Made available in DSpace on 2014-06-11T19:28:35Z (GMT). No. of bitstreams: 0 Previous issue date: 2006Bitstream added on 2014-06-13T19:16:38Z : No. of bitstreams: 1 almeida_fd_me_guara.pdf: 1139748 bytes, checksum: 725c9f2e59c64e577a3d7de4c87f51f4 (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Os conseqüentes avanços na medicina esportiva incluem a busca por novos métodos tecnológicos que viabilizam uma melhor e mais eficaz avaliação muscular e articular no corpo humano. Associados a isso, a grande ocorrência de lesões de membros inferiores em especial aquelas da articulação do joelho, faz com que a procura por novos métodos de avaliação seja incentivada. Um recurso valioso consiste num método auxiliar de avaliação das lesões esportivas onde o exame deverá ser realizado através da aplicação de uma resistência constante. Na prática esportiva, há por um lado a importância da proporção do equilíbrio muscular agonista/antagonista, ou seja, do equilíbrio flexor/extensor representado, respectivamente, pelos isquiotibiais/quadríceps da coxa. De outro, a comparação dos valores absolutos da função muscular dos membros inferiores, quer seja para o quadríceps, ou para os isquiotibiais. Resultados alterados podem estar relacionados às lesões esportivas ou suas seqüelas. De interesse para o atleta e para a equipe multidisciplinar é poder dispor de um método de avaliação funcional muscular objetivo e seguro, que forneça dados confiáveis e reprodutíveis. Neste contexto um estudo foi desenvolvido objetivando-se a avaliação dos valores de torque bidirecional (flexão-extensão), potência, tempo e trabalho muscular do joelho quando submetido a uma resistência constante. Para tanto um dispositivo capaz de avaliar esses parâmetros foi desenvolvido no laboratório de biomecânica do Departamento de Mecânica da Unesp de Guaratinguetá, para gerar dados que caracterizem o estado físico e o desempenho dos indivíduos avaliados. Foram utilizados no estudo 19 voluntários do sexo masculino com idade entre 20-30 anos sem histórico de lesão na articulação do joelho, que foram submetidos a exercícios de flexão e extensão com amplitude de movimentos de 90 a 180° durante 40 segundos. / The consequent advances in sports medicine include the search for new technological methods that permit a more efficient evaluation of the musculature and joints of the human body. The search for new methods of evaluation has been stimulated by the increased occurrence of injuries to inferior members and in particular knee articulation. A valuable approach consists of an auxiliary method of evaluation of sportive injuries. This examination is carried out through the application of a constant resistance. In sports practice, the agonist / antagonist muscle balance, that is, the flexor/extensor balance represented, respectively, by the hamstring muscle/quadriceps femuris, plays an important role. On the other hand, the comparison between the absolute values of the inferior members is also relevant. Changed results usually relate to sports lesions or their sequels. The development of an objective and safe method to evaluate muscular functionality will provide for reliable and reproducible results of the utmost importance to athletes and multidisciplinary teams. Therefore, a study was carried out proposing to evaluate values of bi-directional torque (flexion-extension), power, time and muscular effort of the knee when submitted to a constant resistance. To accomplish this, a device capable of evaluating these parameters was developed in the biomechanics laboratory of the Department of Mechanics at UNESP - Guaratinguetá. This device generated data that characterized the physical state and performance of the evaluated individuals. The apparatus was used in the study of 19 male volunteers, 20 - 30 years old without pathological history of joint injuries. These volunteers performed flexion and extension exercises during 40 seconds, with an amplitude of movements from 90 to 180°. From these results, a minimum performance standard was determined that characterized good performance among individuals evaluated by the system.

Pitting and delamination wear of ultra high molecular weight polyethylene (UHMW-PE) tibial plateaux for total joint replacements have habitually been attributed to a fatigue crack growth mechanism associated with a combination of high sub-surface cyclic shear stresses and degradation of the chemistry and structure of UHMW-PE caused by the gamma-irradiation sterilisation standard procedure. However, the exact mechanisms by which cracks initiate and grow in UHMWPE are not known and the relationships between these mechanisms and pitting and delamination are only assumptions based on qualitative observations. A fracture mechanics approach based on the J-integral concept of plane strain crack initiation toughness was therefore applied in order to firstly obtain the fracture toughness and crack growth stability of UHMW-PE and secondly to determine the mechanisms by which pitting and delamination occur in vivo. It was necessary to modify the existing standard ASTM E813-89 for the treatment of experimental J data in order to accommodate for the large crack tip plasticity and pronounced ductile tearing. This modified method was then applied to a detailed investigation of the influence of sterilisation and ageing on the chemical, physical and mechanical properties of UHMW-PE. Simulated shelf and in vivo environments enabling a rapid ageing of UHMW-PE corresponding to 10 years of natural ageing were developed. Sterilisation was either conducted by gamma-irradiation in air or nitrogen, or by gas plasma. In virgin UHMW-PE, cracks propagated by a succession of plastic deformation and craze nucleation over thin layers of material, yielding a very high value of J (90 kJ/m 2 ) at 37 : C. Gammairradiation in air followed by 10 years ageing resulted in a highly brittle material with a crack initiation fracture toughness reduced by 78% and a mechanical behaviour approaching that of a linear elastic material i.e. creation of a "cup-and-cone" in tension and formation of 45" shear lips in threepoint bending. On the other hand, gas plasma sterilised UHMW-PE could not be differentiated from unsterile UHMW-PE in either its physical nor mechanical properties. Qualitative correlations existed between the presence and location of highly oxidised regions and the crack initiation fracture toughness of the material. Quantitatively, the J-initiation toughness exhibited a hyperbolic decrease with increasing density and oxidation index while the tensile secant modulus linearly increased with density. From these empirical relationships, a model was created which described the variation of the fracture toughness with depth within a UHMW-PE sample. This model indicated that the zones of high density, oxidation and crystallinity correspond to the areas of maximum shear stress and minimum fracture toughness and that the propensity of UHMW-PE to suffer pitting, delamination and high wear rates through a fracture mechanism is significantly increased by extensive oxidative degradation.

Anterior cruciate ligaments (ACL) are among the most common reported ligament injuries in athletes. This injury has been linked to changes in joint stability, neuromuscular activity and contact mechanics. In vitro simulators have proven to provide valuable insights on the potential effects of muscle activity on joint stability. The University of Ottawa Knee Simulate (UOKS) is a mechanical load driven quasi-static apparatus that provides the framework to explore pressure changes in knee compartments and the resultant kinematics in response to six individual muscle loads applied around an unconstrained joint. The main objective of the present work was to develop an automated loading mechanism for the UOKS. Furthermore, the secondary objective was to evaluate the accuracy, precision, reliability and validity of the newly automated system. Six transmission units were designed, built and tested as part of the development of the automated mechanism adapted to the UOKS. Load cells were used to obtain real time feedback of the load created by the transmission units. A software controller was programmed using LABVIEW to control these transmissions as a graphic user interface (GUI). Each transmission was tested independently and compared to an external master load cell. Furthermore, four cadaveric knee joints were mounted and suspended inside the UOKS for experimentation. Seven different loading conditions were tested with the ACL intact and after the ACL was severed. Pressure and kinematic data were recorded to correlate the changes in these variables due to changes in loading conditions simulated by the UOKS. The controlled loading experiment of the automated mechanism showed the accuracy of the controller to be within +/-1N, and multiple trials showed the system’s capability to produce loads. Additionally, the results showed the controller to have an ICC of 0.99 between the load produced and the target load. The comparison between feedback load cells and the master load cell displayed unique results regarding each transmission and the loads being applied. The results showed overestimations and underestimations with unique load difference trends for each transmission. Nevertheless, the relative difference measured by the master load cell was below 10% in all the transmissions. This study demonstrated that the controller was accurate and reliable when producing loads. On the other hand, the results of the integration analysis showed the presence of losses in the system when transmitting the loads from the actuators to the front of the UOKS. These losses were different for each transmission, likely due to the independence of each pulley system. Nevertheless, the automated loading mechanism proved to be a valid replacement for the original static loading mechanism previously used by the UOKS and is capable of reliably simulating six independent loading conditions.

Introduction: Understanding the relationship between muscle loads crossing the knee joint and knee joint mechanics is critical for understanding knee stability and the effects of altered muscle forces on healthy and ACL injured knees. In vitro measurement can be used to elucidate this if the simulation is biofidelic, allowing the physiological levels of applied loads to dictate the tibiofemoral kinematics in all degrees of freedom (DoF). The objectives of this study were to describe and apply the University of Ottawa knee simulator as well as measure the reliability of the device. In addition, this device was used to quantify the effect of muscle loads and anterior cruciate ligament (ACL) resection on contact mechanics and kinematics of the tibiofemoral joint. Methods: Muscle forces were determined from an electromyography-driven musculoskeletal model of a healthy male during gait. Six knee specimens were loaded into the simulator and subjected to 100%, 75% and 50% in vivo muscle forces applied through the 6 simulated muscles, in addition to a quadriceps weakness and a hamstring weakness condition. Tibiofemoral mechanics were measured with all 5 loading conditions before and after ACL transection. Results: With the ACL intact, very high reliability in contact area and pressures among loading conditions were observed as the intra-class correlation coefficients (ICC) ranged from 0.932 to 0.99. After ACL transection, reliability remained very high as ICCs ranged from 0.926 to 0.99. In all simulated conditions, muscle forces maintained the knee joint in a stable position resulting in minimal kinematic differences, but altered contact mechanics in both the ACL and non-ACL condition. Removal of the ACL significantly reduced both the medial and lateral contact areas in all loading conditions compared to the ACL intact condition. Conclusion: In summary, the UOKS has demonstrated high reliability within repeated measures. Additionally, small, normally undetectable alterations in joint kinematics resulted in significant alterations to contact mechanics, which can be linked to the degenerative process.

As the number of total knee arthroplasty (TKA) procedures increases annually, the patient demographic is shifting to include younger patients with higher expectations for post-operative function. The aim of this study was to compare movement patterns during activities of daily living among TKA patients and a healthy, age-matched group using 3D motion analysis. Specifically, this analysis looked at walking on level and inclined surfaces, as well as sitting up and down from a chair. It was predicted that (1) TKA patients would exhibit reduced knee extension moments at the operated limb and increased adduction moments at the contralateral limb during gait, (2) walking downhill would result in greater differences between TKA and control groups, compared to level walking, and (3) TKA participants would have greater flexion angles, moments and power values at the hip, compared to controls, during the sit-stand tasks. Seventeen participants (age=62±6 years, BMI=30±3 kg/m2, time after surgery=11±5 months) were recruited from the Ottawa Hospital, having undergone unilateral TKA by the same surgeon. An age-matched control group was composed of 17 individuals (age=63±8 years, BMI=27±4 kg/m2) who were recruited from the local community. Three dimensional (3D) biomechanical assessment was conducted with all participants performing five trials of walking on level and inclined surfaces, stair ascent and descent as well as sit-stand tasks. Results from this study were focused on gait and sit-stand transitions, showing that TKA participants exhibited altered gait patterns on both walking surfaces, with significantly smaller knee flexion angles and moments, as well as reduced peak power at the knee. The TKA group also experienced reduced knee extension moments; however, this was only significant for downhill walking. Consistent with our hypothesis, downhill walking resulted in greater discrepancies between the groups compared to level walking. Contrary to our third hypothesis, TKA participants exhibited significantly smaller peak hip flexion angles and moments during the sit-stand task, along with reduced hip abduction angles and knee abduction moments. The reduced knee flexion kinematics and kinetics observed during gait tasks, combined with the differences in frontal plane mechanics observed during the sit-stand task suggest that altered loading patterns persist six to twelve months after surgery. This may be a result of continued pre-operative movement patterns as well as the surgery itself, and should be kept in mind when developing rehabilitation programs for this patient population.

A number of investigators have determined the joint forces acting at the hip and knee for normal human locomotion as related to the design of prosthetic devices. This research has been extended to allow the calculation or estimation of the muscular and ligamentous forces operating at the knee joint for normal walking. The current study expanded upon the past research to evaluate the magnitude and temporal sequence of.the muscle, ligament and articular forces acting at the knee joint for a simulated skating thrust. A skilled ice hockey player was filmed in two reference planes while making a skating thrust from a laboratory force platform. The cine film data was synchronized with the force plate output to allow calculation of the orthogonal forces and moments imposed on the knee joint. The orthogonal force system was determined from a knowledge of the inertial, gravitational and reaction forces acting on the lower limb during the skating thrust. The muscle, ligament and joint forces were determined from equations derived from the conditions of joint equilibrium. The equations of equilibrium were indeterminate and had to be reduced by making assumptions from electromyographic records to allow solution. Forces were calculated for a simplified muscle and ligament system which included the hamstrings, quadriceps and gastrocnemius muscle groups, the collateral ligaments and the cruciate ligaments of the knee joint. In addition, the articular joint force, joint torque and centre of pressure of the joint force were determined. Results of the investigation revealed that the magnitude of the muscle, ligament and joint forces developed in a skating thrust were considerably greater than respective forces exerted during level walking while the temporal sequence of the skating forces was comparable to walking upstairs. The quadriceps muscle group exerted the greatest contractile force while the gastrocnemius and hamstrings groups developed much smaller forces. The largest ligament forces were developed in the collateral ligaments and the posterior cruciate ligament to maintain stability of the joint. The knee joint is subject to the combined effects of a joint force six times body weight and a large joint torque superimposed upon each other during the skating thrust and this fact is considered important when discussing the cause of menisci knee injuries. / Education, Faculty of / Curriculum and Pedagogy (EDCP), Department of / Graduate

Studies have shown that the alignment of the knee in the coronal plane has a significant effect on the joint contact stress. However, gait analysis demonstrated that factors other than alignment contributed significantly to the outcome of corrective surgery. It was therefore hypothesized that muscle contraction can alter the stress distribution within the knee joint and that overloading can occur in the absence of a deformity. Six normal knees were harvested from different donors. The exact orientation of all muscle groups was recorded and their tendinous insertions carefully preserved. Custom built pressure transducers (6 per compartment, 0.5 mm thick, 10 mm diameter) were inserted through 2 small, posterior, capsular incisions and placed on the tibial surface and the menisci. The knees were mounted in a loading system which allowed free self-alignment of the joint under load. All muscles were replaced by wire cables instrumented with force transducer, tensioner and grip. Several alignment models (5, 10 degree varus, neutral, 5 degree valgus and 15 degree of flexion) as well as the effect of contraction of all major muscles crossing the knee joint were tested. An even pressure distribution was seen in neutral alignment. In a varus deformity the peak pressure shifted medially and laterally in valgus. Unloading of the opposite compartment was seen for deformities as small as 5 degrees. A flexion deformity produced a postero-lateral shift of the peak pressure area. Muscle contraction increased the pressure significantly in a region next to the muscle. Generally, unloading - though less significant - was seen in a region diagonally across the joint. These results suggest that muscular hyperactivity may considerable increase the contact stresses. However, muscle weakness or lack of muscular contraction may indirectly play a significant role in affecting the contact pressure distribution. If the muscle force is insufficient to counterbalance the external moment condylar lift-off occurs. This increases the angulation between femur and tibia thereby overloading the compartment where contact takes place; One can therefore conclude that abnormal gait patterns or neuromuscular control mechanisms may result in unphysiologically high contact stresses which may cause the development of unicompartmental osteoarthritis and subsequently, a deformity.

A research report submitted to the Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, in partial fulfilment of the requirements for the degree of Master of Medicine Johannesburg, 2018. / The knee is indispensable in everyday life and injuries to it can be debilitating with significant loss of earnings incurred. Clinical diagnosis may not always be made with certainty and Magnetic Resonance Imaging (MRI) helps further elucidate intra-articular injuries. MRI reporting has its shortcomings and may provide spurious results according to the interpretor’s level of experience. This study aims to test the diagnostic reliability of MRI done in a teaching hospital for the evaluation of anterior cruciate ligament and meniscal injuries using arthroscopy as the baseline for comparison. Due to the long waiting times to have surgery we also determined if there was a change in the reliability of an MRI result as time elapsed. A retrospective review of records of patients who had knee arthroscopies at Chris Hani Baragwanath Academic Hospital (Johannesburg, South Africa) from May 2009 to May 2015 was done. Adults (16 − 60 years) with one major episode of trauma to the knee and had MRI done prior to surgery at the above institution were included. Arthroscopy was performed by 2 senior surgeons or by residents under their direct supervision. Arthroscopic findings of anterior cruciate ligament (ACL) and medial (MM) or lateral meniscal (LM) injuries were compared to MRI findings. Data was analysed by STATA version 13.1 to determine injury demographics, sensitivity, specificity and diagnostic accuracy of MRI. The effect of time interval from MRI to surgery on the diagnostic accuracy was determined. A total of 72 patients (74 knees) qualified for review. The median age was 35 years (IQR 26 − 43) with a significant difference between males and females (28 vs 41 years, p = 0.0019). Leading causes of injury were traffic accidents (32.4%), falls (27.0%) and sports injuries (17.6%). Median interval from MRI to surgery was 71.5 days (IQR 29 − 143). The sensitivity of MRI for ACL, MM and LM injuries was (63.6%, 58.8% and 52.6%), specificity (92.7%, 86.0% and 80.0%) and diagnostic accuracy (79.7%, 79.7% and 73.0%) respectively. The patients were divided into subgroups of early (< 6 weeks), intermediate (6 − 16 weeks) and late intervention (> 16 weeks) post-MRI. There were marked differences in the diagnostic accuracy in the three groups for the ACL (70.8% vs 92.6% vs 73.9%) and LM (62.5% vs 81.5% vs 73.9%). This was unremarkable for the MM (75.0% vs 81.5% vs 82.6%). MRI findings correlate well with arthroscopic findings making it a reliable preoperative screening tool for ACL and meniscal injuries. However its diagnostic accuracy appears to change with time. It is apparent that the diagnostic accuracy is higher between 6 − 16 weeks post MRI. A bigger cohort would help determine an ideal waiting time interval without significant depreciation in diagnostic accuracy. / LG2018

The annual incidence of knee replacement (KR) procedures in the United States is predicted to reach over 3.5 million by the year 2030. KR is the current definitive treatment for debilitating knee osteoarthritis (KOA). There has yet to be substantial research regarding the impact of KR on participation in community activities and quality of life. The hypotheses evaluated in this dissertation were that persons following KR will have 1) faster gait speed and 2) lower risk of participation restrictions than persons without KR; and 3) a decreased risk of all-cause mortality compared to persons without KR. To address the first two hypotheses, we collected data from subjects with KOA from the Multicenter Osteoarthritis Study and the Osteoarthritis Initiative, large cohorts of older adults with or at risk of KOA at the time of enrollment. In the first study, KR did not have an effect on gait speed overall and among most subgroups, however subjects with a slow gait speed prior to KR did have an 80% increased risk (RR 1.8, 95% CI 1.1, 3.0) of having a healthy gait speed compared with non-KR subjects. In the second study, KR was associated with a small decreased risk of having participation restriction (RR 0.82, 95% CI 0.67, 0.99). The third study used data on patients with KOA from the Clinical Practice Research Datalink, a database of clinical information on > 8 million people throughout the United Kingdom. There was a decrease in the death rate among KOA subjects who had a KR compared to those who did not, and the hazard of death was reduced by over one half in the first five years after the procedure (HR 0.46 (95% CI 0.43, 0.51). For most subjects, this benefit did not extend longer than five years, and patients least likely to have KR (due to clinical and medical presentation) showed an increased hazard of death compared to the non-KR subjects. In conclusion, the results of this dissertation support the hypotheses that KR confers a positive benefit to activity and participation related pursuits which may extend to survival in the short term for some people.

Varus knee thrust is an abnormal frontal-plane movement (i.e., an out-bowing) of the knee that occurs during the weight-acceptance phase of gait. Varus thrust is of clinical interest, as it is a potentially-modifiable biomechanical risk factor for knee osteoarthritis (OA) progression and has been associated with knee pain. The overall aim of this dissertation is to identify the structural and symptomatic consequences of varus thrust at the knee and along the lower limb, and the possible anatomical and sensorimotor causes of varus thrust in older adults with or at risk for OA. Varus thrust was assessed in Multicenter Osteoarthritis (MOST) Study participants using high-speed videos of self-paced walking. Varus thrust was observed in 31.3% of 3730 knees. We investigated the longitudinal relation of varus thrust to MRI lesions and found that thrust was associated with increased odds of incident and worsening bone marrow lesions and worsening cartilage loss. We then investigated the longitudinal association of varus thrust with WOMAC knee pain and found that thrust was associated with increased odds of incident and worsening total WOMAC knee pain and worsening pain during weight-bearing and non-weight bearing activities. In an ancillary quantitative gait analysis of a single subject with unilateral varus thrust, we found altered joint moments at the hip, knee, and ankle in the thrust limb compared to the non-thrust limb. We bolstered this pilot data with an investigation of low back and lower extremity pain in the presence of thrust in MOST participants: limbs with thrust had increased odds of incident frequent pain proximal (hip or low back) and distal (ankle and foot) to the knee compared to limbs without thrust. Finally, we investigated the cross-sectional relation of anatomical and sensorimotor impairments at the knee and lower extremity to the prevalence of varus thrust. Thrust was most prevalent in limbs with static varus malalignment and supinated feet during gait, while increasing static knee laxity had a protective effect against thrust. These results fill substantial gaps in the narrative regarding the role of varus thrust in OA development.