1,721,054 research outputs found
Can CT image deblurring improve finite element predictions at the proximal femur?
No full textObjective: Clinical application of computed tomography (CT) based finite element (FE) estimates of bone strength recently showed encouraging results [1]. However, model performance may be improved. In fact, in-vitro valida- tion studies showed systematic errors in strain prediction, especially where bone cortex is thin (i.e. the femoral neck) [2].
This work seeks to verify if, and to what extent, a CT deblurring algorithm restoring both geometry and intensity data in thin bone structures [3], can improve strain and failure load prediction accuracy of CT-based FE models of the prox- imal femur.
Material and Methods: CT scans were acquired of 14 fresh-frozen human cadaveric femora. An estimate of the 3D Point Spread Function for each CT scan was used within a deconvolution solver to perform deblurring. Using the restored images, FE models of the proximal femur were generated [4]. Each femur was tested non- destructively in both stance and fall loading configurations to measure surface strains, and then loaded to failure in stance or fall.
Deblurred FE predictions of strains and failure load were com- pared to experimental measurements, and FE predictions ob- tained from the original CT data (no deblurring).
Results: An enhancement in strain prediction accuracy was obtained using deblurred FE models, with the Standard Error of Estimate reduced by 11 % with respect to reference FE models. Marked improvements at the femoral neck were achieved (e.g. peak error reduced by 38 %). Using deblurred models, the regression equation between FE-predicted and measured failure loads was characterized by a slope not sig- nificantly different from one, with R2 = 0.89, unchanged with respect to reference models. Absolute differences between estimated and measured failure loads were consistently re- duced by deblurring in stance (mean error 10 vs. 15 %) but not in fall (32 vs. 17 %).
Conclusions: The proposed CT deblurring technique yielded moderate but significant improvements in femo- ral FE predictions, and can thus be seen as a first and worthwhile step in the improvement of CT-based FE models of the human femur
Forehead Flap Templates for Nasal Reconstruction Digitally Developed From 2D and 3D Images
Full text linkThis is a non-final version of an article published in final form in Fishman, Zachary PhD; Whyne, Cari M. PhD; Fialkov, Jeffery A. MD. Forehead Flap Templates for Nasal Reconstruction Digitally Developed
From 2D and 3D Images, Journal of Craniofacial Surgery: August 03, 2021 DOI: 10.1097/SCS.0000000000008023The forehead flap is the gold standard procedure for nasal reconstruction to address a partial or
complete rhinectomy. Traditionally, the 3D nasal defect is manually templated intra-operatively to
design the 2D flap shape on intact morphology. In this clinical study, digital pre-operative planning is
used to template with computer-assisted design and manufacturing (CAD-CAM). Pre-operative digital
templates were implemented for 3 representative patients (1 in supplementary material). This includes
designs for a hemi-rhinectomy case from 3D mirroring, a partial total rhinectomy case generated from a
3D scan, and a total rhinectomy case generated from a 3D morphable model based on a pre-pathology
2D photo. Digital unwrapping flattened the patient’s 3D nasal geometry designs to 2D skin flap shapes.
Finally, the 2D designs were printed as traceable intra-operative templates at a 1:1 scale. This clinical
study demonstrates the application of digital 3D preoperative templating to improve workflow for nasal
reconstruction.Support for this work has been provided by the Natural Sciences and Engineering Research Council of Canada
Structural Effects of Photodynamic Therapy and Bisphosphonates on Healthy and Metastatically Involved Vertebral Bone
Full text linkThe vertebral column is the most common site of skeletal metastatic development secondary to breast cancer. Multiple clinical treatments are available for spinal metastasis, including systemic bisphosphonates and radiation therapy, however the success of current treatment approaches varies considerably. Alternative treatment strategies for spinal metastatic destruction must be aimed at both reducing tumor burden and restoring mechanical stability. Photodynamic therapy (PDT) has been shown to be successful at destroying osteolytic lesions in preclinical models of breast cancer spinal metastasis. However, the clinical feasibility of PDT for spinal metastasis is dependent on its potential effects on the structural integrity of vertebral bone. This thesis aims to determine the effects of PDT alone and in combination with bisphosphonate therapy on the structural architecture and mechanical properties of healthy and metastatically involved vertebrae. PDT was shown to have a positive effect on vertebral bone structure, alone and in combination with previous bisphosphonate therapy.MAS
Identifying Challenges and Understanding Culture in the Operating Room through a Surgical Process Analysis of Orthopaedic Teams
Full text linkThis thesis explores multidisciplinary teamwork in orthopaedic trauma surgery through two studies of hip fracture repair following an ethnographic approach. The first study maps the surgical workflow across surgeons, anesthesiologists, nurses, and radiation technologists (RTs), identifying discipline-specific responsibilities, interactions, and critical moments. The resulting surgical process map and thematic analysis reveal how misaligned critical points and communication breakdowns can disrupt team coordination and patient care. The second study builds on these findings by examining team culture using the framework of work-as-imagined versus work-as-done. Interview data revealed expectations versus reality in operating room (OR) collaboration, with particular attention to teaching practices, communication, and the RT role. The findings expose cultural tensions and hierarchies that impact team functioning, and opportunities for improving team familiarity, inclusion, and shared understanding. Together, these studies offer a human factors perspective on OR dynamics and provide a foundation for targeted interventions to strengthen surgical teamwork and safety.M.A.S
Image-based Characterization of the Mechanical Behaviour of Healthy and Metastatically-involved Vertebrae
No full textSkeletal metastasis leads to changes in bone architecture, quality and strength, including microdamage accumulation. This dissertation aims to combine image-based computational and experimental techniques to study trabecular bone microdamage in healthy and metastatic whole bones. Deformable image registration was used to demonstrate proof of concept that post-euthanasia strain analysis of µCT images represents in vivo quasi static mechanical behavior of whole rat vertebrae. The ability to concurrently identify microdamage in whole vertebrae using histologic techniques (calcein and fuschin) and contrast enhanced BaSO4 µCT imaging was demonstrated and compared to stresses and strains calculated through micro finite element analysis. Significantly higher stresses and strains were found in regions of trabecular microdamage compared to undamaged regions, and in metastatic compared to healthy vertebrae. The techniques and knowledge developed through this work improve understanding of trabecular bone microdamage and form a solid platform for modeling the material and structural behaviour of skeletal tissue.M.A.S
Knee Tissue Strains and Effectiveness of a Novel Functional ACL Knee Brace during Dynamic In-Vitro Loading
No full textFunctional knee braces are commonly prescribed to help stabilize and protect the knee after an ACL injury or reconstruction. Newer brace designs employ a dynamic tensioning system to apply directional forces to the knee. The purpose of this thesis was to characterize meniscal loading under dynamic loading conditions and test the efficacy of a functional knee brace equipped with a dynamic tensioning system to reduce ACL and meniscal strain. A combined in-vivo/in-silico/in-vitro testing method was used to quantify tissue strains and the effect of the brace on cadaveric specimens. Tissue strains were quantified and validated before and after reconstruction, and the brace was found to lower tissue strains during most conditions. This work provides supportive evidence for the use of braces with a dynamic tensioning system for patients who are ACL deficient or following reconstruction.M.Sc
Image Based and Biomechanical Characterization of Osteoblastic Vertebral Metastases
Full text linkThe negative consequences of fracture in the metastatic spine motivates improved bone quality assessment and fracture risk prediction. This study aims to automate preclinical microcomputed tomography (µCT) image identification of osteoblastic metastatic disease in vertebrae, characterize how metastases affect the material/mechanical properties of bone tissue and extend finite element (FE) modeling to include pathological changes to evaluate damage and fracture behaviour. A combination of image analysis techniques (µCT-based stereological analysis, back scatter electron microscopy) and computational modeling (voxel-based µFE modeling of post-yield mechanical behaviour experimentally validated through sequentially imaged mechanical testing) is used to characterize the structural and material level impact of osteoblastic disease in vertebral trabecular bone. Methods for automated segmentation of osteoblastic lesions are also developed with µCT feature extraction and random forest classification methods to enable identification of pathologic tissue. Advanced preclinical understanding of osteoblastic disease can provide a foundation for improved guidelines for clinical treatment decision-making.M.A.S
Short and Longer-term Effects of Photodynamic Therapy and Combination Treatments on Healthy and Metastatically-involved Vertebrae
No full textCurrent treatment for spinal metastasis involves a multimodal approach, including bisphosphonates and radiation therapy. Yet, tumour response varies considerably, thus novel treatments or combination therapies are needed to treat these metastases while preserving stability and integrity of the spinal column. Photodynamic therapy (PDT) has been shown to be successful in destroying vertebral osteolytic tumours and enhancing vertebral structure, particularly in combination with bisphosphonates. This thesis aims to evaluate the longer-term effects of PDT alone and in combination with bisphosphonate or radiation therapy on healthy vertebrae, and the short-term effects of PDT combined with radiation therapy on healthy and metastatically-involved vertebrae. The benefits of PDT on vertebral structure, both at short-term and longer-term time-points, were greatest in combination with previous bisphosphonate therapy. Similar effects, to a lesser magnitude, were seen with PDT in combination with radiation therapy. This work supports future translation of PDT for the treatment of spinal metastases.MAS
Biomechanics of Medial Opening-wedge High Tibial Osteotomy in Healthy and Arthritic Knees
Full text linkMedial opening-wedge high tibial osteotomy (MOW-HTO) is a well-established treatment option for patients with medial knee osteoarthritis. This thesis aimed to investigate the difference between healthy and arthritic knees in response to MOW-HTO alignment correction. Additionally, we aimed to investigate the effect of partial and complete superficial medial collateral ligament (sMCL) release across a range of clinically relevant alignment corrections. Cadaver knees were tested under axial loading while measuring tibiofemoral compartment pressure. Arthritic knees did not differ from healthy knees in response to alignment corrections. Compared to constitutional alignment, medial pressure decreased at post-operative mechanical axes crossing the tibial plateau at 50–55% of its width, while sMCL release did not impact medial pressure. This work shows that arthritic status was not a significant factor in MOW-HTO biomechanics and that significant unloading occurs after correcting the mechanical axis to 50–55% of the tibial plateau width, irrespective of sMCL release.M.Sc
Design and Evaluation of Orthopedic Alignment Tools for Guidewire and Screw Insertion
Full text linkThe Femoral Antegrade Starting Tool (FAST) was invented to facilitate guidewire alignment in femoral intramedullary nailing procedures. Previous cadaver studies demonstrated FAST’s potential to reduce surgical time and radiation exposure. This thesis continued the development of FAST through a first in human trial and expanded the guidewire insertion technology to be applicable to pelvic reconstruction procedures.
The FAST design was enhanced for usability, manufacturability, assembly, sterilization and cleaning. A clinical pilot study to evaluate the tool’s safety and surgical workflow was planned and successfully executed (n=10). Expanding the technology to pelvic reconstruction included consultations with surgeons, substantial design changes, prototyping and simple usability studies. This resulted in the creation of two proof of concept prototypes. Initial surgeon feedback supports the potential of FAST and the pelvic guidewire/screw positioning tool. Further improvements to the FAST and pelvic tool workflows and designs are suggested towards ultimately bringing these technologies into clinical practice.M.H.Sc.2021-06-22 00:00:0
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