of data. In particular,the method is the favourite to show complex biomechanical analyses especiallyfor the clinical audience that replied to a survey. Furthermore, the differentmodels tailored to address specific clinical questions collected useful biomechanicalresults, to provide clinical advice or industrial guidelines, and can beconsidered as examples of what should be included in a knee model for similarscenarios.The results of this thesis offer several contributions. Generally, these findingscould provide useful guidelines for knee-model developers to achievea more balanced approach to subject-specific intact knee models based upongeneral sources in order to improve the understanding of personalized kneebiomechanics.To address a general comment to the title of this thesis, there is no singleanswer. In fact, the selection of data sources is case-dependent using, forexample, the subject’s or literature available data to describe material’s behavioror the boundary conditions of a specific motor task. Moreover, differentclinical questions can be addressed with different numerical approaches, e.g.finite element analysis is necessary especially in the case that stress outputs arerequested, but can be too time-consuming for addressing complex sensitivityanalyses.Once the knee model developer has identified the necessary data sources andthe approaches to be implemented, the question-tailored knee models can thusbe used for several applications such as predicting subject-specific abnormalknee kinematics and kinetics for different TKA designs, polyethylene wear,patellofemoral dislocation and bone remodeling, choosing the best fitting TKAdesign for a specific patient, and developing a procedure to optimize TKAimplant designs. / Doctorat en Sciences de l'ingénieur et technologie / info:eu-repo/semantics/nonPublished

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