115 research outputs found
Forehead Flap Templates for Nasal Reconstruction Digitally Developed From 2D and 3D Images
No full textThis 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
Characterization of the Mechanical Impact of Focal and Systemic Cancer Treatments on Healthy and Metastatically Involved Vertebral Bone
No full textApproximately one third of cancer patients are diagnosed with vertebral metastasis and associated bone quality impairment. Treatments for metastatic disease have proven beneficial to overall prognosis, yet their effects on bone quality are not fully characterized. This research utilizes image analysis, physical testing, and generative deep learning (DL) approaches to characterize bone quality and treatment-associated changes in a preclinical rat model of osteolytic vertebral metastasis. The specific aims are to enhance barium sulfate (BaSO4) labelled microdamage visualization in μCT images of vertebrae, determine tissue level material and mechanical properties of healthy and osteolytic vertebrae with and without treatment, and develop generative DL models predicting vertebral fracture. μCT image acquisition parameters were iteratively adjusted to enhance BaSO4 contrast and spatial resolution. Enhanced μCT image acquisition parameters yielded BaSO4 labels with high probability of pixelwise spatial correlation (83% within 20 μm) to microdamage evaluated in gold-standard backscatter electron (BSE) images. This work provides a high-resolution protocol for 3D μCT analysis of microdamage accumulation in vertebral bone.
Microdamage accumulation, load-to-failure, and microstructural parameters were measured in healthy and osteolytic rat vertebrae with and without treatment (stereotactic body radiotherapy (SBRT), docetaxel, zoledronic acid). Microdamage was increased in metastatic vertebrae and was reduced by all treatments. Load-to-failure was decreased in untreated and SBRT tumor-injected rats compared to healthy controls. Strong correlations were found between microstructural parameters, load-to-failure and microdamage accumulation.
A DL approach was developed to produce sample-specific synthetic μCT images of rat vertebrae undergoing destructive testing. The cGAN generated realistic 3D µCT images of rat vertebrae through the fracture process. This motivated the development of a hybrid modeling approach using a dual encoder cGAN to augment input μCT images with physics models, including axial rigidity and linear elastic strain. The axial rigidity model significantly improved fracture prediction precision compared to the baseline model, with the F1-score trending to significance. This work has provided recommendations for future DL approaches using improved loss functions for identifying generated fractures.
This research has contributed new imaging, physical testing, and DL methods for assessing bone quality in the metastatic spine and has quantified the impact of disease and clinically relevant cancer treatments. The outcomes of this work may better inform treatment planning to prevent bone quality degradation in patients with vertebral metastatic disease.Ph.D
Characterizing the Mechanical Behaviour of the Human Pelvis Through Finite Element Analysis
No full textIn the human musculoskeletal system, the pelvis functions as a crucial transfer point for upper body loads to the lower extremities. Existing treatments in the field of pelvic reconstructive surgery do not account for versatile structural differences in pelvic geometries and variations in pelvic bone properties. This thesis aims to develop a novel approach to facilitate and automate the creation of multiple specimen-specific finite element (FE) models of the pelvis and to utilize these models to characterize mechanical behavior of the pelvis, under healthy and pathologic conditions. Robust generation of pelvic FE models is necessary to understand variations in mechanical behaviour resulting from differences in gender, aging, disease, and injury. A new semi-automated landmark-based FE morphing and mapping approach was developed for pelvic FE model generation without the need for segmentation. A cohort of specimen-specific pelvic FE models was generated using the new approach and the models were validated against experimental data in double leg stance configuration. The validated cohort of specimen-specific pelvic FE models was utilized to examine pelvic strains at different phases of the gait cycle (double leg stance, heel-strike/heel-off and midstance/midswing). The FE models revealed that the strain patterns throughout the pelvic structure between the double leg stance and heel-strike/heel-off configurations are not significantly different, whereas a significant difference was found in the midstance/midswing configuration. The morphing methodology was further extended to generate pelvic FE models of different shapes and to analyze their biomechanical behaviour. A significant difference was found in the strain patterns between the android (classic male shape) and gynecoid (classic female shape) pelvises. Finally, a specimen-specific pelvic FE model of an open book fracture was developed and validated against experimental data. The strain patterns identified in the fractured model aligned with the clinical understanding of open book fracture pathology. Overall, the findings of this thesis provide new understandings into the complex biomechanical behaviour of the human pelvis. This work creates a platform for more complex future FE modeling investigations to continue to study the behaviour of this multifaceted skeletal structure.Ph.D
The Impact of Photodynamic and Radiation Therapies in the Metastatic Spine
No full textThere is an increasing number of treatment options for spinal metastasis including stereotactic body radiotherapy (SBRT), and emerging modalities such as photodynamic therapy (PDT). Quantifying the impact of treatments on bone quality is critical to improve fracture risk prediction and multimodal treatment planning, towards optimizing quality of life for patients with spinal metastases. Treatment efficacy for these local minimally invasive therapies requires personalized treatment planning. This is standard of care for SBRT. In the context of PDT however, treatment planning protocols are needed to optimize the number, power and interstitial locations of the fiber-based diffusers. Critical to safety in this process is knowledge of the photodynamic threshold of the spinal cord. As such, this work accomplishes two objectives: 1) derives the PDT spinal cord threshold value for a preclinical model of spinal bone metastasis, and 2) characterizes changes in healthy and metastatically involved vertebral bone secondary to SBRT and PDT.M.A.S
Computer Vision and Machine Learning in Orthopaedic Shoulder Surgery
No full textThis thesis describes the design, implementation, and pre-clinical validation of two distinct biomedical technologies that address current challenges in orthopaedic shoulder surgery. The first is an intra-operative optical surface imaging system based on a hand-held structured light sensor for improving glenoid positioning in total shoulder arthroplasty. The second is a system for tracking adherence to shoulder physiotherapy using inertial sensors embedded in a smart watch and machine learning.
Glenoid implant positioning is an important and challenging step in total shoulder arthroplasty. Accurate glenoid positioning is essential for prosthesis longevity and functional outcomes. This thesis presents Bullseye, a novel method to ensure accurate glenoid guide pin placement using intra-operative structured light imaging combined and computer vision. Pre-clinical validation on sawbone and cadaveric scapulae demonstrates this system accurately and efficiently measures the glenoid guide pin position within a verification workflow that integrates well into routine surgical practice. Clinical validation is required to determine if use of the Bullseye technology improves component positioning outcomes and patient clinical outcomes in the context of a clinical trial.
Physical therapy is considered essential for the successful rehabilitation of common shoulder injuries and following shoulder surgery. Patients may receive some training and supervision for shoulder physiotherapy through private pay or private insurance, but they are typically responsible for performing most of their physiotherapy independently at home. It is unknown how often patients perform their home exercises and if these exercises are done correctly without supervision. There are no established tools for measuring this. It is therefore unclear if the full benefit of shoulder physiotherapy treatments are being realized. This thesis presents the Smart Physiotherapy Activity Recognition System (SPARS) for tracking home shoulder physiotherapy exercises using inertial sensors in a consumer smart watches and a machine learning approach. SPARS was successful in classifying shoulder exercises in healthy adults in the laboratory setting. Clinical validation to establish the performance of this technology with patients and investigate the potential individual and societal impacts of its use is ongoing.Ph.D
Machine Learning to Predict and Optimize Lower Extremity Arthroplasty Resource Utilization
No full textTotal knee and hip arthroplasty (TKA and THA, respectively) are common and resource intensive procedures contributing to significant burden on healthcare systems. The overall aim of this thesis project is to identify and develop strategies to improve elective surgical scheduling for TKA and THA. Machine learning and optimization to predict resource utilization-related outcomes such as duration of surgery and length of stay for arthroplasty patients were identified. A predict-then-optimize approach utilizing neural network models and linear programming was compared to historic scheduling strategies. Data sources for this work include the administrative National Surgical Quality Improvement Program and an institutional database from the Holland Centre at Sunnybrook Health Sciences Centre. The most important features of the neural network models for outcome prediction were identified and compared between databases. Together, these findings are the foundation upon which to develop a “smart” surgical scheduling system and improve the efficiency of operating room utilization.M.A.S
Simulation Optimization of Operating Room Schedules for Elective Surgeries
No full textThis is an accepted manuscript version of a conference paper published as Maltseva, D., Chen, S., Lex, J., Abbas, A., Whyne, C. (2024). Simulation Optimization of Operating Room Schedules for Elective Surgeries. In: Fujita, H., Cimler, R., Hernandez-Matamoros, A., Ali, M. (eds) Advances and Trends in Artificial Intelligence. Theory and Applications. IEA/AIE 2024. Lecture Notes in Computer Science(), vol 14748. Springer, Singapore. https://doi.org/10.1007/978-981-97-4677-4_31Our specific problem is to create daily schedules of elective surgeries in a multiple operating room setting with the goals of minimizing the amount of overtime incurred and maintaining patient volumes. While surgical durations cannot always be perfectly estimated and vary by procedure and surgeon, our approach relies on leveraging the stochastic nature of surgical durations to simulate each operating day and understand the probability of incurring overtime under a certain schedule of surgeries. The heuristic optimization component of our approach investigates the probabilistic evaluation and strategically re-schedules surgeries. Through experimentation with three optimization techniques, two showed promising results being able to reduce the total number of overtime surgeries by 12–15%, equivalent to approximately 1h of total monthly overtime. Compared to the literature, this approach serves solely as a tool for improving schedules and can be used for supporting decision making at the hospital. Our contribution involves introducing the simulation optimization model and describing the data-driven approach to analyzing the scheduling problem.(Natural Sciences and Engineering Research Council of Canada|RGPIN-2022-04524
Hip Replacement Head-Neck Taper Connection Tribocorrosion Reduction by Head Material, Head Size and Taper Geometric Optimization
No full textModular femoral head hip replacement components connect to the femoral stem via matching tapers. Metals commonly used to manufacture femoral heads and stems rely on a passive oxide layer to resist corrosion. Under cyclic loading (i.e. gait) relative micromotion between the head and stem causes wear, removal of the oxide layer and subsequent corrosion by a process called tribocorrosion. Metallic debris released by tribocorrosion may result in adverse local tissue reactions called trunnionosis and may require revision surgery.The objective of this research was to investigate factors affecting head-neck taper tribocorrosion, including head size, material and taper geometry. A systematic review of prosthetic design, manufacturing and surgical technique factors related to taper connection tribocorrosion was performed. The review included 91 studies investigating 35 unique factors, of which only 7 had adequate evidence to support a recommendation. In particular, a gap in evidence related to taper connection design was identified. It was found that poor study design resulted in inconclusive or contradictory evidence for the majority of factors.
A second review was performed of taper tribocorrosion in-vitro test methods to improve study design and increase clinical translation of results. A deficiency in current in-vitro test methods was identified where samples are only cyclically axially compressed. Frictional torques due to joint movement that may be larger with larger femoral heads are excluded. Therefore, a novel instrumented hip simulator was developed to measure corrosion related electrical activity during simulated gait.
The test apparatus was employed to investigate susceptibility to corrosion of different head sizes (28 vs 36mm cobalt-chrome femoral heads), materials (cobalt-chrome, ceramic and oxidized zirconium) and taper geometry (angle, diameter, length and surface finish). The study of taper geometry followed design of experiments methodology. Twenty-five uniquely designed test samples with a range of taper angles, diameters, lengths and surface finishes were custom manufactured and tested. It was found that large diameter cobalt-chrome femoral heads are most susceptible to corrosion, oxidized zirconium exhibits similar corrosion resistance to ceramic, and that thicker, shorter tapers with either low roughness and high angle, or high roughness and low angle, are least susceptible to short term corrosion.Ph.D.2022-11-29 00:00:0
Bone Targeted Radiofrequency Ablation (RFA) Electrodes for the Treatment of Appendicular and Vertebral Metastases
No full textBone metastases, an unfortunate and frequent occurrence in cancer, can result in skeletal related events, including pain, pathologic fractures, and hypercalcemia. Treatment strategies, such as surgery and/or radiation therapy, can be limited by invasiveness, maximum dose levels, and radio-resistivity. In this context, image-guided minimally invasive thermal treatment modalities such as radiofrequency ablation (RFA) have gained interest in the treatment of bone metastases. RFA conducts an alternating current through a probe placed within the tumour, resulting in ionic excitation of cells and frictional heating. RFA is reliant upon thermal and conductive properties of the tissue and leads to coagulative necrosis. Current technology developed and tested in soft tissues is limited by carbonization, small and unpredictable zones of ablation, particularly when used in bone. The lower conductive properties of bone tissue and proximity of bone to critical structures further challenge RFA application. This thesis focuses on design and evaluation of two novel bone-targeted RFA electrodes, a bipolar cooled RF (BCRF) and a solenoid-shaped (Bone Coil) RF probe, to improve the size and efficacy of RFA in bone. RFA was evaluated using healthy porcine and diseased lapine models with outcomes assessed through Magnetic
Resonance Imaging (MRI) and histologic analysis of bone and tumour tissue. A cadaveric model was used to evaluate the role of RFA on spinal stability alone and in combination with vertebroplasty. Both BCRF and Bone Coil RF ablation were safe and effective in the spine. T2-weighted and contrast-enhanced T1-weighted MRI sequences two weeks post treatment were found to be most effective for image-based therapeutic evaluation. BCRF ablation yielded an eight-fold reduction in tumour volume in the rabbit femur. Treatment necrotized osteoblasts and osteoclasts comprehensively, whereas osteocytes were found to be more resilient to RFA. New bone formation and remodelling was observed at the ablation zone periphery. RFA alone led to reduced vertebral stability, but a restoration of strength and stability comparable to healthy levels was achieved when RFA treatment was combined with cement injection localized into the posterior portion of the vertebral body. Overall, this work motivates the future use of bone-targeted RF technology in the treatment of skeletal metastases.Ph.D
The Craniomaxillofacial Skeleton: New Approaches in Computational Biomechanics and Fracture Stabilization
No full textThe mechanical behaviour of the craniomaxillofacial skeleton (CMFS) under physiological loads is among the least understood in the field of musculoskeletal biomechanics. The highly complex structure of the CMFS defies reduction to analogous or simpler components. Its modelling demands a holistic and integrated approach in order to gain insight into its structural function. As such, the biomechanical foundations upon which the practises for open-reduction internal-fixation are developed are controversial. A systematic and quantitative biomechanical framework is needed to guide the treatment of CMFS injuries and pathologies. This research aims to address these issues on two fronts: through characterization of the loading patterns of the CMFS derived from computational modelling, as well as the development of an innovative internal stabilization device for the CMFS. This thesis first addresses the challenges through a practical and novel approach whereby a deblurring algorithm is applied to clinical CT images which restores the geometry and intensity of the thin cortical bone structures. Using these restored images a biomechanical framework was further developed to produce high fidelity subject-specific finite element models of the CMFS. Validation of this approach was demonstrated through strong correlation with multi-subject in vitro experiments (r = 0.93, regression slope of unity). These models elucidated the patterns of stress and strain on the CMFS subject to a simulated physiological masticatory bite load. The observed patterns invite a critical re-analysis of the classic CMFS buttress hypothesis. Finally, a pilot experimental investigation into the mechanical efficiency of "Bone Tape", a bioresorbable polymer-ceramic composite device for internal fixation of CMFS fractures, was conducted. In vitro experiments demonstrated an initial flexibility which conferred an ability to conform to complex 3-D bone topologies and a potential to equate the strength of commercially available bioresorbable systems. A prototype concept for its use was deployed in an in vivo rabbit model. The structural biomechanics knowledge gained based on the validated computational biomechanical framework will ultimately provide a robust platform which will enable the rational design and optimization of new treatment hardware and practises, such as Bone Tape, toward improved outcomes in reconstruction of the CMFS.Ph.D.2016-06-16 00:00:0
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