Analysis of the three-dimensional anatomical variance of the distal radius using 3D shape models.

BACKGROUND: Various medical fields rely on detailed anatomical knowledge of the distal radius. Current studies are limited to two-dimensional analysis and biased by varying measurement locations. The aims were to 1) generate 3D shape models of the distal radius and investigate variations in the 3D shape, 2) generate and assess morphometrics in standardized cut planes, and 3) test the model's classification accuracy. METHODS: The local radiographic database was screened for CT-scans of intact radii. 1) The data sets were segmented and 3D surface models generated. Statistical 3D shape models were computed (overall, gender and side separate) and the 3D shape variation assessed by evaluating the number of modes. 2) Anatomical landmarks were assigned and used to define three standardized cross-sectional cut planes perpendicular to the main axis. Cut planes were generated for the mean shape models and each individual radius. For each cut plane, the following morphometric parameters were calculated and compared: maximum width and depth, perimeter and area. 3) The overall shape model was utilized to evaluate the predictive value (leave one out cross validation) for gender and side identification within the study population. RESULTS: Eighty-six radii (45 left, 44% female, 40 ± 18 years) were included. 1) Overall, side and gender specific statistical 3D models were successfully generated. The first mode explained 37% of the overall variance. Left radii had a higher shape variance (number of modes: 20 female / 23 male) compared to right radii (number of modes: 6 female / 6 male). 2) Standardized cut planes could be defined using anatomical landmarks. All morphometric parameters decreased from distal to proximal. Male radii were larger than female radii with no significant side difference. 3) The overall shape model had a combined median classification probability for side and gender of 80%. CONCLUSIONS: Statistical 3D shape models of the distal radius can be generated using clinical CT-data sets. These models can be used to assess overall bone variance, define and analyze standardized cut-planes, and identify the gender of an unknown sample. These data highlight the potential of shape models to assess the 3D anatomy and anatomical variance of human bones.

Intra-operative disruptions, surgeon's mental workload, and technical performance in a full-scale simulated procedure.

BACKGROUND AND AIM: Surgical flow disruptions occur frequently and jeopardize perioperative care and surgical performance. So far, insights into subjective and cognitive implications of intra-operative disruptions for surgeons and inherent consequences for performance are inconsistent. This study aimed to investigate the effect of surgical flow disruption on surgeon's intra-operative workload and technical performance. METHODS: In a full-scale OR simulation, 19 surgeons were randomly allocated to either of the two disruption scenarios (telephone call vs. patient discomfort). Using a mixed virtual reality simulator with a computerized, high-fidelity mannequin, all surgeons were trained in performing a vertebroplasty procedure and subsequently performed such a procedure under experimental conditions. Standardized measures on subjective workload and technical performance (trocar positioning deviation from expert-defined standard, number, and duration of X-ray acquisitions) were collected. RESULTS: Intra-operative workload during simulated disruption scenarios was significantly higher compared to training sessions (p < .01). Surgeons in the telephone call scenario experienced significantly more distraction compared to their colleagues in the patient discomfort scenario (p < .05). However, workload tended to be increased in surgeons who coped with distractions due to patient discomfort. Technical performance was not significantly different between both disruption scenarios. We found a significant association between surgeons' intra-operative workload and technical performance such that surgeons with increased mental workload tended to perform worse (ß = .55, p = .04). CONCLUSIONS: Surgical flow disruptions affect surgeons' intra-operative workload. Increased mental workload was associated with inferior technical performance. Our simulation-based findings emphasize the need to establish smooth surgical flow which is characterized by a low level of process deviations and disruptions.

Using self-drilling screws in volar plate osteosynthesis for distal radius fractures: a feasibility study.

BACKGROUND: Symptomatic extensor tendon irritation is a frequent complication in volar plate osteosynthesis of distal radius fractures. It is typically caused by dorsal screw protrusion and overdrilling of the dorsal cortex. The use of self-drilling locking screws (SDLS) could overcome both causes. The practical applicability of SDLS depends on two prerequisites: (1) the feasibility of preoperative distal screw length determination, and (2) sufficient primary biomechanical stability of SDLS compared to standard locking screws (SLS). METHODS: We first assessed the feasibility of preoperative screw length determination (1): Distal radius width, depth and distal screw lengths were measured in 38 human radii. Correlations between distal radius width and depth were assessed, a cluster analysis (Ward's method and squared Euclidean distance) for distal radius width conducted, and intra-cluster screw lengths analyzed (ANOVA). The biomechanical performance of SDLS (2) was assessed by comparison to SLS in a distal radius fracture model (AO-23 A3). 75 % distal screw length was chosen for both groups to simulate a worst-case scenario. Uniaxial compression tests were conducted to measure stiffness, elastic limit, maximum force and residual tilt. Statistics comprised of independent sample t-tests and a Bonferroni correction (p < 0.0125). RESULTS: (1) Distal radius width and depth showed a high correlation (R (2) = 0.79; p < 0.001). Three distal radius width clusters could be identified: small <34 mm; medium 34-36.9 mm; large >36.9 mm. ANOVA and Tukey post-hoc analysis revealed significantly different volar-dorsal depths (p < 0.05) for nearly all screws. (2) To assess biomechanical stability nine specimens were tested each; no significant differences were found between the SDLS and SLS groups. CONCLUSIONS: This feasibility study demonstrates that (1) distal radius width can be used as a predictor for distal screw length and (2) that SDLS provides mechanical stability equivalent to SLS. These results highlight the feasibility of applying SDLS screws in volar plate osteosynthesis at least in extraarticular fractures.

Personalized augmented reality for anatomy education.

Anatomy education is a challenging but vital element in forming future medical professionals. In this work, a personalized and interactive augmented reality system is developed to facilitate education. This system behaves as a "magic mirror" which allows personalized in-situ visualization of anatomy on the user's body. Real-time volume visualization of a CT dataset creates the illusion that the user can look inside their body. The system comprises a RGB-D sensor as a real-time tracking device to detect the user moving in front of a display. In addition, the magic mirror system shows text information, medical images, and 3D models of organs that the user can interact with. Through the participation of 7 clinicians and 72 students, two user studies were designed to respectively assess the precision and acceptability of the magic mirror system for education. The results of the first study demonstrated that the average precision of the augmented reality overlay on the user body was 0.96 cm, while the results of the second study indicate 86.1% approval for the educational value of the magic mirror, and 91.7% approval for the augmented reality capability of displaying organs in three dimensions. The usefulness of this unique type of personalized augmented reality technology has been demonstrated in this paper.

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.

[Prophylactic fasciotomy in tibial osteotomies: functional results]. / Prophylaktische Fasziotomie bei Tibia-Osteotomien: funktionelle Ergebnisse.

BACKGROUND: Intramedullary nailing in tibial osteotomy (TO) can be combined with minimally invasive prophylactic fasciotomy (PF) of the anterior compartment of the lower leg to prevent postoperative acute compartment syndrome (CS). So far no studies are available on the effects of TO or PF on specific functions of the extensor muscles. OBJECTIVE: To investigate the medium-term outcome after PF in TO in patients without preoperative functional impairment. MATERIAL AND METHODS: In 41 cases (28 women, 13 men) the patients were questioned with respect to clinical function on average 6.1 years after elective TO and PF fixed with intramedullary nails. Of the cases 23 were examined measuring isometric strength and range of motion (ROM) of dorsiflexion (DF) of the foot. Strength was compared to the 10% standard percentile to test for clinical relevance and to the contralateral side if applicable. RESULTS: In an average of 86% of the cases no or minor functional impairment of the extensors was reported. The DF of the foot was rated as the leading impairment. Mean strength did not differ significantly from the gender-specific 10% standard percentiles but was significantly lower on the operated side with 16.0 ± 6.5 kgf compared to the healthy side with 17.5 ± 6.3 kgf (p < 0.01). Subjective impairments of DF of the foot correlated clearly negatively with ROM (rs = -0.46, p < 0.05) but not with strength. CONCLUSION: The results indicate a low occurrence of subjectively relevant functional impairment of the extensor muscles. The decrease of strength was not found to be clinically relevant. Subjective impairments appeared to be caused by a decrease of ROM, not strength.

Complications and Effectiveness of Intramedullary Limb Lengthening: A Matched Pair Analysis of Two Different Lengthening Nails.

BACKGROUND: Intramedullary limb lengthening has become an accepted concept in reconstructive surgery, but as yet comparative clinical studies are missing. We compared the complications and effectiveness of two types of intramedullary limb lengthening devices (ISKD®; Fitbone®). MATERIALS AND METHODS: In a retrospective series of 278 consecutive patients with internal limb lengthening, we found 17 matching pairs in terms of predefined matching parameters (group I with ISKD® and group II with Fitbone®). The surgeries were all performed with the same technique and managed with equivalent pre- and postoperative treatment protocols. The performance of the implants was evaluated using the distraction index and the weight-bearing index. Complications were rated according to Paley's classification for external lengthening. RESULTS: The distraction index in group I (ISKD®) was 0.99 mm/day (range 0.55-1.67) and in the group II (Fitbone®) 0.55 mm/day (range 0.14-0.92) (p value = 0.001). The mean weight-bearing index differed between group I and group II from 32.0 day/cm (range 16.4-64.0) to 51.6 day/cm (25.8-95.0) (p value = 0.001). There were 17 recorded incidents in group I and 19 in group II during lengthening. CONCLUSION: Specific technical handicaps of the two systems, such as the so-called runaway of the ISKD® and backtracking of the Fitbone® nails seem to result in different distraction index and weight-bearing index. Further comparative studies might induce technical progress in intramedullary limb lengthening. HOW TO CITE THIS ARTICLE: Thaller PH, Frankenberg F, Degen N, et al. Complications and Effectiveness of Intramedullary Limb Lengthening: A Matched Pair Analysis of Two Different Lengthening Nails. Strategies Trauma Limb Reconstr 2020;15(1):7-12.

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.

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.

Camera-augmented mobile C-arm (CamC): A feasibility study of augmented reality imaging in the operating room.

BACKGROUND: In orthopaedic trauma surgery, image-guided procedures are mostly based on fluoroscopy. The reduction of radiation exposure is an important goal. The purpose of this work was to investigate the impact of a camera-augmented mobile C-arm (CamC) on radiation exposure and the surgical workflow during a first clinical trial. METHODS: Applying a workflow-oriented approach, 10 general workflow steps were defined to compare the CamC to traditional C-arms. The surgeries included were arbitrarily identified and assigned to the study. The evaluation criteria were radiation exposure and operation time for each workflow step and the entire surgery. The evaluation protocol was designed and conducted in a single-centre study. RESULTS: The radiation exposure was remarkably reduced by 18 X-ray shots 46% using the CamC while keeping similar surgery times. CONCLUSIONS: The intuitiveness of the system, its easy integration into the surgical workflow, and its great potential to reduce radiation have been demonstrated.

An augmented reality C-arm for intraoperative assessment of the mechanical axis: a preclinical study.

BACKGROUND: Determination of lower limb alignment is a prerequisite for successful orthopedic surgical treatment. Traditional methods include the electrocautery cord, alignment rod, or axis board which rely solely on C-arm fluoroscopy navigation and are radiation intensive. STUDY OBJECTIVES: To assess a new augmented reality technology in determining lower limb alignment. METHODS: A camera-augmented mobile C-arm (CamC) technology was used to create a panorama image consisting of hip, knee, and ankle X-rays. Twenty-five human cadaver legs were used for validation with random varus or valgus deformations. Five clinicians performed experiments that consisted in achieving acceptable mechanical axis deviation. The applicability of the CamC technology was assessed with direct comparison to ground-truth CT. A t test, Pearson's correlation, and ANOVA were used to determine statistical significance. RESULTS: The value of Pearson's correlation coefficient R was 0.979 which demonstrates a strong positive correlation between the CamC and ground-truth CT data. The analysis of variance produced a p value equal to 0.911 signifying that clinician expertise differences were not significant with regard to the type of system used to assess mechanical axis deviation. CONCLUSION: All described measurements demonstrated valid measurement of lower limb alignment. With minimal effort, clinicians required only 3 X-ray image acquisitions using the augmented reality technology to achieve reliable mechanical axis deviation.

Preclinical usability study of multiple augmented reality concepts for K-wire placement.

PURPOSE: In many orthopedic surgeries, there is a demand for correctly placing medical instruments (e.g., K-wire or drill) to perform bone fracture repairs. The main challenge is the mental alignment of X-ray images acquired using a C-arm, the medical instruments, and the patient, which dramatically increases in complexity during pelvic surgeries. Current solutions include the continuous acquisition of many intra-operative X-ray images from various views, which will result in high radiation exposure, long surgical durations, and significant effort and frustration for the surgical staff. This work conducts a preclinical usability study to test and evaluate mixed reality visualization techniques using intra-operative X-ray, optical, and RGBD imaging to augment the surgeon's view to assist accurate placement of tools. METHOD: We design and perform a usability study to compare the performance of surgeons and their task load using three different mixed reality systems during K-wire placements. The three systems are interventional X-ray imaging, X-ray augmentation on 2D video, and 3D surface reconstruction augmented by digitally reconstructed radiographs and live tool visualization. RESULTS: The evaluation criteria include duration, number of X-ray images acquired, placement accuracy, and the surgical task load, which are observed during 21 clinically relevant interventions performed by surgeons on phantoms. Finally, we test for statistically significant improvements and show that the mixed reality visualization leads to a significantly improved efficiency. CONCLUSION: The 3D visualization of patient, tool, and DRR shows clear advantages over the conventional X-ray imaging and provides intuitive feedback to place the medical tools correctly and efficiently.

Multi-modal intra-operative navigation during distal locking of intramedullary nails.

The interlocking of intramedullary nails is a technically demanding procedure which involves a considerable amount of X-ray acquisitions; one study lists as many as 48 to successfully complete the procedure and fix screws into 4-6 mm distal holes of the nail. We propose to design an augmented radiolucent drill to assist surgeons in completing the distal locking procedure without any additional X-ray acquisitions. Using an augmented reality fluoroscope that coregisters optical and X-ray images, we exploit solely the optical images to detect the augmented radiolucent drill and estimate its tip position in real-time. Consequently, the surgeons will be able to maintain the down the beam positioning required to drill the screws into the nail holes successfully. To evaluate the accuracy of the proposed augmented drill, we perform a preclinical study involving six surgeons and ask them to perform distal locking on dry bone phantoms. Surgeons completed distal locking 98.3% of the time using only a single X-ray image with an average navigation time of 1.4 ± 0.9 min per hole.

Intra-operative augmented reality in distal locking.

PURPOSE: To design an augmented reality solution that assists surgeons during the distal locking of intramedullary nailing procedures. METHOD: Traditionally, the procedure is performed under X-ray guidance and requires a significant amount of time and radiation exposure. To absolve these complications, we propose video guidance that allows surgeons to achieve both the down-the-beam position of the intramedullary nail and its subsequent locking. For the down-the-beam position, the IM nail pose in X-ray is calculated using a 2D/3D registration scheme and later related to the patient leg pose which is calculated using video-tracked AR markers. For the distal locking, surgeons use an augmented radiolucent drill in which its tip position is detected and tracked in real-time under video guidance. VALIDATION: To evaluate the feasibility of our solution, we performed a preclinical study on dry bone phantom with the participation of four clinicians. RESULTS: Participants achieved 100 % success rate in the down-the beam positioning and 93 % success rate in distal locking using only two X-ray images in 100 s. CONCLUSIONS: We confirmed that intra-operative navigation using augmented reality provides an alternative way to perform distal locking in a safe and timely manner.

Machine learning-based augmented reality for improved surgical scene understanding.

In orthopedic and trauma surgery, AR technology can support surgeons in the challenging task of understanding the spatial relationships between the anatomy, the implants and their tools. In this context, we propose a novel augmented visualization of the surgical scene that mixes intelligently the different sources of information provided by a mobile C-arm combined with a Kinect RGB-Depth sensor. Therefore, we introduce a learning-based paradigm that aims at (1) identifying the relevant objects or anatomy in both Kinect and X-ray data, and (2) creating an object-specific pixel-wise alpha map that permits relevance-based fusion of the video and the X-ray images within one single view. In 12 simulated surgeries, we show very promising results aiming at providing for surgeons a better surgical scene understanding as well as an improved depth perception.

C-arm-based three-dimensional navigation: a preliminary feasibility study.

OBJECTIVE: With the new Siremobil Iso-C3D C-arm, three-dimensional (3D) datasets can be acquired intraoperatively in near-real time. Preliminary studies investigated the advantages of this system for depiction in joint and spinal surgery. Three-dimensional navigation seems feasible using the DICOM dataset of the Siremobil Iso-C3D in navigation devices. An experimental study was designed to investigate the feasibility and accuracy of this new technique. MATERIALS AND METHODS: After implantation of fiducial markers (titanium mini-screws, Leibinger), a Siremobil Iso-C3D C-arm with standard imaging options was used to acquire pre-interventional 3D datasets of the specimens. These isotropic voxel data were transferred via DICOM to a medivision navigation system using the spine module. After registration of the fiducials, a total of 20 pedicle screws were implanted (in 4 artificial-bone vertebral bodies and 6 cadaver vertebrae in situ) with the use of the navigation system in real-time mode. Post-interventionally, Iso-C3D and CT scans were obtained to control for implant position in the cadaver study. RESULTS: Fiducial marker implantation and registration require a special protocol to ensure correct identification and patient orientation in the DICOM dataset. The obtained accuracy was within 2 mm. Post-interventional imaging of the cadaveric vertebrae showed 10 of 12 screws to be correctly placed, with the other two in marginal intraosseous positions. CONCLUSIONS: Three-dimensional navigation with the Siremobil Iso-C3D data set is feasible, the accuracy being comparable to that of CT-based navigation and adequate for clinical interventions. Fiducial marker-based registration allows navigation of different bones in the same dataset without additional 3D scanning. This method is very useful as an additional tool in registration-free Iso-C3D-based navigation, since the navigation system allows the use of only one dynamic reference base (DRB).

C-arm-based mobile computed tomography: a comparison with established imaging on the basis of simulated treatments of talus neck fractures in a cadaveric study.

OBJECTIVE: To analyse the image quality and diagnostic effectiveness of a new C-arm-based 3D imaging method (C-arm-CT) for intraoperative evaluation of screw osteosyntheses adjacent to a peripheral joint. MATERIALS AND METHODS: Insertion of screws into four cadaveric specimens simulated the surgical treatment of talus neck fractures. Ten orthopedic surgeons and 10 radiologists evaluated X-ray, C-arm fluoroscopy, C-arm-CT and CT images. RESULTS: The best image quality was obtained with X-rays (p < 0.001), followed by C-arm fluoroscopy (2D) and CT, with the C-arm-CT (3D) being rated lowest (p < 0.001). The most correct diagnoses were obtained with CT and C-arm-CT (with no statistical difference between them), while C-arm-fluoroscopy was inferior (p < 0.001) and X-rays were the worst (p < 0.05). CONCLUSIONS: Even if the image quality of C-arm-CT is definitely inferior to that of CT, screw misplacements can be reliably detected using C-arm-CT. As compared to the current standard procedures (intraoperative fluoroscopy and postoperative radiography), C-arm-CT performed better. C-arm-CT is ideally suited to the intraoperative diagnosis of high-contrast inquiries like bone fragments and OS material, especially at the extremities. Coupling of the new 3D imaging to existing navigation systems is possible. C-arm-CT will support the further development and implementation of open and minimally invasive surgical procedures.

Necrotizing fasciitis in a young patient with acute myeloid leukemia - a diagnostic challenge.

BACKGROUND: Necrotizing fasciitis is characterized by a fulminant destruction of the soft tissue with an alarmingly high mortality rate. One of the main reasons for the continued high mortality is due to the challenge to punctual recognize and diagnose this disease, as specific cutaneous signs can vary or even be missing early in its evolution - especially in case of simultaneous first manifestation of an acute leukemia. CASE PRESENTATION: An untypical case of necrotizing fasciitis disease in a young patient with the first diagnosis of acute myeloid leukemia is presented. After her induction chemotherapy the only presenting clinical sign was fever in the presence of severe neutropenia without an evident infectious focus. After a few days a painless confluent, erythematous, pustular skin rash with a central necrosis on lateral thigh appeared. Escherichia coli was isolated from blood cultures. Surgical debridement was performed and showed subcutaneous tissue, fascia and underlying muscle around the site of initial cutaneous manifestation with typical necrosis on exploration. But, initially taken skin biopsy did not show any typical histopathological findings like bacteria or inflammatory cells confirming necrotizing fasciitis. Nevertheless, the intraoperative findings were impressive and highly indicative for a necrotizing soft tissue infection, so that the patient was treated according to clinical guidelines with extensive recurrent surgical debridement, broad-spectrum antibiotics and intensive care therapy. After recovering from NF, she successfully underwent further chemotherapy and stem cell transplantation. CONCLUSION: The presented case highlights the risk of potential misinterpretation, delayed diagnosis and treatment of necrotizing fasciitis in patients presenting with an untypical clinical and histopathological manifestation of necrotizing fasciitis as a result of severe neutropenia following chemotherapy for acute myeloid leukemia.

Radiation-free drill guidance in interlocking of intramedullary nails.

Intramedullary nailing is a technically demanding procedure which involves an excessive amount of x-ray acquisitions; one study lists as many as 48 to successfully complete the procedure. In this work, a novel low cost radiation-free drilling guide is designed to assist surgeons in completing the distal locking procedure without any x-ray acquisitions. Using an augmented reality fluoroscope that coregisters optical and x-ray images, we exploit solely the optical images to detect the drilling guide in order to estimate the tip position in real-time in x-ray. We tested over 200 random drill guide poses showing a mean tip-estimation error of 1.72 +/- 0.7mm which is significantly robust and accurate for the interlocking. In a preclinical study on dry bone phantom, three expert surgeons successfully completed the interlocking 56 out of 60 trials with no x-ray acquisition for guidance and an average time of 2 min.

Intra-op measurement of the mechanical axis deviation: an evaluation study on 19 human cadaver legs.

The alignment of the lower limb in high tibial osteotomy (HTO) or total knee arthroplasty (TKA) must be determined intraoperatively. One way to do so is to deform the mechanical axis deviation (MAD), for which a tolerance measurement of 10 mm is widely accepted. Many techniques are proposed in clinical practice such as visual inspection, cable method, grid with lead impregnated reference lines, or more recently, navigation systems. Each has their disadvantages including reliability of the MAD measurement, excess radiation, prolonged operation time, complicated setup and high cost. To alleviate such shortcomings, we propose a novel clinical protocol that allows quick and accurate intraoperative calculation of MAD. This is achieved by an X-ray stitching method requiring only three X-ray images placed into a panoramic image frame during the entire procedure. The method has been systematically analyzed in a simulation framework in order to investigate its accuracy and robustness. Furthermore, we validated our protocol via a preclinical study comprising 19 human cadaver legs. Four surgeons determined MAD measurements using our X-ray panorama and compared these values to a gold-standard CT-based technique. The maximum average MAD error was 3.5mm which shows great potential for the technique.