A Virtual University Infrastructure For Orthopaedic Surgical Training With Integrated Simulation

This thesis pivots around the fulcrum of surgical, educational and technological factors. Whilst there is no single conclusion drawn, it is a multidisciplinary thesis exploring the juxtaposition of different academic domains that have a significant influence upon each other. The relationship centres on the engineering and computer science factors in learning technologies for surgery. Following a brief introduction to previous efforts developing surgical simulation, this thesis considers education and learning in orthopaedics, the design and building of a simulator for shoulder surgery. The thesis considers the assessment of such tools and embedding into a virtual learning environment. It explains how the performed experiments clarified issues and their actual significance. This leads to discussion of the work and conclusions are drawn regarding the progress of integration of distributed simulation within the healthcare environment, suggesting how future work can proceed

Developing a Finite Element Model for Evaluating the Posterior Tibial Slope in a Medial Opening Wedge High Tibial Osteotomy

This thesis aimed to develop and validate a computation finite element (FE) model to investigate the effect of hinge axis orientation on the posterior tibial slope (PTS) and mechanical medial proximal tibial angle (mMPTA) while analyzing the mechanical response around the hinge in a medial opening wedge high tibial osteotomy (MOWHTO). Chapter 2 highlights the importance of selecting an appropriate modeling method that best represents the clinical scenario. Chapter 3 validated a FE model using the Bland-Altman agreement analysis which yielded 95% limits of agreement of −0.9° to 1.2° for PTS and −1.4° to 1.9° for mMPTA. A parametric study was presented in Chapter 4 to investigate the effect of a 15° internal and external hinge axis rotation (with respect to a neutral hinge axis orientation) on the PTS and quantified the stresses and strains between each hinge axis orientation through the anterior and posterior region of the hinge

Doctor of Philosophy

dissertationGeometric abnormalities of the human hip joint, as found in femoroacetabular impingement (FAI) and acetabular dysplasia, alter hip biomechanics and may be the primary causes of osteoarthritis in young adults. However, empirical evidence of direct correlations between abnormal geometry, altered biomechanics, and osteoarthritis is scarce. Also, clinical measures used to diagnose FAI and dysplasia still have substantial limitations, including questions about their reliability, assumptions about hip joint geometry and their ability to definitively distinguish pathologic from normal hips. The goals of this dissertation are twofold. First, a set of tools are presented and applied to quantify three-dimensional (3D) anatomical differences between hips with FAI and control subjects. The 3D tools were developed, validated and applied to patients with a subtype of FAI, called cam FAI, to improve basic understanding of the spectrum of FAI deformities, and to provide meaningful new metrics of morphology that are relatable to current diagnostic methods and translate easily for clinical use. The second goal of this dissertation is to improve our understanding of intra-articular hip contact mechanics as well as hip joint kinematics and muscle forces. To do so, a finite element study of intraarticular cartilage contact mechanics was completed with a cohort of live human subjects, using a validated modeling protocol. Finally, musculoskeletal modeling was used with gait data from healthy subjects and acetabular dysplasia patients to provide preliminary estimates of hip joint kinematics, kinetics, and muscle forces and compare differences between the groups. The translational methods of this dissertation utilized techniques from orthopaedics, computer science, physical therapy, mechanics, and medical imaging. Results from this dissertation offer new insight into the complex pathomechanics and pathomorphology of FAI and acetabular dysplasia. Application and extension of the work of this dissertation has the potential to help establish links between FAI and dysplasia with osteoarthritis and to improve patient care

Hip deformities and femoroacetabular impingement

RESUMO: Conceptualmente, a conservação de uma estrutura anatómica é mais benéfica do que a sua substituição. No caso das articulações humanas, este conceito é particularmente importante face aos múltiplos problemas, ainda não resolvidos, relacionados com próteses e materiais usados na cirurgia ortopédica. Na articulação coxofemoral, o conceito de preservação, melhorando os parâmetros biomecânicos, assume uma complexidade técnica acrescida maioritariamente pelo facto de a circulação epifisária do fémur ser intra-articular e dada a proximidade de importantes estruturas neurovasculares. O conflito femoroacetabular (CFA) e a displasia acetabular no adulto jovem, são duas entidades patológicas comuns embora com múltiplas áreas ainda por investigar. A displasia infantil, não diagnosticada e não tratada, pode originar displasia acetabular residual na idade adulta e consequente sintomatologia e limitação funcional. O diagnóstico de CFA no adulto é baseado em critérios clínicos e radiográficos. Clinicamente apresenta-se igualmente com dor e limitação funcional. Radiologicamente, dois subtipos de CFA são habitualmente reconhecidos, o tipo Cam (mecanismo patológico decorrente de asfericidade femoral) e o tipo Pincer (por hipercobertura acetabular). Embora com padrões diferentes de envolvimento articular, os dois mecanismos de conflito condicionam dor, lesão estrutural do labrum e condropatia. Atualmente, a morfologia Cam é considerada como um dos principais fatores de risco morfológico que contribuem para o desenvolvimento de osteoartrose precoce da coxofemoral, eventualmente com necessidade de recurso a prótese total da anca. Apesar de a investigação inicial na área da cirurgia conservadora da anca ter documentado bons resultados cirúrgicos, atualmente a controvérsia é francamente superior ao consenso relativamente à melhor abordagem diagnóstica e terapêutica. Caracteristicamente, apesar de em muitos casos os achados clínicos e radiológicos serem inequívocos para o diagnóstico de CFA, um número substancial de doentes apresenta achados frustes ou equívocos. Por outro lado, múltiplos estudos descreveram uma alta prevalência de morfologia compatível com CFA na população adulta e em indivíduos saudáveis assintomáticos. Atualmente, não existe uma ferramenta de imagem ideal que facilite a alocação fidedigna de todos os doentes a um grupo patológico específico ou, por outro lado, exclua com confiança o diagnóstico de conflito. No entanto, os parâmetros de imagem podem ser utilizados para analisar e descrever as diferentes características morfológicas da anca e adicionalmente confirmar o diagnóstico de CFA. Esta tese enfoca, por um lado, a avaliação da morfologia coxofemoral em diferentes populações, investigando quais articulações estão mais predispostas ao desenvolvimento de sintomas e, por outro, os resultados do tratamento cirúrgico de uma coorte com o diagnóstico de CFA tipo Cam. Especificamente, a investigação efetuada: 1) examinou características morfológicas específicas da coxofemoral em diferentes populações (sintomáticas ou não sintomáticas); 2) desenhou um modelo estatístico baseado em preditores anatómicos no sentido de estabelecer as articulações em risco de desenvolvimento sintomático, incorporando geometrias articulares específicas e parâmetros espinhopélvicos; e 3) analisou os resultados de terapêutica cirúrgica numa coorte de doentes com o diagnóstico CFA tipo Cam. Durante a progressão clínica na área da imagiologia e nesta área patológica em particular, apercebemo-nos da existência de múltiplas lacunas de conhecimento que procurámos colmatar com a investigação agora publicada e descrita nesta tese. A sistematização por capítulos reflete precisamente a necessidade de abordar a questão em áreas de conhecimento, simultaneamente distintas e complementares. Os seis capítulos desta tese abrangem o espectro clínico desde o diagnóstico até ao tratamento da anca jovem. De modo a apresentar os objetivos desta tese numa sequência lógica, desde a anatomia geral até à morfologia e tratamento específicos do CFA, a análise da anca assintomática será descrita em primeiro lugar seguida pela análise da relação anatomoclínica entre morfologia articular e sintomas. Por último será abordada a terapêutica do doente sintomático. Na PARTE I, apresentamos os tópicos essenciais para compreender a abrangência do espectro da presente tese, designadamente a relevância e a contemporaneidade do tema “CFA” e adicionalmente o enquadramento anatómico, morfológico e vascular desta articulação. O Capítulo 1 é dedicado ao desenvolvimento e morfogénese da anca. No Capítulo 2, sublinhamos a importância e o papel da imagem através de uma revisão enfocada nas perspetivas atuais e futuras sobre este tópico (Artigo I). No Capítulo 3, realizamos uma revisão sistemática da literatura no sentido de descrever o estado da arte com foco na prevalência da morfologia de CFA em populações assintomáticas e sintomáticas. Este capítulo destaca as múltiplas lacunas de conhecimento relativas ao papel da morfologia da articulação coxofemoral na patogénese do CFA (Artigo II). Com base nesta parte introdutória, abordamos seguidamente os objetivos da presente tese, gerais e específicos, na PARTE II.Na PARTE III, descrevemos o corpo da investigação clínica original efetuada. O Capítulo 4 é dedicado à caracterização detalhada da morfologia da anca, designadamente óssea e vascular. A morfologia coxofemoral foi quantificada utilizando software com capacidade de semi-automatização analítica, permitindo estudar a prevalência e relação entre as diferentes morfologias articulares e o género, dominância e simetria articular (Artigo III). A morfologia Cam foi ainda alvo de caracterização mais aprofundada, através do desenvolvimento de um novo parâmetro quantitativo com potencialidade diagnóstica e de planeamento cirúrgico/ /prognóstico, primariamente testado numa coorte assintomática (Artigo IV) e seguidamente também em doentes com indicação cirúrgica (Artigo V). Na nossa atividade clínica diária apreciámos a necessidade urgente de melhor caracterizar a topografia da deformidade Cam e a respetiva relação com as artérias nutritivas da epífise femoral. A impressão clínica referida sugeria que a morfologia Cam frequentemente se estendia posteriormente ao quadrante póstero-superior, intersectando a região retinacular vascular. No entanto, por imagem a natureza arterial destas estruturas nunca havia sido confirmada. Por esta razão, a importância do parâmetro mencionado foi sublinhada e comprovada no estudo cadavérico com avaliação topográfica vascular do fémur proximal (Artigo VI). No Capítulo 5 testámos múltiplos parâmetros imagiológicos e respetivas variações/relações com diferentes morfologias coxofemorais, no sentido de identificar as articulações com risco clínico aumentado de desenvolvimento sintomático. Para este fim efetuámos estudos baseados em computação avançada com modelação estatística (Artigo VII) e também em ressonância magnética (RM) tridimensional (Artigo VIII). O Capítulo 6 descreve as opções de tratamento (Artigo IX) e os resultados clínicos num estudo clínico de uma coorte com follow-up mínimo de 2 anos, comparando a abordagem cirúrgica aberta e artroscópica (Artigo X). Os resultados dos diferentes capítulos estão sumarizados na PARTE IV, onde apresentamos a síntese geral, a discussão crítica dos resultados obtidos à luz da literatura atual e finalmente as conclusões relevantes. As oportunidades futuras de investigação são igualmente abordadas neste capítulo. Em resumo o trabalho constante da presente tese sugere: Primeiro, que a avaliação imagiológica detalhada da morfologia coxofemoral é essencial no sentido de compreender aprofundadamente não só a própria articulação como também a morfologia pélvica (Artigo I). Segundo, paradoxalmente, a definição clínica de um caso patológico e das diferentes entidades relacionadas, é ainda inexistente. Os parâmetros quantitativos e qualitativos que comummente estão associados com CFA tipo Pincer e Cam são francamente frequentes em diferentes populações (sintomáticas e assintomáticas) (Artigo II).Terceiro, em populações assintomáticas adultas, os intervalos de referência específicos para os parâmetros quantitativos associados a morfologia de CFA e displasia são mais latos e com limites superiores mais elevados do que os atualmente utilizados na prática clínica (Artigo III). A morfologia femoral bem como os epicentros/magnitudes das deformidades Cam são específicos de género, observando-se maiores valores de ângulo alfa e ómega em indivíduos do sexo masculino (Artigo IV). Quarto, é frequente a interseção entre a extensão póstero-superior da deformidade Cam e a convergência epifisária das estruturas vasculares retinaculares observadas em RM, aspetos que se revestem de primordial importância no planeamento cirúrgico. Adicionalmente a extensão radial da deformidade Cam (ângulo ómega) está significativamente mais relacionada com a sintomatologia clínica pré-cirúrgica do que o parâmetro mais comummente utilizado na prática clínica (ângulo alfa) (Artigo V). A origem das estruturas vasculares observadas por RM na prega retinacular é inequivocamente arterial, sendo que abrange uma extensão mais anterior do que classicamente assumido (Artigo VI). Quinto, as geometrias ovalares (em detrimento das morfologias esféricas e elipsoides) são melhor representativas de ambas as superfícies articulares da coxofemoral, designadamente do fémur e acetábulo, bem como das ancas sintomáticas que clinicamente exibem sinais de CFA (Pincer, Cam e misto) (Artigo VII). Indivíduos com maiores deformidades Cam, aspetos de hipocobertura acetabular e acentuação da anteflexão pélvica apresentam uma maior probabilidade de desenvolverem sintomas articulares (Artigo VIII). Esta observação é crítica, dado que fornece, na prática clínica, informação essencial acerca da potencial predisposição para fenómenos de exacerbação sintomática futura, permitindo desta forma instituição de medidas terapêuticas/preventivas adequadas. Na perspetiva do doente, um diagnóstico precoce e preciso, pode conceptualmente prevenir, numa primeira fase, alterações condropáticas articulares e, numa segunda instância, progressão para artrose estabelecida. Sexto, documentamos resultados clínicos e funcionais significativamente favoráveis quando comparamos a abordagem artroscópica e aberta no tratamento cirúrgico da deformidade Cam, sendo de observar que o género feminino está associado a menor score funcional na avaliação pré-operatória (Artigos IX e X). Futuramente, a imagiologia e a cirurgia conservadora da anca irão desenvolver-se conjuntamente e em paralelo com novos e maiores desafios. A descrição de novos parâmetros analíticos para avaliação da patoanatomia coxofemoral, associada à inovação tecnológica crescente e à implementação da inteligência artificial, impõem uma evolução clínica oposta à assunção de classificações patológicas demasiadamente simplistas. Nesse sentido a existência de guidelines de diagnóstico e terapêutica mais efetivas e baseadas na evidência, que nos levem além da pura diferenciação entre CFA e displasia, são urgentes. A história natural das deformidades Cam e Pincer, sintomáticas ou assintomáticas, é ainda grandemente desconhecida, assumindo-se como uma área determinante de investigação no que concerne ao diagnóstico, terapêutica e prognóstico.ABSTRACT: Conceptually, the preservation of a human anatomical structure makes more sense than its replacement. This concept is even more striking in the case of human joints due to the multitude of unsolved problems related to implants used in orthopaedic surgery. With respect to the hip, joint preservation assumes an increased technical complexity when compared to other joints; this is due to two main reasons: the intra-articular epiphyseal circulation of the femur and the proximity of large neurovascular structures. Femoroacetabular impingement (FAI) and acetabular dysplasia (DHD) in young adults are two common but poorly characterised pathological entities. If undiagnosed and untreated, dysplasia in childhood may lead to residual DHD in young adults, as diagnosed on radiographs, and may also give rise to symptoms such as hip pain and restricted range of motion. The diagnosis of FAI in adults is based on clinical and imaging criteria. The most frequently noticed symptoms of FAI include hip pain and restricted function. Radiologically, two main subtypes of FAI are recognised: The Cam-type, with the pathoanatomical mechanism located on the femoral side, and the Pincertype on the acetabular side. Although with different pathological patterns, both types cause pain and articular damage of the labrum and cartilage. While Cam-type FAI is believed to be a major contributing factor to the early onset of hip osteoarthritis (OA), which eventually requires a total hip replacement, the relationship of other shapes and morphologies with OA are still under debate. Despite the initial promising reports on outcomes following surgical management of these conditions, the best approach to diagnose and manage them still remains controversial. Although for some patients there are unambiguous clinical and imaging findings of FAI, for a substantial number of patients there are minimal or intermediate findings. Moreover, several studies have reported a high prevalence of FAI morphology among the “normal” population and in asymptomatic healthy individuals. At present, there is no adequate imaging tool to facilitate the reliable allocation of all patients into the correct diagnostic group or to confidently rule out diagnosis. However, imaging parameters can be used to describe different hip morphological characteristics and additionally confirm or preclude the diagnosis of FAI.This thesis focuses on assessing hip morphology in different populations by investigating which specific joints are more prone to developing symptoms and by evaluating treatment outcomes of a FAI cohort. Specifically, this research concentrates on the following: 1) examining population-specific (symptomatic and non-symptomatic) characteristics of hip morphology; 2) developing an anatomic-based model to establish “at-risk” hip joints, incorporating subject-specific hip geometries and spinopelvic parameters and 3) investigating treatment outcomes in a Cam-type FAI cohort. In our clinical progression in imaging and in this particular area of pathology, we became aware of the existence of several gaps that we sought to fill with the now published research hereby described. The systematisation by chapters precisely reflects the need to address the issue in simultaneously distinct and complementary areas of knowledge. This thesis consists of six chapters, which cover the entire spectrum from the diagnosis to treatment of the young hip. To present the aims of this thesis in a sequential manner from general morphology to more specific FAI-related topics, the analysis of the asymptomatic hip will be presented first, followed by how joint morphology is associated with symptoms and, finally, will conclude with treatment. In PART I, we introduce the topics that are relevant to understand the full scope of our thesis; we aim to accomplish this by addressing the relevance and contemporariness of the “FAI” theme and by describing the general and vascular anatomy of the hip. Chapter 1 is devoted to hip development and morphogenesis. In Chapter 2, we address the importance of imaging by conducting a thorough review of current and future perspectives on this topic (Paper I). In Chapter 3, we perform a systematic review of the literature to write a state-of-the-art overview, focussing on asymptomatic and symptomatic FAI morphology prevalence and highlighting the multiple gaps in knowledge regarding the role of hip morphology in the pathogenesis of FAI (Paper II). Building on the first part, we address the rationale and aims of this thesis in PART II. In PART III, we describe the original research that was performed and published. Chapter 4 focusses on the detailed characterisation of hip morphology, both osseous and vascular. Bony hip morphology was quantified using a semi-automated software, which allows to robustly study in detail shape variants in an asymptomatic population and their relationship with sex, side and limb dominance (Paper III). Cam morphology was further defined by developing a novel quantitative parameter, with diagnostic and treatment planning capabilities using a cohort of both asymptomatic individuals (Paper IV) and patients undergoing surgery (Paper V). Moreover, we felt the need to better characterise the topography of the deformity and its relationship with the nourishing arteries of the femoral head, as Cam morphology frequently has a posterior a bstr extension that overlaps the retinacular vascular structures. However, its arterial origin has never been described or confirmed in the literature. For this reason, the importance of the aforementioned parameter has been outlined by the cadaveric arterial topographic study of the proximal femur (Paper VI). In Chapter 5, we test multiple parameters and their associated shape variants to detect which ones allow identifying a risk-increased joint in various populations. To this end, we use both advanced computing for shape modelling (Paper VII) and three dimensional (3D) magnetic resonance imaging (MRI) (Paper VIII). Chapter 6 describes the various treatment options (Paper IX) and outcomes in a cohort clinical study, comparing open surgery with arthroscopic surgery in terms of treating Cam deformities (Paper X). The results of the aforementioned chapters are summarised in PART IV, presenting the general synthesis, discussing the results in the light of current literature and detailing the conclusions of this thesis. The scope of potential future research within this field is also presented in this chapter. In brief, this thesis suggests the following: First, detailed imaging assessment of hip morphology is paramount to better understanding both the hip joint and pelvic morphology (Paper I). Second, the case definitions of different morphologies and clinical entities are missing as far as FAI and related disorders are concerned. Qualitative and quantitative radiographic findings thought to be associated with Cam- and Pincer-type FAI, as well as the coexistence between them, are quite common among different populations (Paper II). Third, in adult asymptomatic populations, sex-specific reference intervals for hip measurements for DHD and FAI morphology are wider than currently accepted values (Paper III). Moreover, femoral morphology with distinct Cam magnitudes and epicentres is also sex-specific, with higher mean alpha angle (α°) and omega angle (Ω°) values seen in males (Paper IV). Forth, Cam deformity frequently overlaps with the retinacular vascular structures seen in an MRI; this finding has practical surgical relevance. Additionally, the radial extension of the Cam deformity (Ω°) is more significantly associated with the patients’ symptoms prior to surgery than the α° (paper V). The origin of the vascular structures seen in the retinacular fold is unequivocally arterial in nature, and these structures have a more anterior distribution than classically assumed (Paper VI). Fifth, ovoid geometries are more representative of both articular surfaces of the hip joint as well as of Cam, Pincer and mixed impinged hips when compared to spherical or ellipsoidal shapes (Paper VII). Individuals with larger Cam deformities, decreased acetabular coverage and increased pelvic anteflexion are more likely to experience hip symptoms (Paper VIII). This provides clinicians with indications of how the pathology exacerbates, allowing them to perform the correct clinical assessments and proceed with the correct form of care. From a patient’s perspective, an early and accurate diagnosis could prevent cartilage degradation and progression to OA. Sixth, similar outcomes and significant functional improvement are observed when comparing open and arthroscopic surgery in the treatment of Cam deformities (follow-up time of two years). It should be noted that the female gender was associated with poor hip function in the preoperative evaluation (papers IX and X). Looking ahead, imaging and hip preserving surgery (HPS) will evolve hand-in-hand in the face of new and greater challenges. The increasing number of analytic parameters describing hip joint pathomorphologies as well as new sophisticated 3D imaging-analysis together with emerging artificial intelligence-based technologies have transported us beyond simple classification systems. Moreover, more reliable diagnostic and treatment guidelines that go beyond differentiation into pure FAI and dysplasia are paramount. The largely unknown natural course of both hips with symptomatic FAI and asymptomatic individuals continues to present research opportunities as far as diagnosis, treatment and prognosis are concerned

Novel Process for Designing Topology Optimized Femoral Stems Printable by Metal Additive Manufacturing

Total hip arthroplasty faces an issue of the high cost and risks of revision surgeries. Studies show that more than 50% of the revision surgeries are the consequence of the aseptic loosening of the implant. The cause of the loosening is the bone resorption during the bone remodeling due to poor load transfer to the bone because of the stiff metal used for the implant. The aim of this work is illustrating a novel process of designing topology optimized femoral stems printable by additive manufacturing to increase the load transfer. The proposed manual penalization process is used to produce the required stems followed by a multiple simulations process to select the optimum stem extraction iso-surface threshold value. The results show printable stems that increased the strain energy in the bone by 20% and had better micromotions uniform distribution resulting in more uniform bone growth

Proficiency-based progression training: quality assured preparation for the practice of surgery

Purpose: Investigate the effectiveness of proficiency-based progression (PBP) training coupled with simulation for the acquisition of surgical skills and to define the essentials for the development of a comprehensive, validated, PBP training curriculum. Methods: Task deconstruction of an arthroscopic Bankart repair (ABR) in which step, error, and sentinel (more serious) error metrics was conducted. Novice and experienced surgeons were evaluated using the metrics with a medium fidelity shoulder model (training tool) and separately with a cadaver shoulder (assessment tool). A randomized, controlled, blinded trial was conducted comparing operative performance for 4th and 5th year orthopedic residents for one of 3 training curriculums: 1) control: traditional Arthroscopy Association resident training (‘apprenticeship model’ N = 14); 2) a simulator enhanced curriculum (N = 14); and 3) a PBP curriculum coupled with a model simulator (N = 16). Results: Face and content validity were confirmed for the ABR metrics with a modified Delphi panel. Construct validity of the metrics coupled with the model simulator and with a cadaver shoulder was verified and proficiency benchmarks established. The PBP-trained group (Group C) made 56% fewer objectively assessed errors than the traditionally trained residents (Group A) and 41% fewer than Group B. Compared with Group A, Group B participants were 1.4 times and Group C, 5.5 times as likely to achieve the final proficiency benchmark for an ABR. Conclusions: The randomized trial comparing three different training curricula demonstrated unambiguous superiority of the PBP curriculum coupled with a medium fidelity simulator. Performance metrics must be unambiguously defined and able to be reliably scored. Error metrics are the most valuable in discriminating between levels of operative performance. Simulators are most useful when they serve as a vehicle to deliver a strong, metric based curriculum, which must be developed prior to the selection of specific simulations

A virtual university infrastructure for orthopaedic surgical training with integrated simulation

This thesis pivots around the fulcrum of surgical, educational and technological factors. Whilst there is no single conclusion drawn, it is a multidisciplinary thesis exploring the juxtaposition of different academic domains that have a significant influence upon each other. The relationship centres on the engineering and computer science factors in learning technologies for surgery. Following a brief introduction to previous efforts developing surgical simulation, this thesis considers education and learning in orthopaedics, the design and building of a simulator for shoulder surgery. The thesis considers the assessment of such tools and embedding into a virtual learning environment. It explains how the performed experiments clarified issues and their actual significance. This leads to discussion of the work and conclusions are drawn regarding the progress of integration of distributed simulation within the healthcare environment, suggesting how future work can proceed.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Doctor of Philosophy

dissertationAltered mechanics are believed to initiate osteoarthritis in hips with acetabular dysplasia. Periacetabular osteotomy (PAO) is the preferred surgical treatment; however, it is unknown if the procedure normalizes joint anatomy and mechanics. Changes in three-dimensional (3D) morphology and chondrolabral mechanics were quantified after PAO. Finite element (FE) models demonstrated that PAO improved the distribution of coverage, reduced stress, increased congruity, and prevented cartilage thinning. However, changes in mechanics were not consistent. In fact, one patient exhibited increased stress after surgery, which was believed to be a result of over-correction. Therefore, methods to integrate morphologic and biomechanical analysis with clinical care could standardize outcomes of PAO. FE simulations are time-intensive and require significant computing resources. Therefore, the second aim was to implement an efficient method to estimate mechanics. An enhanced discrete element analysis (DEA) model of the hip that accurately incorporated cartilage geometry and efficiently calculated stress was developed and analyzed. Although DEA model estimates predicted elevated magnitudes of contact stress, the distribution corresponded well with FE models. As a computationally efficient platform, DEA could assist in diagnosis and surgical planning. Imaging is a precursor to analyzing morphology and biomechanics. Ideally, an imaging protocol would visualize bone and soft-tissue at high resolution without ionizing radiation. Magnetic resonance imaging (MRI) with 3D dual-echo-steady-state (DESS) is a promising sequence to image the hip noninvasively, but its accuracy has not been quantified. Therefore, the final aim was to implement and validate the use of 3D DESS MRI in the hip. Using direct measurements of cartilage thickness as the standard, 3D DESS MRI imaged cartilage to ~0.5 mm of the physical measurements with 95% confidence, which is comparable to the most accurate hip imaging protocol presented to date. In summary, this dissertation provided unique insights into the morphologic and biomechanical features following PAO. In the future, DEA could be combined with 3D DESS MRI to efficiently analyze contact stress distributions. These methods could be incorporated into preoperative planning software, where the algorithm would predict the optimal relocation of the acetabulum to maximize femoral head coverage while minimizing contact stress, and thereby improve long-term outcomes of PAO

Motor Imagery to Facilitate Sensorimotor Re-Learning (MOTIFS): Integrating Dynamic Motor Imagery in Current Treatment of Knee Injury

Traumatic knee injury is common in physical activity that includes jumping and cutting movements, and most commonly include anterior cruciate ligament (ACL) or meniscus injuries. Surgical or non-surgical intervention strategies may be chosen, but treatment will include a physical-therapist led physical training program. The aim of this training is to strengthen and stabilize the knee. Despite receiving best-practice treatment, many are unable to return to their pre-injury activity level. Recent research has suggested that this may be explained, in part, by psychological factors such as fear of re-injury or lack of confidence. In addition to physical treatment, guidelines include recommendations to address psychological factors. The detail of how this can be done is lacking, and the extent to which psychological variables are adequately addressed is questionable. In response to this gap, we have developed the novel Motor Imagery to Facilitate Sensorimotor Re-Learning (MOTIFS) model, which integrates psychological training into physical rehabilitation protocols using a dynamic motor imagery intervention. MOTIFS increases realism and relevance while simultaneously physically and psychologically simulating activity-specific and individualized rehabilitation exercises. The aim of this thesis is therefore to develop and explore the efficacy of the MOTIFS model in physically and psychologically preparing knee-injured people for return to activity compared to care-as-usual rehabilitation. The primary hypothesis of this thesis is that the MOTIFS model will provide greater effects on patient-relevant outcomes and muscle function than current programs. In a first step, the effect of MOTIFS model on enjoyment and other self-reported outcomes was evaluated in a cross-over study (Paper I) in which uninjured people underwent training according to both MOTIFS and care-as-usual training protocols. Next, a protocol detailing an ongoing randomized controlled trial (Paper II) which will compare 12 weeks of MOTIFS and care-as-usual training in terms of psychological readiness to return to activity and functional performance. Finally, two interview studies were conducted in which physical therapists (Paper III) and Patients (Paper IV) in both MOTIFS and care-as-usual groups were interviewed about the experiences of rehabilitation training following traumatic knee injury.Results of this thesis show that the MOTIFS model has the potential to increase enjoyment of knee injury prevention and treatment exercises. Other self-reported outcomes were also improved, and the MOTIFS model does not seem to sacrifice movement quality, indicating that it is possible to modify exercises by integrating a dynamic motor imagery intervention. Results of the interview study with physical therapists indicates that those in the MOTIFS group perceive a greater focus on psychological factors while using the new training model, and believe that it is an effective method of increasing patient readiness to return to activity. Those in the care-as-usual group described their perception of rehabilitation training as having a mainly physical focus. They expressed a desire for more tools to address psychological factors, as they perceived patient reactions to be psychological in nature and felt they were ill equipped to handle these factors. Patients in the MOTIFS group perceived MOTIFS to be meaningful and a positive method of increasing their readiness to return to sport, owing to early exposure to activity, which helps them to feel that they have longer to prepare for their return. Those in the care-as-usual group perceive a lack of psychological focus, and their success was measured in terms of their physical progress through rehabilitation. Results indicate that the MOTIFS model may be a feasible and clinically implementable method of addressing psychological factors in rehabilitation training. As the randomized controlled trial is still ongoing, no conclusions can be drawn regarding the efficacy of the intervention on rehabilitation outcomes. However, given the results of Papers I, III and IV, it seems a promising start to bridge the gap between physical and psychological rehabilitation outcomes

The soft-tissue restraints of the knee and its balancing capacity in total knee arthroplasty procedures

Total knee arthroplasty is a successful surgical treatment for patients with severe knee joint arthrosis. However, restoring soft-tissue function is a major challenge. Depending on the positioning of the prosthesis, the implantation procedure and the pathology of the patient, it is necessary to adjust the soft-tissue structures of the joint in order to restore the function of the knee. The assessment and adaptation of the soft-tissue envelope is a subjective process that is strongly dependent on the surgeon. This dissertation addresses these challenges and seeks quantitative guidelines for softtissue management based on a meta-analysis of the laxity of the natural knee joint. A further aim of the present study was to clarify in the scope of in-vitro investigations to what extent the loosening and removal of individual structures alters joint laxity and how far the joint can be balanced by targeted resection of soft-tissue structures. In addition, in-silico investigations within the scope of this thesis form the basis for a numerical tool to better understand the function of the ligaments and to better plan soft-tissue balancing preoperatively in the future. The investigations of the natural laxity of the knee jointin different flexion angles and loading directions by utilizing a meta-analysis show a strong dependency of the joint laxity on the flexion angle. Furthermore, the results show a distinct asymmetry of joint laxity when comparing translations in opposite directions within a certain degree of freedom. The data collected provide the surgeon with quantitative target parameters for natural soft-tissue balancing in knee arthroplasty procedures. The in-vitro investigations on 19 human knee specimens show that the restoration of soft-tissue function of the knee after arthroplasty cannot be achieved by kinematic alignment alone. The use of a bicruciate-retaining knee arthroplasty is the only way to keep the anterior and posterior stability of the joint in balance. To correct varus deformities, balancing of the medial collateral ligament appears to be a safe method. Correction of valgus laxity can be achieved by partially or completely resecting the lateral collateral ligament, however this increases the risk of instability in joint flexion. Within the scope of this work, subject-specific multi-body simulation models could be developed with which the laxity of the knee joint can be predicted, especially for low flexion angles. The presented procedure for the approximation of the ligament attachment sites represents a time-saving alternative to the segmentation of the attachments in MRI images.Deutsche Forschungsgemeinschaft/Sachbeihilfe/HU 873/7-1/E