Acrylic bone cement is used in orthopaedic surgery for total joint replacements as a means of fixation of the prosthesis to the bone. One of the main problems associated with total joint replacements is aseptic loosening which can be caused by the brittle fracture of the cement. The purpose of this research was to improve the resistance of bone cement to brittle fracture by creating new experimental cements containing the thermoplastic rubber, acrylonitrile-butadiene-styrene (ABS), and to determine if improvements could be furthered by using ABS surface coated with a silane coupling agent, the latter having never been investigated before. Incorporating the ABS into the cement will affect the cements' rheological/handling characteristics, therefore these properties were investigated over the entire curing process both at 25 C and 37 C. The results showed that the introduction of either ABS or silane-coated ABS significantly improved the fracture resistance of the cement. The fracture toughness of cements containing 30% ABS increased by 19%. and 40% silane-coated ABS by 31%. There was also a substantial improvement in fatigue crack propagation behaviour with cements containing 30% and 40% ABS or silane-coated ABS showing a minimum three-fold increase in stress intensity at failure. Furthermore, by monitoring changes in the rheological properties over the entire curing process it was found that the incorporation of silane-coated ABS particles increased the maximum complex viscosity by 35% and maximum elastic modulus by 33%. The curing rates of the cements containing 30% and 40% ABS/silane-coated ABS remained comparable with commercial cements. These results are of major significance as the enhanced ability of the new acrylic cements to resist catastrophic failure by brittle fracture could dramatically lengthen the working lifetime of a total joint replacement.

Animal models have been used for many years to generalise the human condition of various neurological diseases. It is important that the behavioural attributes from the animal model directly correlate with those found in the human pathology. Motion analysis (MA) techniques provide a platform for direct correlation analysis between the two species, which is an important step for translational medicine. A novel three dimensional (3D) MA protocol was developed to investigate temporal and postural gait variables in both rats and humans. Gait studies involving rats are mainly based on movement scores or descriptive approaches to discerning differences in behaviour or function. Therefore, a protocol utilising a quantitative 3DMA technique during gait was developed. Data was acquired to describe function and behavioural attributes in animal models of Parkinson‟s disease (PD) and stroke in terms of temporal gait and postural adjustments and on a healthy cohort of humans. The study explored the practicality of the developed protocol to investigate the effects of unilateral dopamine depletion on rat locomotion while walking on beams of varying widths (wide, narrow and graduated). Temporal and postural gait parameters of ten male Lister Hooded rats (five controls (CNL) and five hemi-parkinsonian (PNL)) were observed using passive markers placed in locations that were representative of their four limbs and their body axis. Significant differences (p<0.05) were found between the PNL and CNL rats for speed along the wide beam and stride lengths for the left (impaired) fore-limb; on the narrow beam and the wide beam and for the left (impaired) hind limb on the graduated beam. The PD rats moved on the wide beam with a significantly greater roll range of motion (ROM) coupled with a positively biased roll kinematic waveform during one gait cycle. Whilst walking on the narrow beam, they displayed an increased use of the ledge and placed their tail towards the right. The results demonstrate that marker-based MA can provide an effective and simple approach to quantifying temporal gait parameters for rat models of PD. They also reveal how the width of the path affects the locomotion in both experimental cohorts. ii The novel protocol was applied to investigate the effects of Middle Cerebral Artery Occlusion (MCAO) and graft on rat locomotion while walking on a wide beam. The data collection was carried out before and after surgery to investigate temporal and postural gait parameters of 50 male Wister rats. Significant differences (p<0.05) were found between the control and MCAO rats for roll ROM coupled with a positively biased roll kinematic waveform during one gait cycle. Using the data collected, a classification tool based around the Dempster-Shafer theory enabled the objective classification of the rat cohorts into a MCAO group, a control group and a graft group. The roll ROM and swing time data were transformed into a set of belief values that the animals had graft, lesion or normal gait. The belief values were then represented on a simplex plot, which enables the final classification of a rat, and the level of benefit achieved by lesion or graft surgery to be visualised. The tool was able to classify rats with an accuracy of between 81% and 94.84% accuracy. The tool also indicated that swing time and roll were the most influential variables in distinguishing differences in gait after MCAO lesion and graft. Further work is required on the graft data as some inconsistencies were found, but the classification allowed better comparisons between groups than just using ANOVA alone by taking this level of uncertainty and producing a clear comparison between the cohorts. Initial studies have demonstrated a practical and visual approach that can discriminate between gait function in the rat model. Therefore to achieve the aim of the thesis, a cohort of healthy humans were tested to replicate the data collection and processing protocols developed for animal MA. The marker based protocol was carried out to investigate temporal and postural gait parameters of 10 healthy human subjects (five male: five female). The data collected compared well with published data for normal human gait therefore validating the human based protocol. The results identified variables that were easily correlated with rat data. Similarities in body orientation patterns were recorded and discussed. In conclusion, a novel protocol was developed that allowed a simple, non-invasive, practical, and sensitive approach to over ground gait data acquisition for the rat models and a healthy human cohort. Further work that would involve patients with neurological disease will enable the full validation of the protocol. This is turn would provide answers to the argument: „Is the use of animal models of the disease effective approach for clinical research?‟

Improper manipulation of real-world objects increases the risk of developing work- related back injuries. In an effort to reduce such a risk and encourage appropriate lifting and moving methods, a Virtual Environment (VE) was employed. Virtual simulations can be used for ergonomic analysis. In this work, the VEs made use of multiple feedback techniques to allow a person to estimate the forces acting on their lower back. A person's head and hand movements were tracked in real-time whilst manipulating an object. A NIOSH lifting equation was used to calculate and determine the Lifting Index whereby the results were conveyed in real time. Visual display feedback techniques were designed and the effect of cues to enhance user performance was experimentally evaluated. The feedback cues provide the user with information about the forces acting on their lower back as they perform manual lifting tasks in VEs. Four different methods were compared and contrasted: No Feedback, Text, Colour and Combined Colour and Text. This work also investigated various types of auditory feedback technique to support object manipulation in VEs. Auditory feedback has been demonstrated to convey information in computer applications effectively, but little work has been reported on the efficacy of such techniques, particularly for ergonomic design. Four different methods were compared and contrasted: No Feedback, White-noise, Pitch and Tempo. A combined Audio-Visual (AV) technique was also examined by mixing both senses. The effect of Tactile Augmentation was also examined. Three different weights (real) were used and the results obtained by experiment were compared with the experiment using virtual weights in order to evaluate whether or not the presence of a real weighted object enhanced people's sense of realism. The goals of this study were to explore various senses of feedback technique (visual, auditory and tactile), compare the performance characteristics of each technique and understand their relative advantages and drawbacks.

Articular cartilage is found on the surface of opposing long bones within the synovial joint and aids to dissipate loads. Adult cartilage lacks the ability to initiate a repair response when injured due to its aneural and avascular nature. Surgical techniques have been developed to enhance this repair process but none to date rival that of natural cartilage. Repair tissue is often of a fibrocartilaginous nature which does not have the biomechanical stability of articular cartilage. Integration between newly synthesised tissue and the endogenous cartilage is invariably poor as well, leading to degeneration of the repair tissue and surrounding cartilage with time. The aim of this study was to develop strategies for the enhancement of integration between new and pre-existing articular cartilage to form a more biomechanically stable repair tissue. The migratory capacities of chondrocytes isolated from young and mature articular cartilage have been investigated using a Boyden chamber system, as well as the effects of different matrix substrates and chemoattractants on this process. Using this system the substrate dependent chemotactic effects of insulin-like growth factor 1 (IGF-1) and transforming growth factor beta 1 (TGFbeta1) were only seen if the cells were seeded onto a fibronectin substrate. The inhibitory effect of chondroitin sulphate (CS) chains on chondrocyte migration was also demonstrated. Further experiments using an in vitro model of cartilage injury confirmed this, as it was demonstrated that chondrocytes migrated into chondroitinase ABC treated cartilage but not into untreated controls. Biosynthesis studies were used to demonstrate the anabolic effects of IGF-1 and TGFpi on chondrocytes. Radiolabelled sulphate and proline were used as a measure of sulphated glycosaminoglycan and collagen biosynthesis respectively. These experiments demonstrated increased biosynthesis of both matrix molecules by chondrocytes from both age groups in response to these growth factors. In addition, these results suggest that the newly synthesised molecules were assembled into an extracellular matrix by the cells. The results from both the migration and biosynthesis experiments demonstrated the potential of IGF-1 and TGFbeta1 for enhancing cartilage repair, but also illustrated the limitations of their short half lives. Constructs encoding the mature peptides of IGF-1 and TGFbeta1 were therefore developed for transfection into chondrocytes. The ability of these transfected cells to migrate was investigated on a chondroitinase ABC treated aggrecan substrate. Here a constant trend of increased migration with the transfected cells was seen when compared to controls. This study demonstrates the ability of chondrocytes from both young and mature articular cartilage to migrate. This is the first study to report this using skeletally mature articular cartilage. In addition, the inhibitory effects of CS chains in chondrocyte migration have been shown using both the Boyden chamber system and an in vitro model of cartilage injury. The over-expression of IGF-1 and TGFbeta1 in articular chondrocytes demonstrated the possibility of increasing both the migration of cells into articular cartilage as well as up- regulating their capacity for matrix biosynthesis, thereby creating an integrated repair tissue improving on current repair strategies.

BACKGROUND: The purpose of this study was firstly to evaluate functional recovery following anterior cruciate ligament (ACL) rupture from acute injury over the course of rehabilitation. Insights from this analysis were then used to integrate movement feedback into rehabilitation to investigate if this resulted in improved functional outcome and participation level following this injury. METHOD: In the initial modelling phase a prospective repeated measures longitudinal design was used to measure functional recovery from acute injury over time of 63 ACL patients and 61 matched controls, using a two dimensional (2D) video based analysis system. Time-distance variables and joint angles for gait, jog, distance hop and run and stop were analysed monthly. A least squares 3rd order polynomial was used to model the functional recovery of ACLD (anterior cruciate ligament deficient) individuals and functional sub-groups. A second exploratory study using a prospective cohort design compared recovery between 115 ACLD individuals randomized into movement feedback (FB) and no feedback (no-FB) rehabilitation. The feedback criterion was based on the movement data from the longitudinal analysis of functional recovery. Independent t-tests were used to evaluate group differences at 5 months post injury. Semi structured interviews evaluated the physiotherapists usage of the feedback and rehabilitation given to the ACLD patients. RESULTS: Functional recovery was found on average to take 3 months for gait and 5 months for hopping. ACLD non-copers were distinguishable at 40 days post injury due to failure of gait variables to recover to within 'normal limits'. In study two 52 ACLD subjects were followed up at 5 months post injury. No statistically significant differences in functional performance between the FB and no-FB groups were found (p&lt;0.05), for any of the movement variables for gait, one legged squat, distance hop or run and stop. Physiotherapists treating the FB group reported difficulties interpreting the movement feedback, incorporating it into rehabilitation due to its timing and identified a perceived learning effect on treatment. DISCUSSION: Functional recovery was successfully modelled and shown to take longer than expected. This has implications for advising patients on recovery times and length of time for attendance at rehabilitation. Further clarification is required but failure of simple gait variables to recover by 40 days post injury could direct ACLD management. If the potential for recovery can be identified early then the appropriate treatment can be given. Incorporating this type of movement feedback into rehabilitation did not result in improved functional outcome or level of participation. Factors related to its application and insufficient patient numbers at follow-up may have weakened the experimental treatment effect and the power of the study. The modelling and exploratory phases of this investigation need to be revisited to identify the most relevant variables for feedback, refine functional cut-off scores, develop methods that allow feedback to be delivered immediately and more focused training for physiotherapists before progress to a randomized control trial can be considered. This study demonstrated that the clinically based video analysis system provided detailed insight at all stages of rehabilitation on the speed, timing and completeness of recovery for functional tasks that are directly relevant to the rehabilitation goals.

Motion capture is increasingly being used to assess the upper limb. The earliest study of the upper limb performed at Cardiff University was an investigative study using retro-reflective markers attached to the skin overlying the bony land marks of the thorax, clavicle, scapula, and humerus. Throughout the course of the current study this initial model and the experimental protocol have been revised. Particular attention was paid to accurate measurement of the kinematics of the scapula. The original model used markers placed directly over the bony land marks of the scapula to track its movement. In this study two alternative methods were assessed: a scapula locator, which is considered the "gold standard" in non invasive scapula tracking, but can only be used during static measurements and an acromion marker cluster, which can be used to assess dynamic movements of the shoulder. It was found that markers attached directly to the skin overlying the scapula bony landmarks can only be used to assess the level of glenohumeral elevation for arm elevations up to 80 during forward flexion. The acromion marker cluster was found to be suitable for tracking the movement of the scapula in most cases, except that it underestimated glenohumeral elevation during forward flexion due to a necessary design constraint. The first two applications of the model assessed the hypothesis that common activities of daily living can be performed without the capacity for full physiological range of motion of the scapulothoracic and glenohumeral articulations. It was found that there is an excess capacity of glenohumeral joint elevation not required for the majority of everyday tasks. However it was also found that there is no excess capacity in lateral rotation of the scapulothoracic articulation. Finally ethical approval was obtained to assess subjects with shoulder pathologies. Subjects were recruited from three different cohorts: mid-shaft clavicle fractures subjects with one or more previous glenohumeral dislocations and subjects with multi-directional instability. It was found that the method was able to distinguish between healthy subjects and patient cohorts, and also potentially between different patient cohorts. This study has served to develop the methods necessary to assess the kinematics of healthy and pathological shoulders and has provided preliminary results on the functionality of three patient cohorts.

The Cardiff Dempster-Shafer (DS) classifier is a generic automated technique for analysing motion analysis (MA) data. It can accurately discriminate between level gait characteristics of non-pathological (NP) and osteoarthritic (OA) knee function. It can also quantify and visualise the functional outcome of a total knee replacement (TKR). A number of studies were undertaken to explore and enhance this method. The training set for the classifier was increased by 48% by collecting additional knee function data for level gait. Knee function for nine new patients was classified pre and post-TKR surgery. At 12 months post-TKR, two patients exhibited non-dominant NP knee function. The remaining patients did not recover NP gait. This finding is similar to previous classifications of level gait. To improve the distinction between varying degrees of knee function, stair gait was introduced into the trial. A staircase was designed and validated. Adduction and flexion moments acting about the knee joint and medial component of the ground reaction force were found to be important in the classification of OA and NP knee function from stair gait. Using a combination of these variables the DS classifier was able to characterise OA and NP function for 15 subjects correctly with 100% accuracy, determined using a leave-one-out method of cross validation. The variables were tested to assess the outcome of TKR surgery. The patient assessed recovered NP stair gait post surgery. An image based study was undertaken to investigate the quality of the MA data used in the DS classifier. A step up/down activity for 5 NP and 5 TKR subjects was recorded using non-simultaneous MA and dynamic fluoroscopy. Accurate knee kinematics were computed from the fluoroscopy images using KneeTrack image registration software. MA measured significantly larger knee joint translations and non-sagittal plane rotations. The largest errors in MA derived kinematics were 9.53 for adduction-abduction range of motion (ROM) measured from the NP cohort and 2.63cm compression-distraction ROM of the tibio-femoral joint, measured from the TKR cohort. The generic nature of the DS classifier was tested by its application to distinguish hip function following a lateral (LA) and posterior (PA) approach to total hip arthroplasty. The use of different variables was investigated with the classifier. The best classifier was able to distinguish between NP and LA function with 96.7% accuracy, LA and NP with 86.2% accuracy and between LA and PA with 81.5% accuracy. The PA approach was found to lead to more characteristic NP hip function than LA. These studies show that variables from stair gait should be included in addition to level gait in the classifier. Due to errors when measuring non-sagittal plane rotations using MA, these should be interpreted with caution. The generic nature of the classifier has been proven by its application to another joint, thus answering another orthopaedic question.

No description available.

Magnetic resonance imaging (MRI) was used to study shape, area, and volume changes of KFP between ankle plantarflexion and neutral positions. Although area in the saggital plane appeared to decrease on average by 10% (SD = 2.4%) between ankle plantarflexion and neutral positions, no obvious volume changes were detected as the area of KFP in the transverse plane increased from ankle plantarflexion to neutral positions by approximately 10.2% (SD = 2.14%), which indicates that KFP is a non-compressible tissue in-vivo. This, in addition to the existence of fibrosis in PW's tip, support hypotheses that PW can assist in load bearing within the AT enthesis organ. AT bends were observed in this study using US scanning, and were typically found when the ankle was flexed passively or actively against low loads (0-1 kg). AT kinds were found typically below the KFP anchorage to AT and only momentarily (max of 0.2s), suggesting KFP can reduce AT kinking during flexion.

A tribological investigation of ceramic on metal hip replacements was carried out using in vitro wear testing methods. Two ceramic materials, pure alumina and an alumina matrix compound (zirconia toughened alumina (ZTA)), were articulated against as-cast CoCrMo alloy cups. The diameter was changed from 38 mm to 60 mm to explore the effect of diameter on the tribological performance. Three distinct wear tests were undertaken to allow a direct comparison between materials and sizes. These were; wear testing using standard loading and motion profiles, microseparation (edge loading) in which the loading and motion profiles were modified to allow medial-lateral and inferior-superior displacement of the head, and third body particle tests which incorporated 0.5 g of <1 μm alumina particle in the lubricant. The Durham Mark I Hip Wear Simulator was used to simulate the standard walking cycle, and was further modified to incorporate microseparation during the swing phase of the walking cycle. All simulator tests were gravimetrically analysed and linear regression analysis was used to determine running in and steady state wear rates. In addition, surface analytical techniques including non contacting profilometery, atomic force, scanning electron and optical microscopy were used to identify changes in surface topography throughout the wear tests. Parameters such as the root mean squared roughness and skewness were monitored to provide quantitative changes in the surface features. The roughness was also used to calculate the ratio of minimum film thickness to equivalent roughness known as the lambda ratio. This provided an theoretical indication of the lubrication regime. Dynamic friction measurements were undertaken on the Durham Friction Simulator, using water based bovine serum based lubricants, which allowed the lubrication mechanism to be identified through the generation of a Stribeck Curve. The results showed low wear rates for all materials and sizes tested, compared with standard metal on polyethylene and metal on metal components. The wear of the ceramic heads was unmeasurable using the gravimetric method, as the volume change of the heads fluctuated with a similar trend and magnitude to the control head which did not experience wear. Wear was detected for the softer metallic cups in all tests. The standard wear test produced the lowest cup wear rates, compared with microseparation and third body tests which showed increased wear rates through extensive abrasive and adhesive wear mechanisms. After microseparation testing, characteristic stripe wear patterns were found on the ceramic heads and a flattened lip on the metallic cups. Metal transfer was also identified, which was thought to be due to impact during dislocation of the head during the swing phase of the walking cycle. Third body tests resulted in significant grain loss from the ceramic components compared with both standard or microseparation testing. Low friction factors were recorded for all ceramic on metal components, generally showing the joints to be working close to full fluid film lubrication during the high load stance phase of the walking cycle.