Abstract Background: The Gluteus Medius (GM) muscle has an important role in stabilizing the pelvis and controlling the knees during athletic activities. Weakness in the GM can affect performance negatively and increase the risk of lower extremity (LE) injuries. During functional activities different parts of the muscle becomes activated depending on the degree of hip flexion. However, many GM strength exercises only train the GM in one fixed degree of hip flexion. Purpose: The purpose of the present study was to develop and validate a new training device designed to increase the muscle activation of the GM during progressive hip flexion in squats. Methods: The new device was developed to offer resistance training against hip abduction during squats. To be able to validate the new device in activating the GM, 32 female athletes (mean age 20 ± 3) with various athletic backgrounds was included in the study. All subjects performed squats on and off the device while surface electromyographical (SEMG) activity was recorded from GM on both sides of the body. Results: All test subjects were able to perform the squat and to activate the GM. When the squats were performed on the new device the muscle activation in GM was significantly higher compared to bodyweight squats (Z=-4.9, p < 0.001). Correlation tests between a complete sequence of five squats and one selected repetition revealed that activation was consistent throughout the exercise, (right GM: rs = 0.93, p < 0.001, left GM: rp = 0.92, p < 0.001) . No differences in activation were found between the right and left GM when squatting on the device. Conclusion: This study showed that the newly developed training device increased the muscle activity in GM during squats. Moreover, the results showed that squatting on the device activates the left and right side of the body equally and that the GM was activated during the whole exercise, under ongoing hip flexion. This information could be used to develop new training methods with the aim to improve stabilization of the pelvis and lower extremities during functional activities. / Sammanfattning Bakgrund: Gluteus medius (GM) fyller en viktig funktion vid idrottsliga aktiviteter genom att den stabiliserar bäckenet och kontrollerar knäna. Svaghet i GM kan påverka prestationen negativt samt öka risken för skador i de lägre extremiteterna (LE). Vid funktionella aktiviteter aktiveras olika delar av GM beroende på graden av höftflexion. Många styrkeövningar för GM tränar emellertid muskeln i endast en fixerad grad av höft flexion. Syfte: Syftet med den här studien har varit att utveckla samt validera ett nytt träningsredskap, designat för att optimera muskelaktiveringen av GM under höftflexion. Metod: Träningsredskapet utvecklades för att erbjuda motstånd mot abduktion vid knäböj. För att validera redskapets förmåga att aktivera GM inkluderades 32 kvinnliga idrottare (medelålder, 20 ± 3 år) med varierande idrottslig bakgrund. Alla försökspersoner utförde knäböjningar med och utan träningsredskapet samtidigt som elektromyografisk aktivitet mättes i höger och vänster GM. Resultat: Alla försökspersoner kunde utföra knäböjningar och lyckades aktivera GM. Knäböjningar som utfördes på träningsredskapet resulterade i signifikant högre aktivering av GM jämfört med knäböjningar utan redskapet (Z=-4.9, p < 0.001). Korrelations test mellan kompletta sekvenser om fem repetitioner och enstaka repetitioner visade att aktiveringen var konstant under hela övningen, (höger GM: rs = 0.93, p < 0.001, vänster GM: rp = 0.92, p < 0.001). Inga skillnader i aktivering hittades mellan höger och vänster GM vid knäböjningar på redskapet. Slutsats: Studien visade att det utvecklade träningsredskapet ökade aktiveringen av GM vid knäböjningar. Resultaten visade också att denna aktivitet var jämnt fördelad mellan höger och vänster GM samt att aktiveringen var konstant under hela övningen. Resultaten i denna studien kan användas för att utveckla nya träningsmetoder med syfte att förbättra stabiliseringen av bäckenet och de lägre extremiteterna vid funktionella aktiviteter.

Wear of the polyethylene (PE) bearing surface and wear particle-induced osteolysis (bone resorption) can lead to failure of modular total knee replacements and make expensive revision surgery necessary. Gamma-in-air sterilization of the PE insert and having a modular tibial component are both risk factors for excessive backside wear that contribute to osteolysis and implant failure. The overall wear (backside and topside) of modular total knee replacements has been subjected to considerable research in order to avoid such implant failure. The investigations reported in the present thesis evaluated both the clinical and in vitro wear performance of modular total knee replacements. The clinical investigations included damage assessment of retrieved PE inserts. A semi-quantitative grading method was developed and used to assess backside surface damage on 52 PE inserts retrieved from contemporary total knee replacement surgeries. Statistical analyses, such as univariate and multiple linear regression analysis, were performed to identify factors that influence backside damage including implant design features and patient characteristics. The damage features on the retrieved tibial PE inserts were also assessed with surface characterization techniques, such as scanning electron microscopy, energy dispersive X-ray analysis, and surface profilometry. To reduce surface damage and thus wear, PE inserts should be either gas-plasma or ethylene-oxide sterilized, used with polished tibial trays and held in place with a partial-peripheral locking mechanism. Synovial fluid samples were aspirated from a total of twenty patients and some basic biochemical analyses were performed. The total protein concentration, protein constituent fractions, the level of osmolality, and trace element concentrations were measured and compared with the same characteristics of four serum lubricants that were frequently used in simulator wear testing to mimic synovial fluid. In vitro investigations were conducted to explore the effects of some major constituents of the serum lubricants on the wear rate using a knee simulator apparatus. Increased protein constituent degradation led to increased wear. Such findings suggested that a protein layer acted as a boundary lubricant to protect the PE surfaces of knee implants. The protein constituent fractions of alpha calf serum (ACS) were similar to those measured for synovial fluid. These ACS lubricants were used in further wear studies in which hyaluronic acid (HA) and phosphate buffer solution (PBS) were successively added. The PBS was used in place of the distilled water to generate a serum lubricant with a clinically relevant level of osmolality. The thermal stability of the ACS lubricants and synovial fluid were measured. The thermal stability of the ACS lubricant that contained HA and PBS was about the same as that of human synovial fluid. The simulator wear rate of PE was significantly influenced by both HA and PBS. In further investigations, sodium azide, which has been used to inhibit microbial growth in simulator wear testing, was shown to be highly ineffective. Microbial contamination was recognized and the organism responsible was identified using standard microbiological methods. The use of an antibiotic-antimycotic mixture as the microbial inhibitor in the ACS + PBS + HA lubricant created a sterile environment and thus very clinically relevant environment for wear testing. The content of this thesis represents a comprehensive data collection on retrieval analysis and lubricant-specific knee simulator wear testing of modular total knee replacements. A more clinically relevant lubricant composition for simulator wear testing was proposed (U.S. patent Serial number 60/899,894; pending since February 9th, 2007) that improved upon the current guideline from the International Standards Organization for knee simulator wear testing. The present thesis should serve as a guide for the surgeon, researcher and the implant manufacturer to evaluate retrieved implant components and to select lubricant additives for wear testing that closely mimics the in vivo wear conditions.

No description available.

Syfte: Syftet var att finna skillnader och samband i self-efficacy (SE) – med avseende på typ av artroplastik, kön och ålder – inför två förflyttningar. Detta för att se vilka patienter som kan vara i större behov av att stärka SE postoperativt. Metod: Studien gjordes på inneliggande patienter som genomgått en höft- eller knäartroplastik. Ett för undersökningen framställt frågeformulär undersökte de 117 deltagarnas SE inför att sätta sig upp på sängkanten samt gå med hjälpmedel. Deltagarna skattade SE inför förflyttningarna första eller andra dagen efter operationen. Resultat: Deltagare som hade genomgått en knäartroplastik skattade signifikant högre SE inför att sätta sig upp på sängkanten än de som hade genomgått en höftartroplastik. Männen skattade signifikant högre SE inför båda momenten jämfört med kvinnorna. Det fanns en låg korrelation mellan stigande ålder och låg SE inför att gå med hjälpmedel. Konklusion: Resultaten tyder på att SE inför förflyttningarna skiljer sig mellan patienter. Detta bör behandlande sjukvårdspersonal ta hänsyn till i ett postoperativt skede för att undvika immobiliseringskomplikationer hos patienterna.

Syfte och frågeställningar: Syftet med studien var att undersöka om slingträning av nedre bålen för individer med löparknä kan ge en reducering av skadeproblematiken. Syftet var även att studera om upplevelsen av smärta och begränsning i aktivitet förändrats hos dessa individer i en subjektiv bedömning. Löparknä innebär smärta på den yttre sidan av knät, mest vanligt hos löpare men även andra idrottare drabbas. Frågeställningar: I vilken omfattning kan slingträning av nedre bålen för individer med löparknä ge en mer funktionell styrka och även större uthållighet? Hur upplever individer med löparknä vid en subjektiv skattning att denna träning leder till en förändring av smärta och begränsning i aktivitet? Metod: Studien genomfördes som en kvantitativ experimentell studie, där en interventionsgrupp på sex löpare med löparknäproblem genomförde slingträning av nedre bålen. Detta skedde två gånger i veckan under sex veckor. Tester av funktionell styrka och uthållighet genomfördes den första veckan, efter tre veckor och efter sex veckor. Testerna innebar ett isometriskt test av höftabduktorer, ett balanstest på ett ben och att samtidigt sträcka sig framåt på samma sida, ett balanstest på ett ben med sträckning över huvudet i frontalplan, och ett test av svag länk vid sidliggande höftabduktion. En kontrollgrupp på fyra löpare utan skador genomförde enbart testerna vid samma tidpunkter. Därtill följde en subjektiv bedömning, i form av skattning på en skala 0-10, av hur individen upplevde smärta av löparknät, samt hur det begränsade hans/hennes aktivitet. Resultat: En signifikant förbättring över tid erhölls i både det skadade och friska benet hos interventionsgruppen i tre av testerna, närmare bestämt isometriskt test av höftabduktorer (51 %), balanstest på ett ben med sträckning över huvudet i frontalplan (8 %), och test av svag länk vid sidliggande höftabduktion (27 %). Ingen förändring erhölls hos kontrollgruppen. Slutsats: Denna studie tyder på att slingträning av nedre bålen för individer med löparknäproblem kan ge en mer funktionell styrka och även större uthållighet. Denna träning kan också vara orsaken till att deras upplevelse av smärta och begränsning i aktivitet tenderade att minska.

Aim: To investigate if physical exercise in combination with coaching will reduce pain and improve knee function in patients with mild to moderate osteoarthritis in the knee compared to physical exercise alone. Method: The study consisted of 42 patients who were randomized to either an intervention group or a control group. Both groups followed a standardized training program at home, but the intervention group received additional support with regard to the aim of their training, as well as extra coaching during the training period of ten weeks. A Visual Analog Scale (VAS) was used to evaluate the patients’ pain. A 10 metre walking test, the Index of Muscle Function (IMF) and the Knee injury and Osteoarthritis Outcome Score (KOOS) were also used to evaluate knee function. Patients’ compliance with the training program was also assessed. Results: No significant difference was found between the two groups with regard to the pain scores, walking speed, muscle function in the lower extremities or the knee function. A significant difference was found within the experimental group for the pain, the muscle function in the lower extremities and the related function of the knee. A significant difference was also found within the control group for the muscle function in the lower extremities and the related function of the knee. The level of compliance to the physical training program was comparable in the both groups. Conclusion: Use of coaching in combination with physical training at home did not show better results in the pain reduction, walking speed, muscle strength or functional improvement compared to the use of physical training alone. No difference was found in the compliance to the training program between the two groups despite the additional coaching to the intervention group.

High-tone extensor thrust is common to those with cerebral palsy and those suffering spinal cord injuries. It is a muscle-control phenomenon that causes the body to straighten spastically. One goal of this thesis is to design a dynamic seating system that moves with respect to the wheelchair frame, allowing the seat to move with the user during an extensor thrust and reduce forces. One unique challenge is that the seat needs to remain rigid during normal functional activities and only become dynamic when an involuntary thrust is detected. A second goal of this thesis is to design a control scheme that is able to differentiate between these two types of motion. These design goals are initially investigated with a hinged-seatback system, instrumented with sensors to allow for the detection of thrusts and to actively control seating components. A full seating system is then built to allow for full-body extensor thrusts, involving the seatback, seat bottom, and leg rest of the wheelchair. This system is analyzed for effectiveness of reducing forces on the body during an extensor thrust. Another serious problem for this segment of the population is pressure ulcers. These are caused by prolonged pressure on the skin from weight-bearing bony prominences. Various seating system configurations are known to help with pressure relief. The three standard configurations for a chair are tilt, recline, and standing. The final goal of this thesis is to measure and compare the effectiveness of these three methods for their ability to relieve pressure on the seat bottom. To accomplish this, a powered wheelchair with built-in capabilities for recline and standing is mounted to a tilting mechanism. Test subjects are used to experimentally compare the effectiveness of each method for pressure reduction using pressure mats on all weight-bearing surfaces. A 2D model is also developed and validated with the experimental results.

This work is initiated from an observation of the rolling-sliding kinematic behavior observed in the motion of the knee joint. We use the slip ratio as a parameter to analyze the rolling-sliding properties of a mechanism, and also propose a method to design new mechanisms with specific slip ratio. In this research, we first verify the many definitions of the slip ratio, then modify a best definition to suit various rolling-sliding motions. Most importantly, we propose two types of rolling-sliding mechanism design. By changing the parameters of the mechanism, we can adjust its slip ratio curve to be close to a desired curve. In addition, when the idea of adjustable link length is used in the design of the mechanism, exact slip ratio curve as specified can be generated by the use of some cams.

Gait analysis is one of the primary applications of biomechanics and deals with scientific description of human locomotion, which is a qualitative concept as observed through the human eye. METU Gait Analysis Laboratory has been operating in various fields of gait and motion analyses since 1999. Although several studies have previously been undertaken about METU Gait Analysis System, until now, the effects of methodology and protocol related system parameters on kinematic analysis results have not been fully and exhaustively investigated. This thesis presents an assessment on sensitivity and compatibility of METU Gait Analysis Protocol to variations in experimental methodology and implementation of various joint center estimation methods, performed through investigation of the resulting joint kinematics. It is believed that the performance and reliability of METU Gait Analysis System will be improved based on the findings of this study.

Gait analysis is the process of collecting and analyzing quantitative information about walking patterns of the people. Gait analysis enables the clinicians to differentiate gait deviations objectively. Diagnostic decision making from gait data only requires high level of medical expertise of neuromusculoskeletal system trained for the purpose. An automated system is expected to decrease this requirement by a &lsquo / transformed knowledge&rsquo / of these experts. This study presents a clinical decision support system for the detecting and scoring of a knee disorder, namely, Osteoarthritis (OA). Data used for training and recognition is mainly obtained through Computerized Gait Analysis software. Sociodemographic and disease characteristics such as age, body mass index and pain level are also included in decision making. Subjects are allocated into four OA-severity categories, formed in accordance with the Kellgren-Lawrence scale: &ldquo / Normal&rdquo / , &ldquo / Mild&rdquo / , &ldquo / Moderate&rdquo / , and &ldquo / Severe&rdquo / . Different types of classifiers are combined to incorporate the different types of data and to make the best advantages of different classifiers for better accuracy. A decision tree is developed with Multilayer Perceptrons (MLP) at the leaves. This gives an opportunity to use neural networks to extract hidden (i.e., implicit) knowledge in gait measurements and use it back into the explicit form of the decision trees for reasoning. Individual feature selection is applied using the Mahalanobis Distance measure and most discriminatory features are used for each expert MLP. Significant knowledge about clinical recognition of the OA is derived by feature selection process. The final system is tested with test set and a success rate of about 80% is achieved on the average.