Are Magnetic Resonance Imaging-Generated 3Dimensional Models Comparable to Computed Tomography-Generated 3Dimensional Models for Orbital Fracture Reconstruction? An In-Vitro Volumetric Analysis.

BACKGROUND: Magnetic resonance imaging (MRI) is being increasingly considered as an alternative for the evaluation and reconstruction of orbital fractures. No previous research has compared the orbital volume of an MRI-imaged, three-dimensional (3D), reconstructed, and virtually restored bony orbit to the gold standard of computed tomography (CT). PURPOSE: To measure the orbital volumes generated from MRI-based 3D models of fractured bony orbits with virtually positioned prebent fan plates in situ and compare them to the volumes of CT-based virtually reconstructed orbital models. STUDY DESIGN: This retrospective in-vitro study used CT and MRI data from adult patients with orbital trauma assessed at the Royal Brisbane and Women's Hospital Outpatient Maxillofacial Clinic from 2011 to 2012. Only those with orbital blowout fractures were included in the study. PREDICTOR VARIABLE: The primary predictor variable was imaging modality, with CT- and MRI-based 3D models used for plate bending and placement. MAIN OUTCOME VARIABLE: The primary outcome variable was the orbital volume of the enclosed 3D models. COVARIATES: Additional data collected was age, sex, and side of fractured orbit. The effect of operator variability on plate contouring and orbital volume was quantified. ANALYSES: The Wilcoxon signed rank test was used to assess differences between orbital volumes with a significance level P < .05. RESULTS: Of 11 eligible participants, six patients (four male and two female; mean age 31 ± 8.6 years) were enrolled. Two sets of six CT-based virtually restored orbits were smaller than the intact contralateral CT models by an average of 1.02 cm3 (95% CI -0.07 to 2.11 cm3; P = .028) and 0.99 cm3 (95% CI 0.07 to 1.91 cm3; P = .028), respectively. The average volume difference between the MRI-based virtually restored orbit and the intact contralateral MRI model was 0.97 cm3 (95% CI -1.08 to 1.94 cm3; P = .75). Imaging modality did affect orbital volume difference for 1 set of CT and MRI models (0.63 cm3; 95% CI -0.11 to 1.29 cm3; P = .046) but not the other (0.69 cm3; 95% CI -0.11 to 1.23 cm3; P = .075). Single operator variability in plate bending did not result in significant (P = .75) volume differences. CONCLUSIONS: MRI can be used to reconstruct orbital volume with a clinically acceptable level of accuracy.

A Simple Method to Improve Detection of Femoral Nail Abutment in the Distal Femur: A Computer Modeling Study.

BACKGROUND: Proximal femur fractures are more frequently treated with long femoral nails. Lateral radiographs are used to assess the nail position in the distal femur. However, because of the asymmetric shape of the distal femur, standard lateral radiographs alone are suboptimal for assessing anteriorly positioned nails in the distal femur. Consequently, instances of nail abutment or even perforation might be missed intraoperatively. QUESTION/PURPOSE: Using a three-dimensional (3D) modelling approach, we asked: When the nail is in the anterior fifth of the canal, will rotating the femur to align the simulated x-ray beam with the anterior femoral condyles instead of the posterior femoral condyles increase the diagnostic accuracy of detecting nail perforation of the anterior cortex? METHODS: 3D models of 42 unilateral femora from a population sample representative of patients with hip fractures (mean age of 76 ± 7 years, 10 males and 32 females, and 16 left and 26 right femora) were used. The patients had a mean height of 158 ± 9 cm; 27 femora were from Asians and 15 were from Caucasians. Clinically appropriately sized nails had already been virtually implanted previously as part of a quantitative nail fit assessment study. In a preliminary step, the mean angles of inclination of the distal anterior supracondylar region were quantified using four axial sections of the distal femur. For the femora with the nail tip in the anterior fifth of the canal, projections representing a lateral radiograph were generated along with rotated projections at mean angle (5°, 8°) rotations, with the anterior femoral condyles aligned, and anterior femoral condyle alignment followed by internal and external rotation to detect maximum nail perforation. The distance from the nail to the distal anterior cortex was measured for each rotational projection and used to detect anterior nail perforation. The accuracy of detection was assessed using the area under the curve (AUC) of the receiver operating characteristic (ROC) analysis. RESULTS: Rotating the 3D models by aligning the x-ray beam with the anterior femoral condyles improves the diagnostic ability of detecting anterior nail perforation compared with standard lateral radiographs. The AUC increased with rotation from 0.50 (95% confidence interval 0.50 to 0.50) on the lateral projection to 0.73 (95% CI 0.57 to 0.88, difference = -0.23; p = 0.004) at 5° of rotation, 0.77 (95% CI 0.62 to 0.93, difference = -0.27; p = 0.001) at both 8° of rotation and with the anterior femoral condyles aligned, and to 0.82 (95% CI 0.67 to 0.97, difference = -0.32; p < 0.001) with internal/external rotations past the anterior femoral condyles. There were no differences in accuracy between the four methods of rotation. CONCLUSION: This study shows that rotating the femur to align the anterior femoral condyles on a lateral radiograph and then internally/externally rotating it, improves the accuracy assessed via the AUC of detecting anterior perforation when long nails are positioned in the anterior fifth of the distal femur. CLINICAL RELEVANCE: This approach can easily be used in a clinical setting. Intraoperatively, the image intensifier can be rotated around the leg to produce an image with the anterior femoral condyle aligned, providing surgeons with an opportunity to identify and improve the nail's position or exchange the nail while the patient is still under anesthesia.

Potential pitfalls of lateral radiographic assessment of the nail position in the distal femur.

INTRODUCTION: Antegrade nailing of proximal femur fractures is a widely accepted treatment that relies on lateral radiographs to assess distal nail positioning. However, the distal femur is trapezoidal in cross section, consequently standard lateral radiographs may be insufficient. This study aimed to utilise 3D modelling to virtually assess the accuracy of lateral radiographs in defining the position of a femoral nail in the distal femur, specifically considering distal cortical encroachment. MATERIALS AND METHODS: Three-dimensional models of a commonly used nail, were positioned in 3D models of 63 femora, generated from CT scans. Lateral projections, representative of lateral radiographs, were generated and measurements of the closest point distance between the distal nail and anterior inner cortex were recorded. Axial slices through the model at the same distal position were produced for any nails located in the canal's anterior 1/5th and used to quantify the shortest nail to anterior cortex distance. RESULTS: A significant (p = 0.000) difference exists between the positions of the nail in the lateral projection (- 1.7 ± 1.24 mm) compared with axial position (- 0.23 ± 1.41 mm) with reference to the inner cortical surface. In the lateral projection, 30 nails were located in the canal's anterior 1/5th, of these, 14 nails were identified in the axial position as perforating the inner cortex, with four also perforating the outer cortex surface. CONCLUSION: Femoral nails are often anteriorly located in the distal femur and reviewed using lateral radiographs. However, this research demonstrates that owing to the geometry of the distal femur, a lateral radiograph may be inadequate for determining the true position of a femoral nail within the distal femur. Accurately assessing the position of femoral nails may help to address and prevent thigh pain, and iatrogenic fracture or perforation which have been associated with anterior positioning.

Effects of ethnicity on proximal femoral intramedullary nail protrusion-a 3D computer graphical analysis.

INTRODUCTION: Antegrade nailing of proximal femur or femoral shaft fractures is a proven treatment with good to excellent results. Nonetheless, clinical evidence from Asia indicates that proximal femur nails can be too proud at the greater trochanter (GT) causing irritation for some Asian patients. This study aimed to identify any significant differences in proximal nail misfit for a set of Asian and Caucasian femora. MATERIALS AND METHODS: Two nails (Gamma3, TFNA) were virtually inserted into 63 femoral 3D models (28 Japanese, 4 Thai, 31 Caucasian). In AP, the entry point was 4° lateral for Gamma3 and 5° for TFNA; laterally the same location was used for both. Insertion depth was controlled by aligning the lag screw centre head. The distance of the nail end from the GT was measured at five (medial, lateral, anterior, posterior and centre) reference points (RPs). The correlation between GT height, CCD angle and proximal nail distance to GT was analysed. RESULTS: There was no significant difference between either nail (p = 1.0). The TFNA was overall less prominent than the Gamma3, and significantly less prominent at all RPs except lateral. The Asian femora were 3.76 (p = 0.016) times more likely to have the nail protruding proximally. The Asian subjects were shorter (p < 0.05) than the Caucasians. Their GT height was slightly shorter and CCD angles larger compared to Caucasian (Asian: 41.1 mm, 128.1°, Caucasian: 42.2 mm, 126.4°), but the differences were not significant (p = 0.36). Stature, GT height and CCD angle significantly correlated with nail distance to GT. CONCLUSIONS: This study illustrated a significantly increased incidence of proximal nail protrusion in Asian compared to Caucasian femora, corroborating clinical findings. The combination of shorter stature and GT height and a larger CCD angle in Asians likely contributes to this difference.

Morphological analysis of Gissane's angle utilising a statistical shape model of the calcaneus.

INTRODUCTION: Gissane's crucial angle (GA) facilitates to diagnose calcaneal fractures, and serves as an indicator of the quality of anatomical reduction after fixation. The study aimed to utilise statistical shape models (SSM) for analysing the complex 3D surface anatomy of the calcaneus represented by the simplified GA measurement on lateral radiographs. MATERIALS AND METHODS: SSMs were generated from CT scans of paired adult calcanei from 10 Japanese and 31 Thai specimens. GA measurements in 3D and 2D were obtained for the lateral, central and medial anatomy of the posterior facet and sinus tarsi. The correlation between calcaneal length and GA was analysed. Regression and principal component (PC) analyses were conducted for analysing morphological variability in calcaneal shape relating to GA. The bilateral symmetry of the obtained measurements was analysed. RESULTS: The mean GA (lateral) for the Japanese specimens was 105.1° ± 7.5 and 105.4° ± 8.5 for the Thai. The projected 2D angles of the central and medial measurements were larger (P < 0.00) than the 3D values. The medial projected 2D angles were larger (P ≤ 0.02) compared to the lateral. Despite the bilateral symmetry of GA and calcaneal length, their correlation displayed clear signs of asymmetry, which was confirmed by regression and PC analyses. CONCLUSIONS: Japanese and Thai specimens revealed lower GAs (both range and mean) compared to reported reference values of other ethnicities. As a reduced GA is generally indicative of a calcaneal fracture, our results are important to surgeons for their diagnostic assessment of Japanese and Thai patients. The results indicate that the GA measurement on a plain radiograph is a simplified representation of the lateral-to-central 3D calcaneal anatomy but significantly underestimates the angle measurement on the medial aspects of the respective surface areas.

Secular evolution of femoral morphology from a clinical perspective.

INTRODUCTION: Intramedullary nailing is the surgical method of choice for the treatment of proximal femur or femoral shaft fractures. Implant manufacturers aim to design implants fitting for the broadest possible population segment. As complete morphological data sets of long bones are not widely available, anatomical collections of historical dry bone specimens may represent abundant additional sources of morphological three-dimensional (3D) data for implant design, provided they are consistent with present populations. This study aims to investigate secular trends and age-related changes of femoral morphology of the Caucasian population over the past 800 years. MATERIALS AND METHODS: Computer graphical measurements of 3D-datasets of right and left femora derived from computed tomography (CT) scans, representative of the present Caucasian population, were compared to computer graphical measurements of 3D-datasets of right and left femora derived from CT scans of specimens from a historical medieval European bone collection. RESULTS: Clinically relevant parameters of historical medieval European femora were found mostly consistent with correlative data of the present Caucasian population. Additionally, for some of the evaluated parameters, particularly anteversion, morphological differences significantly correlated to individual age and sex could be identified, whereas other parameters such as caput-collum-diaphyseal angle or radius of anterior femoral bowing were not correlated to individual age or sex. CONCLUSION: The findings suggest that more recent historical specimen collections may be a convenient and easily accessible source of new 3D morphological data, as well as to complement existing data, to be used by researchers and manufacturers for the development of intramedullary femoral nails.

3D Computer graphical anatomy study of the femur: a basis for a new nail design.

BACKGROUND: Current intramedullary nails with a radius of curvature (ROC) of 1500-2000 mm sometimes cause distal anterior cortical encroachment. Furthermore, clinical data indicate that the proximal nail end is too long for some Asian patients. The objective of our study was to develop a comprehensive 3D measurement protocol that measures both the anatomy of the canal and the proximal region. The protocol was used to obtain measurements from Caucasian and Asian (Japanese and Thai) specimens. MATERIALS AND METHODS: A total of 90 3D bone models representative of hip fracture patients were reconstructed from CT data. RapidForm 2006 was used to generate the reference geometries required for determining radius and angulation of shaft antecurvature as well as measurements of the proximal anatomy. Multiple linear regression analyses were used to determine the relative contribution of height, age, ethnicity, gender, and body side on the total variance. RESULTS: The mean ROC in the natural 3D antecurvature plane was 885 mm overall, 974 mm in Caucasians and 787 mm in Asians. Height, age, ethnicity, gender, and body side significantly predicted ROC (R = 0.53, p = 0.000). The mean values of anteversion measurements for Asians (Japanese: 22.1°; Thai: 22.7°) were significantly larger than those of the Caucasians (14.5°; p = 0.001). There was virtually no difference (p = 0.186) between the measurements pertaining to the length of the proximal nail end between Caucasian and Asian samples. There was no significant difference between the mean neck-to-shaft angles (Caucasian: 126°; Japanese: 128.2°; Thai: 125.7°; p = 0.198 for Asians vs Caucasians). CONCLUSIONS: The developed comprehensive anatomical 3D measurement protocol could serve as standardised approach for anthropometric studies in the future. Our data suggest that the ROC of current nail designs should be reduced from between 1500 and 2000 to 1000 mm to achieve an improved fit for the investigated population.

A cadaveric biomechanical study comparing the ease of femoral nail insertion: 1.0- vs 1.5-m bow designs.

INTRODUCTION: Anatomic fit of intramedullary nails was suggested by previous studies to improve significantly when the nail radius of curvature (ROC) is closer to the average femoral anatomy. However, no attempt has been made to investigate the impact of different ROC designs on the nail insertion process. Therefore, this biomechanical study quantitatively compared the ease of insertion between femoral intramedullary nails with a 1.0-m and a 1.5-m bow radius. MATERIALS AND METHODS: Long TFN-ADVANCED™ (TFNA, 1.0 m ROC) and Proximal Femoral Nail Antirotation nails (PFNA, 1.5 m ROC) were implanted pairwise into seven paired cadaver femora. All bones were reamed 1.5 mm larger than the nail diameter. Using a material testing machine, intramedullary nailing was then performed stepwise with 20-mm steps and a 10-mm/s insertion rate, and force was measured. The nail deformation caused by the insertion was assessed through 3D computer models built from pre- and post-nailing CT scans. The ease of insertion between TFNA and PFNA nails was quantified in terms of insertion force, insertion energy and nail deformation. RESULTS: There was no significant difference in the peak force generated during nailing between TFNA and PFNA nails (P = 0.731). However, the force measured at the end of insertion (P = 0.002) was significantly smaller in TFNA nails compared to PFNA nails. After implantation, TFNA nails showed significantly smaller deformation when compared to PFNA nails (P = 0.005, both ends aligned). Furthermore, less energy was required to insert TFNA nails; however, the difference was not significant (P = 0.25). CONCLUSIONS: Compared to PFNA nails, a significant decrease in insertion force and nail deformation was found at the end of insertion for TFNA nails. Results suggest that TFNA having a 1.0-m ROC is easier to insert for the set of femora used in this study compared to PFNA with a 1.5-m ROC.

Magnetic resonance imaging: an accurate, radiation-free, alternative to computed tomography for the primary imaging and three-dimensional reconstruction of the bony orbit.

PURPOSE: To determine the extent to which the accuracy of magnetic resonance imaging (MRI) based virtual 3-dimensional (3D) models of the intact orbit can approach that of the gold standard, computed tomography (CT) based models. The goal was to determine whether MRI is a viable alternative to CT scans in patients with isolated orbital fractures and penetrating eye injuries, pediatric patients, and patients requiring multiple scans in whom radiation exposure is ideally limited. MATERIALS AND METHODS: Patients who presented with unilateral orbital fractures to the Royal Brisbane and Women's Hospital from March 2011 to March 2012 were recruited to participate in this cross-sectional study. The primary predictor variable was the imaging technique (MRI vs CT). The outcome measurements were orbital volume (primary outcome) and geometric intraorbital surface deviations (secondary outcome) between the MRI- and CT-based 3D models. RESULTS: Eleven subjects (9 male) were enrolled. The patients' mean age was 30 years. On average, the MRI models underestimated the orbital volume of the CT models by 0.50 ± 0.19 cm(3). The average intraorbital surface deviation between the MRI and CT models was 0.34 ± 0.32 mm, with 78 ± 2.7% of the surface within a tolerance of ±0.5 mm. CONCLUSIONS: The volumetric differences of the MRI models are comparable to reported results from CT models. The intraorbital MRI surface deviations are smaller than the accepted tolerance for orbital surgical reconstructions. Therefore, the authors believe that MRI is an accurate radiation-free alternative to CT for the primary imaging and 3D reconstruction of the bony orbit.

An evolutionary perspective to intramedullary nail fit - comparing present-day data with a historical specimen collection.

Manufacturers aim to design implants fitting for the broadest possible population segment. Due to the scarcity of available morphological data of intact long bones, anatomical collections of historical bone specimens may represent valuable additional sources. Previous work on femoral morphology measurements suggests that historical specimens are widely consistent with data from present-day populations. This study aimed to investigate whether this also applies to the anatomical fitting of a clinically used femoral nail. Nail fit was computer-graphically quantified through virtual implantation into CT-based 3D models of 52 femora, comprising a subset representative of the present-day Caucasian population (n = 31), a subset from a historical medieval European bone collection (n = 20), and additionally, a dataset from a natural ice mummy from the Neolithic period. Nail fit was assessed by nail protrusion (area and distance) to the inner cortex surface and the distal nail tip's position in the medullary canal. Assessed measurements and parameters of the present-day Caucasian subset were mostly consistent with those of the medieval European subset. After adjusting for multiple testing, only the distance from lateral nail entry point to shaft axis remained significantly (p = 0.03) different when comparing our modern and medieval subsets. Subsequent bivariate (Spearman) correlation analyses for both subsets (modern and medieval) combined showed that of the three variables representing basic demographic parameters, individual age, biological sex, and femur length, most statistically significant associations to the examined nail fit measurements were found for age (six measurements at a level of p < 0.05), however, with a relatively weak monotonic correlation (rho values ranging between ±0.31 and ±0.37). The measurements for the Iceman's femur lie within the range of the modern and historical subgroups, but in some cases, differ by more than one standard deviation from the mean. Our results confirm previous findings, suggesting that more recent historical bone specimen collections may indeed be a convenient and easily accessible source of new 3D morphological data and complement existing data to be used for the development of femoral nails.

Extraction force, energy and nail deformation for 1.5 m versus 1.0 m intramedullary femoral nail bow design: A biomechanical investigation.

BACKGROUND: The impact of the nail radius of curvature, as one of the most important design features in modern femoral nails on the ease of nail removal, remains unknown. Therefore, the aim of this study was to investigate force, energy, and nail deformation of different nail designs. METHODS: Nail insertion and extraction was performed on six pairs of fresh-frozen human cadaveric femora on a material testing machine with two different nail systems - Trochanter femoral nail ADVANCED™ Nailing System with a radius of curvature of 1.0 m and Proximal Femoral Nail Antirotation System with a radius of curvature of 1.5 m. Deformation was measured after insertion (plastic and elastic deformations) and extraction (plastic deformations). FINDINGS: The peak force during nail removal was significantly lower in the first group (274.5 ± 130.4 N) compared to the second group (695.2 ± 158.8 N, p = 0.001). Plastic deformation was observed in all implants, being significantly larger in the Proximal Femoral Nail Antirotation System (p = 0.027). There was a strong positive correlation between the first peak force during nail removal and nail insertion (r = 0.802, p = 0.002) as well as between extracting energy and insertion energy (r = 0.943, p < 0.001). INTERPRETATION: The results from this study showed that a radius of curvature of 1.0 m is easier to remove from the set of cadaver femora. Furthermore, our findings support the idea of further reducing the nail radius of curvature below 1.0 m in order to more closely match the anatomy of populations with strong-bowed femora.

Local Antibiotic Delivery Options in Prosthetic Joint Infection.

Prosthetic Joint Infection (PJI) causes significant morbidity and mortality for patients globally. Delivery of antibiotics to the site of infection has potential to improve the treatment outcomes and enhance biofilm eradication. These antibiotics can be delivered using an intra-articular catheter or combined with a carrier substance to enhance pharmacokinetic properties. Carrier options include non-resorbable polymethylmethacrylate (PMMA) bone cement and resorbable calcium sulphate, hydroxyapatite, bioactive glass, and hydrogels. PMMA allows for creation of structural spacers used in multi-stage revision procedures, however it requires subsequent removal and antibiotic compatibility and the levels delivered are variable. Calcium sulphate is the most researched resorbable carrier in PJI, but is associated with wound leakage and hypercalcaemia, and clinical evidence for its effectiveness remains at the early stage. Hydrogels provide a versatile combability with antibiotics and adjustable elution profiles, but clinical usage is currently limited. Novel anti-biofilm therapies include bacteriophages which have been used successfully in small case series.

Automatic classification of distal radius fracture using a two-stage ensemble deep learning framework.

Distal radius fractures (DRFs) are one of the most common types of wrist fracture and can be subdivided into intra- and extra-articular fractures. Compared with extra-articular DRFs which spare the joint surface, intra-articular DRFs extend to the articular surface and can be more difficult to treat. Identification of articular involvement can provide valuable information about the characteristics of fracture patterns. In this study, a two-stage ensemble deep learning framework was proposed to differentiate intra- and extra-articular DRFs automatically on posteroanterior (PA) view wrist X-rays. The framework firstly detects the distal radius region of interest (ROI) using an ensemble model of YOLOv5 networks, which imitates the clinicians' search pattern of zooming in on relevant regions to assess abnormalities. Secondly, an ensemble model of EfficientNet-B3 networks classifies the fractures in the detected ROIs into intra- and extra-articular. The framework achieved an area under the receiver operating characteristic curve of 0.82, an accuracy of 0.81, a true positive rate of 0.83 and a false positive rate of 0.27 (specificity of 0.73) for differentiating intra- from extra-articular DRFs. This study has demonstrated the potential in automatic DRF characterization using deep learning on clinically acquired wrist radiographs and can serve as a baseline for further research in incorporating multi-view information for fracture classification.

A humanised rat model of osteosarcoma reveals ultrastructural differences between bone and mineralised tumour tissue.

Current xenograft animal models fail to accurately replicate the complexity of human bone disease. To gain translatable and clinically valuable data from animal models, new in vivo models need to be developed that mimic pivotal aspects of human bone physiology as well as its diseased state. Above all, an advanced bone disease model should promote the development of new treatment strategies and facilitate the conduction of common clinical interventional procedures. Here we describe the development and characterisation of an orthotopic humanised tissue-engineered osteosarcoma (OS) model in a recently genetically engineered x-linked severe combined immunodeficient (X-SCID) rat. For the first time in a genetically modified rat, our results show the successful implementation of an orthotopic humanised tissue-engineered bone niche supporting the growth of a human OS cell line including its metastatic spread to the lung. Moreover, we studied the inter- and intraspecies differences in ultrastructural composition of bone and calcified tissue produced by the tumour, pointing to the crucial role of humanised animal models.

Typical accuracy and quality control of a process for creating CT-based virtual bone models.

A pragmatic method for assessing the accuracy and precision of a given processing pipeline required for converting computed tomography (CT) image data of bones into representative three dimensional (3D) models of bone shapes is proposed. The method is based on coprocessing a control object with known geometry which enables the assessment of the quality of resulting 3D models. At three stages of the conversion process, distance measurements were obtained and statistically evaluated. For this study, 31 CT datasets were processed. The final 3D model of the control object contained an average deviation from reference values of -1.07 ± 0.52 mm standard deviation (SD) for edge distances and -0.647 ± 0.43 mm SD for parallel side distances of the control object. Coprocessing a reference object enables the assessment of the accuracy and precision of a given processing pipeline for creating CT-based 3D bone models and is suitable for detecting most systematic or human errors when processing a CT-scan. Typical errors have about the same size as the scan resolution.

A deep learning method for automatic segmentation of the bony orbit in MRI and CT images.

This paper proposes a fully automatic method to segment the inner boundary of the bony orbit in two different image modalities: magnetic resonance imaging (MRI) and computed tomography (CT). The method, based on a deep learning architecture, uses two fully convolutional neural networks in series followed by a graph-search method to generate a boundary for the orbit. When compared to human performance for segmentation of both CT and MRI data, the proposed method achieves high Dice coefficients on both orbit and background, with scores of 0.813 and 0.975 in CT images and 0.930 and 0.995 in MRI images, showing a high degree of agreement with a manual segmentation by a human expert. Given the volumetric characteristics of these imaging modalities and the complexity and time-consuming nature of the segmentation of the orbital region in the human skull, it is often impractical to manually segment these images. Thus, the proposed method provides a valid clinical and research tool that performs similarly to the human observer.

Anatomical fitting of a plate shape directly derived from a 3D statistical bone model of the tibia.

INTRODUCTION: Intra- and inter-population variations of bone morphology have made the process of designing an anatomically well-fitting fracture fixation plate challenging. Although statistical bone models have recently been used for analysing morphological variabilities, it is not known to what extent they would also provide the basis for the design of a new plate shape. This would be particularly valuable in the case where no existing plate shape is available to start the process of fit optimisation. Therefore, this study investigated the anatomical fitting of a plate shape (statistical plate) derived from the mean shape of a statistical 3D tibia bone model in comparison to results available from two other plate shapes. METHODS: Forty-five 3D bone models of tibiae from Japanese cadaver specimens, as well as 3D models of the plate undersurface of both a commercial and shape optimised Medial Distal Tibia Plate, were utilised from earlier studies. The mean shape of the 3D statistical bone model was generated from the tibia models utilising the Statismo framework. With reverse engineering software, the plate undersurface of the statistical plate shape was derived directly from the mean surface of the statistical 3D bone model. Through an iterative process, the statistical plate model was placed at the correct surgical position on each bone model for fit assessment. RESULTS: The statistical plate was fitting for 20% of the tibiae compared to 13% for the commercial and 67% for the optimised plate, respectively. CONCLUSIONS: The plate shape derived directly from a statistical bone model was fitting better than the commercial plate, but considerably inferior to that of an optimised plate. However, the results do clearly indicate that this approach provides an appropriate and solid basis for commencing shape optimisation of the statistical plate. Studies of other anatomical regions are required to confirm whether these findings can be generalised.

Approach for analytical characterization and toxicological assessment of ozonation products in drinking water on the example of acesulfame.

The monitoring and control of drinking water quality is generally important as it significantly contributes to the health of the population. In this context, particular attention has to be paid to the use of treatment techniques during drinking water treatment. It is known that the formation of reaction products (transformation products) has to be taken into account when oxidizing agents such as ozone are used. Different transformation products are classified as critical to health and require analytical examination. The risk assessment for previously unknown transformation products can be difficult as far as not all transformation products are present as single substances or the individual substances are not present in a sufficient high concentration or cannot be isolated from the original solution. The aim of this work is to show exemplarily the identification and quantification of ozonation products (OPs) after ozonation and their toxicological characterization, using the artificial sweetener acesulfame. It was shown that OPs can be fully characterized using ion chromatography in combination with different detection systems. A major OP could be recovered as a pure substance by crystallization and direct genotoxicological testing was possible without previous enrichment processes. Acesulfame samples of different concentrations in ultrapure and in drinking water after ozonation were tested in several genotoxicity tests. These tests revealed genotoxic effects of acesulfame after ozonation in ultrapure water in several genotoxicological test systems (micronucleus test, umu test, Ames-fluctuation-test and comet assay). In contrast, the crystallized ozonation product OP168 did not show any positive effects. Therefore, it seems likely that the observed effect was caused by the second major product OP170. However, a sufficiently large amount of analytically pure substance OP170 could not be obtained. It was also shown that the rate of the OP170 formation in drinking water is significantly lower than in ultrapure water and that ozonation in drinking water did not induce genotoxic effects.

Fit assessment of anatomic plates for the distal medial tibia.

OBJECTIVES: With the development and popularization of minimally invasive surgical methods and implants for fracture fixation, it is increasingly important that the available implants are precontoured to the specific anatomic location for which they are designed. The objective of this study was to develop a noninvasive method and criteria for quantifying the fit of a distal periarticular medial tibia plate and to test the method on a small set of tibia models. METHODS: The undersurface of the plate was extracted from a digital model of the plate. The surface of the plate was fitted to 21 computer tomography (CT)-based 3-dimensional (3-D) models of human tibiae. Four criteria were defined that constitute an anatomic plate fit and subsequently were applied for the quantitative fit assessment. The fitting of the plate undersurface to the bone was entirely conducted in a virtual environment. RESULTS: An anatomic fit of the plate was achieved for 4 of the models (19%). The individual categories generated fits of 62% (n = 13) for the proximal end; 43% (n = 9) for the proximal angle; 57% (n = 12) for the middle distance; and 57% (n = 12) for a distal fit. CONCLUSIONS: Although for the 4 individual criteria plate fits of 43%-62% were achieved, a global/anatomic fit only occurred for 19% of the bone models. This outcome is likely a result of bone morphology variations, which exist in a random population sample combined with the effects of a nonoptimized plate shape. Recommendations for optimizing the fit of the plate are discussed.

Bayesian modeling predicts age and sex are not required for accurate stature estimation from femoral length.

Despite the recognized flaws in applying traditional stature estimation equations such as those of Trotter and Gleser (1952) [5] to a contemporary population, there are currently no available alternatives for stature estimation in Australia that address these limitations. Post mortem computed tomography (PMCT) DICOM scans of the left and right femora were acquired from 76 Australian deceased individuals aged 17-76 years for metric analysis. Femoral bicondylar length, femoral epicondylar breadth and anterior-posterior (AP) diameter, medial-lateral (ML) diameter, circumference and cortical area at the femoral midshaft were measured on three-dimensional (3D) models to build statistical models for estimating stature. In addition, Australian individuals aged 16-63 years (n=111) were measured in standing and supine positions to aid in the adjustment of supine stature of deceased individuals utilized in this study to standing stature. The results of this preliminary evaluation strongly indicate that the optimal model for estimating stature includes bicondylar femoral length and epicondylar breadth, that the effect of sex as an independent variable is very low, and there is limited practical benefit in including age in the estimation of stature. Our study indicates that the Australian population sampled represents a small yet significant shift in stature from the original Trotter and Gleser sample. Additionally, in the case of fragmentary remains, it was found that epicondylar breadth and AP diameter had the highest probability of accurate stature estimation in the absence of bicondylar femoral length. As stature forms a significant component of a biological profile and therefore aids in the personal identification of human remains, it is important that forensic anthropologists utilize the most accurate methodologies available. Stature estimation of Australian individuals is therefore achieved with higher accuracy through utilizing the femoral equations proposed in this study.