Objective: Despite three decades of pre-clinical and clinical research into image guidance solutions as a more accurate and less invasive alternative for instrument and anatomy localization, translation into routine clinical practice for surgery in the lateral skull has not yet happened. The aim of this review is to identify challenges that need to be solved in order to provide image guidance solutions that are safe and beneficial for use during lateral skull surgery and to synthesize factors that facilitate the development of such solutions. Methods: Literature search was conducted via PubMed using terms relating to image guidance and the lateral skull. Data extraction included the following variables: image guidance error, imaging resolution, image guidance system, tracking technology, registration method, study endpoints, clinical target application, and publication year. A subsequent search of FDA 510(k) database for identified image guidance systems and extraction of the year of approval, intended use, and indications for use was performed. The study objectives and endpoints were subdivided in three time phases and summarized. Furthermore, it was analyzed which factors correlated with the image guidance error. Factor values for which an error ≤0.5 mm (μerror + 3σerror) was measured in more than one study were identified and inspected for time trends. Results: A descriptive statistics-based summary of study objectives and findings separated in three time intervals is provided. The literature provides qualitative and quantitative evidence that image guidance systems must provide an accuracy ≤0.5 mm (μerror + 3σerror) for their safe and beneficial application during surgery in the lateral skull. Spatial tracking accuracy and precision and medical image resolution both correlate with the image guidance accuracy, and all of them improved over the years. Tracking technology with accuracy ≤0.05 mm, computed tomography imaging with slice thickness ≤0.2 mm, and registration based on bone-anchored titanium fiducials are components that provide a sufficient setting for the development of sufficiently accurate image guidance. Conclusion: Image guidance systems must reliably provide an accuracy ≤0.5 mm (μerror + 3σerror) for their safe and beneficial use during surgery in the lateral skull. Advances in tracking and imaging technology contribute to the improvement of accuracy, eventually enabling the development and wide-scale adoption of image guidance solutions that can be used safely and beneficially during lateral skull surgery.

Surgeons, scientists and development engineers of surgical devices require phantoms and materials for testing and training purposes. Human or animal bones are the gold standard, but difficult to obtain, prepare and handle. While polyurethane foams can be used as a substitute for trabecular bone, cortical bone substitutes have not been evaluated. In this study, a standard surgical drill bit (empty set 3.2 mm) with clinical process parameters was used to compare 5 different materials with bovine cortical bone: polyurethane with three different densities, short-fiber-filled epoxy and an artificial bone material. Drillings were repeated 100 times with 6 drill bits for each material. The results indicate that none of the substitute materials can be used without compromises. Axial drilling thrust forces in short-fiber-filled-epoxy are similar to bone. However, its hard fibers significantly deteriorate the chisel edge and flank face and increases the thrust force with each drilling (doubles within the first 10 repetitions) so that drill bits should only be used very limited times. The densest polyurethane (Renshape BM-5166) has the advantage of comparable torque values with bovine cortical bone (up to 60 repetitions). Additionally to these findings, a significant and potentially clinical relevant increase of axial drilling force (80%) and torque (56%) was found during 100 drillings in bovine cortical bone. (C) 2019 IPEM. Published by Elsevier Ltd. All rights reserved.

OBJECTIVES:Recently, more accurate description of the femoral geometry has become of interest to engineers and orthopedic surgeons. However, an appropriate database is lacking. Therefore, the aim of this study is to present morphological parameters and their correlations, which are relevant for medical issues such as impingement after total hip replacement, as well as for implant design and the etiology of hip fractures.METHODS:We investigated 12 well-known morphological parameters of the femur in 169 healthy human subjects through evaluation of 3D-reconstructed CT scans. Pearson's coefficients of correlations were calculated using a statistical t-test method for each pair of parameters.RESULTS:The mean, maximum, minimum, median, and standard deviation values are reported for all parameters. Histograms showing the distribution of each morphological parameter are also presented. It is shown that absolute and horizontal offsets, total femur length, and NCVD parameters are normally distributed, but NCDF and NCDS are not. Furthermore, an inter-correlation matrix was reported to reveal statistical correlations between these parameters. The strongest positive correlation existed between absolute offset (OSA) and horizontal offset (OSH), while the least positive correlation was found between NCDF and total femur length (TFL), and also between NCDS and NCDF. Anteversion angle (ATA) and OSA showed the least negative correlation. However, the strongest negative correlation was found between neck-shaft angle (NSA) and greater trochanter height (GTH), as well as between OSA and NCVD.CONCLUSIONS:Comprehending patients' native bone morphology, including the variations and correlations, is essential for orthopedic surgeons to undertake preoperative planning and surgery as well as to appropriately design medical devices. Thus, more population-based detailed databases are necessary. We investigated an extensive set of proximal femoral morphology parameters using a statistically standardized method to expand the existing knowledge. The results of our study can be used for diverse medical and biomechanical purposes.

The growing social significance of international sport competition, and the benefits of sport at socio-political level, have resulted in increased recognition for systems in sport that promote the development of elite athletes. Elite sport systems are globally becoming increasingly more uniform, with local variations characterising the differences in implementation such as higher levels of complexity, greater financial investment and optimising talent identification and talent development processes to function more effectively. The question therefore arises as to what extent differences could be measured amongst elite sport systems of different national judo federations. The aim of this study was to conduct a comparative analysis of elite sport systems of three national judo federations (Great Britain, South Africa and The Netherlands). Judo in England forms part of the British Judo Association. The study followed an international comparative case study design utilising qualitative methods (document analysis and interviews), in order to explore the management of elite judo systems in depth. The research model consisted of a vertical (micro, meso and macro-levels), and horizontal analyses, with multilevel elements articulated as a subset within a subsequent higher level for analysis. The horizontal analysis assisted in seeking similar and distinct trends between the judo federations at each level. Qualitative data were gathered through semi-structured interviews with one (n=1) executive member of the British and South African judo federations (n=1), as well as a sample of elite judo coaches from Britain (n=3), South Africa (n=3) and the Netherlands (n=2). Results indicated that elite sport systems are guided by a sound vision, mission, strategy and plan supported by relevant and sufficient human, financial and physical resources systems. The extent to which these systems are aligned and integrated with the strategy and plan, will determine the success of the input of elite sport systems. Britain, South Africa and the Netherlands have are similar in terms of structural components; however the main differences that exist are related to the contextual realities of these countries.Keywords: Elite sport systems, long-term athlete development, strategic management.

This chapter introduces a solution called ”3X-knee” that can robustly derive 3D models of the lower extremity from 2D long leg standing X-ray radiographs for preoperative planning and postoperative treatment evaluation of total knee arthroplasty (TKA). There are three core components in 3X-knee technology: (1) a knee joint immobilization apparatus, (2) an X-ray image calibration phantom, and (3) a statistical shape model-based 2D-3D reconstruction algorithm. These three components are integrated in a systematic way in 3X-knee to derive 3D models of the complete lower extremity from 2D long leg standing X-ray radiographs acquired in weight-bearing position. More specifically, the knee joint immobilization apparatus will be used to rigidly fix the X-ray calibration phantom with respect to the underlying anatomy during the image acquisition. The calibration phantom then serves two purposes. For one side, the phantom will allow one to calibrate the projection parameters of any acquired X-ray image. For the other side, the phantom also allows one to track positions of multiple X-ray images of the underlying anatomy without using any additional positional tracker, which is a prerequisite condition for the third component to compute patient-specific 3D models from 2D X-ray images and the associated statistical shape models. Validation studies conducted on both simulated X-ray images and on patients’ X-ray data demonstrate the efficacy of the present solution.

Introduced more than two decades ago, computer-aided orthopaedic surgery (CAOS) has emerged as a new and independent area, due to the importance of treatment of musculoskeletal diseases in orthopaedics and traumatology, increasing availability of different imaging modalities and advances in analytics and navigation tools. The aim of this chapter is to present the basic elements of CAOS devices and to review state-of-the-art examples of different imaging modalities used to create the virtual representations, of different position tracking devices for navigation systems, of different surgical robots, of different methods for registration and referencing, and of CAOS modules that have been realized for different surgical procedures. Future perspectives will be outlined. It is expected that the recent advancement on smart instrumentation, medical robotics, artificial intelligence, machine learning, and deep learning techniques, in combination with big data analytics, may lead to smart CAOS systems and intelligent orthopaedics in the near future.

During surgical procedures, the heat development of bone cutting can lead to thermal cell necrosis and secondary implant instability. Therefore, fundamental knowledge on heat development and temperature control is crucial. This paper investigates the basic principles of the machining of cortical bone in an orthogonal cutting process. Cutting forces, temperature elevation and chip formation were measured in real time for two different rake angles and six different cutting depths. A non-linear relationship between cutting depth and cutting forces as well as temperature elevation was found. The cutting behavior changed from a ductile to two distinguishable fracture cutting modes with increasing cutting depth. A linear correlation between cutting forces and temperature elevation of both bone chip and workpiece was determined (R2=0.8697). An increasing rake angle lowered cutting forces and temperature elevations significantly and was explained using a fracture mechanics approach. Additionally, a new method to calculate the fracture toughness of (quasi-)brittle materials from orthogonal cutting tests was introduced.

Plans for Long-Term Athlete Development (LTAD) can only have effect by way of optimal management of resources. The Sports Policy Factors Leading to International Sporting Success (SPLISS) provides a theoretical model for policy factors that account for the functioning of elite sport systems and ultimately the performance of elite athletes. Underpinned by resource dependence theory, this study reports on the impact of the management of elite sport systems on the career development of elite judo athletes in three countries. A mixed-methods comparative case study between elite judo coaches, defined by their status as national coaches, from South Africa (n=14) and two internationally successful judo countries, the Netherlands (n=6) and England (n=6), was conducted. Data was gathered by means of questionnaires (n=26) and semi-structured interviews (n=6). The results indicate that the optimal management of multiple resources anticipates successful performance pathways in elite sport systems.

Purpose The pararectus approach has been validated for managing acetabular fractures. We hypothesised it might be an alternative approach for performing periacetabular osteotomy (PAO).Methods Using four cadaver specimens, we randomly performed PAO through either the pararectus or a modified Smith-Petersen (SP) approach. We assessed technical feasibility and safety. Furthermore, we controlled fragment mobility using a surgical navigation system and compared mobility between approaches. The navigation system's accuracy was tested by cross-examination with validated preoperative planning software.Results The pararectus approach is technically feasible, allowing for adequate exposure, safe osteotomies and excellent control of structures at risk. Fragment mobility is equal to that achieved through the SP approach. Validation of these measurements yielded a mean difference of less < 1 mm without statistical significance.Conclusion Experimental data suggests the pararectus approach might be an alternative approach for performing PAO. Clinical validation is necessary to confirm these promising preliminary results.

The correct rotational alignment of the proximal and the distal bone fragments is an essential step in a long-bone deformity correction process. In order to plan the deformity correction, plain radiographs are conventionally used. But as three-dimensional information of the complex situation is not available, the correct amount of rotation can only be approximated. Thus, the objective of this study was to develop a system to assess the rotational relationship between the proximal and distal fragments of a long bone (tibia or femur) based on a set of two calibrated X-ray radiographs.

This paper introduces a solution that can robustly derive 3D models of musculoskeletal structures from 2D X-ray Images. The present method, as an integrated solution, consists of three components: (1) a musculoskeletal structure immobilization apparatus; (2) an X-ray image calibration phantom; and (3) a statistical shape model-based 2D-3D reconstruction algorithm. These three components are integrated in a systematic way in the present method to derive 3D models of any musculoskeletal structure from 2D X-ray Images in a functional position (e.g., weight-bearing position for lower limb). More specifically, the musculoskeletal structure immobilization apparatus will be used to rigidly fix the X-ray calibration phantom with respect to the underlying anatomy during the image acquisition. The calibration phantom then serves two purposes. For one side, the phantom will allow one to calibrate the projection parameters of any acquired X-ray image. For the other side, the phantom also allows one to track positions of multiple X-ray images of the underlying anatomy without using any additional positional tracker, which is a prerequisite condition for the third component to compute patient-specific 3D models from 2D X-ray images and the associated statistical shape models. Validation studies conducted on both simulated X-ray images and on patients’ X-ray data demonstrate the efficacy of the present solution.

In this note we summarize the history of computer aided surgery in orthopaedics and traumatology from the end of the nineteenth century to currently observable future trends. We concentrate on the two major components of such systems, pre-operative planning and intra-operative execution. The evolution of the necessary technological components, the numerous platforms and components offered commercially as well as their clinical use are surveyed.

Purpose The correct rotational alignment of a fractured long bone is an important step in the fracture reduction process. In order to plan the fracture reduction and the appropriate external fixation, plain radiographs are conventionally used. But as three-dimensional information of the complex situation is not available, the correct amount of rotation can only be approximated. Thus, the objective of this study is to develop a system to assess the rotational relationship between proximal and distal fragments of the tibia and femur based on a set of two calibrated X-ray radiographs. Methods In order to robustly determine the rotational alignment of proximal and distal bone fragments, a 2D/3D reconstruction approach was employed to reconstruct the fractured bone fragments. Two different studies were performed to evaluate the accuracy of the complete system for the purpose of fracture reduction. Results The reconstruction accuracy was evaluated in terms of major bone axis and in-plane rotational alignment. The long bone axis of the femur and tibia could be derived an average with an error of 0.33 ± 0.27◦, while an average inplane rotational error of 2.27 ± 1.76◦and 2.67 ± 1.80◦was found for the proximal S. Schumann · L.P. Nolte · G. Zheng Institute for Surgical Technology and Biomechanics (ISTB) University of Bern, Bern, Switzerland Tel.: +41-31-6315949 E-mail: steffen.schumann@ieee.org, E-mail: guoyan.zheng@ieee.org R. Bieck · R. Bader Biomechanics and Implant technology research laboratory Department of Orthopaedics University of Rostock, Rostock, Germany P.A. Grützner BG Trauma Centre Ludwigshafen at Heidelberg University Hospital Ludwigshafen, Germany J. Heverhagen Department of Radiology, Inselspital University of Bern, Bern, Switzerland 2 Steffen Schumann et al. and distal fragment, respectively. The overall mean surface reconstruction error of tibial fragments was 0.81 ± 0.59 mm and 1.12 ± 0.87 mm for femoral fragments. Conclusions A new approach for estimating the rotational parameters of fractured bone fragments has been proposed. This approach is based on two conventional radiographs and 2D/3D reconstruction technology. It is generally applicable to the reduction of any simple long bone fracture and could provide an important means for external fracture fixations.

In this paper, we propose a new method for stitching multiple fluoroscopic images taken by a C-arm instrument. We employ an X-ray radiolucent ruler with numbered graduations while acquiring the images, and the image stitching is based on detecting and matching ruler parts in the images to the corresponding parts of a virtual ruler. To achieve this goal, we first detect the regular spaced graduations on the ruler and the numbers. After graduation labeling, for each image, we have the location and the associated number for every graduation on the ruler. Then, we initialize the panoramic X-ray image with the virtual ruler, and we "paste" each image by aligning the detected ruler part on the original image, to the corresponding part of the virtual ruler on the panoramic image. Our method is based on ruler matching but without the requirement of matching similar feature points in pairwise images, and thus, we do not necessarily require overlap between the images. We tested our method on eight different datasets of X-ray images, including long bones and a complete spine. Qualitative and quantitative experiments show that our method achieves good results.

Introduced about two decades ago, computer-assisted orthopedic surgery (CAOS) has emerged as a new and independent area, due to the importance of treatment of musculoskeletal diseases in orthopedics and traumatology, increasing availability of different imaging modalities, and advances in analytics and navigation tools. The aim of this paper is to present the basic elements of CAOS devices and to review state-of-the-art examples of different imaging modalities used to create the virtual representations, of different position tracking devices for navigation systems, of different surgical robots, of different methods for registration and referencing, and of CAOS modules that have been realized for different surgical procedures. Future perspectives will also be outlined.

Landmark detection from 2D cephalometric X-ray images is a basic and important function for cephalometric analysis which widely used in oral surgery planning and evaluation. We present a fully automatic landmark detection method for cephalometric analysis. Our method works by combining random forest (RF) regression based landmark detection with sparse shape composition model based landmark correction. Validation on 100 cephalometric X-ray images show that 77.79% landmarks can be detected by our method with an error less than 4.0 mm.

Consistent longitudinal segmentation of brain tumor images is a critical issue in treatment monitoring and in clinical trials. Fully automatic segmentation methods are a good candidate for reliably detecting changes of tumor volume over time. We propose an integrated 4D spatio-temporal brain tumor segmentation method, which combines supervised classification with conditional random field regularization in an energy minimization scheme. Promising results and improvements over classic 3D methods for monitoring the temporal volumetric evolution of necrotic, active and edema tumor compartments are demonstrated on a longitudinal dataset of glioma patient images from a multi-center clinical trial. Thanks to its speed and simplicity the approach is a good candidate for standard clinical use.

BACKGROUND:Complete-pelvis segmentation in antero-posterior pelvic radiographs is required to create a patient-specific three-dimensional pelvis model for surgical planning and postoperative assessment in image-free navigation of total hip arthroplasty.METHODS:A fast and robust framework for accurately segmenting the complete pelvis is presented, consisting of two consecutive modules. In the first module, a three-stage method was developed to delineate the left hemi-pelvis based on statistical appearance and shape models. To handle complex pelvic structures, anatomy-specific information processing techniques were employed. As the input to the second module, the delineated left hemi-pelvis was then reflected about an estimated symmetry line of the radiograph to initialize the right hemi-pelvis segmentation. The right hemi-pelvis was segmented by the same three-stage method,RESULTS:Two experiments conducted on respectively 143 and 40 AP radiographs demonstrated a mean segmentation accuracy of 1.61±0.68 mm. A clinical study to investigate the postoperative assessment of acetabular cup orientations based on the proposed framework revealed an average accuracy of 1.2°±0.9° and 1.6°±1.4° for anteversion and inclination, respectively. Delineation of each radiograph costs less than one minute.CONCLUSIONS:Despite further validation needed, the preliminary results implied the underlying clinical applicability of the proposed framework for image-free THA.

In this paper, reconstruction of three-dimensional (3D) patient-specific models of a hip joint from two-dimensional (2D) calibrated X-ray images is addressed. Existing 2D-3D reconstruction techniques usually reconstruct a patient-specific model of a single anatomical structure without considering the relationship to its neighboring structures. Thus, when those techniques would be applied to reconstruction of patient-specific models of a hip joint, the reconstructed models may penetrate each other due to narrowness of the hip joint space and hence do not represent a true hip joint of the patient. To address this problem we propose a novel 2D-3D reconstruction framework using an articulated statistical shape model (aSSM). Different from previous work on constructing an aSSM, where the joint posture is modeled as articulation in a training set via statistical analysis, here it is modeled as a parametrized rotation of the femur around the joint center. The exact rotation of the hip joint as well as the patient-specific models of the joint structures, i.e., the proximal femur and the pelvis, are then estimated by optimally fitting the aSSM to a limited number of calibrated X-ray images. Taking models segmented from CT data as the ground truth, we conducted validation experiments on both plastic and cadaveric bones. Qualitatively, the experimental results demonstrated that the proposed 2D-3D reconstruction framework preserved the hip joint structure and no model penetration was found. Quantitatively, average reconstruction errors of 1.9 mm and 1.1 mm were found for the pelvis and the proximal femur, respectively.