The purpose of this study was to examine the relationship between leg dominance and knee mechanics to provide further information about the etiology of ACL injury. Sixteen healthy females between the ages of 18 and 22 who were NCAA Division I varsity soccer players participated in this study. Subjects were instructed to perform a cutting maneuver; where they sprinted full speed and then performed an evasive maneuver (planting on one leg and pushing off to the other leg in a new direction) at a 45° angle with their dominate leg (DL) and non-dominate leg (NDL). Subjects were required to perform five successful cuts on each side given in a random order. Bilateral kinematic and kinetic data were collected during the cutting trials. After the cutting trials, subjects performed bilateral isometric and isokinetic testing using a Cybex Norm dynamometer at a speed of 60°/sec to evaluate knee muscle strength. During the braking phase the NDL showed greater (P=0.003) power absorption, greater (P=0.01) peak internal rotation angle and greater (P=0.005) peak flexion velocity. During the propulsive phase the DL showed greater (P=0.01) power production, greater (P=0.038) peak internal adductor moment and greater (P=0.02) peak extension velocity. In addition, no differences (P>0.05) in knee extensor and flexor isometric and isokinetic torques between the two limbs were shown. The results of this study show that a difference in knee mechanics during cutting does exist between the DL and NDL. The findings of this study will increase the knowledge base of ACL injury in females and aid in the design of more appropriate neuromuscular, plyometric and strength training protocols for injury prevention. / School of Physical Education, Sport, and Exercise Science

Conventional anterior cruciate ligament (ACL) reconstruction grafts have not been able to replicate the mechanical behaviour of the native ACL, reproduce normal knee mechanics and kinematics, or prevent degenerative disease progression of the knee. The aim of this thesis was to investigate a novel ACL design to more closely mimic the normal mechanical behaviour of the ACL, reconstruct the isometric ACL fibre and potentially reproduce the normal kinematics and mechanics of the knee. The designed artificial ACL reconstruction (ACLR) system could be used as a stand-alone device or in conjunction with a total knee replacement (TKR). The nominated design option for the ACLR system consisted of a connecting cord made of ultra-high molecular weight polyethylene (UHMWPE) fibres and an elastic system made of cobalt-chrome-molybdenum (CoCrMo) alloy with similar load-elongation characteristics to the native ACL. The design requirements were defined based on the mechanical properties of the native ACL, size constraints from the bony geometry and TKR components, and the location of the isometric fibres of the native ACL. The in vitro mechanical tests performed in this project on the designed cord showed a 2-3 times greater ultimate tensile load compared to the ACL in young human cadavers. The decreasing creep modulus of the UHMWPE cord under fatigue loading in simulated body conditions (3118 MPa at 6.5×10⁶ cycle) indicated nominal creep and stabilised mechanical properties by the 3000^th loading cycle. To replicate the non-linear stiffness of the ACL with ~38 N mm^-1 toe and ~100 N mm^-1 linear regions, the artificial ACLR device consisted of a femoral spring (~60 N mm^-1) in series with a tibial spring (~100 N mm^-1) and a connecting cord (~2000 N mm^-1). Two helical springs in series were used for the stand-alone ACLR, whereas a helical spring in series with a spiral spring was designed for the ACLR-TKR. As both the helical and spiral springs had a constant stiffness, stop mechanisms were added to the springs to create a non-linear stiffness and control the maximum safe deformation limit of each spring. To understand the mechanical behaviour of the reconstructed isometric fibre of the ACL, passive and loaded motions were simulated in 18 sets of segmented MRI models of healthy human knees. Constant load and elongation was observed throughout flexion during the passive movements, whereas maximal load and elongation in the reconstructed ACL was identified at 50 º of flexion during loaded motion. An ACL attachment placement sensitivity study, conducted in this project to assess the effect of surgical implantation error on the behaviour of the reconstructed ACL, revealed that misplacement of the femoral attachment would significantly influence the load-elongation of the reconstructed ACL. Finite element (FE) models of the designed ACLR devices enabled their behaviour under simulated axial loading, squatting and the Lachman test to be assessed. Both ACLR devices successfully reproduced stiffness of the native ACL with a multi-linear stiffness curve, however, elongation greater than 3.1 mm could not be achieved. It can be concluded that the designed artificial ACLR devices were able to mimic the mechanical behaviour of the ACL provided it was positioned at the isometric attachment points; potentially enabling achievement of more natural kinematics and mechanics of the reconstructed knee. However, ACL placement was shown to have a significant impact on the behaviour of the reconstructed ACL, therefore, placement error may over-constrain the joint. For this reason, a more forgiving design with a lower stiffness and a larger deformation limit would be advised.

Title: The Effect of Taping on Postural Stability in Patients with Anterior Cruciate Ligament Reconstruction on Posturomed Platform after Rehabilitation using Postural Therapy Aim: Objective evaluation of the effects of kinesiotaping and functional taping on postural stabilization during standing on one foot in patients after anterior cruciate ligament reconstruction on the defined unstable Posturomed platform. Methods: The thesis is based on analytical-comparative study. The subjects of the study were patients after ACL reconstruction, who have done fifteen rehabilitation sessions which included postural therapy. The patients were subjected to a "3-step stand on one foot" test to standardize measurement. Three kinds of measurement were applied: without taping, kinesiotaping, and rigid-functional taping taped bilaterally above the m. vastus medialis. Results: The measurements on the Posturomed suggest that the ability of postural stabilization differs on each lower limb in patients after an ACL reconstruction. The application of taping had an effect in the majority of cases, although it was a negative effect on postural stabilization in most kinesiotaped measurements compared to un-taped measurements. The functional taping, on the other hand, had mostly positive reactions unlike with the...

Title: Impact evaluation of a anterior cruciate ligament rupture on postural stabilization by a method postural somatooscillography before and after the reconstruction surgery Objective: Compare measured postural stability values by postural somatooscillography which will be carried out before planned ACL reconstruction surgery rupture, early after the surgery and in a longer time period after rehabilitation. Methods: This thesis has been created as a pilot study using a descriptive and associative form. Research part focuses on measurements done on the Posturomed surface during postural provocation test. Platform movement has been recorded by accelerometer and transferred into Microswing diagnostic system and evaluated using the Postural somatooscillography Posturomed Commander application. Results: After reconstruction surgery is the ability of postural stabilization better than before surgery. Postural stabilization has been improving within the group of probands during all measurements. However, the ability of long-term stabilization is at very low level in comparison to healthy subjects. Postural stabilization of uninjured limb is better than stabilization of injured limb in all research stages. Key words: anterior cruciate ligament, injury, postural stabilization, Posturomed

O ser humano desenvolve uma série de atividades motoras bilaterais que, aparentemente, deveriam ser simétricas, tais como o salto, o agachamento e o caminhar. Porém, quando um dos membros inferiores sofre um acometimento estrutural, estas tarefas passam a ser realizadas de forma assimétrica. Quando uma assimetria está presente mesmo após um período de reabilitação, devida atenção deve ser tomada, pois, provavelmente, o membro acometido ainda apresenta algum déficit e o membro contralateral está sendo sobrecarregado. Um exemplo disso é a lesão do Ligamento Cruzado Anterior (LCA) que, mesmo após o período total de reabilitação, os sujeitos podem apresentar déficits no membro operado. A pesar da grande quantidade de trabalhos relacionados à lesão e à reconstrução do LCA, poucos analisam a simetria do movimento entre os membros inferiores durante a realização de tarefas bipedais. Sendo assim, o objetivo do presente estudo foi analisar a simetria entre os membros inferiores desses sujeitos, durante a realização das seguintes tarefas: agachamento bipedal com e sem carga e salto bipedal com contramovimento. A amostra foi composta por 34 indivíduos, divididos em dois grupos: 17 sujeitos do grupo LCA (todos submetidos à reconstrução do LCA, tendo como enxerto os tendões flexores e com mais de um ano de cirurgia) e 17 indivíduos do grupo controle (sem qualquer afecção nos membros inferiores). Para coleta dos dados foi utilizado um sistema de análise cinemática 3D, composto por seis câmeras de emissão de sinais infra-vermelhos, além de um sistema de análise cinética, composto por duas plataformas de força. Pôde-se observar que, durante o 6 agachamento sem carga, não foram detectadas assimetrias. Já no agachamento com carga, observou-se que os sujeitos do grupo LCA são mais assimétricos nas variáveis: potência articular do joelho e razão entre os momentos de quadril e joelho. Na realização do salto, além dessas assimetrias, o grupo LCA apresentou déficits nos seu membro operado, em relação ao membro contralateral, nas seguintes variáveis: potência mecânica, potência articular do joelho e razão entre os momentos de quadril e joelho. Os resultados do presente estudo mostram que os sujeitos submetidos à reconstrução do LCA, mesmo após um ano de pós-operatório, e mesmo após o retorno à prática esportiva, ainda apresentam assimetrias entre seus membros inferiores. Sugere-se a revisão dos protocolos de reabilitação, tendo em vista que a presença dessas assimetrias pode predispor esses sujeitos à lesão do membro contralateral, assim como de casos de recidiva. Os protocolos atuais enfatizam a realização de exercícios bipedais em cadeia fechada os quais possibilitam alguns padrões de compensação, enquanto que exercícios unipedais em cadeia aberta isolam mais o grupo muscular a ser exercitado. / Human beings develop various bilateral motor activities that should supposedly be symmetrical, for example; jumping, squatting and walking. However, when one of the lower limb suffers from a structural injury, these tasks are then performed asymmetrically. When asymmetry is present, even after a rehabilitation period special attention must be paid to it, because the injured limb may still present some deficits and the contralateral limb may be overloaded. An example of this is the Anterior Cruciate Ligament (ACL) injury. The patient can present deficits in the operated limb even after the rehabilitation period has been completed. In spite of the vast amount of studies related to ACL injuries and reconstruction, only few of them analyze the symmetry of the movement between the lower limbs during the execution of bipedal tasks. Therefore, the objective of this study was to analyze the symmetry between the lower limbs of these patients, during the accomplishment of the following tasks: bipedal squat with and without load and bipedal jump with countermovement. The analysis was based on 34 people, divided in two groups: 17 patients in ACL group (all admitted for ACL reconstruction, having the flexor tendons as graft and more than a year after the surgery) and 17 people in the control group (without any lesion in the lower limbs). For data collection, a 3D-kinematics analysis system was used, composed of six cameras with an infrared signal emission, also in addition to a kinetic analysis system composed of two force plates. It was possible to observe that asymmetries were not detected during the squat without a load. However, in the squat with a load, it was observed that the ACL group were more asymmetrical in the 8 following variables: knee power and ratio between hip and knee moments. During jumping, beyond these asymmetries, deficits were observed in the operated limbs of the ACL group, in relation to the contralateral limb, in the following variables: mechanical power, knee power and ratio between hip and knee moments. The results of this study show that the patients admitted for ACL reconstruction, even after one year of postoperative treatment and returning to practical sports, still present lower limb asymmetries. It is suggested to review the rehabilitation protocols considering that the presence of these asymmetries can predispose these people to contralateral limb injuries, as well as cases of reinjury. The current protocols emphasize the accomplishment of closed chain bipedal exercises which make some compensations possible, whereas unipedal open chain exercises isolate the muscular group to be exercised.

Exercícios em cadeia cinética aberta e fechada tem sido propostos para a reabilitação no pós operatório de reconstrução do ligamento cruzado anterior. Não há consenso na literatura sobre qual o tipo de exercício é mais apropriado e ao mesmo tempo seguro, não pondo em risco o procedimento cirúrgico. O propósito deste estudo foi verificar os efeitos da utilização de protocolos de reabilitação em cadeia cinética aberta e fechada de indivíduos em pós operatório de reconstrução do ligamento cruzado anterior, através de respostas comportamentais verificadas por indicadores biomecânicos. A amostra experimental foi constituída de trinta indivíduos, divididos em três grupos amostrais independentes: (CON) dez indivíduos normais que não sofreram nenhum tipo de intervenção; (CCF) dez pacientes submetidos ao programa de reabilitação em cadeia cinética fechada e (CCA) dez pacientes submetidos ao programa de reabilitação em cadeia cinética aberta. Os testes para avaliar os parâmetros biomecânicos selecionados foram realizados em duas etapas: avaliação clínica (deslocamento tibial anterior e escore de Lysholm) e avaliação da marcha (análise dinâmica, cinemática e eletromiográfica). O tratamento foi realizados três vezes por semana, durante doze semanas. Os pacientes foram submetidos a três testes; o primeiro no pré-operatório; o segundo após quatro semanas da cirurgia e o terceiro após quatro meses de cirurgia. O grupo controle realizou apenas um teste e não foi submetido a nenhum tipo de tratamento. Para a xx análise do deslocamento tibial anterior foi utilizado o aparelho KT1000. A análise da marcha foi realizada através da esteira rolante Gaitway Kistler, a análise da atividade eletromiográfica através do sistema Bagnoli 8, composta de eletrodos de superfície e a análise da variação angular do joelho através do eletrogoniômetro Elgon-Burns. Os dados foram registrados, armazenados, processados e analisados estatisticamente, levando-se em consideração o nível de significância de 0,05. As variáveis relativas à força de reação do solo foram analisadas através da determinação de componentes principais. O deslocamento tibial anterior diminuiu ao final do tratamento e o escore de Lysholm aumentou em ambos os grupos, sem diferença significativa entre eles. Das variáveis analisadas relativas à marcha o tempo de apoio simples, as taxas de crescimento para os picos da força vertical, a deflexão da força mínima, a força mínima e o segundo pico parecem-nos serem as variáveis mais sensíveis para identificar diferenças na forma de andar em função do protocolo de reabilitação. Ao analisar a amplitude de movimento percebe-se que esta variável é sensível a mudanças expressivas na variação angular do joelho, como ocorreram no teste após quatro semanas de pós-operatório. Pela análise descritiva, diferenças angulares menores devem ser analisadas através dos ângulos em momentos específicos da marcha. Em relação à atividade elétrica muscular o M.bíceps femoral foi o que apresentou maior variação na sua atividade. E os valores de simetria demonstram que o grupo cadeia cinética aberta foi o que apresentou maiores diferenças entre as pernas no teste após quatro semanas de cirurgia, o que demonstra maior instabilidade no andar. O presente estudo permite concluir que as alterações da marcha são mais expressivas um mês após a cirurgia do que no período pré-operatório. O escore de Lysholm, os componentes principais das variáveis relativas a força de reação do solo e a variação angular do joelho indicam que os exercícios em cadeia cinética fechada são mais eficientes para a recuperação da marcha do que os de cadeia cinética aberta. No entanto, os dois tipos de exercícios propiciam melhora dos parâmetros da marcha e parecem ser eficientes na recuperação da marcha dos pacientes submetidos à reconstrução do ligamento cruzado anterior. O período de quatro meses de reabilitação assegura uma marcha sem riscos para o paciente, mas ainda distinta da característica da marcha de indivíduos não acometidos pela lesão / Open kinetic chain and closed kinetic chain exercises have been proposed for rehabilitation protocol in the reconstruction of the anterior cruciate ligament. There is no consensus in the literature regarding which exercise is more appropriate and at the same time safe without putting in risk the surgical procedure. The purpose of this study was to evaluate the results of the open kinetic chain and closed kinetic chain protocols in the rehabilitation of those individuals that were subject to the reconstruction of the anterior cruciate ligament based on biomechanical indicatives. The sample was made of thirty individuals, divided in three independent groups: (CON) ten normal individuals that were not submitted to the surgical intervention; (CCF) ten patients submitted to the closed kinetic chain rehabilitation program, and (CCA) ten patients submitted to the open kinetic chain rehabilitation program. Tests to evaluate the desired biomechanical parameters had been carried out through two stages: clinical evaluation (anterior tibial displacement and Lysholm`s score) as well as gait evaluation (dynamic, kinematic and electromyografic analysis). The treatment was carried out three times per week, during twelve weeks. Each patient had been evaluated in three occasions: before the surgery; four weeks after the surgery; and four months after the surgery. The group control was submitted to only one evaluation test and no treatment at all. KT1000 equipament was used for evaluating the tibial displacement. The gait analysis was carried out through the Gaitway Kistler treadmill; the electromyography analysis was evaluated through xxii the System Bagnoli 8 composed of surface electrodes and the analysis of the angular variation of the knee through Elgon-Burns electrogoniometer. Data had been collected and analyzed considering the 0,05 significance level. The ground reaction force variable had been analyzed through of the determination of main components. The anterior tibial displacement diminished at the end of the treatment and the Lysholm`s score increased in both groups without significant difference between them. From the analyzed variables regarding gait, the time of simple support, the taxes of growth for peaks of the vertical force, the deflection of the minimum force, the minimum force and as the peak, seem to be the most sensible variables to identify gait differences due to the rehabilitation protocol. Upon analyzing the amplitude of movement it was noticed that this variable was sensible to huge changes in the angular variation, as those observed after four weeks from the surgery. By the descriptive analysis, lesser angular differences must be analyzed through the angles at specific moments of the gait. Regarding the muscular activity the femoral biceps femoris (long head) presented greater variation in its activity. And, the symmetry values demonstrate that the open kinetic chain group presented greater differences between both legs in the test four weeks after the surgery, demonstrating greater instability in walking. The current study permit to conclude that the variations in the gait are higher in one month after the surgery than in the pre-surgery period. The Lysholm`s score, the ground reaction force, variable the main components and the angular variation of the knee indicates that the exercises in closed kinetic chain are more efficient than opened kinetic chain for recovering the gait. However, the two exercises improved the parameters of gait and seem to be efficient in recovering the gait pattern of patients submitted to the anterior cruciate ligament reconstruction. Although the four months period of rehabilitation is enough to reinstate a harmless gait pattern to patients, it is still not sufficient to return the patients` gait standards to those of individuals without injury

Li Chi Kei. / Thesis (M.Phil.)--Chinese University of Hong Kong,1995. / Includes bibliogrpahical references (leaves 54-68). / Abstract --- p.1 / Acknowledgments --- p.4 / Lists of Figures --- p.5 / List of Tables --- p.8 / Chapter Chapter 1 --- Introduction --- p.9 / Chapter 1.1 --- Ligamental Injury --- p.9 / Chapter 1.2 --- ACL Injury --- p.10 / Chapter 1.3 --- Patellar Tendon and Anterior Cruciate Ligament --- p.11 / Chapter 1.4 --- Patellar Tendon Bone Graft --- p.13 / Chapter 1.41 --- Strength of the Patellar Tendon Bone Graft --- p.13 / Chapter 1.42 --- Use of the Patellar Tendon Bone Graft --- p.14 / Chapter 1.5 --- Patellar Tendon Bone Graft in Anterior Cruciate Ligament Reconstruction --- p.14 / Chapter 1.6 --- Complications of Anterior Cruciate Ligament Reconstruction after the Use of Patellar Tendon Bone Graft --- p.16 / Chapter 1.7 --- Healing of the Patellar Tendon Donor Site --- p.17 / Chapter 1.8 --- Objective of the Study --- p.22 / Chapter 1.9 --- Significance of the Study --- p.22 / Chapter Chapter 2 --- Material & Method --- p.24 / Chapter 2.1 --- Animal Model --- p.24 / Chapter 2.2 --- Grouping --- p.24 / Chapter 2.3 --- Operative Procedure --- p.24 / Chapter 2.4 --- Method of Assessment --- p.26 / Chapter 2.41 --- Gross Morphology --- p.26 / Chapter 2.42 --- Biomechanical Testing --- p.27 / Chapter 2.43 --- Biochemical Assay --- p.28 / Chapter 2.43.1 --- Water Content --- p.29 / Chapter 2.43.2 --- Collagen Content --- p.29 / Chapter 2.44 --- Histology --- p.30 / Chapter 2.45 --- Immunohistochemistry --- p.31 / Chapter 2.5 --- Statistics --- p.32 / Chapter Chapter 3 --- Results --- p.33 / Chapter 3.1 --- Operation Complications --- p.33 / Chapter 3.2 --- Gross Morphology --- p.33 / Chapter 3.21 --- Dimension of the Patellar Tendon --- p.33 / Chapter 3.22 --- Dimension of the Patellar Tendon Bone Graft --- p.33 / Chapter 3.23 --- Dimension of the Remain Patellar Tendon --- p.34 / Chapter 3.24 --- Gross Appearance of the Patellar Tendon Donor Site --- p.35 / Chapter 3.3 --- Biomechanical Testing --- p.36 / Chapter 3.31 --- Failure Load --- p.36 / Chapter 3.32 --- Ultimate Stress --- p.37 / Chapter 3.33 --- Stiffness --- p.37 / Chapter 3.34 --- Energy Absorbed before Failure --- p.38 / Chapter 3.4 --- Biochemical Assay --- p.38 / Chapter 3.41 --- Water Content --- p.38 / Chapter 3.42 --- Collagen Content --- p.39 / Chapter 3 .5 --- Histology & Immunohistochemistry --- p.39 / Chapter 3.51 --- Morphology of Control Tendon --- p.40 / Chapter 3.52 --- Morphology of Experimental Tendon with 'Open' Procedure --- p.40 / Chapter 3.53 --- Morphology of Experimental Tendon with 'Close' Procedure --- p.41 / Chapter 3.54 --- Healing at the Patellar and Tibial Insertion Site --- p.41 / Chapter 3.55 --- Morphology of the Cartilage Surface --- p.42 / Chapter Chapter 4 --- Discussion & Conclusion --- p.43 / Chapter 4.1 --- Gross Morphology --- p.43 / Chapter 4.2 --- Biomechanical Testing --- p.45 / Chapter 4.3 --- Biochemical Assay --- p.47 / Chapter 4.4 --- Histology & Immunohistochemistry --- p.49 / Chapter 4.5 --- Conclusion --- p.51 / References --- p.54 / Figures / Tables / Appendix

Introdução: O ligamento cruzado anterior (LCA) é o principal restritor à translação tibial anterior. O tratamento indicado para indivíduos atleticamente ativos é cirúrgico. Apesar de serem encontradas descrições de bons-excelentes resultados em mais de 90% dos casos, ainda há complicações relevantes, sendo a evolução para a artrose uma ocorrência frequente. Sabese que pacientes com desvio do eixo em varo, lesões condrais mediais e/ou meniscectomia medial têm maior evolução para artrose do compartimento medial. A realização da reconstrução intra-articular clássica, com tensionamento do enxerto e fixação do mesmo no túnel tibial, o qual tem ponto de entrada na metáfise medial, pode ser causa de sobrecarga medial. Objetivo: O presente estudo visa comparar duas técnicas de reconstrução intra-articular do LCA distintas entre si apenas no que tange ao ponto de entrada tibial (metáfise medial ou lateral) e o resultante grau de sobrecarga medial. Método: Estudo transversal, não randomizado, experimental em cadáveres. Três cadáveres (06 joelhos) foram submetidos à reconstrução intra-articular do ligamento cruzado anterior. Foi mensurado o grau de abertura articular medial em milímetros (mm) a 0 e 20° de flexão durante o estresse controlado em valgo (40 N) em quatro situações: LCA íntegro (grupo I), LCA seccionado (Grupo S), LCA reconstruído com o ponto de entrada do túnel tibial na posição clássica anteromedial (Grupo RC) e LCA reconstruído com o ponto de entrada do túnel tibial na posição alternativa anterolateral (Grupo RA). Resultados: A média de abertura medial a 0 e a 20 graus de flexão foram respectivamente de 3,48 e 3,55 (grupo I), 5,82 e 5,97 (grupo S), 3,22 e 3,27 (grupo RC), 5,27 e 5,28 (Grupo RA). Houve diferença significativa entre todos os grupos, com exceção da comparação Grupo I x Grupo RC, tanto a 0 como a 20 graus de flexão. Conclusão: O túnel tibial com entrada na região anterolateral da metáfise tibial lateral causa menor restrição medial do que a técnica de posicionamento clássico do túnel. / Introduction: Anterior Cruciate Ligament (ACL) is the main stabilizer of the anterior tibial translation. Surgical treatment usually is indicated for Young and active individuals. Even though good to excellent results are expected in 90% of the cases, there are several complications, and arthrosis progression still is a concern. Varus, condral and menisci injuries are well known risk of factors to gonarthrosis. Classic intra-articular ACL reconstruction with medial sided tibial tunnel positioning and tensioning can be a cause of medial compartment overload. Purpose: The present study aims to compare two similar intra-articular ACL reconstructions, differing one another only by the tibial tunnel entry, and its effect on medial compartment load. Methods: Transversal, non-randomized, experimental biomechanical study. ACL reconstruction was performed in three fresh cadavers (06 knees). Medial joint opening was measured in terms of millimeters (mm) during controlled valgus stress (40 N) both at 0 and 20 degrees of flexion. The specimens were tested in the intact state (group I) and after sectioning of ACL (group S). Also, they were tested after ACL reconstruction with medial (group MT) and lateral tunnel fixation (group LT). Results: Mean medial joint opening at 0 and 20 degrees of flexion were respectively 3,48 and 3,55 (group I), 5,82 and 5,97 (group S), 3,22 and 3,27 (group MT), 5,27 and 5,28 (group LT). Statistically significant difference occurred in comparisons between all groups, but in group I x MT, both at 0 and 20 degrees of flexion. Conclusion: The lateral based tibial tunnel for ACL reconstruction leads to lesser medial joint overload than the classic medial one.

The anterior cruciate ligament (ACL) is the most frequently injured ligament of the knee, with upwards of 100,000 ACL reconstructions performed annually. Current grafting techniques are limited by insufficient integration with subchondral bone and donor site morbidity issues related to graft harvest, potentially resulting in revision surgery and long-term joint pain. Therefore, significant demand exists for alternative grafting solutions that do not require additional surgery and can regenerate the native ACL-to-bone interface to promote biological fixation of the implanted ACL graft. To address this need, the ideal system must be able to withstand the functional demands of the native tissue by demonstrating physiologically equivalent mechanical properties, be comprised of compositionally varying phases in order to recapitulate the inherent heterogeneity of the native ligament to bone transition and be biodegradable such that it is gradually replaced by the regenerated tissue following implantation. It is hypothesized that a biomimetic, multi-phased scaffold comprised of optimized bone, interface and ligament regions coupled with controlled chemical and/or mechanical stimulation in vitro will guide phase-specific differentiation of mesenchymal stem cells (MSC) and result in a biologically integrated bone-ligament-bone complex in vivo. Mesenchymal stem cells are particularly attractive for this application as they can be routinely harvested from bone marrow, have been shown to respond to chemical, mechanical and structural cues, and are capable of differentiating towards the primary cell types (fibroblasts, osteoblasts and chondrocytes) found within ligament, bone and the ligament-to-bone interface. To this end, a nanofiber-based synthetic graft was designed with compositionally-varying phases to regenerate ligament, bone and interface tissues. The ligament phase was optimized in terms of nanofiber alignment, composition, mechanical stimulation and chemical stimulation. It was demonstrated that an aligned nanofiber substrate coupled with controlled mechanical stimulation was necessary to differentiate MSCs towards a fibroblastic phenotype. The bone phase was optimized in terms of ceramic content and it was shown that a threshold of mineral incorporation into nanofibers was necessary to differentiate MSCs towards an osteogenic phenotype. Lastly, a mechanoactive nanofiber collar was designed to induce interface formation. It was demonstrated that compressive stimulation applied via nanofiber collar contraction induced chondrogenic differentiation of MSCs. Subsequently, the three phases were incorporated to form a synthetic graft, for which graft architecture and cell seeding density were optimized. The resulting graft was cultured in vitro under the optimized parameters, demonstrating the formation of distinct and structurally continuous regions of bone, interface and ligament tissue. The graft was implanted in vivo where it was shown to be suitable for ACL reconstruction as it maintained knee stability and promoted ligament regeneration. In summary, this thesis focuses on the design of a biomimetic, nanofiber-based, integrated bone-ligament-bone construct, and elucidates chemical, mechanical and scaffold design-related parameters that can guide MSC differentiation towards desired tissue types. The impact of these studies extends beyond ligament reconstruction as they yield valuable scaffold design criteria, establish scaffold and culturing-related parameters to induce stem cell differentiation and can readily be applied to the formation of interfaces between soft-to-hard tissues as well as other complex tissues.

No description available.