Man versus machine: Automatic pedicle screw planning using registration-based techniques compared with manual screw planning for thoracolumbar fusion surgeries.

OBJECTIVE: This study evaluates the precision of a commercially available spine planning software in automatic spine labelling and screw-trajectory proposal. METHODS: The software uses automatic segmentation and registration of the vertebra to generate screw proposals. 877 trajectories were compared. Four neurosurgeons assessed suggested trajectories, performed corrections, and manually planned pedicle screws. Additionally, automatic identification/labelling was evaluated. RESULTS: Automatic labelling was correct in 89% of the cases. 92.9% of automatically planned trajectories were in accordance with G&R grade A + B. Automatic mode reduced the time spent planning screw trajectories by 7 s per screw to 20 s per vertebra. Manual mode yielded differences in screw-length between surgeons (largest distribution peak: 5 mm), automatic in contrast at 0 mm. The size of suggested pedicle screws was significantly smaller (largest peaks in difference between 0.5 and 3 mm) than the surgeon's choice. CONCLUSION: Automatic identification of vertebrae works in most cases and suggested pedicle screw trajectories are acceptable. So far, it does not substitute for an experienced surgeon's assessment.

Computer-assisted simulated workplace-based assessment in surgery: application of the universal framework of intraoperative performance within a mixed-reality simulation.

Objectives: Workplace-based assessment (WBA) is a key requirement of competency-based medical education in postgraduate surgical education. Although simulated workplace-based assessment (SWBA) has been proposed to complement WBA, it is insufficiently adopted in surgical education. In particular, approaches to criterion-referenced and automated assessment of intraoperative surgical competency in contextualized SWBA settings are missing.Main objectives were (1) application of the universal framework of intraoperative performance and exemplary adaptation to spine surgery (vertebroplasty); (2) development of computer-assisted assessment based on criterion-referenced metrics; and (3) implementation in contextualized, team-based operating room (OR) simulation, and evaluation of validity. Design: Multistage development and assessment study: (1) expert-based definition of performance indicators based on framework's performance domains; (2) development of respective assessment metrics based on preoperative planning and intraoperative performance data; (3) implementation in mixed-reality OR simulation and assessment of surgeons operating in a confederate team. Statistical analyses included internal consistency and interdomain associations, correlations with experience, and technical and non-technical performances. Setting: Surgical simulation center. Full surgical team set-up within mixed-reality OR simulation. Participants: Eleven surgeons were recruited from two teaching hospitals. Eligibility criteria included surgical specialists in orthopedic, trauma, or neurosurgery with prior VP or kyphoplasty experience. Main outcome measures: Computer-assisted assessment of surgeons' intraoperative performance. Results: Performance scores were associated with surgeons' experience, observational assessment (Objective Structured Assessment of Technical Skill) scores and overall pass/fail ratings. Results provide strong evidence for validity of our computer-assisted SWBA approach. Diverse indicators of surgeons' technical and non-technical performances could be quantified and captured. Conclusions: This study is the first to investigate computer-assisted assessment based on a competency framework in authentic, contextualized team-based OR simulation. Our approach discriminates surgical competency across the domains of intraoperative performance. It advances previous automated assessment based on the use of current surgical simulators in decontextualized settings. Our findings inform future use of computer-assisted multidomain competency assessments of surgeons using SWBA approaches.

A method for finding high accuracy surface zones on 3D printed bone models.

The use of three-dimensional (3D) printing for surgical applications is steadily increasing. Errors in the printed models can lead to complications, especially when the model is used for surgery planning or diagnostics. In patient care, the validation of printed models should therefore be performed routinely. However, there currently is no standard method to determine whether the printed model meets the necessary quality requirements. In this work, we present a method that not only finds surface deviations of a printed model, but also shows high accuracy zones of a potentially corrupted model, that are safe to be used for surgery planning. Our method was tested on printed patient bone models with acetabular fractures and was compared to two common methods in orthopedics, simple landmark registration as well as landmark plus subsequent iterative closest point registration. In order to find suitable parameters and to evaluate the performance of our method, 15 digital acetabular bone models were artificially deformed, imitating four typical 3D printing errors. A sensitivity of over 95% and a specificity of over 99% was observed in finding these surface deformations. Then, the method was applied to 32 printed models that had been re-digitized using a computed tomography scanner. It was found that only 25% of these printed models were free of significant deformations. However, focussing on two common implant locations, our method revealed that 72% of the models were within the acceptable error tolerance. In comparison, simple landmark registration resulted in a 9% acceptance rate and landmark registration followed by iterative closest point registration resulted in a 41% acceptance rate. This outcome shows that our method, named Similarity Subgroups Registration, allows clinicians to safely use partially corrupted 3D printed models for surgery planning. This improves efficiency and reduces time to treatment by avoiding reprints. The similarity subgroups registration is applicable in further clinical domains as well as non-medical applications that share the requirement of local high accuracy zones on the surface of a 3D model.

Deep learning-based X-ray inpainting for improving spinal 2D-3D registration.

BACKGROUND: Two-dimensional (2D)-3D registration is challenging in the presence of implant projections on intraoperative images, which can limit the registration capture range. Here, we investigate the use of deep-learning-based inpainting for removing implant projections from the X-rays to improve the registration performance. METHODS: We trained deep-learning-based inpainting models that can fill in the implant projections on X-rays. Clinical datasets were collected to evaluate the inpainting based on six image similarity measures. The effect of X-ray inpainting on capture range of 2D-3D registration was also evaluated. RESULTS: The X-ray inpainting significantly improved the similarity between the inpainted images and the ground truth. When applying inpainting before the 2D-3D registration process, we demonstrated significant recovery of the capture range by up to 85%. CONCLUSION: Applying deep-learning-based inpainting on X-ray images masked by implants can markedly improve the capture range of the associated 2D-3D registration task.

Cementless hip revision cup for the primary fixation of osteoporotic acetabular fractures in geriatric patients.

BACKGROUND: Elderly patients suffering from hip fractures are usually not able to fulfil postoperative weight-bearing restrictions. Therefore, the operative fixation construct has to be as stable as possible. Aim of the present study was to determine (1) whether a therapeutic advantage could be achieved when using hip arthroplasty to treat acetabular fractures in geriatric patients; (2) whether an acetabular revision cup would be suitable for achieving fast postoperative mobilization and full weight-bearing; and (3) when a treatment with an uncemented hip revision cup for the primary fixation of osteoporotic acetabular fractures in geriatric patients is indicated. MATERIALS AND METHODS: The functional outcome of THA using a reconstruction cup for an acetabular fracture was evaluated in ten patients using standardized scoring instruments. In addition, an analysis of the preexisting literature referring to total hip replacement in geriatric acetabular fractures was conducted and an algorithm for standardizing the treatment approach for geriatric patients with acetabular fractures was developed. RESULTS: The mean EQ-5D-3L quality of life score 0.7. The mean VAS Score was 58.2. The average Barthel Index was 80.0 points [range: 0-100]. The mean HHS was 72.0 points, while the MHH Score yielded an average of 63.4 points. The average AP Score was 7.5. The literature analysis showed that total hip arthroplasty could be a feasible option for geriatric acetabular fractures. CONCLUSION: Primary hip arthroplasty using uncemented revision cup fixed with angular stable screws showed good results and is a feasible treatment option of acetabular fractures in geriatric patients. The approach is especially beneficial in patients with poor bone stock and allows postoperative full weight-bearing. The presented treatment algorithm could be a useful tool for identifying the most appropriate treatment option. LEVEL OF EVIDENCE: IIb.

Biomechanical stability of sacroiliac screw osteosynthesis with and without cement augmentation.

BACKGROUND: Percutaneous sacroiliac (SI) screw fixation is the standard operative treatment of traumatic disruptions to the posterior pelvic ring. The technique offers good outcomes and early postoperative mobilization, which is vital in elderly patients with fragility fractures of the pelvis. While a double-screw technique has been shown to provide optimal biomechanical stability compared to a single-screw construct, anatomic variations and patient-specific characteristics may prevent the safe insertion of two SI screws. We aimed to determine whether cement augmentation of a single SI screw would provide biomechanical stability comparable to that of the double-screw technique. METHODS: Three sacroiliac screw osteosynthesis configurations were tested on 10 human cadaveric pelvis specimens: a single cannulated screw; two cannulated screws; and a single, cement-augmented cannulated screw. Displacement and stiffness of the anterior and posterior pelvic ring after fixation with each technique were measured under axial load. Results where compared using linear regression and paired t-tests. RESULTS: A single uncemented screw offered significantly worse stability in the anterior pelvis compared to a double-screw technique (P < 0.05) and to a single cement-augmented screw technique (P < 0.05). There was no significant difference in anterior pelvic ring stability between the single cement-augmented screw technique and the double-screw technique (P > 0.05). There was no significant difference in the stability of the posterior pelvic ring between the three techniques (P > 0.05). CONCLUSIONS: A single cement-augmented cannulated sacroiliac screw provides biomechanical stability similar to that of a non-augmented double-screw technique in the treatment of posterior pelvic ring fractures.

Three-dimensional-Printed Computed Tomography-Based Bone Models for Spine Surgery Simulation.

INTRODUCTION: We present a novel 3-dimensional (3D) printing method for low-cost and widely available reproduction of computed tomography (CT)-based synthetic bone models for spine surgery simulation, optimized to reproduce realistic haptic properties. The method allows reproduction of either normal or abnormal patient anatomy. The models are fluoroscopy compatible and contain deformities and fractures present in the underlying CT data. METHODS: Spine models created from CT data were printed on a 3D printer using 2 different materials for cortical and cancellous bone. Printing parameters were iteratively optimized with surgical experts and 3 candidate spine models were evaluated in a study regarding haptic properties. X-ray images of a spine section printed with final printing parameters were evaluated by surgical experts regarding fluoroscopic properties. RESULTS: Eleven surgical experts performed a trocar insertion, a typical workflow step in spine surgery procedures, on the models. We observed agreement that cortical structures and strong agreement that cancellous structures of the final model are haptically comparable with human vertebral bone. Ten surgical experts evaluated x-ray images of the model. They expressed strong agreement on the similarity with x-ray images of the human spine and confirmed the presence of a fracture. Material cost of a typical spine model is around US $11. CONCLUSIONS: Models created using the novel methodology realistically reproduce the haptic properties during a trocar placement into the vertebral body. The models are compatible with conventional x-ray imaging. Because the models correspond to real patient CT data, those can alternatively be used in simulation environments that simulate fluoroscopy or CT image guidance to produce highly realistic, radiation-free imaging output.

3D printing method for next-day acetabular fracture surgery using a surface filtering pipeline: feasibility and 1-year clinical results.

INTRODUCTION: In orthopedic surgery, 3D printing is a technology with promising medical applications. Publications show promising results in acetabular fracture surgery over the last years using 3D printing. However, only little information about the workflow and circumstances of how to properly derive the 3D printed fracture model out of a CT scan is published. MATERIALS AND METHODS: We conducted a retrospective analysis of patients with acetabular fractures in a level 1 trauma center. DICOM data were preoperatively used in a series of patients with acetabular fractures. The 3D mesh models were created using 3D Slicer (https://www.slicer.org) with a newly introduced surface filtering method. The models were printed using PLA material with FDM printer. After reduction in the printed model, the acetabular reconstruction plate was bent preoperatively and sterilized. A clinical follow-up after 12 months in average was conducted with the patients. RESULTS: In total, 12 patients included. Mean printing time was 8:40 h. The calculated mean printing time without applying the surface filter was 25:26 h. This concludes an average printing time reduction of 65%. Mean operation time was 3:16 h, and mean blood loss was 853 ml. Model creation time was about 11 min, and mean printing time of the 3D model was 8:40 h, preoperative model reduction time was 5 min on average, and preoperative bending of the plate took about 10 min. After 12 months, patients underwent a structured follow-up. Harris Hip Score was 75.7 points, the Modified Harris Hip Score 71.6 points and the Merle d'Aubigne Score 11.1 points on average. CONCLUSIONS: We presented the first clinical practical technique to use 3D printing in acetabular fracture surgery. By introducing a new surface filtering pipeline, we reduced printing time and cost compared to the current literature and the state of the art. Low costs and easy handling of the 3D printing workflow make it usable in nearly every hospital setting for acetabular fracture surgery.

Fluoroscopic Marker-Based Guidance System Improves Gamma Lag Screw Placement During Nailing of Intertrochanteric Fractures: A Randomized Controlled Trial.

OBJECTIVES: To determine whether a fluoroscopy-based navigation system would improve tip-apex distance (TAD) compared with the conventional technique. DESIGN: Randomized controlled trial. SETTING: Level 1 trauma center. PATIENTS: A total of 161 patients were screened for inclusion in the study. After meeting inclusion and exclusion criteria, 31 patients were randomized (n = 18 navigated vs. n = 13 control group), with the patient blinded to the result. INTERVENTION: Fluoroscopy-based navigated guidance of lag screw length and position. MAIN OUTCOME MEASURES: Average TAD and the proportion of TAD over 25 mm. RESULTS: TAD was lower in the navigated group compared with the control group (mean = 17.5 vs. 24.2 mm; P = 0.0018). No navigated cases exceeded the 25 mm TAD threshold, compared with 39% of conventional cases (P = 0.0076). Navigation resulted in fewer drilling attempts compared with the conventional technique (median = 1 vs. 4 attempts; P < 0.0001). We detected no significant differences in operation time or total number of fluoroscopic images (P > 0.05). CONCLUSIONS: Fluoroscopy-based computer navigated Gamma nailing for intertrochanteric fractures improved TAD and reduced the number of drilling attempts without increasing operation time compared with the conventional fluoroscopy-guided technique in a teaching hospital setting. LEVEL OF EVIDENCE: Therapeutic Level I. See Instructions for Authors for a complete description of levels of evidence.

A comparative analysis of intensity-based 2D-3D registration for intraoperative use in pedicle screw insertion surgeries.

PURPOSE: Although multiple algorithms have been reported that focus on improving the accuracy of 2D-3D registration techniques, there has been relatively little attention paid to quantifying their capture range. In this paper, we analyze the capture range for a number of variant formulations of the 2D-3D registration problem in the context of pedicle screw insertion surgery. METHODS: We tested twelve 2D-3D registration techniques for capture range under different clinically realistic conditions. A registration was considered as successful if its error was less than 2 mm and 2° in 95% of the cases. We assessed the sensitivity of capture range to a variety of clinically realistic parameters including: X-ray contrast, number and configuration of X-rays, presence or absence of implants in the image, inter-subject variability, intervertebral motion and single-level vs multi-level registration. RESULTS: Gradient correlation + Powell optimizer had the widest capture range and the least sensitivity to X-ray contrast. The combination of 4 AP + lateral X-rays had the widest capture range (725 mm2). The presence of implant projections significantly reduced the registration capture range (up to 84%). Different spine shapes resulted in minor variations in registration capture range (SD 78 mm2). Intervertebral angulations of less than 1.5° had modest effects on the capture range. CONCLUSIONS: This paper assessed capture range of a number of variants of intensity-based 2D-3D registration algorithms in clinically realistic situations (for the use in pedicle screw insertion surgery). We conclude that a registration approach based on the gradient correlation similarity and the Powell's optimization algorithm, using a minimum of two C-arm images, is likely sufficiently robust for the proposed application.

[3D printing in orthopedic and trauma surgery education and training : Possibilities and fields of application]. / 3D-Druck in der unfallchirurgischen Fort- und Weiterbildung : Möglichkeiten und Anwendungsbereiche.

The 3D printing technology enables precise fracture models to be generated from volumetric digital imaging and communications in medicine (DICOM) computed tomography (CT) data. Apart from patient treatment, in the future this technology could potentially play a significant role in education and training in the field of orthopedic and trauma surgery. Preliminary results show that the understanding and classification of fractures can be improved when teaching medical students. The use of life-size and haptic models of real fractures for education is particularly interesting. Even experienced surgeons show an improved classification and treatment planning with the help of 3D printed models when compared to plain CT data. Especially for complex articular fractures, such as those of the acetabulum and tibial plateau, initial evidence shows patient benefits in terms of reduced surgery time and blood loss with the help of 3D models. The use of 3D printing on-site at the hospital is of particular interest in orthopedic and trauma surgery as it promises to provide products within a short time. The low investment and running costs and the increasing availability of convenient software solutions will spur increasing dissemination of this technology in the coming years.

Modified less invasive anterior subcutaneous fixator for unstable Tile-C-pelvic ring fractures: a biomechanical study.

BACKGROUND: Operative procedures for unstable pelvic ring fractures remain controversially discussed. Minimally invasive treatment options for pelvic ring fractures have several benefits for the patient. But they can also provide disadvantages. Anterior subcutaneous pelvic fixation (INFIX) has shown promising biomechanical results in pelvic ring fractures, but there is a high complication rate of nerve injuries. An additional screw to the INFIX seems to be more stable. The aim of this study is to compare biomechanical stability of a new modified unilateral INFIX fixing the unilateral injured pelvic ring with the standard INFIX. METHODS: 24 composite synthetic full pelvises were used in this study. 4 groups each with a number of six pelvic specimens were randomly assigned. A C1.3-type pelvic fracture was made with an osteotomy of the sacrum and an osteotomy of the anterior pelvic ring. Fracture fixation was performed within the four groups: (1) unilateral INFIX, (2) "extended" unilateral INFIX + additional pubic ramus pedicle screw, (3) bilateral INFIX, (4) "extended" bilateral INFIX + additional pubic ramus pedicle screw. All specimens were cyclic loaded with 200 N until maximum of 300 N. Distance/dislocation of the fracture fragments were detected with 3D-ultrasound measuring system. Stiffness was calculated. RESULTS: Extended unilateral INFIX showed the lowest mean dislocation. Lowest rotational stability was displayed by the standard bilateral INFIX. A significant difference (P = 0.04) was shown between the extended unilateral INFIX and the "standard" bilateral INFIX in terms of rotational stability. Extended unilateral INFIX showed significantly improved stability of anterior fracture dislocation (P = 0.01) and unilateral INFIX showed the highest rotational stiffness. Anterior fixation stiffness of the unilateral INFIX was significantly improved using an additional symphysis/pubic ramus screw (P = 0.002). CONCLUSION: Extended unilateral INFIX (+ additional pubic ramus pedicle screw) is a feasible minimally invasive treatment for anterior pelvic ring fractures. Higher stability and lower probability of bilateral nerve damage is provided by the extended unilateral INFIX compared to the standard bilateral INFIX.

Video-augmented fluoroscopy for distal interlocking of intramedullary nails decreased radiation exposure and surgical time in a bovine cadaveric setting.

BACKGROUND: We aimed to assess the feasibility of a video-augmented fluoroscopy (VAF) technique using a camera-augmented mobile C-arm (CamC) for distal interlocking of intramedullary nails. METHODS: Three surgeons performed distal interlocking on seven pairs of cadaveric bovine carpal bones using the VAF system and conventional fluoroscopy. We compared radiation exposure, procedure time, and drilling quality between the VAF system and conventional fluoroscopic guidance. RESULTS: Distal interlocking using VAF significantly reduced the number of fluoroscopic images compared with conventional fluoroscopy (P < 0.05). No significant difference in overall procedure time (P = 0.96) or drilling quality (P = 0.12) was detected. VAF demonstrated improvement in radiation exposure when used by a less experienced surgeon (P < 0.05). CONCLUSION: VAF is a feasible technique for distal interlocking. Overlaid visualization of the osseous anatomy in relation to the surgical field of view appears to improve surgeons' perception of relevant structures and their spatial orientation for the use of surgical instruments.

Radiographic cortical thickness parameters as predictors of rotational alignment in proximal femur fractures: A cadaveric study.

Radiographic assessment tools such as the cortical step sign (CSS) or the diameter difference sign (DDS) aim to identify clinically relevant rotational malalignment after long bone fracture fixation. We aimed to analyze the effect of rotational malalignment on CSS and DDS parameters in a subtrochanteric fracture model and to construct a prognostic model to identify clinically relevant rotational malalignment. A subtrochanteric transverse osteotomy was set in human femora. Rotation was set stepwise from 0° to 30° in internal and external rotation. Images were obtained using a C-arm and transferred for measuring the medial cortical thickness (MCT), lateral cortical thickness (LCT), femoral diameter (FD) in AP and the anterior cortical thickness (ACT) as well as the posterior cortical thickness (PCT) and the FD of the proximal and the distal main fragment. There were significant differences between the various levels of rotation for each of the absolute values of the evaluated variables. MCT, PCT and FD (AP & lat.) were the most affected parameters. In internal rotation, the MCT, PCT and the FD were the most affected variables. The parameters with the highest correlation with femoral rotation were ACT, PCT and FD. A model combining ACT, LCT, PCT and FD AP was most suitable model in identifying rotational malalignment. The best prediction of clinically relevant rotational malalignment was obtained with the FD and the PCT. The CSS and the DDS are promising tools for detecting rotational deformities of the proximal femur and should be used intra- and postoperatively. © 2018 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res.

Minimally invasive screw fixation is as stable as anterior plating in acetabular T-Type fractures - a biomechanical study.

INTRODUCTION: Operative treatments of T-type acetabular fractures are challenging surgical procedures. Open reduction and internal fixation is the standard method for the operative management of these fractures, however this is associated with high blood loss, long hospital stay and longer rehabilitation. Anterior subcutaneous pelvic fixation (internal fixation=INFIX) and retrograde pubic screw fixation have shown promising results in minimally invasive treatment of pelvic ring fractures. For T-type acetabular fractures, however, minimally invasive treatment concepts are still rare. Therefore we performed a mechanical in vitro study to: - investigate the potential favorability of minimally invasive treatment options over the already established open anterior locking plate osteosynthesis of acetabular T-fractures regarding biomechanical stability and post-surgical stiffness; - explore the biomechanical feasibility of the INFIX; - assess its potential ability to reduce the anterior acetabular column. HYPOTHESIS: A minimally invasive treatment of acetabular T-type fractures is biomechanically equivalent to an open anterior plate osteosynthesis. METHODS: Twenty-four synthetic hemipelvis specimens with a T-type acetabular fracture were divided in four groups. A posterior column screw was placed in every pelvis of every group. The anterior column was fixed with: - anterior column screw; - anterior column screw incl. INFIX; - INFIX alone; - 14-hole angular stable locking plate (standard fixation method). Displacement of the anterior column was reduced in group 2+3 using the INFIX. All specimens were cyclically loaded with 200N until a maximum of 600N. Movement/displacement of the fracture fragments were detected with a 3D-ultrasound measuring system. Displacement (mm) and Stiffness (N/mm) of the construction were analyzed. RESULTS: Statistical assessment showed no significant differences between the four fixation types (p>0.05). The 14-whole locking plate (group 4) displayed the overall highest stability with a displacement of 1.3±0.04mm and stiffness of 76.3±2.4N/mm. Anterior screw fixation (group 1) proved to be the minimally invasive fixation method with the least displacement and highest stiffness (1.5±0.2mm, 68.3±6.8N/mm). The combination of an INFIX and an anterior column screw (group 2), showed a mean stiffness of 62.1±6.0N/mm and a mean displacement of 1.7±0.2mm. INFIX only (group 3) presented a displacement of 1.6±0.1mm and a stiffness of 64.5±4.5N/mm. DISCUSSION: Minimally invasive fixation techniques for T-type acetabular fractures show promising biomechanical stability in non- or slightly displaced fractures. Furthermore, INFIX could be a feasible tool for the reduction of the anterior acetabular column. LEVEL OF EVIDENCE: III, case control prospective experimental study.

[Diagnostic and Treatment Strategies in Morel-Lavallee Lesions in the Spinal Column and Pelvis]. / Diagnostik und Behandlungsstrategien bei Morel-Lavallée-Läsionen im Wirbelsäulen- und Beckenbereich.

BACKGROUND: The Morel-Lavallée lesion is one of the concomitant soft tissue lesions of pelvic fractures. Its role in spine fractures and its treatment in combination with osteosynthesis of pelvic or spine fractures have not yet been determined. The aim of this study was to analyse the best diagnostic and treatment options of both spine and pelvic fractures combined with Morel-Lavallée lesions (MLL). METHODS: An analysis of the literature was performed via PubMed and Medline. This revealed a total of 197 studies and case reports. After analysing the literature, 19 studies/case reports met our inclusion criteria. RESULTS: There are several diagnostic options for MLL, including ultrasound, computed tomography or MRI. In spinal and pelvic lesions, ultrasound is capable of detecting MLL. Some authors tend to perform open debridement of the MLL, whereas others recommend percutanous treatment. Open debridement and vacuum-assisted closure are recommended in late diagnosed MLL, where primary suture of the soft tissue is impossible. Fracture fixation should be performed simultaneously to treatment of the MLL. Broad-spectrum cephalosporins combined with an aminoglycoside or piperacilline/tazobactam should be initiated. CONCLUSION: Radical debridement and drainage are recommended, especially when MLL is diagnosed late. Repeated ultrasound examinations should be performed of the surrounding soft tissue of the fracture. When MLL is diagnosed within 2 days, percutanous fracture and MLL treatment should be performed. After more than 2 days, both fracture and MLL should be treated with open debridement, open fracture fixation and primary suture if possible.

Vibroarthrography for early detection of knee osteoarthritis using normalized frequency features.

Vibroarthrography is a radiation-free and inexpensive method of assessing the condition of knee cartilage damage during extension-flexion movements. Acoustic sensors were placed on the patella and medial tibial plateau (two accelerometers) as well as on the lateral tibial plateau (a piezoelectric disk) to measure the structure-borne noise in 59 asymptomatic knees and 40 knees with osteoarthritis. After semi-automatic segmentation of the acoustic signals, frequency features were generated for the extension as well as the flexion phase. We propose simple and robust features based on relative high-frequency components. The normalized nature of these frequency features makes them insusceptible to influences on the signal gain, such as attenuation by fat tissue and variance in acoustic coupling. We analyzed their ability to serve as classification features for detection of knee osteoarthritis, including the effect of normalization and the effect of combining frequency features of all three sensors. The features permitted a distinction between asymptomatic and non-healthy knees. Using machine learning with a linear support vector machine, a classification specificity of approximately 0.8 at a sensitivity of 0.75 could be achieved. This classification performance is comparable to existing diagnostic tests and hence qualifies vibroarthrography as an additional diagnostic tool. Graphical Abstract Acoustic frequency features were used to detect knee osteoarthritis at 80% specificity and 75% sensitivity.

On-the-fly augmented reality for orthopedic surgery using a multimodal fiducial.

Fluoroscopic x-ray guidance is a cornerstone for percutaneous orthopedic surgical procedures. However, two-dimensional (2-D) observations of the three-dimensional (3-D) anatomy suffer from the effects of projective simplification. Consequently, many x-ray images from various orientations need to be acquired for the surgeon to accurately assess the spatial relations between the patient's anatomy and the surgical tools. We present an on-the-fly surgical support system that provides guidance using augmented reality and can be used in quasiunprepared operating rooms. The proposed system builds upon a multimodality marker and simultaneous localization and mapping technique to cocalibrate an optical see-through head mounted display to a C-arm fluoroscopy system. Then, annotations on the 2-D x-ray images can be rendered as virtual objects in 3-D providing surgical guidance. We quantitatively evaluate the components of the proposed system and, finally, design a feasibility study on a semianthropomorphic phantom. The accuracy of our system was comparable to the traditional image-guided technique while substantially reducing the number of acquired x-ray images as well as procedure time. Our promising results encourage further research on the interaction between virtual and real objects that we believe will directly benefit the proposed method. Further, we would like to explore the capabilities of our on-the-fly augmented reality support system in a larger study directed toward common orthopedic interventions.