Objective: The purpose of this study was to examine social cognitive constructs as predictors of preoperative exercise (PE) in a sample of individuals waiting for total joint replacement (TJR) surgery using the framework of Bandura’s Social Cognitive Theory (SCT). Methods: Participants (N = 78) were individuals waiting for TJR at the two major urban centres on Vancouver Island, Canada who completed measures of the SCT (barrier self-efficacy, outcome expectancy, self regulation, task efficacy & sociocultural factors of pain, physical function and neighbourhood walking environment) framed for (PE). Results: Independent t-tests suggested no differences between type of surgery (hip versus knee), gender or age for PE (p<.05). Over half of the sample was considered inactive (55%) using a definition of physical activity as accumulating at least 30 minutes of exercise at a moderate or vigorous intensity at least 3 days per week in bouts of 10 minutes or more. Bivariate correlations relating to PE were significant (p<.05) between self regulation (SR) (.25), task efficacy for exercise (TEE) (.27) and pain (-.28). Hierarchical regression analysis revealed that SR (β=.17) and TEE (β=.20) explained 10% of the variance in PE behaviour, but were not significant predictors of PE independently. The addition of pain to the regression analysis added 4% of the explained variance, and remained the only significant predictor (p<.05) of Pe behaviour. Conclusions: SCT showed modest capability in predicting PE in this sample, suggesting further testing of theoretical models is warranted in this area. These findings highlight the influence of pain on exercise before TJR surgery, and support the importance of considering individual factors such as pain when designing targeted interventions to increase activity in this population.

Surfaces exposed to wear always transform and typically a layer of new structure and composition is formed. This layer, often called tribofilm, changes the friction and wear properties. Tribofilms formed on ceramic surfaces may consist of products from chemical reactions between the materials in contact and the environment or consist of compacted wear debris. In this thesis, focus has been to understand the friction and wear mechanisms of ceramic surfaces, as well as acquiring knowledge about the properties of the new surfaces created during wear. Ultimately, this understanding can be used to develop ceramic systems offering high or low friction, while the material loss in both cases should be minimised. Such ceramics could improve numerous tribological systems and applications, out of which ultrasonic motors, low-friction ceramic coatings and hip joint replacements have been treated in this thesis. Friction and wear tests, and subsequently various surface analyses have been essential for the knowledge about the friction, wear and tribofilm formation.  For ultrasonic motors of the studied type, the highest driving force is achieved when the friction is high between the alumina components in the friction drive system. The highest friction was here accomplished with a thick tribofilm on the surfaces. The formation of such tribofilms was favoured by dry conditions, and using an initially rough surface, which increased the initial generation of wear debris. In a detailed investigation of the importance of microtopography on tribofilm formation and friction behaviour, a low-friction, PVD coating of TaC/a-C was studied. This coating showed a very low, stable friction. High sensitivity to the microtopography was demonstrated, smooth coating exhibited a faster build-up of a dense tribofilm of fine ground material on the counter steel surface and subsequently a faster running in and friction decrease.  The life span for total hip joint replacements can be prolonged by minimising the wear particles that cause inflammation and subsequent implant loosening. In this work coatings of amorphous/nanocrystalline silicon nitride have shown low wear rate, and hence produce a minimum of wear particles. Furthermore, these particles that are expected to resorb in vivo. This system therefore has potential to reduce problems with inflammation and osteolysis connected to wear particles.

This diploma thesis deals with an experimental analysis of lubrication of total hip joint replacement using fluorescence microscopy, focusing on so-called soft bearing pairs. Experiments were realized using a hip joint simulator, which was modified and refined for fluorescence microscopy. The aim of this diploma thesis was to determine the effect of the individual components of the synovial fluid on the lubrication mechanisms. For this purpose, different model fluids were designed to represent the composition of proteins and other synovial fluid constituents to elucidate the effect of albumin, -globulin and hyaluronic acid on the resulting lubrication performance. The experiments were separate into two categories different in type of load, dynamic (representative walking) and combined (representing standing with short walk). The experimental results were time-dependent fluorescence intensity values, representing dimensionless film thickness parameters. The values were recorded on the graphs and supplemented with fluorescence images taken during the characteristic sections of the measurements. The measured data was subsequently confronted with previously published articles. It was found that the dominant constituent responsible form film thickness is albumin, while -globulin and hyaluronic acid forms thin stable layer enhancing adsorption ability of albumin which contributes to increase of film thickness eventually.

This diploma thesis deals with an experimental analysis of knee joint replacement lubrication. The experiments were realized at a knee joint simulator which can apply conditions according to certain standard and survey the phenomena by using fluorescence microscopy. The aim of thesis is to clarify the influence of particular components of synovial fluid on the lubrication process. The intensity of fluorescence expresses dimensionless parameter of a lubrication film thickness. There was a fundamental study with mineral oils before the experiments with the synovial fluid. The study allows to have a look at contact transformation during walk. Results are shown in graphs as dependency of intensity on time, including pictures showing phenomena in the contact zone. Experiment results show that protein -globulin creates a layer on the surface. There is albumin on the layer and it makes the lubricating film thicker. The protein interaction is supported by hyaluronic acid and fosfolipids which stabilizes the created structure. According to lubrication is behaviour of film related to a complex structure of synovial fluid. Thesis gives more information about behaviour of synovial fluid and can be used for future development of knee replacements.

Biotribology, the study of lubrication, wear and friction within the body, has become a topic of high importance in recent times as we continue to encounter debilitating diseases and trauma that destroy function of the joints. A highly successful surgical procedure to replace the joint with an artificial equivalent alleviates dysfunction and pain. However, the wear of the bearing surfaces in prosthetic joints is a significant clinical problem and more patients are surviving longer than the life expectancy of the joint replacement. Revision surgery is associated with increased morbidity and mortality and has a far less successful outcome than primary joint replacement. As such, it is essential to ensure that everything possible is done to limit the rate of revision surgery. Past experience indicates that the survival rate of the implant will be influenced by many parameters, of primary importance, the material properties of the implant, the composition of the synovial fluid and the method of lubrication. In prosthetic joints, effective boundary lubrication is known to take place. The interaction of the boundary lubricant and the bearing material is of utmost importance. The identity of the vital active ingredient within synovial fluid (SF) to which we owe the near frictionless performance of our articulating joints has been the quest of researchers for many years. Once identified, tribo tests can determine what materials and more importantly what surfaces this fraction of SF can function most optimally with. Surface-Active Phospholipids (SAPL) have been implicated as the body’s natural load bearing lubricant. Studies in this thesis are the first to fully characterise the adsorbed SAPL detected on the surface of retrieved prostheses and the first to verify the presence of SAPL on knee prostheses. Rinsings from the bearing surfaces of both hip and knee prostheses removed from revision operations were analysed using High Performance Liquid Chromatography (HPLC) to determine the presence and profile of SAPL. Several common prosthetic materials along with a novel biomaterial were investigated to determine their tribological interaction with various SAPLs. A pin-on-flat tribometer was used to make comparative friction measurements between the various tribo-pairs. A novel material, Pyrolytic Carbon (PyC) was screened as a potential candidate as a load bearing prosthetic material. Friction measurements were also performed on explanted prostheses. SAPL was detected on all retrieved implant bearing surfaces. As a result of the study eight different species of phosphatidylcholines were identified. The relative concentrations of each species were also determined indicating that the unsaturated species are dominant. Initial tribo tests employed a saturated phosphatidylcholine (SPC) and the subsequent tests adopted the addition of the newly identified major constituents of SAPL, unsaturated phosphatidylcholine (USPC), as the test lubricant. All tribo tests showed a dramatic reduction in friction when synthetic SAPL was used as the lubricant under boundary lubrication conditions. Some tribopairs showed more of an affinity to SAPL than others. PyC performed superior to the other prosthetic materials. Friction measurements with explanted prostheses verified the presence and performance of SAPL. SAPL, in particular phosphatidylcholine, plays an essential role in the lubrication of prosthetic joints. Of particular interest was the ability of SAPLs to reduce friction and ultimately wear of the bearing materials. The identification and knowledge of the lubricating constituents of SF is invaluable for not only the future development of artificial joints but also in developing effective cures for several disease processes where lubrication may play a role. The tribological interaction of the various tribo-pairs and SAPL is extremely favourable in the context of reducing friction at the bearing interface. PyC is highly recommended as a future candidate material for use in load bearing prosthetic joints considering its impressive tribological performance.

This thesis deals with stress analysis strain proximal end of tibia with total joint replacements. The analysis is done on the basis of deformation characteristics of voltage, through the finite element method (FEM). We have developed two-dimensional models of the proximal end of tibia with tibial components total endoprosthesis (TEP), without loss and bone loss. Geometry model is created based on data obtained from computerized tomography, which were further processed in the program, Rhinoceros 3.0 and SolidWorks 2009th Computational solution was carried out by finite element method in Ansys Workbench 12.0. The model without loss of bone tissue was tested the hypothesis that the deformation is very small and there is no violation of the shank prosthesis. Due to loss of bone tissue is lost support to the tibial pulse in the proximal tibia and by a progressive increase in stress, which can lead to a breach of the shank total joint replacement. The analysis results show that, if the loss of bone tissue, so that the tibial part of the TEP will lose support, there is a crack stem total hip replacement due to stress.

This diploma thesis describes the design of filling element with trabecular structure for revision implant of total knee arthroplasty. Design of the filling element is created by the digital data of the patient tissue. Production of a functional sample is performed using additive technology Selective Laser Melting. This work also include analyze of the accuracy of this technology for the production of titanium alloy Ti6Al4V.

No description available.

Background: Sophisticated guided surgery has not been implemented into total joint replacement-surgery (TJR) of the temporomandibular joint (TMJ) so far. Design and in-house manufacturing of a new advanced drilling guide with vector and length control for a typical TJR fossa component are described in this in vitro study, and its accuracy/utilization was evaluated and compared with those of intraoperative real-time navigation and already available standard drilling guides. Methods: Skull base segmentations of five CT-datasets from different patients were used to design drilling guides with vector and length control according to virtual surgical planning (VSP) for the TJR of the TMJ. Stereolithographic models of the skull bases were printed three times for each case. Three groups were formed to compare our newly designed advanced drilling guide with a standard drilling guide and drill-tracking by real-time navigation. The deviation of screw head position, screw length and vector in the lateral skull base have been evaluated (n = 72). Results: There was no difference in the screw head position between all three groups. The deviation of vector and length was significantly lower with the use of the advanced drilling guide compared with standard guide and navigation. However, no benefit in terms of accuracy on the lateral skull base by the use of real-time navigation could be observed. Conclusion: Since guided surgery is standard in implant dentistry and other CMF reconstructions, this new approach can be introduced into clinical practice soon, in order to increase accuracy and patient safety.

This project attempts to quantify the integrity of the fixation of total hip arthro- T plasties (THAs) by observing vibration signal features. The aim of this thesis is, therefore, to find the signal differences between firm and loose prosthesis. These difference will be expressed in different transformed domains with the expectation that a certain domain will provide superior results. Once the signal differences have been determined they will be examined for their ability to quantify the looseness. Initially, a new definition of progressive, femoral component loosening was created, based on the application of mechanical fit, involving four general conditions. In order of increasing looseness the conditions (with their equivalent engineering associations) are listed as, firm (adherence), firm (interference), micro-loose (transition) and macro-loose (clearance). These conditions were then used to aid in the development and evaluation of a simple mathematical model based on an ordinary differential equation. Several possible parameters well suited to quantification such as gap displacement, cement/interface stiffness and apparent mass were the identified from the model. In addition, the development of this model provided a solution to the problem of unifying early and late loosening mentioned in the literature by Li et al. in 1995 and 1996. This unification permitted early (micro loose) and late (macro loose) loosening to be quantified, if necessary, with the same parameter. The quantification problem was posed as a detection problem by utilising a varying amplitude input. A set of detection techniques were developed to detect the quantity of a critical value, in this case a force. The detection techniques include deviation measures of the instantaneous frequency of the impulse response of the system (accuracy of 100%), linearity of the systems response to Gaussian input (total accuracy of 97.9% over all realisations) and observed resonant frequency linearity with respect to displacement magnitude (accuracy of 100%). Note, that as these techniques were developed with the model in mind their simulated performance was, therefore, considerably high. This critical value found by the detector was then fed into the model and a quantified output was calculated. The quantification techniques using the critical value approach include, ramped amplitude input resonant analysis (experimental accuracy of 94%) and ramped amplitude input stochastic analysis (experimental accuracy of 90%). These techniques were based on analysing the response of the system in the time-frequency domain and with respect to its short-time statistical moments to a ramping amplitude input force, respectively. In addition, other mechanically sound forms of analysis, were then applied to the output of the nonlinear model with the aim of quantifying the looseness or the integrity of fixation of the THA. The cement/interface stiffness and apparent mass techniques, inspired by the work of Chung et.al. in 1979, attempt to assess the integrity of fixation of the THA by tracking the mechanical behaviour of the components of the THA, using the frequency and magnitude of the raw transducer data. This technique has been developed fron the theory of Chung etal but with a differing perspective and provides accuracies of 82% in experimentation and 71% in simulation for the apparent mass and interface stiffness techniques, respectively. Theses techniques do not quantify all forms of clinical loosening, as clinical loosening can exist in many different forms, but they do quantify mechanical loosening or the mechanical functionality of the femoral component through related parameters that observe reduction in mechanical mass, stiffness and the amount of rattle generated by a select ghap betweent he bone/cement or prosthesis/cement interface. This form of mechanical loosening in currently extremely difficult to detect using radiographs. It is envisaged that a vibration test be used in conjunction with radiographs to provide a more complete picture of the integrity of fixation of the THA.