Mosaic Arthroplasty is a well-accepted surgical approach to treating focal cartilage defects of the knee. However, the task of creating the mosaic of osteochondral grafts that optimally restores the cartilage surface is technically demanding. Conventional techniques require the surgeon to reconstruct a complex, three-dimensional surface by eye and experience only. There is evidence that this type of procedure is sensitive to technique: grafts that are transplanted proud of the native cartilage surface tend to show evidence of cartilage fissuring and fibrillation prematurely. Two computer-assisted techniques (navigation by optical tracking and guidance by patient-specific templates) were investigated to determine whether they would have a beneficial effect on surgical execution, and whether any differences in execution had any correlation to surgical outcome. The experimental work can be broken into two parts: an in vitro study that compared the accuracy of execution of an optically navigated group versus a template guided group, and an in vivo animal trial that compared both computer assisted techniques to the conventional, non-assisted approach. The results of the pilot study indicated that, while there were higher errors in the individual measures of position, orientation, and plug depth in the optically navigated group, there was no significant difference in the overall fidelity of the geometric surface produced between the two groups. The results of the animal trial indicated that both computer assisted techniques produced morphological results that were superior to the conventional technique. The two computer-assisted techniques also showed a significantly better treatment effect as seen by their higher histological scoring. Furthermore, a significant linear correlation was found between morphological results and histological score. Overall, the experiments demonstrated that surgeons and patients could potentially benefit from the use of computer-assisted techniques in the short term. Further work is required to prove long-term beneficial effect. / Thesis (Master, Mechanical and Materials Engineering) -- Queen's University, 2012-11-02 20:50:33.957

This dissertation presents a thesis on the use of additive manufacturing in the development and evaluation of a computer-assisted system for wrist-fracture repair. The work developed tools for performing navigated wrist surgery, developed methods for evaluating surgical performance, and provided novel experience with model-based surgical evaluation. Patient-derived bone models, fabricated using additive manufacturing, were proposed as an alternative to cadaver specimens for testing and validating the new surgical system. The accuracy of fabricating these models from computed-tomography imaging was investigated using laser scanning and was found to be reproducible to within half a millimeter. Three generations of a surgical system for navigated wrist-fracture repair were developed and evaluated using a wrist model that was produced by additive manufacturing. Compared to cadaver specimens, the model was less expensive and performed equally well under simulated surgical conditions. The model-based evaluation permitted larger study sizes that increased the statistical power of the experimental results. Criteria for surgical performance included surgical and technical measurement of screw placement. The navigation system was superior in optimizing screw placement compared to conventional surgical methods. Navigation also reduced the risk of radiation exposure and clinical complications of wrist-fracture repair. Surgical tools, including a drill guide and wrist-stabilization device were developed with the use of additive manufacturing. Prototype devices could be quickly and economically fabricated for testing under realistic conditions. A system for performing navigated wrist fracture repair was successfully developed through the use of additive-manufacturing prototyping and evaluation. Additive manufacturing was integral to the successful evaluation of the system's improvement in performance. / Thesis (Ph.D, Mechanical and Materials Engineering) -- Queen's University, 2012-12-19 11:40:46.269

Image-guided interventions using intraoperative three-dimensional (3D) imaging can be less cumbersome than systems dependent on preoperative images, especially by needing neither image-to-patient registration nor a lengthy process of segmenting and generating a 3D model. In this dissertation, a method for computer-assisted surgery using direct navigation on intraoperative images is presented. In this system the registration step of a navigated procedure was divided into two stages: preoperative calibration of images to a ceiling-mounted optical tracking system, and intraoperative tracking during acquisition of the 3D image. The preoperative stage used a custom-made multi-modal calibrator that could be optically tracked and also contained fiducial spheres for radiological detection; a robust registration algorithm was used to compensate for the high false-detection rate that arose from the optical light-emitting diodes. Intraoperatively, a tracking device was at- tached to bone models that were also instrumented with radio-opaque spheres; a calibrated pointer was used to contact the latter spheres as a validation. The fiducial registration error of the calibration stage was approximately 0.1 mm with the Innova 3D X-ray fluoroscope and 0.7 mm with the mobile-gantry CT scanner. The target registration error in the valida- tion stage was approximately 1.2 mm with the Innova 3D X-ray fluoroscope and 1.8 mm with the mobile-gantry CT scanner. These findings suggest that direct registration can be a highly accurate means of performing image-guided interventions in a fast, simple manner. / Thesis (Master, Computing) -- Queen's University, 2009-08-17 11:14:03.275

No description available.

In image-guided surgical navigation, instruments tools are tracked by a position sensor and their locations rendered along with the patient's anatomy. Conventional methods require an invasive, time-consuming and potentially uncertain process of intra-operative registration of the images to the patient. In a direct navigation system, such an intra-operative registration is replaced with pre-operative patient-independent calibration in a process that determines the relationship between the coordinate frame of imaging equipment and the coordinate frame of the position sensor. This dissertation presents a method for pre-operatively calibrating a direct navigation system that used an optical position sensor and a mobile gantry CT scanner. A custom bi-local calibration device was designed and manufactured, after which existing navigation software was augmented with components that used the pre-operatively determined transformation to provide image-guided surgical navigation. The resulting system was tested in an image-guided operating suite using plastic bone models. In the validation stage, the inherent error was less than 0.4 mm and the target registration error was approximately 1.6 mm for a ceiling-mounted position sensor and 0.7 mm for a portable position sensor. This accuracy is consistent with the best intra-operative registrations reported in the literature and this calibration method may be useful in future surgical systems. / Thesis (Master, Computing) -- Queen's University, 2013-09-05 12:53:08.994

Thesis (M. S. in Biomedical Engineering)--Vanderbilt University, Dec. 2007. / Title from title screen. Includes bibliographical references.

A dissertation submitted to the Faculty of Health Sciences, University of the Witwatersrand, 5 February 2019, in fulfilment of the requirements for the degree Master of Science in Medicine / Adult age estimation is of value when creating a biological profile for an unknown set of human remains. Two age estimation methods, the well-known Suchey-Brooks method and the newly introduced Enhanced Computational methods were investigated. Differences between males and females as well as between populations necessitate further research to ascertain whether these methods were accurate enough to be used within a white South African population. A total of 184 well-preserved os coxae were sampled from white South African individuals with known age and sex. The selected os coxae represented male (n=99) and female (n=85) individuals aged 15 to 84 years. The os coxae were subjected to phase analysis, during which the symphyseal surface of the pubis was assigned a phase according to descriptions and pubic symphyseal casts. Following phase analysis, the pubic symphyses were scanned using an Artec Spider 3D scanner. After processing, the laser scans were uploaded into two versions of the forAge program to obtain seven different point estimates for the age-at-death of an individual. The Suchey-Brooks method performed well in a white South African population with statistically significant moderate positive correlations and relatively low biases in both males and females. In contrast, the Enhanced Computational methods performed poorly with weak correlations and higher biases than that observed for the Suchey-Brooks method. The Enhanced Computational methods, however, show a decrease in the intra and inter-observer error typically associated with phase-based methods. Currently, the Suchey-Brooks method can be used in a white South African population, although room for improvement exists. On the other hand, population specific formulae need to be developed for the Enhanced Computational methods before they can used in a white South African population. / E.K. 2019

Computer assisted mosaic arthroplasty (CAMA) is a surgical technique that transplants cylindrical osteochondral grafts to repair damaged cartilage. An earlier in vivo study on sheep showed that short-term clinical outcomes are improved with the use of computer assistance, as compared to the conventional technique. This thesis reports on a study comparing three mosaic arthroplasty techniques -- one conventional and two computer assisted -- on human anatomy. This in vitro study used solid foam femur models modified to incorporate simulated cartilage defects. There were five participating surgeons ranging from a third year resident to a senior orthopedic surgeon. Each of the five participating surgeons performed a total of nine trials. There were three distinct sets of identical solid foam femur models with simulated cartilage defects. Three surgical techniques (conventional, opto-electronic, and patient-specific template) were performed on each. Several measures were made to compare surgical techniques: operative time; surface congruency; defect coverage; graft surface area either too high or too low; air volume below the grafts; and distance and angle of the grafts from the surgical plan. The patient-specific template and opto-electronic techniques resulted in improved surface congruency, defect surface coverage, graft surface within 0.50mm recessed and 0.25mm proud of the original surface, and below-graft air gap volume in comparison to the conventional technique. However, the conventional technique had a shorter operative time. The patient-specific template technique had less variance in surface congruency and shorter operative time than did the opto-electronic technique. / Thesis (Master, Computing) -- Queen's University, 2013-11-28 17:06:06.961

Femoral shaft fractures are commonly encountered in orthopaedics and are typically treated using intramedullary (IM) nailing under fluoroscopic guidance. Inaccuracies in the location of the entry point of the nail and the alignment of the reduced fracture are not uncommon during this procedure. This can greatly increase the risk of iatrogenic fractures, malunions and, potentially, secondary degenerative joint disease. Fluoroscopy-based computer-assisted navigation workflows have been developed but are, as yet, not widely used. As such, there is a need to investigate the performance of these systems as well as the possibility of using newer imaging methods to enhance the reduction accuracy. This body of work investigated the impact of off-angle fluoroscopic images on the accuracy and precision of the selection of the entry points used in IM nailing and found that, while images were considered to be clinically acceptable, they resulted in large deviations in the selection of the entry point. Although higher precision was achieved with navigation, it did not improve the accuracy. This work extended the investigation of off-angle images by investigating the impact of the variation in the landmarks used by current navigation methods on quantification of femoral anteversion. The observed landmark variations were propagated through the calculation of femoral anteversion and yielded errors exceeding current clinical tolerances. As an alternative to fluoroscopy, this work developed two, semi-automated algorithms to quantify femoral shaft fracture alignment in six degrees of freedom (6DOF) based on a single, intraoperative cone-beam CT scan. Both algorithms were able to accurately quantify malalignment in all 6DOF with high repeatability and limited user interaction over a range of complex femoral shaft fractures, even in cases with severe comminution. The time requirements for the utilization of these algorithms were reasonable with respect to the time required for current, fluoroscopy-based navigation. Therefore, both of these algorithms would provide an efficient, robust and accurate alternative for the quantification of malalignment in 6DOF. Such an accurate and robust quantification of malalignment, when paired with the high precision tracking in current navigation systems, may enable the improvement of reduction accuracy in the treatment of complex femoral shaft fractures.

In computer-assisted surgery, a computer display provides 3D guidance of tools during surgery. However, current guidance displays have a number of drawbacks. This thesis considers the advantages of a prototype guidance system for drilling tasks. We attached a small LCD screen and video camera to a surgical drill. The screen's point of view was controlled by moving the drill. A user study showed that the tool-mounted LCD screen can provide significantly better positional and angular accuracy than the conventional display. The study also showed that a video camera might not be useful for guidance. / Thesis (Master, Computing) -- Queen's University, 2007-09-18 00:31:10.965