Exploratory investigation of virtual lesions in gastrointestinal endoscopy using a novel phase-shift method for three-dimensional shape measurement.

Accurate measurement of the size of lesions or distances between any two points during endoscopic examination of the gastrointestinal tract is difficult owing to the fisheye lens used in endoscopy. To overcome this issue, we developed a phase-shift method to measure three-dimensional (3D) data on a curved surface, which we present herein. Our system allows the creation of 3D shapes on a curved surface by the phase-shift method using a stripe pattern projected from a small projecting device to an object. For evaluation, 88 measurement points were inserted in porcine stomach tissue, attached to a half-pipe jig, with an inner radius of 21 mm. The accuracy and precision of the measurement data for our shape measurement system were compared with the data obtained using an Olympus STM6 measurement microscope. The accuracy of the path length of a simulated protruded lesion was evaluated using a plaster model of the curved stomach and graph paper. The difference in height measures between the measurement microscope and measurement system data was 0.24 mm for the 88 measurement points on the curved surface of the porcine stomach. The error in the path length measurement for a lesion on an underlying curved surface was <1% for a 10-mm lesion. The software was developed for the automated calculation of the major and minor diameters of each lesion. The accuracy of our measurement system could improve the accuracy of determining the size of lesions, whether protruded or depressed, regardless of the curvature of the underlying surface.

Comparing pill counts and patient self-reports versus DBS tenofovir concentrations as ART adherence measurements with virologic outcomes and HIV drug resistance in a cohort of adolescents and young adults failing ART in Harare, Zimbabwe.

BACKGROUND: Monitoring adherence presents a challenge in adolescents and it is prudent to explore several options for determining their level of adherence. This study sought to determine ART adherence levels in adolescents and young adults (on a tenofovir-containing regimen) failing ART as measured by self-reports, pill counts and DBS tenofovir concentrations and to compare levels of agreement among the methods and determine the ability of each method to predict virological suppression. METHODS: This was a cohort study involving 107 adolescents and young adults between 10 and 24 years failing ART with viral load > 400copies/ml at enrolment. Pill count (PC) records, self-reports (SR) and DBS tenofovir concentrations (done by liquid Chromatography with tandem mass spectrometry (LC-MS/MS)) were used to determine adherence in adolescent participants failing ART in Harare. The latter was used as the reference method with a cut-off of 64 ng/ml. Determination of DBS tenofovir concentrations was also performed to rule out inadequate viral response due to low cumulative drug exposure despite high adherence (≥90 %). Longitudinal analysis was performed to determine the correlation of viral loads (VL) with adherence. The Kappa (k) coefficient was used to evaluate the level of agreement among the 3 methods. RESULTS: Poor level of agreement was found between PC records and DBS tenofovir concentrations (k = -0.115). Moderate agreement was found between DBS and SR methods (k = 0.0557). Slight agreement was found between PC and SR methods (k = 0.0078). Adherence was dependent on age at HIV diagnosis (p = 0.0184) and ART initiation (p = 0.0265). Participants who were adherent were six times more likely to be suppressed at end point than their non-adherent counterparts (OR=5.7 CI 2.1 - 16.5, p < 0.0001). CONCLUSIONS: Self-reported measure of adherence and pill counts exhibited poor agreement with the reference method used i.e. DBS tenofovir concentrations and are thus not effective methods of predicting virological suppression. TRIAL IDENTIFICATION: Participants in the present study were a subset of those in the PESU intervention ClinicalTrials.gov Identifier: NCT02833441.

Accuracy of dynamic computer-assisted implant surgery in fully edentulous patients: An in vitro study.

OBJECTIVES: To compare miniscrew versus bone tracing registration methods on dental implant placement accuracy and time efficiency in edentulous jaws using a dynamic computer-assisted implant surgery (d-CAIS) system. METHODS: Twelve fully edentulous maxillary models were allocated into two groups: miniscrew tracing (MST) group, where registration was performed by tracing four miniscrews; and bone tracing (BT) group, where registration was conducted by tracing maxillary bone fiducial landmarks. Six implants were placed on each model using the X-Guide® d-CAIS system. Pre- and postoperative cone-beam computed tomography (CBCT) scans were superimposed to evaluate implant placement accuracy. The time required for registration and the overall surgery time were also recorded. RESULTS: Thirty-six implants were placed in each group. The MST group showed significantly lower mean angulation deviations (mean difference (MD): -3.33°; 95% confidence interval (CI): -6.56 to -0.09); p = 0.044), 3D platform deviations (MD: -1.01 mm; 95%CI: -1.74 to -0.29; p = 0.006), 2D platform deviations (MD: -0.97 mm; 95%CI: -1.71 to -0.23; p = 0.010), and 3D apex deviations (MD: -1.18 mm; 95%CI: -1.92 to -0.44; p = 0.002) versus the BT group. The overall surgery time was similar for both groups (MD: 6.10 min.; 95%CI: -0.31 to 12.51; p = 0.06), though bone tracing required significantly more time compared with miniscrew registration (MD: 4.79 min.; 95%CI: 2.96 to 6.62; p < 0.05). CONCLUSIONS: Registration with MST increases the accuracy of implant placement with a d-CAIS system in edentulous jaws compared with the BT method, and slightly reduces the overall surgery time. CLINICAL SIGNIFICANCE: Miniscrew tracing registration improves implant placement accuracy in comparison with bone tracing registration.

In-Vitro Accuracy of Digital Versus Conventional Workflows for Complete Arch Implant Supported Frameworks - A Scoping Review.

Purpose: To investigate the available evidence on the accuracy of conventional and digital workflows for complete arch implant supported frameworks. Materials and methods: This scoping review was conducted according to the 5-stage framework of Arksey and O'Malley. A systematic literature search was performed adhering to the PRISMA guidelines to identify studies with a direct comparison of conventional and digital methods for the fabrication of complete arch implant supported frameworks. 58 in-vitro studies with the focus on edentulous arches with at least four implants published between 2000 and 2024 were included. The reported outcomes were examined to determine the value of a statistical analysis for adding up the individual errors to a cumulative error of the workflow. Results: Evidence on the accuracy assessment of digital and conventional workflows for complete arch implant supported frameworks is available. However, also studies with the same assessment methods and outcome units appear to be too heterogeneous to perform a statistical analysis of error accumulation. While there is no consensus in the impression and cast fabrication stage, digital techniques show a superior accuracy for the fabrication of complete arch implant supported frameworks compared to conventional casting. Conclusion: In-vitro studies assessing the accuracy of entire workflows and classifying their outcomes regarding the clinical relevance are lacking.

Minimal Detectable Bone Fracture Gaps in CT Images and Digital Three-Dimensional (3D) Radii Models.

Knowledge of the minimal detectable bone fracture gap is essential in three-dimensional (3D) models, particularly in pre-operative planning of osteosynthesis to avoid overlooking gaps. In this study, defined incisions and bony displacements ranging from 100 to 400 µm were created in diaphyseal radii in 20 paired forearm specimens and verified with light microscopy. The specimens were scanned utilizing different computed tomography (CT) technologies/scanners, specimen positionings, scan protocols, image segmentations, and processing protocols. Inter- and intra-operator variabilities were reported as coefficient kappa. In CT images, fracture gaps of 100 µm and bone lamellae of 300 µm and 400 µm width were identified at a rate of 80 to 100%, respectively, independent of the investigated settings. In contrast, only 400µm incisions and bony displacements were visible in digital 3D models, with detection rates dependent on CT technology, image segmentation, and post-processing algorithm. 3D bone models based on state-of-the-art CT imaging can reliably visualize clinically relevant bone fracture gap sizes. However, verification of fractures to be surgically addressed should be verified with the original CT image series.

Clinical evaluation of a one-piece polyetheretherketone removable partial denture fabricated using a novel digital workflow: A self-controlled clinical trial.

PURPOSE: To explore the clinical application of one-piece polyetheretherketone (PEEK) removable partial dentures (RPDs) fabricated using a novel digital workflow and to evaluate their weights and fits in vivo and patient satisfaction. MATERIALS AND METHODS: Fifteen cases with posterior partially edentulous situations were selected, and each patient received two types of RPDs, including a novel digital workflow (test group) and a conventional workflow (control group). For the test group, one-piece RPDs were designed through three-dimensional (3D) methods by scanning stone casts and fabricated by milling PEEK discs. Each RPD was weighed. The gaps between the oral tissue and RPDs in each group were duplicated using a polyvinylsiloxane (PVS) replica and measured by 3D analysis. A visual analog scale (VAS) was used to evaluate the patient's satisfaction. Paired t-tests were used to compare the differences in the weight, the gaps of each RPD, and VAS values between the two groups. One-way analysis of variance tests was used to compare the differences in the gap among different components in each group. RESULTS: The RPD in the test group weighed less than that in the control group (p < 0.01). No statistically significant differences in the gaps of denture bases and rests (p > 0.05) were found between the two groups, but the gaps of major connectors in the test group were significantly smaller than in the control group (p < 0.05). The VAS scores for comfortableness and masticatory efficiency were not significantly different between the two groups (p > 0.05) but the scores for the aesthetic appearance of the clasps in the test group were significantly higher than that in the control group (p < 0.05). CONCLUSIONS: One-piece PEEK RPDs manufactured using a novel digital workflow weighed less than conventional RPDs and exhibited a clinically acceptable internal fit. Although the aesthetic appearance of the PEEK clasps was superior to the control, there is still room for improvement.

Evaluation of the measurement accuracy and uncertainty of a solid-state detector under diagnostic x-ray beam conditions.

OBJECTIVE: An accurate measurement of x-ray beams is expected to reduce the uncertainties associated with estimating radiation risk to patients in clinical settings. To perform assessment tasks based on the readings of a solid-state detector (SSD) using semiconductor technology, the characteristics of the detector should be elucidated. In this study, we evaluated the measurement accuracy of a new SSD under diagnostic x-ray beam conditions in terms of air kerma, tube voltage, and half-value layer (HVL). The performance of the SSD was then compared with those of reference instruments. METHODS: The tube voltage was varied within the range of 50-120 kV in steps of 10 kV and the thickness and materials of additional filters were concurrently changed (several combinations were tested). In addition, the dose rate and energy dependence of the SSD were also investigated. These effects were analyzed based on statistical significance tests. Furthermore, the expanded uncertainties in the series of measurements were meticulously calculated. RESULTS: The results showed average relative differences of -3.26 ± 1.33%, 0.44 ± 1.01%, and -2.60 ± 3.31% for air kerma, tube voltage, and HVL, respectively. Furthermore, air kerma did not exhibit any dependence on dose rate and energy, in contrast to tube voltage and HVL measurements. CONCLUSION: The measurement values of the SSD fall within the acceptable range of uncertainty, highlighting its measurement accuracy and reliability. Furthermore, based on the characteristics elucidated by this study, valuable insights are provided concerning the assurance of appropriate measurement values in clinical settings.

Evaluating a Novel AI Tool for Automated Measurement of the Aortic Root and Valve in Cardiac Magnetic Resonance Imaging.

Objective Evaluating an artificial intelligence (AI) tool (AIATELLA, version 1.0; AIATELLA Oy, Helsinki, Finland) in interpreting cardiac magnetic resonance (CMR) imaging to produce measurements of the aortic root and valve by comparison of accuracy and efficiency with that of three National Health Service (NHS) cardiologists. Methods AI-derived aortic root and valve measurements were recorded alongside manual measurements from three experienced NHS consultant cardiologists (CCs) over three separate sites in the northeast part of the United Kingdom. The study utilised a comprehensive dataset of CMR images, with the intraclass correlation coefficient (ICC) being the primary measure of concordance between the AI and the cardiologist assessments. Patient imaging was anonymised and blinded at the point of transfer to a secure data server.  Results The study demonstrates a high level of concordance between AI assessment of the aortic root and valve with NHS cardiologists (ICC of 0.98). Notably, the AI delivered results in 2.6 seconds (+/- 0.532) compared to a mean of 334.5 seconds (+/- 61.9) by the cardiologists, a statistically significant improvement in efficiency without compromising accuracy. Conclusion AI's accuracy and speed of analysis suggest that it could be a valuable tool in cardiac diagnostics, addressing the challenges of time-consuming and variable clinician-based assessments. This research reinforces AI's role in optimising the patient journey and improving the efficiency of the diagnostic pathway.

Evaluation of the Dimensional Accuracy of Robot-Guided Laser Osteotomy in Reconstruction with Patient-Specific Implants-An Accuracy Study of Digital High-Tech Procedures.

Background/Objective: With the rapid advancement in surgical technologies, new workflows for mandibular reconstruction are constantly being evaluated. Cutting guides are extensively employed for defining osteotomy planes but are prone to errors during fabrication and positioning. A virtually defined osteotomy plane and drilling holes in robotic surgery minimize potential sources of error and yield highly accurate outcomes. Methods: Ten mandibular replicas were evaluated after cutting-guided saw osteotomy and robot-guided laser osteotomy following reconstruction with patient-specific implants. The descriptive data analysis summarizes the mean, standard deviation (SD), median, minimum, maximum, and root mean square (RMS) values of the surface comparison for 3D printed models regarding trueness and precision. Results: The saw group had a median trueness RMS value of 2.0 mm (SD ± 1.7) and a precision of 1.6 mm (SD ± 1.4). The laser group had a median trueness RMS value of 1.2 mm (SD ± 1.1) and an equal precision of 1.6 mm (SD ± 1.4). These results indicate that robot-guided laser osteotomies have a comparable accuracy to cutting-guided saw osteotomies, even though there was a lack of statistical significance. Conclusions: Despite the limited sample size, this digital high-tech procedure has been shown to be potentially equivalent to the conventional osteotomy method. Robotic surgery and laser osteotomy offers enormous advantages, as they enable the seamless integration of precise virtual preoperative planning and exact execution in the human body, eliminating the need for surgical guides in the future.

Surgeon's Experience and Accuracy of Preoperative Digital Templating in Primary Total Hip Arthroplasty.

Purpose: Preoperative planning has become essential in performance of total hip arthroplasty (THA). However, data regarding the effect of the planner's experience on the accuracy of digital preoperative planning is limited. The objective of this study was to assess the accuracy of digital templating in THA based on the surgeon's experience. Materials and Methods: A retrospective study was conducted. An analysis of 98 anteroposterior pelvic radiographs, which were individually templated by four surgeons (two hip surgeons and two orthopaedic residents) using TraumaCad® digital planning, was performed. A comparison of preoperatively planned sizes with implanted sizes was performed to evaluate the accuracy of predicting component size. The results of preoperative planning performed by hip surgeons and orthopaedic residents were compared for testing of the planner's experience. Results: Femoral stem was precisely predicted in 32.4% of cases, acetabular component in 40.3%, and femoral offset in 76.7%. Prediction of cup size showed greater accuracy than femoral size among all observers. No differences in any variable were observed among the four groups (acetabular cup P=0.07, femoral stem P=0.82, femoral offset P=0.06). All measurements showed good reliability (intraclass correlation coefficient [ICC] acetabular cup: 0.76, ICC femoral stem: 0.79). Conclusion: The results of this study might suggest that even though a surgeon's experience supports improved precision during the planning stage, it should not be restricted only to surgeons with a high level of experience. We consider preoperative planning an essential part of the surgery, which should be included in training for orthopaedics residents.

Influence of Repeated Cut-off and Rescanning on the Trueness of the Intraoral Digital Scans.

OBJECTIVES: To evaluate the effects of repeated cut-off and rescan procedures on the trueness of three intraoral scanners (IOS). METHODS: A tooth model (#16) with a standard class II cavity was prepared, and the complete-arch was scanned using a laboratory scanner (D2000, 3Shape A/S) to obtain a reference scan. Then the typodont was scanned with three IOSs (3Shape TRIOS 3, CEREC Omnicam, and Medit i500) under two rescanning strategies (full-cut and partial-cut), with varying numbers of repeated cut-off and rescanning procedures (0, 1, 3, 5, 7, or 10). The trueness discrepancy between the reference and experimental digital scan was estimated using root mean square (RMS) calculations. Three regions of interest were selected to represent the rescanning, identification, and non-rescan area. And the discrepancies were analyzed using a linear mixed model (α=.05). RESULTS: Cut-off and rescanning procedures significantly decreased the trueness of digital scans in all test conditions compared to the reference. However, no progressive increase in discrepancy was observed under any rescan conditions. Significant influences on trueness were found based on the IOS used, with the 3Shape system exhibiting lower RMS values. The partial-cut strategy showed lower RMS values compared to the full-cut strategy, albeit without statistical significance. CONCLUSIONS: While repeated cut-off and rescanning procedures led to a decline in the quality of digital impressions, they did not result in discrepancy accumulation with repeated rescanning. CLINICAL SIGNIFICANCE: To ensure high scanning accuracy in dental practice, it is advisable to minimize the rescanning area when correcting imperfections in digital scans. Additionally, selecting an appropriate scanner can help mitigate the negative effects of the rescanning technique.

Evaluation of the effect of different core substrates on the accuracy of intraoral scanners.

BACKGROUND: The aim of this study was to determine if different types of core substrates have any effect on the trueness and precision of digital intraoral impressions. MATERIAL AND METHODS: A customized typodont with four similar cores of natural dentine, composite, metal (Ni-Cr), and zirconia in the position of premolars was fabricated. The study model was scanned five times with two types of intraoral scanners (Carestream 3600 and 3Shape Trios 3), and a reference standard scan was obtained using a laboratory scanner (3shape D1000). A metrology software (Geomagic X) was used to align the data of experimental scans and the reference scan to determine deviation values (trueness). Precision values were calculated with random superimposition in each intraoral scanner group. The Kruskal-Wallis test was used to compare differences between different substrates, and the Mann-Whitney test was used to compare the average values between the two scanners. RESULTS: Trios 3 was found to be significantly truer and more precise than Carestream 3600 (p value = .005, <0.001). There were no significant differences in the trueness of different substrates when they were scanned by Trios 3, while different materials showed significantly different trueness values in the Carestream 3600 group (p value = .003). Dentin showed the best trueness, and zirconia performed worse than other substrates. Regarding the precision of the scanners, neither of the scanners was affected by the type of scanning substrate. CONCLUSION: For Carestream 3600, substrate type did impact the trueness of intraoral scans, with dentin and zirconia showing the highest and lowest accuracy, respectively, while Trios 3 was similarly accurate across all substrates. Trios 3 had both higher trueness and precision than Carestream 3600.

Error Analysis of Normal Surface Measurements Based on Multiple Laser Displacement Sensors.

The robotic drilling of assembly holes is a crucial process in aerospace manufacturing, in which measuring the normal of the workpiece surface is a key step to guide the robot to the correct pose and guarantee the perpendicularity of the hole axis. Multiple laser displacement sensors can be used to satisfy the portable and in-site measurement requirements, but there is still a lack of accurate analysis and layout design. In this paper, a simplified parametric method is proposed for multi-sensor normal measurement devices with a symmetrical layout, using three parameters: the sensor number, the laser beam slant angle, and the laser spot distribution radius. A normal measurement error distribution simulation method considering the random sensor errors is proposed. The measurement error distribution laws at different sensor numbers, the laser beam slant angle, and the laser spot distribution radius are revealed as a pyramid-like region. The influential factors on normal measurement accuracy, such as sensor accuracy, quantity and installation position, are analyzed by a simulation and verified experimentally on a five-axis precision machine tool. The results show that increasing the laser beam slant angle and laser spot distribution radius significantly reduces the normal measurement errors. With the laser beam slant angle ≥15° and the laser spot distribution radius ≥19 mm, the normal measurement error falls below 0.05°, ensuring normal accuracy in robotic drilling.

Accuracy of maxillary full-arch digital impressions of tooth and implant models made by two intraoral scanners.

OBJECTIVES: Limited studies are available on the accuracy of intraoral scanners (IOSs) for full-arch implant and tooth models. This study aimed to assess the accuracy of maxillary full-arch digital impressions of tooth and implant models made by two IOSs. MATERIALS AND METHODS: This in vitro, experimental study was conducted on two maxillary dentiform models: one with six prepared natural teeth and the other with six implants at the site of canine, first premolar, and first molar teeth, bilaterally. A highly accurate industrial scanner was used for actual measurements on the models that served as the reference scan. TS (Trios3) and CO (CEREC Omnicam) IOSs were then used to scan each model 10 times according to the manufacturer's instructions. All scans were saved in STL format. The GOM Inspect software was used according to the best-fit algorithm to compare the accuracy of measurements in the groups with the reference scan. The trueness and precision were calculated. Statistical analyses were carried out using SPSS by one-way analysis of variance and t-test (α = .05). RESULTS: TS showed a significantly higher trueness than CO for both tooth and implant models (p < .05). TS also revealed significantly higher precision than CO for the tooth model; however, the difference in precision for the implant model was not significant between the two IOSs (p > .05). CONCLUSIONS: TS showed higher accuracy than CO in both tooth and implant models.

Analytical Analysis of Factors Affecting the Accuracy of a Dual-Heat Flux Core Body Temperature Sensor.

Non-invasive core body temperature (CBT) measurements using temperature and heat-flux have become popular in health, sports, work safety, and general well-being applications. This research aimed to evaluate two commonly used sensor designs: those that combine heat flux and temperature sensors, and those with four temperature sensors. We used analytical methods, particularly uncertainty analysis calculus and Monte Carlo simulations, to analyse measurement accuracy, which depends on the accuracy of the temperature and flux sensors, mechanical construction parameters (such as heat transfer coefficient), ambient air temperature, and CBT values. The results show the relationship between the accuracy of each measurement method variant and various sensor parameters, indicating their suitability for different scenarios. All measurement variants showed unstable behaviour around the point where ambient temperature equals CBT. The ratio of the heat transfer coefficients of the dual-heat flux (DHF) sensor's channels impacts the CBT estimation uncertainty. An analysis of the individual components of uncertainty in CBT estimates reveals that the accuracy of temperature sensors significantly impacts the overall uncertainty of the CBT measurement. We also calculated the theoretical limits of measurement uncertainty, which varied depending on the method variant and could be as low as 0.05 °C.

Effect of different storage conditions on dimensional accuracy of 3D-printed dental models.

PURPOSE: The objective was to determine the accuracy of 3D-printed dental models subjected to different storage conditions using six different material and printer combinations. MATERIALS AND METHODS: Three completely dentate models were designed using dental CAD software (3Shape Dental System). A horseshoe-shaped solid base with a posterior horizontal bar was used. The models were printed in a horizontal direction against the building platform without support. The models were printed using six printers with the corresponding recommended resin material: Carbon M2 (DPR10), HeyGears A2D4K (Model HP UV2.0), Stratasys J5 (MED610), Stratasys Origin One (DM200), Envision One (E-Model LightDLP), and Asiga Pro4K (VeriModel) with a standard layer thickness of 50 µm. All printed models underwent scanning using a laboratory scanner (Sirona inEOS X5) after printing. Subsequently, the models were randomly assigned into three groups of storage conditions, LT: cold environment (4 ± 1°C), HT: hot and dry environment (50 ± 2°C), and RT: room temperature (25 ± 2°C) serving as the control. Each group was kept under the designated condition and was scanned at 1, 2, 3, 4, and 8 weeks. The total number of models (N) was 72, with 6 printers producing 12 models per printer for 3 storage conditions, resulting in 4 models for each storage condition and each printer. The generated STL files were imported into a 3D inspection software for comparison with the original STL files. In-tolerance percentage, the deviation RMS, trueness, and precision were obtained and analyzed with least square mean linear regression using JMP Pro 15 to identify the significant effects (α = 0.05). RESULTS: The in-tolerance percentage as-printed was significantly different among different printers. Significant dimension deviations were observed after the first week of storage at HT and with subsequent weeks of storage. RT and LT did not show significant dimensional changes. Models printed with Carbon M2 showed the highest in-tolerance percentages compared to the other printers. CONCLUSIONS: The model deviations were affected by storage conditions and the printer used, with high-temperature storage showed least stability compared to low and room temperatures. No significant difference was observed between low and room temperature storage conditions. The Carbon M2 printer showed the highest accuracy among all printers tested. The region had a significant effect on the deviation measured, with the abutment body showing the least deviation. Among the 3D printers evaluated, A2D4K by HeyGears and Carbon M2 printers demonstrated the highest accuracy in terms of both precision and trueness.

Reliability, stability during long-term storage, and intra-individual variation of circulating levels of osteopontin, osteoprotegerin, vascular endothelial growth factor-A, and interleukin-17A.

BACKGROUND: Studies in many populations have reported associations between circulating cytokine levels and various physiological or pathological conditions. However, the reliability of cytokine measurements in population studies, which measure cytokines in multiple assays over a prolonged period, has not been adequately examined; nor has stability during sample storage or intra-individual variation been assessed. METHODS: We assessed (1) analytical reliability in short- and long-term repeated measurements; (2) stability and analytical reliability during long-term sample storage, and (3) variability within individuals over seasons, of four cytokines-osteopontin (OPN), osteoprotegerin (OPG), vascular endothelial growth factor-A (VEGF-A), and interleukin-17A (IL-17A). Measurements in plasma or serum samples were made with commercial kits according to standard procedures. Estimation was performed by fitting a random or mixed effects linear model on the log scale. RESULTS: In repeated assays over a short period, OPN, OPG, and VEGF-A had acceptable reliability, with intra- and inter-assay coefficients of variation (CV) less than 0.11. Reliability of IL-17A was poor, with inter- and intra-assay CV 0.85 and 0.43, respectively. During long-term storage, OPG significantly decayed (- 33% per year; 95% confidence interval [- 54, - 3.7]), but not OPN or VEGF-A (- 0.3% or - 6.3% per year, respectively). Intra- and inter-assay CV over a long period were comparable to that in a short period except for a slight increase in inter-assay CV of VEGF-A. Within-individual variation was small for OPN and VEGF-A, with intra-class correlations (ICC) 0.68 and 0.83, respectively, but large for OPG (ICC 0.11). CONCLUSIONS: We conclude that OPN and VEGF-A can be reliably measured in a large population, that IL-17A is suitable only for small experiments, and that OPG should be assessed with caution due to degradation during storage and intra-individual variation. The overall results of our study illustrate the need for validation under relevant conditions when measuring circulating cytokines in population studies.

Rigid fixation of pelvic tracker essential for accurate cup placement in CT-based navigation total hip arthroplasty.

Research is lacking on the effect of intraoperative pelvic tracker displacement relative to the pelvis on cup orientation accuracy in computed tomography (CT)-based navigation (CTN) or multivariable analysis to detect factors associated with CTN accuracy. Here, we asked: (1) how pelvic tracker displacement influences the CTN accuracy of cup orientation in total hip arthroplasty (THA)? and (2) what factors are associated with CTN accuracy on multivariable analysis? Regarding cup orientation in 446 THA procedures using CTN, we evaluated clinical error defined as the difference between postoperative measurement and preoperative planning and measurement error defined as the difference between postoperative and intraoperative measurements. Multivariable regression analyses detected the associated factors. Subjects with an intraoperative tracker displacement of < 2 mm were classified in the verified group. Mean absolute clinical and measurement errors were < 1.5° in the verified group, whereas the measurement error of 2.6° for cup inclination and 1.3° for anteversion was larger in the non-verified versus verified group. Tracker displacement and screw fixation were associated with larger clinical errors, while tracker displacement and surgeon inexperience were associated with larger measurement errors. Clinical and measurement accuracies were high for CTN cup placement with rigid pelvic tracker fixation.