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(1) Background: Lower Limb deformities include many conditions where pain and physical limitations negatively impact the health-related quality of life (HRQL) of children. The ideal way to assess this impact is by using a Patient Reported Outcome Measure (PROM). Such a condition-specific PROM is under development, called LIMB-Q Kids. This study aimed to perform a translation and cultural adaption (TCA) of the LIMB-Q Kids for use in Danish-speaking children. (2) Methods: TCA guidelines established by the World Health Organization (WHO) and the Professional Society for Health Economics and Outcomes Research (ISPOR) were followed. This process consisted of two independent forward translations, a reconciliation meeting, a backward translation with an assessment, an expert meeting, cognitive interviews with patients, editing based on the interviews, and proofreading. (3) Results: The TCA process contributed to the Danish version of LIMB-Q Kids. The reconciliation meeting resulted in a reconciled Danish version. The revision of the backward translation led to 16 corrections, and after the expert panel meeting, 26 changes were made. Twelve cognitive interviews led to nine changes, which were validated by two further interviews. Proofreading led to no further comments. (4) Conclusions: The TCA process led to a linguistically validated and culturally adapted Danish version of LIMB-Q Kids. This version is being used in the international field test study.

The past decade has seen considerable advances in the field of global flood modelling. In the 2010s, it began as a niche academic endeavour building models of the order 103 m horizontal resolution. In the 2020s, it is maturing into an established scientific discipline and yields profitable commercial ventures, with global models emerging of the order 101 m resolution.Building on the original 102 resolution global inland flood model of Sampson et al. (2015) – with a hydraulic engine based on the sub-grid version of the LISFLOOD-FP local inertial formulation of the shallow water equations (Bates et al., 2010; Neal et al., 2012) – we present the critical advances required to create a ~30 m resolution model of considerably greater fidelity and functionality:Using FABDEM as the underlying elevation grid, a machine-learning correction of the Copernicus global digital surface model to a digital terrain model (Hawker et al., 2022). Representing river hydrography with MERIT-Hydro (Yamazaki et al., 2019), ensuring the correct alignment of river channels with valley bottoms. Estimating river bathymetry prior to inundation modelling with a gradually varied flow solver (Neal et al., 2021). Updating boundary condition generation models with new hydrometric datasets and machine-learning hydrologic regionalization techniques (e.g. Zhao et al., 2021). Driving a global coastal flood model with a tide–surge–wave regional frequency analysis using tide gauges and reanalyses (Sweet et al., 2020). Implementing known and estimated flood protection measures as a rapid and adaptable post-process. Generating global climate change factors for fluvial, pluvial, and coastal floods for any plausible 21st century climate state. Applying climate change factors as a tractable post-process to a set of multi-frequency flood maps. These updates form the third version of Fathom's global flood maps. We show that these herald a new era of global flood modelling precision and accuracy, with additional utility wrought from linking climate projections to high-resolution true hydrodynamic models at the global scale for the first time. We also chart the road ahead for global flood modelling: outlining the significant data and modelling challenges our community must address to continue on this unprecedented development trajectory. References:Bates, P., et al. (2010) https://doi.org/10.1016/j.jhydrol.2010.03.027Hawker, L. & Uhe, P., et al. (2022) https://doi.org/10.1088/1748-9326/ac4d4fNeal, J., et al. (2012) https://doi.org/10.1029/2012WR012514Neal, J., et al. (2021) https://doi.org/10.1029/2020WR028301Sampson, C., et al. (2015) https://doi.org/10.1002/2015WR016954Sweet, W., et al. (2020) https://doi.org/10.3389/fmars.2020.581769Yamazaki, D., et al. (2019) https://doi.org/10.1029/2019WR024873Zhao, G., et al. (2021) https://doi.org/10.5194/hess-25-5981-202

In recent years there have been many new global datasets and methodological advancements that could be utilised by hydraulic models to help better understand global flood risk both in the present day and in the future. A major challenge facing modellers is how to incorporate these new datasets to improve the understanding of flood risk in both well, and less well, developed countries using a consistent approach, particularly as the latter of these contain increasingly larger exposures to floods.This new framework presents a computationally efficient yet flexible approach that seeks to utilise new global datasets and allows flood hazard maps to be calculated anywhere in the world, for any event severity (within a pre-defined range) and for any future climate scenario. The framework can be applied to all three of the major flood perils; fluvial, pluvial and coastal.At the heart of the framework is an efficient post-processing methodology that incorporates outputs from leading climate models, flood defence datasets and a baseline set of simulations spanning a range of evert severities. Furthermore, the flexible approach allows users to modify assumptions of flood defences and incorporate new climate simulations as and when they become available to quickly re-calculate flood hazard.We present here the full modelling chain, from input data through to flood hazard outputs covering all aspects of modelling, from determining model boundary conditions and estimating channel bathymetry, to post-processing the presence of flood defences and interpolation to future climate scenarios. We show that such an approach is able to replicate explicitly modelling the scenarios required at a fraction of the computation cost and demonstrate how this is crucial to anyone wanting to understand how exposure to floods may change into the future.

To establish the content validity of LIMB-Q Kids, a new patient-reported outcome measure (PROM) for children with lower limb deformities. This study focused on three key components of content validity, i.e., comprehension, comprehensiveness, and relevance.Cognitive debriefing interviews (CDIs) with children with lower limb deformities were performed, and expert input from parents and clinicians directly involved in the care of children with lower limb deformities was obtained. CDIs were conducted with children from sites in Australia, Canada, and the USA. All interviews were recorded and transcribed verbatim. Analyses were conducted using the reparative approach, which involved close examination of the transcribed interviews and summarising edits after each interview.Forty patients, experts, and parents reviewed LIMB-Q Kids and provided feedback. At the start, LIMB-Q Kids had 10 scales and 124 total items. Five rounds of input was obtained from children, parents, and experts. Overall, 37 new items were added. Thirty-three of the new items were included to measure symptoms experienced in different parts of the legs. Final version of LIMB-Q Kids had 11 scales and 159 items.This study established content validity of the LIMB-Q Kids, a new PROM for children with lower limb deformities. An international field-test study is underway. Translation and cultural adaptation are underway for sites where English is not the first language. Scoring algorithms will be developed, following which the scale could be used to inform clinical practice and research.

Most of the north Cheshire (Knutsford Group) of meres (lakes) in the UK formed naturally by dissolution of Triassic halite after the Devensian glaciation. Anthropogenic brine extraction in the 19th and 20th centuries produced further subsidence that enlarged some meres and formed the new lake of Melchett Mere. The characteristic features of three meres, Rostherne, Melchett and Tatton, are compared here by historical surveys, maps, photographs and light detection and ranging (LiDAR) interpretations. These illustrate the similarities of the natural and anthropogenic subsidence features, which can be separated only by temporal evidence of their formation. Rostherne Mere and Tatton Mere are mainly natural, though deepened or made larger by anthropogenic salt dissolution; Melchett Mere is completely anthropogenic and mainly formed between 1927 and 2003. All three meres are surrounded by landslip scars related to the subsidence. Former brine pumping at Northwich, Plumley and possibly Agden is implicated in the formation of Melchett Mere and the reactivation of natural subsidence at Rostherne and Tatton meres plus The Mere along with Tabley, Pickmere and Budworth meres to the SW. The brine run linkages between these abstraction areas and the subsidence cross the route of the proposed HS2 railway.

(1) Purpose: Lower limb deformities can have a severe impact on health-related quality of life (HRQL). LIMB-Q Kids is a new patient-reported outcome measure (PROM) aiming to elucidate the experience of 8–18-year-old patients before, during and after treatment, and to measure the different aspects of HRQL. The aim of this study was to translate and culturally adapt LIMB-Q Kids to German. (2) Methods: The International Society for Pharmacoeconomics and Outcomes Research (ISPOR) guidelines were followed. Three forward translations, a backward translation, an expert panel meeting with eight participants, and twenty cognitive debriefing interviews led to the final German version of LIMB-Q Kids. (3) Results: In the forward translations, 4/159 items were difficult to translate, and 2/159 items in the backward translation differed from the original English version. Cognitive debriefing interviews with 20 patients identified 7/159 items that were difficult to comprehend/answer, and 2 of these items were changed. (4) Conclusions: Lower limb deformities can have a great impact on children, and it is important to measure and consider the impact on HRQL. In order to be able to use PROMs in different countries, conceptually equivalent translations and cultural adaptations should be performed in order to ensure comprehensibility. The final German version of LIMB-Q Kids is ready for use in an international field test.

Supplemental Digital Content is available in the text., Background: The coronavirus disease 2019 (COVID-19) pandemic required rapid, global health care shifts to prioritize urgent or pandemic-related care and minimize transmission. Little is known about impacts on pediatric orthopaedic surgeons during this time. We aimed to investigate COVID-19-related changes in practice, training, and research among pediatric orthopaedic surgeons globally. Methods: An online survey was administered to orthopaedic surgeons with interest in pediatrics in April 2020 and a follow-up was administered in February 2021. The surveys captured demographics and surgeons’ self-reported experiences during the pandemic. Participants were recruited from web media and available email lists of orthopaedic societies over a 2-month period. Descriptive statistics were used to analyze results, stratified by the severity of local COVID-19-related measures. Results: A total of 460 responses from 45 countries were collected for initial survey. Of these, 358 (78.5%) respondents reported lockdown measures in their region at time of survey. Most (n=337, 94.4%) reported pausing all elective procedures. Surgeons reported a reduction in the average number of surgeries per week, from 6.89 (SD=4.61) prepandemic to 1.25 (SD=2.26) at time of survey (mean difference=5.64; 95% confidence interval=5.19, 6.10). Average number of elective outpatient appointments per week decreased from 67.89 (SD=45.78) prepandemic to 11.79 (SD=15.83) at time of survey (mean difference=56.10, 95% confidence interval=5.61, 60.58). In total, 177 (39.4%) surgeons reported using virtual modes of outpatient appointments for the first time. Of 290 surgeons with trainees, 223 (84.5%) reported implementation of systems to continue training such as webinars or virtual rounds. Of 192 respondents with research, 149 (82.8%) reported continuing research activities during the pandemic with most reporting either cessation (n=75, 64.15%), or reduction (n=25, 29.9%) in participant recruitment. A total of 111 responses from 28 countries were collected during follow-up. Surgeons described policy and circumstantial changes that facilitated resumption of clinical work. Conclusions: The COVID-19 pandemic and its related counter measures have had significant impacts on pediatric orthopaedic practice and increased uptake of technology to provide care continuity. Rigorous epidemiological studies are needed to assess impacts of delayed and virtual care on patient outcomes.

Background Fractures through the physis account for 18–30% of paediatric fractures and can lead to growth arrest in 5–10% of these cases. Long-term radiographic follow-up is usually necessary to monitor for signs of growth arrest at the affected physis. Given plain radiographs of a physeal fracture obtained throughout patient follow-up, different surgeons may hold different opinions about whether or not early growth arrest has occurred despite using identical radiographs to guide decision-making. This study aims to assess the inter-rater and intra-rater reliability of early growth arrest diagnosis among orthopaedic surgeons given a set of identical plain radiographs. Methods A retrospective chart review was conducted on patients aged 2–18 years previously treated for a physeal fracture at a paediatric tertiary care hospital between 2011 and 2018. De-identified anteroposterior (AP) and lateral radiographs of 39 patients from the date of injury and minimum one-year post-injury were administered in a survey to international paediatric orthopaedic surgeons. Each surgeon was asked whether they would diagnose the patient with growth arrest based on the radiographs provided. Surgeons were asked to complete this process again two weeks after the initial review, but using identical shuffled radiographs. Inter-rater and intra-rater reliability was calculated using appropriate kappa statistics. Results A total of 11 paediatric orthopaedic surgeons completed the first round of the survey, and 9 of these 11 completed the second round. The inter-rater reliability for the first round was 0.22 [95% CI (0.06, 0.35)] and 0.21 [95% CI (0.02, 0.32)] for the second round. The average kappa for intra-rater reliability was − 0.05 [95% CI (− 0.31, 0.21)]. Comparison by injury side showed no significant variation in diagnosis {p = 0.509, OR = 0.90, [95% CI (0.67, 1.22)]}, while comparison by location of injury varied significantly (p = 0.003). Conclusions Radiographic diagnosis of growth arrest among paediatric orthopaedic surgeons demonstrated ‘fair’ inter-rater agreement and no intra-rater agreement, suggesting critical differences in identifying growth arrest on plain radiographs. Further research is necessary to develop an improved diagnostic approach for growth arrest among orthopaedic surgeons. Level of Evidence Diagnostic level III.

The discovery of humans with monogenic disorders has a rich history of generating new insights into biology. Here we report the first human identified with complete deficiency of nuclear factor of activated T cells 1 (NFAT1). NFAT1, encoded by NFATC2, mediates calcium-calcineurin signals that drive cell activation, proliferation, and survival. The patient is homozygous for a damaging germline NFATC2 variant (c.2023_2026delTACC; p.Tyr675Thrfs∗18) and presented with joint contractures, osteochondromas, and recurrent B-cell lymphoma. Absence of NFAT1 protein in chondrocytes caused enrichment in prosurvival and inflammatory genes. Systematic single-cell–omic analyses in PBMCs revealed an environment that promotes lymphomagenesis with accumulation of naïve B cells (enriched for oncogenic signatures MYC and JAK1), exhausted CD4+ T cells, impaired T follicular helper cells, and aberrant CD8+ T cells. This work highlights the pleiotropic role of human NFAT1, will empower the diagnosis of additional patients with NFAT1 deficiency, and further defines the detrimental effects associated with long-term use of calcineurin inhibitors.

Guided growth is commonly performed by placing an extraperiosteal 2-hole plate across the growth plate with one epiphyseal and one metaphyseal screw. Recent studies investigated the efficacy of the removal of the metaphyseal screw only (sleeper plate) after correction. They concluded the practice to be unnecessary as only 19% of patients showed recurrence of deformity. This study aims to examine the incidence of rebound and undesired bony in-growth of the plate (tethering) after metaphyseal screw removal only.In this retrospective case series, patient data on 144 plates inserted around the knee were obtained. Plates still in situ (n=69) at the time of study and full hardware removal (n=50) were excluded. The remaining 25 plates had only the metaphyseal screw removed after completed deformity correction. We analyzed the rate of tethering, rebound, and maintenance of correction in 2 age groups at latest follow (mean of 3.5 y). The Fisher exact test with Freeman-Halton extension was used to analyze categorical data and the Student t test for descriptive variables.Twenty-five plates were identified as "sleeper plates" in our series. Thirteen plates (52%) maintained the achieved correction after a mean of 21 months (range: 4 to 39 mo), 9 plates (36%) required screw reinsertion due to rebound after a mean of 22 months (range: 12 to 48 mo) from screw removal, and 4 plates (16%) showed tethering with undesired continuation of guided growth after a mean of 14 months (range: 7 to 22 mo) from screw removal. Younger patients (8 y at time of plate insertion) had higher rates of rebound and tethering ( P =0.0112, Fisher exact test). All tethering occurred in titanium plates, none occurred in steel plates.The sleeper plate is an acceptable treatment strategy for coronal deformities around the knee, however, tethering and rebound may occur, especially in younger patients. Titanium plates may increase the risk of tethering, however, further long-term follow-up is needed as there were only 6 steel plates versus 19 titanium in this study. We stress the importance of close postoperative follow-up to identify signs of tethering and rebound early to prevent over-correction.Level IV-retrospective case study.

Developmental dysplasia of the hip is a hip abnormality that ranges from mild acetabular dysplasia to irreducible femoral head dislocations. While 2-D B-mode ultrasound (US)-based dysplasia metrics or disease metrics are currently used clinically to diagnose developmental dysplasia of the hip, such estimates suffer from high inter-exam variability. In this work, we propose and evaluate 3-D US-derived dysplasia metrics that are automatically computed and demonstrate that these automatically derived dysplasia metrics are considerably more reproducible. The key features of our automatic method are (i) a random forest-based learning technique to remove regions across the coronal axis that do not contain bone structures necessary for dysplasia-metric extraction, thereby reducing outliers; (ii) a bone segmentation method that uses rotation-invariant and intensity-invariant filters, thus remaining robust to signal dropout and varying bone morphology; (iii) a novel slice-based learning and 3-D reconstruction strategy to estimate a probability map of the hypoechoic femoral head in the US volume; and (iv) formulae for calculating the 3-D US-derived dysplasia metrics. We validate our proposed method on real clinical data acquired from 40 infant hip examinations. Results show a considerable (around 70%) reduction in variability in two key 3-D US-derived dysplasia metrics compared with their 2-D counterparts.

Aim and objective Genu recurvatum is a rare deformity for which minimal literature exists. Non-operative management typically gives unsatisfactory results. This study aims to evaluate the treatment of genu recurvatum with a hexapod frame. Materials and methods A single-center retrospective chart review of genu recurvatum cases treated with a hexapod fixator application was performed. Radiographic parameters included the following: leg length discrepancy (LLD), angle of recurvatum, angle of tilt of the tibial plateau, patellar height and anatomic proximal posterior tibial angle (aPPTA). Radiographic and functional results were evaluated. Results A total of five patients with six limbs corrected with a hexapod frame were found. Aetiology included post-traumatic (2), post-infectious (1) and idiopathic (3). The mean age at application was 13.36 (5.5–18.0) years. The total mean time in the fixator was 225 (160–412) days. The LLD decreased from a mean of 35.6 mm (0.7–50) preoperatively to a mean of 14.8 (1.0–39.3) postoperatively. The average patellar height remained similar 0.97 (0.69–1.2)–0.97 (0.51–1.6). The angle of the tilt of the tibial plateau improved from a preoperative mean of 66° (58.5–73.5°)–92.5° (80–98.5°). The angle of recurvatum improved from a preoperative mean of 26.4° (18.5–31°)–5.0° (0–9°). The aPTTA improved from (102–118°)–85.5° (77–96°). Conclusion Osteotomy distal to the tibial tuberosity and deformity correction using a hexapod frame allows for multiplanar correction. Throughout treatment, soft tissue management with physical therapy remained key to prevent knee contracture. Clinical significance A hexapod frame is a safe and accurate technique that allows correction of genu recurvatum along with concomitant deformities with low risk of complications. How to cite this article Johnson L, McCammon J, Cooper A. Correction of Genu Recurvatum Deformity Using a Hexapod Frame: A Case Series and Review of the Literature. Strategies Trauma Limb Reconstr 2021;16(2):116–119.

Discovery of humans with monogenic disorders has a rich history of generating new insights into biology. Here we report the first human identified with complete deficiency of nuclear factor of activated T cells 1 (NFAT1). NFAT1, encoded by NFATC2, mediates calcium-calcineurin signals that drive cell activation, proliferation, and survival. The patient is homozygous for a damaging germline NFATC2 variant (c.2023_2026delTACC; p.Tyr675Thrfs*18) and presented with joint contractures, osteochondromas, and B cell lymphoma. Absence of NFAT1 protein in chondrocytes caused enrichment in pro-survival and inflammatory genes. Systematic single-cell-omic analyses revealed an environment that promotes lymphomagenesis with accumulation of naïve B cells (with oncogenic signatures - MYC, JAK1), exhausted CD4+ T cells, impaired T follicular helper cells, and aberrant CD8+ T cells. This work highlights the pleiotropic role of human NFAT1, will empower the diagnosis of additional patients with NFAT1 deficiency, and further define detrimental effects a long-term use of calcineurin inhibitors.

Aims Though the pathogenesis of Legg-Calve-Perthes disease (LCPD) is unknown, repetitive microtrauma resulting in deformity has been postulated. The purpose of this study is to trial a novel upright MRI scanner, to determine whether any deformation occurs in femoral heads affected by LCPD with weightbearing. Methods Children affected by LCPD were recruited for analysis. Children received both standing weightbearing and supine scans in the MROpen upright MRI scanner, for coronal T1 GFE sequences, both hips in field of view. Parameters of femoral head height, width, and lateral extrusion of affected and unaffected hips were assessed by two independent raters, repeated at a one month interval. Inter- and intraclass correlation coefficients were determined. Standing and supine measurements were compared for each femoral head. Results Following rigorous protocol development in healthy age-matched volunteers, successful scanning was performed in 11 LCPD-affected hips in nine children, with seven unaffected hips therefore available for comparison. Five hips were in early stage (1 and 2) and six were in late stage (3 and 4). The mean age was 5.3 years. All hips in early-stage LCPD demonstrated dynamic deformity on weightbearing. Femoral head height decreased (mean 1.2 mm, 12.4% decrease), width increased (mean 2.5 mm, 7.2% increase), and lateral extrusion increased (median 2.5 mm, 23% increase) on standing weightbearing MRI compared to supine scans. Negligible deformation was observed in contra-lateral unaffected hips, with less deformation observed in late-stage hips. Inter- and intraclass reliability for all measured parameters was good to excellent. Conclusion This pilot study has described an effective novel research investigation for children with LCPD. Femoral heads in early-stage LCPD demonstrated dynamic deformity on weightbearing not previously seen, while unaffected hips did not. Expansion of this protocol will allow further translational study into the effects of loading hips with LCPD. Cite this article: Bone Joint Open 2020;1-7:364–369.

Greulich and Pyle (GP) is one of the most common methods to determine bone age from hand radiographs. In recent years, new methods were developed to increase the efficiency in bone age analysis like the shorthand bone age (SBA) and automated artificial intelligence algorithms. The aim of this study is to evaluate the accuracy and reliability of these two methods and examine if the reduction in analysis time compromises their efficacy. Two hundred thirteen males and 213 females had their bone age determined by two separate raters using the SBA and GP methods. Three weeks later, the two raters repeated the analysis of the radiographs. The raters timed themselves using an online stopwatch. De-identified radiographs were securely uploaded to an automated algorithm developed by a group of radiologists in Toronto. The gold standard was determined to be the radiology report attached to each radiograph, written by experienced radiologists using GP. Intraclass correlation between each method and the gold standard fell within the range of 0.8–0.9, highlighting significant agreement. Most of the comparisons showed a statistically significant difference between the new methods and the gold standard; however, it may not be clinically significant as it ranges between 0.25 and 0.5 years. A bone age is considered clinically abnormal if it falls outside 2 standard deviations of the chronological age; standard deviations are calculated and provided in GP atlas. The shorthand bone age method and the automated algorithm produced values that are in agreement with the gold standard while reducing analysis time.

BackgroundSupracondylar humerus fractures (SCHF) are the most common fractures sustained following a fall onto an outstretched hand among healthy children, and one of the leading causes of hospital admission and surgical intervention. The aim of this study was to examine SCHF occurring at public play spaces—particularly to determine whether or not the playground equipment implicated in injurious falls aligned with Canadian playground safety standards.MethodsCases of children who attended the provincial paediatric orthopaedic clinic following SCHF at a public playground between April 2017 and October 2019 were included in the study. A research assistant visited each playground to measure the play structure type and dimensions, height of the equipment at the point from which the child fell and the type and depth of the surface material, and compare measurements to the 2016 safety standards. Child demographics and injury classification were also noted. Descriptive statistics were calculated and a scatterplot of fall height and surface depth was generated.ResultsForty-three sites, representing 47 SCHF cases (18 female, 29 male), were included in the final analysis. Fourteen children sustained type 1 fracture, 23 had type 2 fracture and the remaining 10 had type 3 fracture. Five children with type 2 fracture and all 10 children with type 3 fracture required surgery. The majority of sites had engineered wood fibre surfacing, with surfacing at 35 sites being less than 300 mm deep. Twenty-six play structures were upper body equipment (ie, monkey bars or similar), seven were track rides, five were rotating structures and the rest comprised a variety of classified and unclassified structures. Twenty-seven children fell from a height exceeding 2 m.ConclusionsThe majority of SCHF cases occurred at playgrounds with insufficient surface depth and/or non-compliant equipment. Upper body equipment, track rides and rotating play structures were of particular concern, as the children fell from heights exceeding the recommended standard, likely reflecting the degradation and compaction of the surfacing material over time.

Neoclassical properties in quasi-axisymmetric (QA) stellarators are analogous to these in tokamaks. Consequently, a substantial bootstrap current could significantly modify the MHD equilibrium properties of a QA stellarator, which is an important characteristic in this type of stellarator. This paper is dedicated to systemically investigate the effects of bootstrap current on the magnetic configuration in Chinese first quasi-axisymmetric stellarator (CFQS). For the first time, self-consistent bootstrap currents in free-boundary equilibria are calculated with an accurate Fokker–Planck neoclassical numerical mode in CFQS. Several important results are achieved: (a) as the bootstrap current grows with increasing volume-averaged normalized pressure β , magnetic shear develops in the bulk plasma and meanwhile, a deep magnetic well is robustly sustained, which leads to improved stabilization of interchange modes up to β ∼ 2.0 % . (b) In the analysis of global ideal MHD instability, as the bootstrap current rises to 39 kA ( β ∼ 1.3 % ), external kink modes become destabilized and the unstable mode with m/n = 2/1 is dominant. (c) From β = 0 to 1.5%, the bootstrap current hardly changes the QA property and a low neoclassical transport is maintained. However, as β is enhanced beyond 2.0%, the substantial bootstrap current gives rise to an increase of non-QA magnetic field components, which weakens the neoclassical transport properties. (d) An increase of the negative magnetic shear at the core region by the bootstrap currents has a favorable effect on the properties of J (second adiabatic invariant). The maximum-J region can be extended by raising bootstrap currents.

Background Subcapital osteotomy by means of surgical hip dislocation is a treatment approach offered for moderate-to-severe cases of Slipped Capital Femoral Epiphysis (SCFE). This procedure is demanding, highly dependent on the surgeon’s experience, and requires considerable radiation exposure for monitoring and securing the spatial alignment of the femoral head. We propose the use of individualized drill guides as an accurate method for placing K-wires during subcapital correction osteotomies in SCFE patients. Methods Five CT scans of the hip joint from otherwise healthy patients with moderate-to-severe SCFE were selected (ages 11–14). Three dimensional models of each patient’s femur were reconstructed by manual segmentation and physically replicated using additive manufacturing techniques. Five orthopaedic surgeons virtually identified the optimal entry point and direction of the two threaded wires for each case. 3D printed drill guides were designed specific to each surgical plan, with one side shaped to fit the patient’s bone and the other side containing holes to guide the surgical drill. Each surgeon performed three guided (using the drill guides) and three conventional (freehand) simulated procedures on each case. Each femur model was laser scanned and digitally matched to the preoperative model for evaluation of entry points and wire angulations. We compared wire entry point, wire angulation, procedure time and number of x-rays between guided and freehand simulated surgeries. Results The guided group (1.4 ± 0.9 mm; 2.5° ± 1.4°) was significantly more accurate than the freehand group (5.8 ± 3.2 mm; 5.3° ± 4.4°) for wire entry location and angulation (p p Conclusions We conclude that CT-based preoperative planning and intraoperative navigation using individualized drill guides allow for improved accuracy of wires, reduced operative time and less radiation exposure in simulated hips. Clinical relevance This preliminary study shows promising results, suggesting potential direct benefits to SCFE patients by necessitating less time under anesthesia and less intra-operative radiation exposure to patients, and increasing surgical accuracy.