Mixed Reality-Based Simulator for Training on Imageless Navigation Skills in Total Hip Replacement Procedures

Imageless navigation systems (INS) in orthopaedics have been used to improve the outcomes of several orthopaedic procedures such as total hip replacement [1, 2]. However, the increased surgical times and the associate learning curve discourage surgeons from using navigation systems in their theatres [2]. This paper presents a Mixed Reality (MR) simulator that helps surgeons acquire the infrared based navigation skills before performing it in reality. A group of 7 hip surgeons tried the application, expressing their satisfaction with all the features and confirmed that the simulator represents a cheaper and faster option to train surgeons in the use of INS than the current learning methods

Machine learning and interactive real-time simulation for training on relevant total hip replacement skills.

Virtual Reality simulators have proven to be an excellent tool in the medical sector to help trainees mastering surgical abilities by providing them with unlimited training opportunities. Total Hip Replacement (THR) is a procedure that can benefit significantly from VR/AR training, given its non-reversible nature. From all the different steps required while performing a THR, doctors agree that a correct fitting of the acetabular component of the implant has the highest relevance to ensure successful outcomes. Acetabular reaming is the step during which the acetabulum is resurfaced and prepared to receive the acetabular implant. The success of this step is directly related to the success of fitting the acetabular component. Therefore, this thesis will focus on developing digital tools that can be used to assist the training of acetabular reaming. Devices such as navigation systems and robotic arms have proven to improve the final accuracy of the procedure. However, surgeons must learn to adapt their instrument movements to be recognised by infrared cameras. When surgeons are initially introduced to these systems, surgical times can be extended up to 20 minutes, maximising surgical risks. Training opportunities are sparse, given the high investment required to purchase these devices. As a cheaper alternative, we developed an Augmented Reality (AR) alternative for training on the calibration of imageless navigation systems (INS). At the time, there were no alternative simulators that using head-mounted displays to train users into the steps to calibrate such systems. Our simulator replicates the presence of an infrared camera and its interaction with the reflecting markers located on the surgical tools. A group of 6 hip surgeons were invited to test the simulator. All of them expressed their satisfaction with the ease of use and attractiveness of the simulator as well as the similarity of interaction with the real procedure. The study confirmed that our simulator represents a cheaper and faster option to train multiple surgeons simultaneously in the use of Imageless Navigation Systems (INS) than learning exclusively on the surgical theatre. Current reviews on simulators for orthopaedic surgical procedures lack objective metrics of assessment given a standard set of design requirements. Instead, most of them rely exclusively on the level of interaction and functionality provided. We propose a comparative assessment rubric based on three different evaluation criteria. Namely immersion, interaction fidelity, and applied learning theories. After our assessment, we found that none of the simulators available for THR provides an accurate interactive representation of resurfacing procedures such as acetabular reaming based on force inputs exerted by the user. This feature is indispensable for an orthopaedics simulator, given that hand-eye coordination skills are essential skills to be trained before performing non-reversible bone removal on real patients. Based on the findings of our comparative assessment, we decided to develop a model to simulate the physically-based deformation expected during traditional acetabular reaming, given the user’s interaction with a volumetric mesh. Current interactive deformation methods on high-resolution meshes are based on geometrical collision detection and do not consider the contribution of the materials’ physical properties. By ignoring the effect of the material mechanics and the force exerted by the user, they become inadequate for training on hand- eye coordination skills transferable to the surgical theatre. Volumetric meshes are preferred in surgical simulation to geometric ones, given that they are able to represent the internal evolution of deformable solids resulting from cutting and shearing operations. Existing numerical methods for representing linear and corotational FEM cuts can only maintain interactive framerates at a low resolution of the mesh. Therefore, we decided to train a machine-learning model to learn the continuum mechanic laws relevant to acetabular reaming and predict deformations at interactive framerates. To the best of our knowledge, no research has been done previously on training a machine learning model on non-elastic FEM data to achieve results at interactive framerates. As training data, we used the results from XFEM simulations precomputed over 5000 frames for plastic deformations on tetrahedral meshes with 20406 elements each. We selected XFEM simulation as the physically-based deformation ground-truth given its accuracy and fast convergence to represent cuts, discontinuities and large strain rates. Our machine learning-based interactive model was trained following the Graph Neural Networks (GNN) blocks. GNNs were selected to learn on tetrahedral meshes as other supervised-learning architectures like the Multilayer perceptron (MLP), and Convolutional neural networks (CNN) are unable to learn the relationships between entities with an arbitrary number of neighbours. The learned simulator identifies the elements to be removed on each frame and describes the accumulated stress evolution in the whole machined piece. Using data generated from the results of XFEM allowed us to embed the effects of non-linearities in our interactive simulations without extra processing time. The trained model executed the prediction task using our tetrahedral mesh and unseen reamer orientations faster per frame than the time required to generate the training FEM dataset. Given an unseen orientation of the reamer, the trained GN model updates the value of accumulated stress on each of the 20406 tetrahedral elements that constitute our mesh during the prediction task. Once this value is updated, the tetrahedrons to be removed from the mesh are identified using a threshold condition. After using each single-frame output as input for the following prediction repeatedly for up to 60 iterations, our model can maintain an accuracy of up to 90.8% in identifying the status of each element given their value of accumulated stress. Finally, we demonstrate how the developed estimator can be easily connected to any game engine and included in developing a fully functional hip arthroplasty simulator

Cost effective, reliable implantation of acetabular cups in Total Hip Arthroplasty

Previously held under moratorium from 23 November 2016 until 23 November 2021Correct positioning of the acetabular cup is critical for success within Total Hip Arthroplasty. Malpositioning of the acetabular cup contributes to many complications, all of which lead to revision surgery. Despite recognition of the importance of correct orientation, there is no consensus on what the optimum orientation of the acetabular cup should be. The suggested orientations in the literature are contradictory and comparison between studies is difficult due to variations in angle definitions, measurement systems and reference systems. These contradictions, the lack of consensus in the literature and results from studies suggest that acetabular orientation must be patient specific. Mechanical guides are the most commonly used device to assist surgeons in positioning the acetabular cup, both in cemented and uncemented arthroplasties. However, these devices have many limitations one of which is a fixed acetabular orientation which does not allow for any patient variability. Using a combination of quantitative and qualitative product design techniques, Harrison User Centred Methodology was developed. This new methodology was adopted to design and develop a device to aid surgeons with positioning the acetabular cup in total hip arthroplasty. The aim was to design a device which could be used for both cemented and uncemented hip arthroplasty. The final device design was a novel positioning guide which addressed the lack of patient variability in current mechanical guides. The device simplified the positioning and limited the movement of the introducer. Feedback from surgeons demonstrated a positive response and with further development, a willingness to try the product. Proof of concept testing was carried out to measure the accuracy of the device. An available (uncemented) introducer was used for testing which demonstrated the device can accurately position the acetabular cup. The accuracy of the developed device and current techniques was compared. The study showed less variation in the position over time using the novel device which highlights an added benefit for cemented procedures demonstrating stability as the cement cures.Correct positioning of the acetabular cup is critical for success within Total Hip Arthroplasty. Malpositioning of the acetabular cup contributes to many complications, all of which lead to revision surgery. Despite recognition of the importance of correct orientation, there is no consensus on what the optimum orientation of the acetabular cup should be. The suggested orientations in the literature are contradictory and comparison between studies is difficult due to variations in angle definitions, measurement systems and reference systems. These contradictions, the lack of consensus in the literature and results from studies suggest that acetabular orientation must be patient specific. Mechanical guides are the most commonly used device to assist surgeons in positioning the acetabular cup, both in cemented and uncemented arthroplasties. However, these devices have many limitations one of which is a fixed acetabular orientation which does not allow for any patient variability. Using a combination of quantitative and qualitative product design techniques, Harrison User Centred Methodology was developed. This new methodology was adopted to design and develop a device to aid surgeons with positioning the acetabular cup in total hip arthroplasty. The aim was to design a device which could be used for both cemented and uncemented hip arthroplasty. The final device design was a novel positioning guide which addressed the lack of patient variability in current mechanical guides. The device simplified the positioning and limited the movement of the introducer. Feedback from surgeons demonstrated a positive response and with further development, a willingness to try the product. Proof of concept testing was carried out to measure the accuracy of the device. An available (uncemented) introducer was used for testing which demonstrated the device can accurately position the acetabular cup. The accuracy of the developed device and current techniques was compared. The study showed less variation in the position over time using the novel device which highlights an added benefit for cemented procedures demonstrating stability as the cement cures

Patient Specific Alignment, Anatomy, Recovery and Outcome in Total Knee Arthroplasty

Total knee arthroplasty (TKA), despite being an otherwise highly successful medical operation, has a recurrent problem of dissatisfaction and recurrent pain rates in the 15-20% range. A variety of factors contribute to this incidence of dissatisfaction which can broadly be considered to fall into one of three groups: factors driven by the surgical outcome, pre-existing factors relating to the patients psychology, appropriateness for surgery or expectation level, and factors driven by the patient’s recovery and their management during that recovery process. With consideration to the extensive variation between patients, it is reasonable to posit that addressing patient specific factors in selection for surgery, alignment of components during surgery and post-operative management may reduce the instance of post-operative dissatisfaction. The first goal of this thesis was to understand the variation of patient anatomy as it relates to standard practice in TKA. Following the finding of extensive variation, a bio-mechanical rigid body dynamics simulation of the knee joint was developed to determine the degree to which this variation was reflected in the kinematic behaviour of the implanted knees. Later studies showed extensive kinematic variation that was responsive to variation in the alignment of the components as well as well as significantly related to patient reported outcome. Later studies further investigated how outcome related to patient selection for surgery and recovery of the patient as measured with simple activity monitoring. From this work, a pre-operative simulation assessment tool has been developed, the Dynamic Knee Score (DKS), and paired with selection and recovery management tools forms the basis of 360 Knee Systems surgical planning and patient management, which has been used in over 3,000 primary TKA’s to date

Augmented Reality and Artificial Intelligence in Image-Guided and Robot-Assisted Interventions

In minimally invasive orthopedic procedures, the surgeon places wires, screws, and surgical implants through the muscles and bony structures under image guidance. These interventions require alignment of the pre- and intra-operative patient data, the intra-operative scanner, surgical instruments, and the patient. Suboptimal interaction with patient data and challenges in mastering 3D anatomy based on ill-posed 2D interventional images are essential concerns in image-guided therapies. State of the art approaches often support the surgeon by using external navigation systems or ill-conditioned image-based registration methods that both have certain drawbacks. Augmented reality (AR) has been introduced in the operating rooms in the last decade; however, in image-guided interventions, it has often only been considered as a visualization device improving traditional workflows. Consequently, the technology is gaining minimum maturity that it requires to redefine new procedures, user interfaces, and interactions. This dissertation investigates the applications of AR, artificial intelligence, and robotics in interventional medicine. Our solutions were applied in a broad spectrum of problems for various tasks, namely improving imaging and acquisition, image computing and analytics for registration and image understanding, and enhancing the interventional visualization. The benefits of these approaches were also discovered in robot-assisted interventions. We revealed how exemplary workflows are redefined via AR by taking full advantage of head-mounted displays when entirely co-registered with the imaging systems and the environment at all times. The proposed AR landscape is enabled by co-localizing the users and the imaging devices via the operating room environment and exploiting all involved frustums to move spatial information between different bodies. The system's awareness of the geometric and physical characteristics of X-ray imaging allows the exploration of different human-machine interfaces. We also leveraged the principles governing image formation and combined it with deep learning and RGBD sensing to fuse images and reconstruct interventional data. We hope that our holistic approaches towards improving the interface of surgery and enhancing the usability of interventional imaging, not only augments the surgeon's capabilities but also augments the surgical team's experience in carrying out an effective intervention with reduced complications

Clinical investigation of the functional outcome of fixed bearing versus mobile bearing knees

Total Knee Arthroplasty is a high-volume and high-cost procedure, with persisting limitations to patient satisfaction. Prosthesis designs aim to restore function whilst providing stability, without joint constraint. This double-blinded randomised controlled trial is the first of its kind where the functional performance of a low congruent fixed (CR DD), ultra-congruent fixed (UC), and ultra-congruent mobile (UCR) bearing Columbus Total Knee Systems were assessed. The pre- and postoperative function of twenty-four osteoarthritic patients was evaluated against nine control participants whilst carrying out activities of daily living. Spatiotemporal, kinematic, and kinetic gait parameters during walking, stair navigation and sloped walking were extracted using fully instrumented motion capture. Questionnaire responses were also recorded. Across all ADLs, postoperative patient function improved, although not to control levels. The average postoperative increase in range of sagittal knee motion across all tasks came to: 7.3±3.1o (CRDD), 4.9±4.9o (UC), 0.7±7.7o (UCR), and peak knee flexion was mostly reduced at postoperative. Both fixed bearing implants presented larger post-surgery hip and ankle kinetics in magnitude, and improved distinction between knee adduction moment maxima, linked to improved loading to the mobile bearing group. Overall, the CRDD group showed more significant changes to preoperative and any significant inter-implant differences at post-surgery was also to this group. The UC and UCR groups showed less improvements during challenging activities, with the UCR group showing some limits to knee extension. The UCR group also self-reported more difficulty, pain, and tiredness than the fixed bearing groups. Kinematic cross talk error significantly impacted the interpretation of non-sagittal kinematics, and small and unequal sample sizes reduced statistical power. Despite the limitations it was concluded that both fixed bearing implants initially outperformed the mobile bearing joint and the CRDD group showed the most prominent improvements. Clinically relevant thresholds for all parameters, would further determine whether functional advantages exist between implant bearing types.Total Knee Arthroplasty is a high-volume and high-cost procedure, with persisting limitations to patient satisfaction. Prosthesis designs aim to restore function whilst providing stability, without joint constraint. This double-blinded randomised controlled trial is the first of its kind where the functional performance of a low congruent fixed (CR DD), ultra-congruent fixed (UC), and ultra-congruent mobile (UCR) bearing Columbus Total Knee Systems were assessed. The pre- and postoperative function of twenty-four osteoarthritic patients was evaluated against nine control participants whilst carrying out activities of daily living. Spatiotemporal, kinematic, and kinetic gait parameters during walking, stair navigation and sloped walking were extracted using fully instrumented motion capture. Questionnaire responses were also recorded. Across all ADLs, postoperative patient function improved, although not to control levels. The average postoperative increase in range of sagittal knee motion across all tasks came to: 7.3±3.1o (CRDD), 4.9±4.9o (UC), 0.7±7.7o (UCR), and peak knee flexion was mostly reduced at postoperative. Both fixed bearing implants presented larger post-surgery hip and ankle kinetics in magnitude, and improved distinction between knee adduction moment maxima, linked to improved loading to the mobile bearing group. Overall, the CRDD group showed more significant changes to preoperative and any significant inter-implant differences at post-surgery was also to this group. The UC and UCR groups showed less improvements during challenging activities, with the UCR group showing some limits to knee extension. The UCR group also self-reported more difficulty, pain, and tiredness than the fixed bearing groups. Kinematic cross talk error significantly impacted the interpretation of non-sagittal kinematics, and small and unequal sample sizes reduced statistical power. Despite the limitations it was concluded that both fixed bearing implants initially outperformed the mobile bearing joint and the CRDD group showed the most prominent improvements. Clinically relevant thresholds for all parameters, would further determine whether functional advantages exist between implant bearing types

Epidemiology of injuries in high-level youth sport in Luxembourg [Abstract]

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