A comparison between Asians and Caucasians in the dimensions of the femoral isthmus based on a 3D-CT analysis of 1189 adult femurs.

INTRODUCTION: For successful intramedullary implant placement at the femur, such as nailing in unstable proximal femur fractures, the use of an implant that at least reaches or exceeds the femoral isthmus and yields sufficient thickness is recommended. A number of complications after intramedullary femoral nailing have been reported, particularly in Asians. To understand the anatomical features of the proximal femur and their ethnic differences, we aimed to accurately calculate the femoral isthmus dimensions and proximal distance of Asians and Caucasians. METHODS: In total, 1189 Asian and Caucasian segmented 3D CT data sets of femurs were analyzed. The individual femoral isthmus diameter was precisely computed to investigate whether gender, femur length, age, ethnicity or body mass index have an influence on isthmus diameters. RESULTS: The mean isthmus diameter of all femurs was 10.71 ± 2.2 mm. A significantly larger diameter was found in Asians when compared to Caucasians (p < 0.001). Age was a strong predictor of the isthmus diameter variability in females (p < 0.001, adjusted r2 = 0.299). With every year of life, the isthmus showed a widening of 0.08 mm in women. A Matched Pair Analysis of 150 female femurs showed a significant difference between isthmus diameter in Asian and Caucasian femurs (p = 0.05). In 50% of the cases the isthmus was found in a range of 2.4 cm between 16.9 and 19.3 cm distal to the tip of the greater trochanter. The female Asian femur differs from Caucasians as it is wider at the isthmus. CONCLUSIONS: In absolute values, the proximal isthmus distance did not show much variation but is more proximal in Asians. The detailed data presented may be helpful in the development of future implant designs. The length and thickness of future standard implants may be considered based on the findings.

Symmetry Matching of the Medial Acetabular Surface-A Quantitative Analysis in View of Patient-Specific Implants.

OBJECTIVE: To quantify intrapelvic surface symmetry in reference to a preshaped suprapectineal acetabular implant. METHODS: In this cross-sectional study, an anatomically preshaped acetabular fracture implant was fitted on 3D surface models of 516 pelvises from a preexisting bone database using a software tool for automated implant fitting (SOMA, Stryker Orthopaedic Modeling and Analytics) of a CAD model of the implant. The distances between bone and the reference implant were measured at 2310 reference points for each hemipelvis. RESULTS: The average distance between the left hemipelvis and the plate was 1.98 mm (median, 10% percentile: 1.45, 90% percentile: 2.78) and 2.0 mm (median, 10% percentile: 1.45, 90% percentile: 2.92) between the right hemipelvis and the plate. There was no significant difference between the 2 hemipelvises (median absolute pairwise delta: 0.25 mm; 10% percentile: 0.04, 90% percentile: 0.82; Wilcoxon, P = 0.064). CONCLUSIONS: With regard to the periacetabular surface of the inner pelvis, the pelvis can be considered sufficiently symmetric for using the mirrored contralateral hemipelvis as a template for patient-specific implants in acetabular fracture fixation.

A numeric approach for anatomic plate design.

Osteosynthesis plate designs with high levels of anatomical compliance have been demonstrated to have numerous clinical benefits. The purpose of this paper is to introduce a systematic numeric approach for anatomic plate design on the example of the distal medial tibia. The advantage of using numeric approaches for plate design is to gain objective and complete anatomical input as opposed to cadaveric investigations with limited sample sizes. A recent development in this area is a proprietary technology called SOMA which is based on a large database of 3D bone models generated from thin-slice computer tomographic scans plus associated software tools. In this paper, one of these associated software tools is described which automatically assesses the anatomic fit of osteosynthesis plates based on a large database of bone models. As an example, this tool was applied to assess the mean plate to bone distance of distal medial tibia plates, when fitted onto 444 Caucasian and 310 Asian 3D bone models respectively. The analyses revealed differences in the anatomical compliance of plates from different generations and manufacturers. The anatomical compliance of SOMA designed plates was statistically significantly better compared to all other plates in all groups "Short", "Intermediate" and "Long" and for both ethnicities "Caucasian" and "Asian" (P<0.001). The study has shown that using an underlying database with accompanying computational tools such as SOMA can be a powerful and efficient approach towards the development and advancement of osteosynthesis plates in trauma surgery, ultimately resulting in plates with high levels of anatomical compliance and potential clinical benefits.

Stryker Orthopaedic Modeling and Analytics (SOMA): A Review.

Due to the differences in bone morphology between demographics such as age, gender, body mass index, and ethnicity, the development of orthopaedic implants requires a large number of anatomical data from various patient populations. In an effort to assess these demographic variations, Stryker Orthopaedic Modeling and Analytics (SOMA) has been developed. SOMA is a suite of tools which utilizes a comprehensive database of computed tomography scans (CT-scans), plus associated three-dimensional (3D) bone models, allowing the user to assess population differences in bone morphology, bone density, and implant fit for the purposes of research and development. Several additional software tools are currently in development to further analyze bone density and have the potential to enhance component fit. These tools, in combination with the database, have been previously utilized for development of many implant designs and techniques in hip and knee arthroplasty, as well as in trauma surgery.

Comparison of 2 versus 3 dimensional fracture mapping strategies for 3 dimensional computerized tomography reconstructions of scapula neck and body fractures.

Fracture mapping has been used in the understanding of injury patterns in different bones. To our knowledge, there are no applications of this technique using three-dimensional (3D) morphologic fracture characteristics. Previously, scapula fractures were mapped by transferring information from 3D computed tomography to a two-dimensional (2D) template. Cole et al. determined that 3D Computerized Tomography (CT) scans were more reliable compared to plain radiographs in terms of scapular angulation, translation, and glenopolar angle measurements. Thus, we hypothesized that if there is a difference between fracture lines drawn in 3D and in 2D, then the 3D mapping would yield more accurate fracture patterns. We completed a retrospective, comparative study (evidence level III) utilizing CT imaging from a single center scapular registry. We studied ten patients with scapula fractures in whom bilateral CT scans were obtained. Fractures were mapped both two and three-dimensionally, and we measured deviations between the fracture lines that were drawn with each approach. The measured deviations ranged from 10.4 mm to 28.0 mm when comparing 2D versus 3D techniques, with the mean deviation being 4.0 mm and 10.4 mm, respectively. Half of the 2D renderings possessed hidden fracture lines that were later revealed on 3D imaging. Three-dimensional renderings were more accurate when compared to 2D fracture mapping methods. This more accurate technique will allow for better understanding of 3D morphology and provide a basis for future fracture mapping in any bone. Accurate mapping is important because surgical approach, reduction, fixation, and implant design and selection are based on fracture patterns. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:265-271, 2018.

Virtual dental surgery as a new educational tool in dental school.

PURPOSE: The virtual environment of the Voxel-Man simulator that was originally designed for virtual surgical procedures of the middle ear has been adapted to intraoral procedures. To assess application of the simulator to dentistry, virtual apicectomies were chosen as the pilot-test model. METHODS: A group of 53 dental students provided their impressions after virtual simulation of apicectomies in the Voxel-Man simulator. RESULTS: Fifty-one of the 53 students recommended the virtual simulation as an additional modality in dental education. The students indicated that the force feedback (e.g. simulation of haptic pressure), spatial 3D perception, and image resolution of the simulator were sufficient for virtual training of dental surgical procedures. CONCLUSION: The feedback from dental students involved in this pilot-test has encouraged our interdisciplinary group to continue further development of the simulator with the goal of creating new training strategies in dental and medical education.

Virtual reality: a new paranasal sinus surgery simulator.

OBJECTIVES/HYPOTHESIS: Virtual surgical training systems are of growing value. Current prototypes for endonasal sinus surgery simulation are very expensive or lack running stability. No reliable system is available to a notable number of users yet. The purpose of this work was to develop a dependable simulator running on standard PC hardware including a detailed anatomic model, realistic tools and handling, stereoscopic view, and force feedback. STUDY DESIGN: Descriptive. METHODS: A three-dimensional voxel model was created based on a high-resolution computed tomography study of a human skull, from which the bony structures were segmented. The mucosa and organs at risk were added manually. The model may be manipulated with virtual surgical tools controlled with a low-cost haptic device, which is also used to adjust microscopic or endoscopic views. Visualization, haptic rendering, and tissue removal are represented with subvoxel resolution. RESULTS: The handling of the model is convincing. The haptic device provides a realistic feeling regarding the interaction between tool tip and anatomy. Three-dimensional orientation and the look and feel of virtual surgical interventions get close to reality. CONCLUSIONS: The newly developed system is a stable, fully operational simulator for sinus surgery based on standard PC hardware. Besides the limitations of a low-cost haptic device, the presented system is highly realistic regarding anatomy, visualization, manipulation, and the appearance of the tools. It is mainly intended for gaining surgical anatomy knowledge and for training navigation in a complex anatomical environment. Learning effects, including motor skills, have yet to be quantified.

Computer-based anatomy a prerequisite for computer-assisted radiology and surgery.

RATIONALE AND OBJECTIVES: The aim of the study is to show the possibilities opened up by three-dimensional (3D) computer-based models of the human body for education in anatomy, training of radiological and endoscopic examinations, and simulation of surgical procedures. MATERIALS AND METHODS: Based on 3D data sets obtained from the Visible Human and/or clinical cases, virtual body models are created that provide an integrated spatial and symbolic description of the anatomy by using interactive color/intensity-based segmentation, ray casting visualization with subvoxel resolution, a semantic network for knowledge modeling, and augmented QuickTime VR (Apple Computer, Inc, Cupertino, CA) movies for presentation. RESULTS: From these models, various radiological, endoscopic, or haptic manifestations of the body can be derived. This is shown with examples from anatomy teaching, correlation of x-ray images with 3D anatomy for education in radiology, gastrointestinal endoscopy, correlation of ultrasound images with 3D anatomy in endoscopic ultrasonography, and simulation of drilling in temporal bone surgery. CONCLUSION: The presented models provide a means for realistic training in interpretation of radiological and endoscopic images of the human body. Furthermore, certain surgical procedures may be simulated realistically. Used as a complement to the current curriculum, these models have the potential to greatly decrease education times and costs.

Volume cutting for virtual petrous bone surgery.

A profound knowledge of anatomy and surgical landmarks of the temporal bone is a basic necessity for any otologic surgeon. Because this knowledge, so far, has been mostly taught by limited temporal bone drilling courses, our objective was to create a system for virtual petrous bone surgery that allows the realistic simulation of specific laterobasal surgical approaches. A major requirement was the development of an interactive drill-like tool, together with a new technique for realistic visualization of simulated cut surfaces. The system is based on a volumetric, high-resolution model of the temporal bone, derived from CT. Interactive volume cutting methods using a new multivolume scheme have been developed. In this scheme, cut regions are modeled independently in additional data volumes using voxelization techniques. The voxelization is adapted to successive cutting operations as needed for the simulation of a drill-like tool. A new visualization technique was developed for artifact-free rendering of sharp edges, as formed by the intersection of a cut and an object surface. The new multivolume visualization technique allows high-quality visualization of interactively generated cut surfaces. This is a necessity for a realistic simulation of petrous bone surgery. Our system therefore facilitates comprehension of the complex morphology, and enables the recognition of surgical landmarks, which is most important if injury to delicate organs (e.g., the facial nerve or auditory ossicles) is to be avoided. The system for virtual petrous bone surgery allows the simulation of specific surgical approaches with high-quality visualization. The user can learn about the complex three-dimensional anatomy of the temporal bone from the viewpoint of a real otosurgical procedure.