Assessment of Normal Knee Kinematics Using High-Speed Stereo-Radiography System

The measurement of dynamic joint kinematics in vivo is important in order to understand the effects of joint injuries and diseases as well as for evaluating the treatment effectiveness. Quantification of knee motion is essential for assessment of joint function for diagnosis of pathology, such as tracking and progression of osteoarthritis and evaluation of outcome following conservative or surgical treatment. Total knee arthroplasty (TKA) is an invasive treatment for arthritic pain and functional disability and it is used for deformed joint replacement with implants in order to restore joint alignment. It is important to describe knee kinematics in healthy individuals for comparison in diagnosis of pathology and understanding treatment to restore normal function. However measuring the in vivo dynamic biomechanics in 6 degrees of freedom with an accuracy that is acceptable has been shown to be technically challenging. Skin marker based methods, commonly used in human movement analysis, are still prone to large errors produced by soft tissue artifacts. Thus, great deal of research has been done to obtain more accurate data of the knee joint by using other measuring techniques like dual plane fluoroscopy. The goal of this thesis is to use high-speed stereo radiography (HSSR) system for measuring joint kinematics in healthy older adults performing common movements of daily living such as straight walking and during higher demand activities of pivoting and step descending in order to establish a useful baseline for the envelope of healthy knee motion for subsequent comparison with patients with TKA. Prior to data collection, validation and calibration techniques as well as dose estimations were mandatory for the successful accomplishment of this study

A 3D computer assisted Orthopedic Surgery Planning approach based on planar radiography

Dissertação de mestrado integrado em Engenharia Biomédica (área de especialização em Informática Médica)The main goal of this work consisted in develop a system to perform the 3D reconstruction of bone models from radiographic images. This system can be then integrated with a commercial software that performs pre-operative planning of orthopedic surgeries. The benefit of performing this 3D reconstruction from planar radiography is that this modality has some advantages over other modalities that perform this reconstruction directly, like CT and MRI. To develop the system it was used radiographic images of the femur obtained from medical image databases online. It was also used a generic model of the femur available in the online repository BEL. This generic model completes the information missing in the radiographic images. It was developed two methods to perform the 3D reconstruction through the deformation of the generic model, one uses triangulation of extracted edge points and the other don't. The first method was not successful, the final model had very low thickness, possibly because the triangulation process was not performed correctly. With the second method it was obtained a 3D bone model of the femur aligned with the radiographic images of the patient and with the same size as the patient's bone. However, the obtained model still needs some adjustment to coincide fully with reality. To perform this is necessary to enhance the deformation step of the model so that it will have the same shape as the patient's bone. The second method is more advantageous because it doesn't need the parameters of the x-ray imaging system. However, it's necessary to enhance the step deformation of this method so that the final model matches patient's anatomy.O principal objetivo deste trabalho consistiu em desenvolver um sistema capaz de realizar a reconstrução 3D de modelos ósseos a partir de imagens radiográficas. Este sistema pode posteriormente ser integrado num produto comercial que realiza o planeamento pré-operativo de cirurgias ortopédicas. O benefício de realizar esta reconstrução 3D a partir de radiografias está relacionado com o facto desta modalidade ter vantagens em relação às outras modalidades que fazem esta reconstrução diretamente, como as modalidades CT e MRI. Para desenvolver este sistema foram usadas imagens radiográficas do fémur obtidas através de bases de dados online de imagens médicas. Também foi usado um modelo genérico do fémur disponível no repositório online BEL. Este modelo genérico completa a informação que está em falta nas imagens radiográficas. Foram desenvolvidos dois métodos, que realizam a reconstrução 3D através da deformação do modelo genérico sendo que num é feita a triangulação de pontos dos contornos e noutro não. O primeiro método não foi bem sucedido, visto que o modelo final tinha uma espessura muito pequena, possivelmente devido ao facto do processo de triangulação não ter sido executado corretamente. Com o segundo método foi obtido um modelo 3D do fémur alinhado com as imagens radiográficas do paciente e com o mesmo tamanho do osso do paciente. No entanto, o modelo obtido carece ainda de alguma afinação de modo a coincidir na íntegra com a realidade. Para fazer isto é necessário melhorar o passo de deformação do modelo, para que este fique com a mesma forma do osso do paciente. O segundo método é mais vantajoso porque não necessita dos parâmetros dos sistema de raios- X. No entanto, é necessário melhorar o passo de deformação deste método para que o modelo final coincida com a anatomia do paciente

Hand X-ray absorptiometry for measurement of bone mineral density on a slot-scanning X-ray imaging system

Includes bibliographical references.Bone mineral density (BMD) is an indicator of bone strength. While femoral and spinal BMDs are traditionally used in the management of osteoporosis, BMD at peripheral sites such as the hand has been shown to be useful in evaluating fracture risk for axial sites. These peripheral locations have been suggested as alternatives to the traditional sites for BMD measurement. Dual-energy X-ray absorptiometry (DXA) is the gold standard for measuring BMD due to low radiation dose, high accuracy and proven ability to evaluate fracture risk. Computed digital absorptiometry (CDA) has also been shown to be very effective at measuring the bone mass in hand bones using an aluminium step wedge as a calibration reference. In this project, the aim was to develop algorithm s for accurate measurement of BMD in hand bones on a slot - scanning digital radiography system. The project assess e d the feasibility of measuring bone mineral mass in hand bones using CDA on the current system. Images for CDA - based measurement were acquired using the default settings on the system for a medium sized patient. A method for automatic processing of the hand images to detect the aluminium step wedge, included in the scan for calibration, was developed and the calibration accuracy of the step wedge was evaluated. The CDA method was used for computation of bone mass with units of equivalent aluminium thickness (mmA1). The precision of the method was determined by taking three measurements in each of 1 6 volunteering subjects and computing the root - mean - square coefficient of variation (CV) of the measurements. The utility of the method was assessed by taking measurements of excised bones and assessing the correlation between the measured bone mass and ash weight obtained by incinerating the bones. The project also assessed the feasibility of implementing a DXA technique using two detectors in a slot-scanning digital radiography system to acquire dual-energy X-ray images for measuring areal and volumetric BMD of the middle phalanx of the middle finger. The dual-energy images were captured in two consecutive scans. The first scan captured the low- energy image using the detector in its normal set-up. The second scan captured the high- energy image with the detector modified to include an additional scintillator to simulate the presence of a second detector that would capture the low-energy image in a two-detector system. Scan parameters for acquisition of the dual-energy images were chosen to optimise spectral separation, entrance dose and image quality. Simulations were carried out to evaluate the spectral separation of the low- and high-energy spectra

Quantitative imaging techniques for the assessment of osteoporosis and sarcopenia

Bone and muscle are two deeply interconnected organs and a strong relationship between them exists in their development and maintenance. The peak of both bone and muscle mass is achieved in early adulthood, followed by a progressive decline after the age of 40. The increase in life expectancy in developed countries resulted in an increase of degenerative diseases affecting the musculoskeletal system. Osteoporosis and sarcopenia represent a major cause of morbidity and mortality in the elderly population and are associated with a significant increase in healthcare costs. Several imaging techniques are currently available for the non-invasive investigation of bone and muscle mass and quality. Conventional radiology, dual energy X-ray absorptiometry (DXA), computed tomography (CT), magnetic resonance imaging (MRI) and ultrasound often play a complementary role in the study of osteoporosis and sarcopenia, depicting different aspects of the same pathology. This paper presents the different imaging modalities currently used for the investigation of bone and muscle mass and quality in osteoporosis and sarcopenia with special emphasis on the clinical applications and limitations of each technique and with the intent to provide interesting insights into recent advances in the field of conventional imaging, novel high-resolution techniques and fracture risk

Doctor of Philosophy

dissertationFemoroacetabular impingement (FAI) describes subtle structural abnormalities, including femoral asphericity and acetabular overcoverage, which reduce clearance in the hip joint. FAI is a common cause of hip pain for young, athletic adults. The first theme of this dissertation investigated if FAI morphology is more prevalent in athletes and if physical exams could be used to identify individuals with underlying FAI morphology. In a cohort of collegiate football players, 95% were found to have radiographic abnormalities consistent with those seen in FAI patients. This finding not only suggests that athletes, such as football players, may have an increased risk for developing symptomatic FAI, but also highlights that FAI morphology may frequently occur in asymptomatic subjects. In the same cohort, radiographic measures of femoral asphericity and femoral head-neck offset were mildly correlated to maximum internal rotation. As such, athletes with diminished internal rotation in whom hip pain develops should be evaluated for FAI. Altered articulation in FAI hips is believed to cause chondrolabral damage and may lead to osteoarthritis, but FAI kinematics have not been accurately quantified. To this end, the second theme of this dissertation focused on developing, validating, and applying a dual fluoroscopy and model-based tracking protocol to accurately quantify three-dimensional in vivo hip kinematics. In a cadaver experiment, model-based tracking was compared to the reference standard, dynamic radiostereometric analysis. Model-based tracking was found to have a positional error less than 0.48 mm and rotational error was less than 0.58°. The methodology was then applied to evaluate a cohort of asymptomatic control subjects and three patients with differing FAI morphology. The results, which represent the most accurate data collected on hip kinematics to date, demonstrate that hip articulation is a highly complex process, including translation, pelvic motion, no bone contact, and labrum involvement in large ranges of motion. Collected data provide necessary baseline results for future comparison studies and could be used to validate computer simulations of impingement, guide pre-operative planning, and serve as boundary conditions in finite element models investigating chondrolabral mechanics

Magnetic Resonance Imaging for the Functional Analysis of Tissues and Biomaterials

Articular cartilage provides mechanical load dissipation and lubrication between joints, and additionally provides protects from abrasion. At present, there are no treatments to cure or attenuate the degradation of cartilage. Early detection and the ability to monitor the progression of osteoarthritis is important for developing effective therapies. However, few reliable imaging biomarkers exist to detect cartilage disease before advanced degeneration in the tissue. One specialized MRI technique, termed displacements under applied loading by MRI (dualMRI), was developed to measure displacements and strain in musculoskeletal tissues, hydrogels and engineered constructs. However, deformation information does not directly describe spatial distributions of tissue properties (e.g. stiffness), which is critical to the understanding of disease progression. To achieve the stiffness measurement, we developed and validated an inverse modeling workflow that combined dualMRI, to directly measure intratissue deformation, with topology optimization in the application of heterogeneous (layered) materials representative of the complex gradient architecture of articular cartilage. We successfully reconstructed bi-layer stiffness from ideal displacements calculated from forward simulation as well as from experimental data measured from dualMRI. To monitor the progression of osteoarthritis, we measured and analyzed biomechanical changes of sheep stifle cartilage after meniscectomy. We found that 2nd principal strain and max shear strain in the femur contact region are sensitive to cartilage degeneration at different stages and compared to more conventional methods like quantitative MRI. To investigate the biomechanical changes in articular cartilage with defect and repair, we implanted decellularized cartilage implant into sheep cartilage defect and evaluate the repair results using quantitative MRI and dualMRI. We found that implants placed in joints demonstrated lower strains compared to joints with untreated defects

DYNAMIC MEASUREMENT OF THREE-DIMENSIONAL MOTION FROM SINGLE-PERSPECTIVE TWO-DIMENSIONAL RADIOGRAPHIC PROJECTIONS

The digital evolution of the x-ray imaging modality has spurred the development of numerous clinical and research tools. This work focuses on the design, development, and validation of dynamic radiographic imaging and registration techniques to address two distinct medical applications: tracking during image-guided interventions, and the measurement of musculoskeletal joint kinematics. Fluoroscopy is widely employed to provide intra-procedural image-guidance. However, its planar images provide limited information about the location of surgical tools and targets in three-dimensional space. To address this limitation, registration techniques, which extract three-dimensional tracking and image-guidance information from planar images, were developed and validated in vitro. The ability to accurately measure joint kinematics in vivo is an important tool in studying both normal joint function and pathologies associated with injury and disease, however it still remains a clinical challenge. A technique to measure joint kinematics from single-perspective x-ray projections was developed and validated in vitro, using clinically available radiography equipmen

Three-dimensional computation of femoral canine morphological parameters: from the theory to the surgery application

The present research was envisioned as a project defined by multiple studies that are strictly correlated each other. The report of the birth, development and practical application to the diagnostic and surgery fields of a novel 3D approach for the computation of femoral measurements was the first aim. Moreover, in the authors’ purpose the description of the translational value of the proposed procedure enhanced with its plausible utility to the daily practice of orthopaedic surgeons, represented another focal point. In this sense, the research started from the validation of the 3D assessment of femoral morphometric parameters. Veterinary literature reports tons of papers describing several methodologies for obtaining femoral measurements through different diagnostic techniques. Furthermore, bibliography presents lot of angles values that are currently adopted and considered as reference parameters for most of the corrective osteotomies. Additionally, in the recent past an increased emphasis on 3D approach grown but little if any attention was devoted to 3D measurements. This trend represented in the authors’ mind the gap with the current knowledge and, thus, an area to be deeply investigated. Indeed, to the best of author knowledge, there were no papers documenting the assessment of 3D femoral axes and angles in veterinary medicine, with no 3D protocol described. In addition, currently available canine femoral measurements related to frontal, sagittal and transverse deformities have only been computed in bi-planar projections, whether acquired from 2D or 3D imaging models. Therefore, starting from the accepted human methods and from the features definition in veterinary literature, we proposed a new approach. The first study was designed to define a 3D methodology, introducing a consistent and quantitative method for the assessment of femoral morphometric parameters in 3D geometrical models. To validate the proposed approach, accurate geometric data were necessary and, therefore, we opted for meshes obtained by a 3D scanner, instead of CT images. Once the validation of the was stated, our focus was directed towards the evaluation of the precision of the proposed 3D protocol. The validation of a novel diagnostic test requires verification of the repeatability, defined as the strength of agreement between repeated measurements of the same samples performed from one examiner, and the reproducibility as well, that express the same variance but between a group of observers. Furthermore, the accuracy of the measurements indicates how close the measurements took with the investigated technique to a true value (gold standard). Therefore, a second project was designed to test the precision of three diagnostic techniques, two largely diffuse (Rx and TC) one recently introduced in veterinary (3D), for the measurement of femoral angles. The second purpose of this study was the investigation of the potential application of the algorithm implemented in a computer-aided-design (CAD) software, using CT data. Considering that for the first study we worked with 3D scanner data, the main aim at this point of the research was represented by the enhancement of the presented 3D protocol for diagnostic purposes. In the author opinion, changing the source of data was necessary because of the availability of CT and MRI equipment in veterinary practice. Finally, the last goal of this project was the translation of the application of 3D computation to the surgical field. The current research contemplates the fact that the augmented interest on 3D computation is not only relevant for diagnostic reasons, but also for surgery. Thus, the correlation between the diagnostic utility of the 3D approach and its plausible practice for surgery purposes was the object of the final study. The starting point was suggested by veterinary literature that reports in few papers the development and application of surgical devices used to perform assisted-correction of bone deformities. These surgical tools are designed through 3D geometrical models and act both as precise intraoperative localizers of osteotomy corrective landmarks and surgical saw guides. Three-dimensional assessment of a bone conformation may improve the understanding and evaluation of bone deformities and occurring joints malalignment. In this sense, the localization of the CORA as well as the accuracy of the orientation of the osteotomy-cutting plane may be significantly upgraded through a 3D approach

Bone marrow Fat - A Novel Quantification Method and Potential Clinical Applications

Ageing bone is characterised by increased marrow fat infiltration altering its composition and microstructure, thus predisposing the person to osteoporosis. Yet to date, non-invasive quantifications of marrow fat are limited to special MRI techniques, and clinical studies examining marrow fat in the ageing skeleton are scarce. Thus, the key aims of this thesis are to: · Validate a new non-invasive technique of marrow fat quantification using CT technology · Determine the effects of dietary fatty acids on marrow fat · Measure marrow fat content in different skeletal regions in healthy older men · Determine the effect of exercise and calcium on marrow fat. The imaging techniques employed in our animal and human studies were micro CT (µCT) and quantitative CT (QCT) respectively. All images were analysed with the imaging software Slice O Matic version 4.1 (Tomovision). Regions of interest [ROIs] were Volumes of interests (VOIs) of bone, fat and blood measured in µm3 or mm3. Individual tissue volumes, expressed as percentages of the total marrow volume, and ratios of tissue volumes were also used in the analysis. Global and local thresholds for individual tissue volumes were determined separately for µCT and QCT. Thresholds for µCT were those derived from the initial validation study, whereas those for QCT were based on previous published data. To account for partial volume averaging effects, further manual refinement of threshold ranges were undertaken by inspection of individual pixels and their neighbours. This manual process was carried out for both µCT and QCT to derive local thresholds for use in manual segmentation and computation of volumes. Our validation study showed that quantification of marrow fat using µCT was reliable and accurate compared to the gold standard technique- histology- when reliably defined thresholds were used. Good agreement between tissue volumes measured by histology and those computed by the imaging software was demonstrated. We applied this technique to quantify marrow fat in an animal model of senile osteoporosis, and showed that fatty acids (ω- 3 and ω-6) had dual effects on bone. With QCT studies, we confirmed the age related increase in marrow adiposity, and more significantly, different ratios between fat and bone in common fracture regions. Similarly, exercise affects marrow fat differently in different regions, and there was a trend to statistically significant changes to marrow fat with exercise. In conclusion, this body of work showed that quantification of marrow fat using CT is promising, and has future clinical implications. However, significantly more clinical studies are needed to confirm these findings and refine shortfalls in quantification capabilities