Objetivo: determinar a prevalência dos sinais radiográficos de impacto femoroacetabular em adultos assintomáticos e correlacionar com dados do exame físico. Métodos: estudo transversal, realizado no Hospital de Clínicas de Porto Alegre, com 82 indivíduos, 164 quadris de pacientes entre 40 e 60 anos de idade assintomáticos. Foram submetidos à anamnese e exame clínico completo do quadril e exame radiográfico com três incidências, AP de bacia, Dunn a 45° e falso perfil de Lequesne de cada quadril, para mensuração das variáveis. Entre elas o ângulo alfa, offset anterior do colo femoral, ângulo cérvico diafisário, ângulo CE de Wiberg, índice acetabular, ângulo de Sharp, além dos sinais do cruzamento, da espinha isquiática e da parede posterior. Resultados: nossa amostra foi formada por 66% de mulheres, com média de idade de 50,4 anos. O ângulo alfa médio foi de 45.10º, DP = 8.6. 25% dos quadris apresentaram ângulo alfa maior ou igual a 50°; entre os homens esse número foi ainda maior, 34% e apenas 11% entre as mulheres. Encontramos sinais radiográficos indicativos de impacto femoroacetabular em 42,6% dos quadris, sejam eles femorais ou acetabulares. O aumento do alfa esteve relacionado com o decréscimo na rotação interna do quadril (p < 0,001). Conclusão: Os achados radiográficos de impacto femoroacetabular em pacientes assintomáticos são freqüentes e o aumento do ângulo alfa esteve relacionado com o decréscimo da rotação interna. / Objective: The objective of this research is to determine the prevalence of radiographic markers of femoroacetabular impingement in asymptomatic adults and correlate with data from physical examination. Methods: A cross-sectional study conducted at Hospital de Clinicas in Porto Alegre, with 82 individuals, 164 hips of asymptomatic individuals between 40 and 60 years old. They were subjected to a complete medical history and examination of the hip, three X-ray incidences, pelvis AP, Dunn 45° view and the Lequesne false profile of each hip, for the measurement of variables. The variables were the alpha angle, anterior femoral offset, neck shaft angle, CE angle of Wiberg, acetabular index, Sharp’s angle, in addition to crossover sign and the posterior ischial spine and the posterior wall sign. Results: the sample was made up of 66% women, average age of 50.4 years old. The average alpha angle was 45.10 º, SD = 8.6. 25% of the hips showed alpha angle greater than or equal to 50 °, among me n the figure was even higher, 34% and only 11% among women. We found radiographic signs indicative of femoroacetabular impingement in 42,6% of hips, whether femoral or acetabular. The increase in alpha angle was related to the decrease in hip internal rotation (p <0.001). Conclusion: The radiographic markers of femoroacetabular impingement were frequent in asymptomatic patients, and the increase in alpha angle was associated with decreased internal rotation of the hip.

Objetivo: determinar a prevalência dos sinais radiográficos de impacto femoroacetabular em adultos assintomáticos e correlacionar com dados do exame físico. Métodos: estudo transversal, realizado no Hospital de Clínicas de Porto Alegre, com 82 indivíduos, 164 quadris de pacientes entre 40 e 60 anos de idade assintomáticos. Foram submetidos à anamnese e exame clínico completo do quadril e exame radiográfico com três incidências, AP de bacia, Dunn a 45° e falso perfil de Lequesne de cada quadril, para mensuração das variáveis. Entre elas o ângulo alfa, offset anterior do colo femoral, ângulo cérvico diafisário, ângulo CE de Wiberg, índice acetabular, ângulo de Sharp, além dos sinais do cruzamento, da espinha isquiática e da parede posterior. Resultados: nossa amostra foi formada por 66% de mulheres, com média de idade de 50,4 anos. O ângulo alfa médio foi de 45.10º, DP = 8.6. 25% dos quadris apresentaram ângulo alfa maior ou igual a 50°; entre os homens esse número foi ainda maior, 34% e apenas 11% entre as mulheres. Encontramos sinais radiográficos indicativos de impacto femoroacetabular em 42,6% dos quadris, sejam eles femorais ou acetabulares. O aumento do alfa esteve relacionado com o decréscimo na rotação interna do quadril (p < 0,001). Conclusão: Os achados radiográficos de impacto femoroacetabular em pacientes assintomáticos são freqüentes e o aumento do ângulo alfa esteve relacionado com o decréscimo da rotação interna. / Objective: The objective of this research is to determine the prevalence of radiographic markers of femoroacetabular impingement in asymptomatic adults and correlate with data from physical examination. Methods: A cross-sectional study conducted at Hospital de Clinicas in Porto Alegre, with 82 individuals, 164 hips of asymptomatic individuals between 40 and 60 years old. They were subjected to a complete medical history and examination of the hip, three X-ray incidences, pelvis AP, Dunn 45° view and the Lequesne false profile of each hip, for the measurement of variables. The variables were the alpha angle, anterior femoral offset, neck shaft angle, CE angle of Wiberg, acetabular index, Sharp’s angle, in addition to crossover sign and the posterior ischial spine and the posterior wall sign. Results: the sample was made up of 66% women, average age of 50.4 years old. The average alpha angle was 45.10 º, SD = 8.6. 25% of the hips showed alpha angle greater than or equal to 50 °, among me n the figure was even higher, 34% and only 11% among women. We found radiographic signs indicative of femoroacetabular impingement in 42,6% of hips, whether femoral or acetabular. The increase in alpha angle was related to the decrease in hip internal rotation (p <0.001). Conclusion: The radiographic markers of femoroacetabular impingement were frequent in asymptomatic patients, and the increase in alpha angle was associated with decreased internal rotation of the hip.

Objetivo: determinar a prevalência dos sinais radiográficos de impacto femoroacetabular em adultos assintomáticos e correlacionar com dados do exame físico. Métodos: estudo transversal, realizado no Hospital de Clínicas de Porto Alegre, com 82 indivíduos, 164 quadris de pacientes entre 40 e 60 anos de idade assintomáticos. Foram submetidos à anamnese e exame clínico completo do quadril e exame radiográfico com três incidências, AP de bacia, Dunn a 45° e falso perfil de Lequesne de cada quadril, para mensuração das variáveis. Entre elas o ângulo alfa, offset anterior do colo femoral, ângulo cérvico diafisário, ângulo CE de Wiberg, índice acetabular, ângulo de Sharp, além dos sinais do cruzamento, da espinha isquiática e da parede posterior. Resultados: nossa amostra foi formada por 66% de mulheres, com média de idade de 50,4 anos. O ângulo alfa médio foi de 45.10º, DP = 8.6. 25% dos quadris apresentaram ângulo alfa maior ou igual a 50°; entre os homens esse número foi ainda maior, 34% e apenas 11% entre as mulheres. Encontramos sinais radiográficos indicativos de impacto femoroacetabular em 42,6% dos quadris, sejam eles femorais ou acetabulares. O aumento do alfa esteve relacionado com o decréscimo na rotação interna do quadril (p < 0,001). Conclusão: Os achados radiográficos de impacto femoroacetabular em pacientes assintomáticos são freqüentes e o aumento do ângulo alfa esteve relacionado com o decréscimo da rotação interna. / Objective: The objective of this research is to determine the prevalence of radiographic markers of femoroacetabular impingement in asymptomatic adults and correlate with data from physical examination. Methods: A cross-sectional study conducted at Hospital de Clinicas in Porto Alegre, with 82 individuals, 164 hips of asymptomatic individuals between 40 and 60 years old. They were subjected to a complete medical history and examination of the hip, three X-ray incidences, pelvis AP, Dunn 45° view and the Lequesne false profile of each hip, for the measurement of variables. The variables were the alpha angle, anterior femoral offset, neck shaft angle, CE angle of Wiberg, acetabular index, Sharp’s angle, in addition to crossover sign and the posterior ischial spine and the posterior wall sign. Results: the sample was made up of 66% women, average age of 50.4 years old. The average alpha angle was 45.10 º, SD = 8.6. 25% of the hips showed alpha angle greater than or equal to 50 °, among me n the figure was even higher, 34% and only 11% among women. We found radiographic signs indicative of femoroacetabular impingement in 42,6% of hips, whether femoral or acetabular. The increase in alpha angle was related to the decrease in hip internal rotation (p <0.001). Conclusion: The radiographic markers of femoroacetabular impingement were frequent in asymptomatic patients, and the increase in alpha angle was associated with decreased internal rotation of the hip.

Introdução: As alterações anatômicas do fêmur proximal ou do acetábulo, como as decorrentes das sequelas da epifisiólise do fêmur proximal, da displasia do quadril da doença de Legg-Perthes-Calvé, podem levar ao desenvolvimento da artrose do quadril. No entanto, em torno de 80% dos indivíduos que desenvolvem essa doença têm uma anatomia óssea considerada normal. Ainda assim, surgiu a hipótese que alterações sutis do fêmur proximal ou do acetábulo, denominadas, respectivamente, cam e pincer, poderiam gerar um contato anormal entre essas estruturas ósseas, desencadear lesão condral e, como consequência, a artrose do quadril. Esse mecanismo foi denominado impacto fêmoro-acetabular. No entanto, a comprovação da relação entre o impacto e a artrose do quadril depende da uniformização dos critérios diagnósticos do cam e do pincer, ainda escassa e variável na literatura. Dessa forma, será possível a definição da prevalência e história natura do impacto fêmoro-acetabular e da sua relação com a artrose do quadril. Objetivo: Avaliar a prevalência do impacto fêmoro-acetabular tipo cam e tipo pincer em uma amostra de indivíduos assintomáticos. Pacientes e Métodos: Foram estudados 106 indivíduos assintomáticos (65 homens e 41 mulheres), com idade entre 20 e 40 anos. A condição determinante para a inclusão no estudo foi à ausência de história de dor no quadril ao longo da vida. Foram obtidas radiografias em ântero-posterior e Dünn 45°. A presença de cam foi determinada por um ângulo alfa, arbitrado, de 55° e a presença de pincer, quando observado o sinal da parede posterior e/ou o sinal de crossover. Resultados: Foi observada prevalência de cam de 29%; o sinal do crossover e da parede posterior ocorreram, respectivamente, em 20% e 29% dos indivíduos estudados. Pelo menos uma das imagens de impacto fêmoro-acetabular estava presente em 65% dos indivíduos da amostra. Conclusão: A prevalência encontrada das imagens de impacto fêmoro-acetabular (65%) está acima daquelas relatadas na literatura. É necessária a ampliação do estudo para confirmar os resultados encontrados e a realização de estudos prospectivos bem controlados para avaliar o papel do cam e do pincer no desenvolvimento da artrose do quadril. / Background: Anatomical abnormalities of the proximal femur or the acetabulum, such as those resulting from the consequences of slipped epiphyses of the proximal femur, the hip dysplasia of Legg-Calve-Perthes disease, could lead to the development of hip osteoarthrosis. Nevertheless, around 80% of individuals who develop this condition have a bone anatomy considered normal. Still, the hypothesis arose that subtle alterations of the proximal femur or the acetabulum, called, respectively, cam and pincer, could generate an abnormal contact between these bony structures, triggering chondral lesion and as a consequence, arthritis of the hip. This mechanism has been named femoroacetabular impingement. Nevertheless, evidence of the relationship between the impact and osteoarthritis of the hip depends on the standardization of diagnostic criteria of cam and pincer, still scarce and variable in the literature. Thus it will be possible to define the prevalence and natural history of femoroacetabular impingement and its relationship with hip osteoarthrosis. Aim: To determine the prevalence of cam-type and pincer-type femoroacetabular impingements in asymptomatic subjects. Patients and Methods: Were studied 106 asymptomatic subjects (65 males and 41 females) aged between 20 and 40 years. The determining condition for inclusion in the study was the absence of history of hip pain throughout life. Radiographs were obtained in anteroposterior pelvic view and Dunn 45° view. The presence of cam was determined by an angle alpha, arbitrated, 55 ° and the presence of pincer when the observed the posterior wall and / or crossover signs. Results: A prevalence of 29% of cam, and 20% and 29% of crossover sign and posterior wall sign respectively was found. At least, one of those radiographic signs of femoroacetabular impingement was found in 65% (68) of the cases. Conclusion: In conclusion, the prevalence of images of femoroacetabular impingement (65%) is above those reported in the literature. Increase of the study is necessary to verify the results found, and the performance of well-controlled prospective studies to evaluate the role of the cam and pincer in the development of osteoarthritis of the hip.

Femoroacetabular impingement (FAI) has been increasingly recognized as a cause of early hip osteoarthritis. FAI is characterized by pathologic contact between the femur and acetabular rim during hip join movement, caused by morphological abnormalities. Arthroscopic technique has become increasingly popular for FAI surgical treatment because of its minimal invasiveness. However, it involves cumbersome procedures and over- or under-resection are likely to occur. To tackle this issue, robot-assisted FAI arthroscopy is a well suited approach because it results in high accuracy and reproducible surgical outcomes. This dissertation provides new approaches and methods for the current challenges in the development of robot-assisted FAI arthroscopy. The study has three objectives: 1) to develop a robust calibration method for the A-mode ultrasound probe used for noninvasive bone registration, 2) to develop a bone registration simulator for verifying the registration accuracy and consistency for any given registration point-pattern, and 3) to develop a hip range of motion simulation system that returns the virtual range of motion and determines the bone resection volume. Carefully designed calibration procedures and simulation experiments have been conducted during the study of this research. From the experimental results, the developed ultrasound calibration method successfully reduces the registration errors and is proved to be robust. The results from the registration simulator indicate that the pattern with widely distributed points lead to better registration accuracy and consistency. The hip range of motion simulation system results in acceptable accuracy and successfully generates the resection volume. With further modifications, the ultrasound probe can be successfully calibrated with the developed method, and will be applied for noninvasive bone registration. The registration simulator can also be served as a useful tool for determining the optimized registration point-pattern, which can lead to reduced surgical trauma and registration time. Finally, the developed range of motion simulation system can allow the surgeon to evaluate the surgical outcome and to determine the resection volume even before the surgery begins. To conclude, this dissertation provides useful approaches, methods, and software for developing robot-assisted FAI arthroscopy.

Femoroacetabular impingement (FAI) is a hip joint deformity that causes joint pain, decreases joint range of motion and results in abnormal kinematic and kinetic characteristics. It is not known whether these biomechanical variations are caused by the actual mechanical impingement aspect of hip deformity or neuromuscular adaptations and soft tissue damage associated with pain. The purpose of this study was to investigate the effects of femoroacetabular cam deformity (FAD) during daily functional tasks. This was accomplished by measuring and comparing the hip joint biomechanics of symptomatic FAI (sFAI), asymptomatic FAD, and control (CON) subjects. Fifty one subjects volunteered to the study (n = 51; CON = 17, FAD = 18, sFAI = 16) and they performed 6 simulated activities of daily living: stair ascent and descent, sit-to-stand and stand-to-sit, dynamic range of motion, maximum depth squats and level walking tasks while motion ground reaction force and muscle activity were recorded. However, only the squat and level walking tasks were analyzed for this thesis. For each task, three-dimensional kinematics and kinetics were recorded and analyzed. Qualitative questionnaires (HOOS and WOMAC) and physical exams were also part of the testing protocol, and maximum voluntary isometric contractions (MVIC) were collected as part of a separate EMG protocol. The EMG results were not analyzed but the MVIC results were and the moments of force were determined. The sFAI group had significantly reduced scores for all HOOS and WOMAC metrics compared to FAD and CON. The sFAI group had significantly reduced external rotation, internal rotation, and a trend indicating reduced hip flexion compared to FAD and CON groups. The FAD group had a trend indicating reduced internal rotation compared to CON. There were no differences in the moments of force between groups for the MVICs. No statistically significant differences were observed between groups for the squat trials, however, the sFAI group showed biomechanical variations. Both the CON and FAD groups were able to squat deeper, had greater pelvic range of motion and a larger maximum hip and knee flexion angle compared to sFAI. Similarly, the walking tasks did not elucidate any between group differences in biomechanical characteristics. Yet, there was a noticeable trend of decreased peak hip abduction angle in the sFAI group compared to CON. This result may be indicative of a gait adaptation based on the pain that sFAI subjects endure over a long period of time. Interestingly, the FAD group did not have obvious gait patterns similar to either the CON or sFAI, making it unclear if the asymptomatic cam deformity has any gait adaptation effects. Since no differences were observed between FAD and CON in squatting and walking, the actual bone deformity may not be the cause of restricted motion during daily activities as previously thought. Internal rotation physical examination appears to indicate potential restrictions in the FAD compared to CON, and may be the best parameter to assess differences between groups and predict the presence of cam deformity. It is suggested that the presence of pain, caused by soft tissue damage over time, may be confounding factors leading to the biomechanical and neuromuscular discrepancies observed in sFAI, and should be the next avenue of study.

Introdução: As alterações anatômicas do fêmur proximal ou do acetábulo, como as decorrentes das sequelas da epifisiólise do fêmur proximal, da displasia do quadril da doença de Legg-Perthes-Calvé, podem levar ao desenvolvimento da artrose do quadril. No entanto, em torno de 80% dos indivíduos que desenvolvem essa doença têm uma anatomia óssea considerada normal. Ainda assim, surgiu a hipótese que alterações sutis do fêmur proximal ou do acetábulo, denominadas, respectivamente, cam e pincer, poderiam gerar um contato anormal entre essas estruturas ósseas, desencadear lesão condral e, como consequência, a artrose do quadril. Esse mecanismo foi denominado impacto fêmoro-acetabular. No entanto, a comprovação da relação entre o impacto e a artrose do quadril depende da uniformização dos critérios diagnósticos do cam e do pincer, ainda escassa e variável na literatura. Dessa forma, será possível a definição da prevalência e história natura do impacto fêmoro-acetabular e da sua relação com a artrose do quadril. Objetivo: Avaliar a prevalência do impacto fêmoro-acetabular tipo cam e tipo pincer em uma amostra de indivíduos assintomáticos. Pacientes e Métodos: Foram estudados 106 indivíduos assintomáticos (65 homens e 41 mulheres), com idade entre 20 e 40 anos. A condição determinante para a inclusão no estudo foi à ausência de história de dor no quadril ao longo da vida. Foram obtidas radiografias em ântero-posterior e Dünn 45°. A presença de cam foi determinada por um ângulo alfa, arbitrado, de 55° e a presença de pincer, quando observado o sinal da parede posterior e/ou o sinal de crossover. Resultados: Foi observada prevalência de cam de 29%; o sinal do crossover e da parede posterior ocorreram, respectivamente, em 20% e 29% dos indivíduos estudados. Pelo menos uma das imagens de impacto fêmoro-acetabular estava presente em 65% dos indivíduos da amostra. Conclusão: A prevalência encontrada das imagens de impacto fêmoro-acetabular (65%) está acima daquelas relatadas na literatura. É necessária a ampliação do estudo para confirmar os resultados encontrados e a realização de estudos prospectivos bem controlados para avaliar o papel do cam e do pincer no desenvolvimento da artrose do quadril. / Background: Anatomical abnormalities of the proximal femur or the acetabulum, such as those resulting from the consequences of slipped epiphyses of the proximal femur, the hip dysplasia of Legg-Calve-Perthes disease, could lead to the development of hip osteoarthrosis. Nevertheless, around 80% of individuals who develop this condition have a bone anatomy considered normal. Still, the hypothesis arose that subtle alterations of the proximal femur or the acetabulum, called, respectively, cam and pincer, could generate an abnormal contact between these bony structures, triggering chondral lesion and as a consequence, arthritis of the hip. This mechanism has been named femoroacetabular impingement. Nevertheless, evidence of the relationship between the impact and osteoarthritis of the hip depends on the standardization of diagnostic criteria of cam and pincer, still scarce and variable in the literature. Thus it will be possible to define the prevalence and natural history of femoroacetabular impingement and its relationship with hip osteoarthrosis. Aim: To determine the prevalence of cam-type and pincer-type femoroacetabular impingements in asymptomatic subjects. Patients and Methods: Were studied 106 asymptomatic subjects (65 males and 41 females) aged between 20 and 40 years. The determining condition for inclusion in the study was the absence of history of hip pain throughout life. Radiographs were obtained in anteroposterior pelvic view and Dunn 45° view. The presence of cam was determined by an angle alpha, arbitrated, 55 ° and the presence of pincer when the observed the posterior wall and / or crossover signs. Results: A prevalence of 29% of cam, and 20% and 29% of crossover sign and posterior wall sign respectively was found. At least, one of those radiographic signs of femoroacetabular impingement was found in 65% (68) of the cases. Conclusion: In conclusion, the prevalence of images of femoroacetabular impingement (65%) is above those reported in the literature. Increase of the study is necessary to verify the results found, and the performance of well-controlled prospective studies to evaluate the role of the cam and pincer in the development of osteoarthritis of the hip.

With a prevalence of 17% in men and 4% in women, Femoroacetabular Impingement (FAI) of type cam is characterized by a decreased femoral head-neck offset and/or asphericity of the lateral femoral head, associated with groin pain and reduced hip range of motion. Since the aetiology is still unclear, the mechanisms of development, progression and degeneration of FAI are largely investigated. Musculoskeletal modeling can support the development of a biomechanical framework to advance the research on FAI pathomechanisms, expand the knowledge about hip contact load distribution in FAI population, and relate the muscle and hip contact forces to the alterations observed during functional tasks. Therefore, this thesis is composed of two parts: the development of a methodological framework, and its application to the investigation of FAI pathomechanisms. The variability of the modelling outcomes (i.e.., body kinematics, torques, contact and muscle forces) to different marker sets, pelvic marker misplacements, and hip joint center (HJC) location was investigated within an inverse kinematic framework. The findings from such studies supported the modelling choices for the clinical investigation of FAI pathomechanisms. In particular, the performance of three different marker sets (Plug-in-Gait, University of Ottawa Motion Analysis Model and a 3-marker-cluster marker set) was compared, and absolute and relative reliability indices were calculated with the purpose of finding a simple yet reliable marker set to be used within an inverse kinematic framework in a clinical study. Thereafter, the sensitivity of joint angles, moments and hip contact forces to simulated inaccurate pelvic tilt was analyzed. The resulting variability indices were high with variations up to 1.3 times the body weight in hip contact forces. The kinematic variations propagated non-linearly to all planes and joints, showing the importance of adjusting possible pelvic misalignments. A methodology was presented to correct the pelvic alignment when the relative position of surface pelvic markers with respect to bony landmarks is known from medical images. The HJC location is a crucial modelling parameter in the analysis of hip kinematics and forces. A certain degree of customization could be introduced in the model by using HJC measured from medical images. Therefore, the performance of a generic musculoskeletal model with customized or non-customized HJC was compared during walking. Hip contact forces were highly sensitive to HJC location, especially because of the dependency of muscle moment arms to HJC changes. However, the variation of HJC without consistent muscle anatomy customization introduced artifacts that could potentially produce inaccurate muscle and joint contact forces estimation. When HJC cannot be measured from medical images, regression equations can be used instead. Therefore, the validity of two popular HJC regression equations (Harrington and Davis) was tested on FAI participants using non-parametric statistical and Bland-Altman tests. The results indicated that the equations were valid for FAI population. In addition, skin thickness measurements were provided for pelvic bony landmarks, and their correlation with body mass index was proposed for systematic error reduction. New adult-specific regression equations were developed from medical images. The described methodological framework was then applied to investigate the functional alterations observed in FAI population. The differences in muscle and hip contact forces were compared between FAI and healthy control groups during level walking. The FAI group showed reduced muscle and hip contact forces, which were linked to the lower normalized walking speed and shorter step length. These results can be interpreted as a protective mechanism developed by FAI patients to prevent high compression at the site of impingement, given that the compressing hip contact force was directed towards the anterior-superior quadrant of the acetabulum, consistent with the localization of the cam-type deformity and the cartilage and labrum damages. Based on these findings, a possible FAI pathomechanism was proposed, which could be used to support the development of preventive treatment and intervention for symptomatic FAI patients.

A major contributing factor to the onset of early hip osteoarthritis is attributed to an enlarged, aspherical femoral head deformity, characterized as cam-type femoroacetabular impingement (FAI). The presence of the cam deformity alone does not explain differences in pathomechanisms and it has been theorized that adverse loading to the subchondral bone may play a predominant mechanical role in early joint degeneration. This doctoral thesis examined the adverse hip joint loading due to cam FAI and characterize mechanical stimuli associated with symptoms. Specifically, this research: 1) examined anatomical and functional characteristics associated with the cam morphology; 2) developed subject-specific finite element hip joint models to examine hip joint stresses, incorporating subject-specific geometries, materials properties, and joint loading; and 3) implemented loading parameters during level walking and squatting to examine hip joint stresses. First, a classification study was conducted to recruit three participant groups: 1) symptomatic (where participants had the cam deformity and pain); 2) asymptomatic (where participants had the cam deformity, but no pain); and 3) control (where participants did not have the cam deformity or clinical signs). Each participant's CT data were evaluated for multiple anatomical hip joint parameters and then re-classified into their respective subgroups, using a discriminant function analysis, based on the most significant parameters. In addition to the cam deformity, symptomatic individuals had a lower femoral neck-shaft angle and reduced pelvic range of motion. Second, using the classified participants, hip joint loading was determined for the various severities of cam FAI, with respect to alterations in hip contact forces and anatomical considerations. Hip joint assemblies were segmented and reconstructed from subject-specific CT and MRI data, where bone densities were quantified from CT data. A parametric study was conducted to understand how varying material properties and loading conditions affected the sensitivity of the predictive models, examining the most appropriate modelling parameters to capture relative measurements. Third, in conjunction with the first two studies, hip contact forces for level walking and squatting tasks were applied to corresponding subject-specific models and simulated. As a cross-sectional analysis, the stress magnitudes and regions described the joint loading in vivo for each subject group and ascertained the risk of remodeling. For each subgroup (symptomatic, asymptomatic, control), the participants with the largest and smallest femoral neck-shaft angles were selected and compared. The symptomatic model with the lowest femoral neck-shaft angle demonstrated the highest stress on the cartilage, during walking and squatting, and on the subchondral bone, during squatting. The asymptomatic models showed cartilage stresses similar to the control group, but experienced high-risk subchondral bone stresses, similar to the symptomatic group. For both symptomatic and asymptomatic groups, the acetabular subchondral bone stresses coincided with known areas of bone adaptation and proteoglycan depletion. The outcome of this research program supported that cartilage degradation might not be due to direct contact shear stresses, but perhaps rather attributed to the indirect effects of a stiffer subchondral bone plate. Individuals with a large cam deformity and decreased femoral neck-shaft angles are likely to experience severe subchondral bone stresses during higher amplitudes of hip motion. This provides clinicians with indications of how the pathology exacerbates and where initial cartilage delamination will likely occur, allowing them to perform the correct assessments and proceed with the correct form of care. From a patient's perspective, an early and accurate diagnosis could inhibit cartilage degradation and the progression of osteoarthritis.

Femoroacetabular impingement (FAI) is a hip joint deformity that causes joint pain, decreases joint range of motion and results in abnormal kinematic and kinetic characteristics. It is not known whether these biomechanical variations are caused by the actual mechanical impingement aspect of hip deformity or neuromuscular adaptations and soft tissue damage associated with pain. The purpose of this study was to investigate the effects of femoroacetabular cam deformity (FAD) during daily functional tasks. This was accomplished by measuring and comparing the hip joint biomechanics of symptomatic FAI (sFAI), asymptomatic FAD, and control (CON) subjects. Fifty one subjects volunteered to the study (n = 51; CON = 17, FAD = 18, sFAI = 16) and they performed 6 simulated activities of daily living: stair ascent and descent, sit-to-stand and stand-to-sit, dynamic range of motion, maximum depth squats and level walking tasks while motion ground reaction force and muscle activity were recorded. However, only the squat and level walking tasks were analyzed for this thesis. For each task, three-dimensional kinematics and kinetics were recorded and analyzed. Qualitative questionnaires (HOOS and WOMAC) and physical exams were also part of the testing protocol, and maximum voluntary isometric contractions (MVIC) were collected as part of a separate EMG protocol. The EMG results were not analyzed but the MVIC results were and the moments of force were determined. The sFAI group had significantly reduced scores for all HOOS and WOMAC metrics compared to FAD and CON. The sFAI group had significantly reduced external rotation, internal rotation, and a trend indicating reduced hip flexion compared to FAD and CON groups. The FAD group had a trend indicating reduced internal rotation compared to CON. There were no differences in the moments of force between groups for the MVICs. No statistically significant differences were observed between groups for the squat trials, however, the sFAI group showed biomechanical variations. Both the CON and FAD groups were able to squat deeper, had greater pelvic range of motion and a larger maximum hip and knee flexion angle compared to sFAI. Similarly, the walking tasks did not elucidate any between group differences in biomechanical characteristics. Yet, there was a noticeable trend of decreased peak hip abduction angle in the sFAI group compared to CON. This result may be indicative of a gait adaptation based on the pain that sFAI subjects endure over a long period of time. Interestingly, the FAD group did not have obvious gait patterns similar to either the CON or sFAI, making it unclear if the asymptomatic cam deformity has any gait adaptation effects. Since no differences were observed between FAD and CON in squatting and walking, the actual bone deformity may not be the cause of restricted motion during daily activities as previously thought. Internal rotation physical examination appears to indicate potential restrictions in the FAD compared to CON, and may be the best parameter to assess differences between groups and predict the presence of cam deformity. It is suggested that the presence of pain, caused by soft tissue damage over time, may be confounding factors leading to the biomechanical and neuromuscular discrepancies observed in sFAI, and should be the next avenue of study.