Computer assisted surgery for fracture reduction and deformity correction of the pelvis and long bones

Many orthopaedic operations, for example osteotomies, are not preoperative planned. The operation result depends on the experience of the operating surgeon. In the industry new developments are not longer curried out without CAD planning or computer simulations. Only in medicine the operation technology of corrective osteotomies are still in their infant stage in the last 30 years. Two dimensional analysis is not accurate that results in operation errors in the operating room. The surgeon usually obtains the preoperative information about the current bone state by radiographs. In case of complex operations (also inserting implants) planning is required. Planning based on radiographs has some system-dependent disadvantages like small accuracy, requirement of time for corrections ( distortions due to the projection) and restrictions, if complex corrections are necessary. Today the computer tomography is used as a solution. It is the only modality that allows to reach the accuracy and the resolution required for a good 3D-planning. However its a high dose rate for the patient is the serious disadvantage. Therefore in dilemma between the low dose rate and an adequate planning the first is often preferred. However in future it is expected that good operation results are guarantied only with implementation of 3D-planung. MR systems provide image information too, from which indirectly bones can be extracted. But due to their large distortions (susceptibility, non non-homogeneity of magnetic field), small spatial dissolution and the high costs, it is not expected that MRI represents an alternative in next time. The solution is the use of other image modalities. Ultrasound is here a good compromise both of the costs of the accuracy. In this work I developed an algorithm, which can produce 3D bone models from ultrasonic data. They have good resolution and accuracy compared with CT, and therefore can be used for 3D planning. In the work an improved procedure for segmenting bone surfaces is realised in combination with methods for the fusion for a three-dimensional model. The novelty of the presented work is in new approaches to realising an operation planning system, based on 3D computations, and implementing the intraoperative control by a guided ultrasound system for bone tracking. To realise these ideas the following tasks are solved: - bone modelling from CT data; - real-time extraction of bone surfaces from ultrasound imaging; - tracking the bone with respect to CT bone model. - integrating and implementing the above results in the development of an operation planning system for osteotomy corrections that supports on-line measurements, different types of deformity correction, a bone geometry design and a high level of automation. The developed osteotomy planning system allows to investigate the pathology, makes its analysis, finds an optimal way to realise surgery and provides visual and quantitative information about the results of the virtual operation. Therefore, the implementation of the proposed system can be considered as an additional significant tool for the diagnosis and orthopaedic surgery. The major parts of the planning system are: bone modelling from 3D data derived from CT, MRI or other modalities, visualisation of the elements of the 3D scene in real-time, and the geometric design of bone elements. A high level of automation allows the surgeon to reduce significantly the time of the operation plane development

Patient-specific modelling in orthopedics: from image to surgery

In orthopedic surgery, to decide upon intervention and how it can be optimized, surgeons usually rely on subjective analysis of medical images of the patient, obtained from computed tomography, magnetic resonance imaging, ultrasound or other techniques. Recent advancements in computational performance, image analysis and in silico modeling techniques have started to revolutionize clinical practice through the development of quantitative tools, including patient#specific models aiming at improving clinical diagnosis and surgical treatment. Anatomical and surgical landmarks as well as features extraction can be automated allowing for the creation of general or patient-specific models based on statistical shape models. Preoperative virtual planning and rapid prototyping tools allow the implementation of customized surgical solutions in real clinical environments. In the present chapter we discuss the applications of some of these techniques in orthopedics and present new computer-aided tools that can take us from image analysis to customized surgical treatment

Intraoperative Quantification of Bone Perfusion in Lower Extremity Injury Surgery

Orthopaedic surgery is one of the most common surgical categories. In particular, lower extremity injuries sustained from trauma can be complex and life-threatening injuries that are addressed through orthopaedic trauma surgery. Timely evaluation and surgical debridement following lower extremity injury is essential, because devitalized bones and tissues will result in high surgical site infection rates. However, the current clinical judgment of what constitutes “devitalized tissue” is subjective and dependent on surgeon experience, so it is necessary to develop imaging techniques for guiding surgical debridement, in order to control infection rates and to improve patient outcome. In this thesis work, computational models of fluorescence-guided debridement in lower extremity injury surgery will be developed, by quantifying bone perfusion intraoperatively using Dynamic contrast-enhanced fluorescence imaging (DCE-FI) system. Perfusion is an important factor of tissue viability, and therefore quantifying perfusion is essential for fluorescence-guided debridement. In Chapters 3-7 of this thesis, we explore the performance of DCE-FI in quantifying perfusion from benchtop to translation: We proposed a modified fluorescent microsphere quantification technique using cryomacrotome in animal model. This technique can measure bone perfusion in periosteal and endosteal separately, and therefore to validate bone perfusion measurements obtained by DCE-FI; We developed pre-clinical rodent contaminated fracture model to correlate DCE-FI with infection risk, and compare with multi-modality scanning; Furthermore in clinical studies, we investigated first-pass kinetic parameters of DCE-FI and arterial input functions for characterization of perfusion changes during lower limb amputation surgery; We conducted the first in-human use of dynamic contrast-enhanced texture analysis for orthopaedic trauma classification, suggesting that spatiotemporal features from DCE-FI can classify bone perfusion intraoperatively with high accuracy and sensitivity; We established clinical machine learning infection risk predictive model on open fracture surgery, where pixel-scaled prediction on infection risk will be accomplished. In conclusion, pharmacokinetic and spatiotemporal patterns of dynamic contrast-enhanced imaging show great potential for quantifying bone perfusion and prognosing bone infection. The thesis work will decrease surgical site infection risk and improve successful rates of lower extremity injury surgery

CT Scanning

Since its introduction in 1972, X-ray computed tomography (CT) has evolved into an essential diagnostic imaging tool for a continually increasing variety of clinical applications. The goal of this book was not simply to summarize currently available CT imaging techniques but also to provide clinical perspectives, advances in hybrid technologies, new applications other than medicine and an outlook on future developments. Major experts in this growing field contributed to this book, which is geared to radiologists, orthopedic surgeons, engineers, and clinical and basic researchers. We believe that CT scanning is an effective and essential tools in treatment planning, basic understanding of physiology, and and tackling the ever-increasing challenge of diagnosis in our society

New Image Processing Methods for Ultrasound Musculoskeletal Applications

In the past few years, ultrasound (US) imaging modalities have received increasing interest as diagnostic tools for orthopedic applications. The goal for many of these novel ultrasonic methods is to be able to create three-dimensional (3D) bone visualization non-invasively, safely and with high accuracy and spatial resolution. Availability of accurate bone segmentation and 3D reconstruction methods would help correctly interpreting complex bone morphology as well as facilitate quantitative analysis. However, in vivo ultrasound images of bones may have poor quality due to uncontrollable motion, high ultrasonic attenuation and the presence of imaging artifacts, which can affect the quality of the bone segmentation and reconstruction results. In this study, we investigate the use of novel ultrasonic processing methods that can significantly improve bone visualization, segmentation and 3D reconstruction in ultrasound volumetric data acquired in applications in vivo. Specifically, in this study, we investigate the use of new elastography-based, Doppler-based and statistical shape model-based methods that can be applied to ultrasound bone imaging applications with the overall major goal of obtaining fast yet accurate 3D bone reconstructions. This study is composed to three projects, which all have the potential to significantly contribute to this major goal. The first project deals with the fast and accurate implementation of correlation-based elastography and poroelastography techniques for real-time assessment of the mechanical properties of musculoskeletal tissues. The rationale behind this project is that, iii in the future, elastography-based features can be used to reduce false positives in ultrasonic bone segmentation methods based on the differences between the mechanical properties of soft tissues and the mechanical properties of hard tissues. In this study, a hybrid computation model is designed, implemented and tested to achieve real time performance without compromise in elastographic image quality . In the second project, a Power Doppler-based signal enhancement method is designed and tested with the intent of increasing the contrast between soft tissue and bone while suppressing the contrast between soft tissue and connective tissue, which is often a cause of false positives in ultrasonic bone segmentation problems. Both in-vitro and in-vivo experiments are performed to statistically analyze the performance of this method. In the third project, a statistical shape model based bone surface segmentation method is proposed and investigated. This method uses statistical models to determine if a curve detected in a segmented ultrasound image belongs to a bone surface or not. Both in-vitro and in-vivo experiments are performed to statistically analyze the performance of this method. I conclude this Dissertation with a discussion on possible future work in the field of ultrasound bone imaging and assessment

Detection and 3D Localization of Surgical Instruments for Image-Guided Surgery

Placement of surgical instrumentation in pelvic trauma surgery is challenged by complex anatomy and narrow bone corridors, relying on intraoperative x-ray fluoroscopy for visualization and guidance. The rapid workflow and cost constraints of orthopaedic trauma surgery have largely prohibited widespread adoption of 3D surgical navigation. This thesis reports the development and evaluation of a method to achieve 3D guidance via automatic detection and localization of surgical instruments (specifically, Kirschner wires [K-wires]) in fluoroscopic images acquired within routine workflow. The detection method uses a neural network (Mask R-CNN) for segmentation and keypoint detection of K-wires in fluoroscopy, and correspondence of keypoints among multiple images is established by 3D backprojection and a rank-ordering of ray intersections. The accuracy of 3D K-wire localization was evaluated in a laboratory cadaver study as well as patient images drawn from an IRB-approved clinical study. The detection network successfully generalized from simulated training and validation images to cadaver and clinical images, achieving 87% recall and 98% precision. The geometric accuracy of K-wire tip location and direction in 2D fluoroscopy was 1.9 ± 1.6 mm and 1.8° ± 1.3°, respectively. Simulation studies demonstrated a corresponding mean error of 1.1 mm in 3D tip location and 2.3° in 3D direction. Cadaver and clinical studies demonstrated the feasibility of the approach in real data, although accuracy was reduced to with 1.7 ± 0.7 mm in 3D tip location and 6° ± 2° in 3D direction. Future studies aim to improve performance by increasing the volume and variety of images used in neural network training, particularly with respect to low-dose fluoroscopy (high noise levels) and complex fluoroscopic scenes with various types surgical instrumentation. Because the approach involves fast runtime and uses equipment (a mobile C-arm) and fluoroscopic images that are common in standard workflow, it may be suitable to broad utilization in orthopaedic trauma surgery

Computer assisted navigation in spine surgery

INTRODUCTION: Computer aided navigation is an important tool which has the capability to enhance surgical accuracy, while reducing negative outcomes. However, it is a relatively new technology and has not yet been accepted as the standard of care in all settings. OBJECTIVES: The objective of the present study is to present the development and current state of technologies in computer aided navigation in Orthopedic Spine Surgery, specifically in navigated placement of pedicle screws, to examine the clinical need for navigation, it's effect on surgical accuracy and clinical outcome and to determine whether the benefits justify the costs, and make recommendations for future use and enhancements. CONCLUSION: Computer aided navigation in pedicle screw placement enhances accuracy, reduces the probability of negative outcomes, reduces the exposure of the patient and staff to radiation, reduces operative time, and provides cost-savings. Future investigations may potentially enhance this effect further with the use of innovative augmented reality type displays