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Aims There is no consensus regarding optimum timing and frequency of ultrasound (US) for monitoring response to Pavlik harness (PH) treatment in developmental dysplasia of the hip (DDH). The purpose of our study was to determine if a limited-frequency hip US assessment had an adverse effect on treatment outcomes compared to traditional comprehensive US monitoring. Methods This study was a single-centre noninferiority randomized controlled trial. Infants aged under six months whose hips were reduced and centred in the harness at initiation of treatment (stable dysplastic or subluxable), or initially decentred (subluxated or dislocated) but reduced and centred within four weeks of PH treatment, were randomized to our current standard US monitoring protocol (every clinic visit) or to a limited-frequency US protocol (US only at end of treatment). Groups were compared based on α angle and femoral head coverage at the end of PH treatment, acetabular indices, and International Hip Dysplasia Institute (IHDI) grade on one-year follow-up radiographs. Results Overall, 100 patients were included; 42 patients completed the standard protocol (SP) and 40 completed the limited protocol (LP). There was no significant difference in mean right α angle at the end of treatment (SP 70.0° (SD 3.2°) ; LP 68.7° (SD 2.9°); p = 0.033), nor on the left (SP 69.0° (SD 3.5°); LP 68.1° (SD 3.3°); p = 0.128). There was no significant difference in mean right acetabular index at follow-up (SP 23.1° (SD 4.3°); LP 22.0° (SD 4.1°); p = 0.129), nor on the left (SP 23.3° (SD 4.2°); LP 22.8° (SD 3.9°); p = 0.284). All hips had femoral head coverage of > 50% at end of treatment, and all were IHDI grade 1 at follow-up. In addition, the LP group underwent a 60% reduction in US use once stable. Conclusion Our study supports reducing the frequency of US assessment during PH treatment of DDH once a hip is reduced and centred. Cite this article: Bone Joint J 2022;104-B(9):1081–1088.

Femoral lengthening is associated with high complication rates often related to the type of surgical device used to perform the lengthening. The advent of intramedullary lengthening devices has promised a reduction in complications when compared with external fixation systems. The purpose of this study was to compare the clinical outcomes of femoral lengthening in children using a motorized intramedullary nail (Precice) versus an external fixation system (Taylor Spatial Frame-TSF; or Monolateral Rail System-MRS) at a single institution, single surgeon practice.This study is a retrospective comparison of pediatric patients who had previously undergone femoral lengthening (±deformity correction). Patients ages 8 to 18 years of age were included and grouped based on whether they had undergone Precice nailing or external fixation (TSF or MRS) between 2010 and 2019.Twenty-seven patients (32 femurs) were included. Thirteen patients (15 femurs) had undergone Precice nailing and 14 patients (17 femurs) had undergone external fixation. The Precice group had significantly fewer problems, obstacles, and complications than the external fixation group, Precice 6.6%, 0%, 0%, respectively, and external fixation 47.1%, 29.4%, 0% respectively (P0.01). Unplanned return to the operating room occurred in 4 cases, solely in the external fixation group. There were no differences in percentage of goal length achieved, Precice (mean 93.6%, range: 66.7% to 114.3%), external fixation (mean 96%, range: 76.9% to 117.5%) P=0.31 and total length achieved, Precice (mean: 44 mm, range: 20 to 80 mm), external fixation (mean: 46 mm, range: 10 to 70 mm) P=0.72. There was no difference in consolidation index, Precice (24.1 d/cm), external fixation (28.5 d/cm) P=0.36. The Precice group had a significantly shorter length of stay (mean: 2.2 d, range: 1 to 4 d), compared with the external fixation group (mean: 3.7 d, range: 2 to 8), P=0.01.Femoral lengthening in children using a motorized intramedullary nail was associated with a markedly reduced rate of complications and shorter length of stay compared with external fixation.Level III.

Supplemental Digital Content is available in the text., Background: Avascular necrosis (AVN) of the femoral head is a concerning complication that can result from treatments for developmental dysplasia of the hip (DDH). AVN can lead to degenerative osteoarthritis, persistent acetabular dysplasia, reduced function, and continuing hip pain. The incidence of AVN reported in the DDH literature is widely varied (0% to 73%). This variability may arise from lack of consensus on what constitutes true AVN in this patient population, and lack of clear criteria provided in studies reporting incidence rates. Methods: A multicentre, prospective database of infants diagnosed with DDH between 2010 and 2014 from 0 to 18 months of age was analyzed for patients treated by closed reduction (CR). Twelve pediatric orthopaedic surgeons completed 2 rounds of AVN assessments. Deidentified anteroposterior radiographs at most recent follow-up were provided to surgeons along with patient age at radiographic assessment, length of follow-up, ands affected hip. Ten of 12 surgeons completed a third round of assessments where they were provided with 1 to 2 additional radiographs within the follow-up period. Radiographic criteria for total AVN described by Salter and colleagues were used. Surgeons rated the presence of AVN as “yes” or “no” and kappa values were calculated within and between rounds. Results: A total of 69 hips in 60 patients were assessed for AVN a median of 22 months (range: 12 to 36) post-CR. Interobserver kappa values for rounds 1, 2, and 3 were 0.52 (range: 0.11 to 0.90), 0.61 (range: 0.21 to 0.90), and 0.53 (range: 0.10 to 0.79), respectively. Intraobserver agreement for AVN diagnosis was an average of 0.72 (range: 0.31 to 0.96). Conclusions: Despite using the most commonly referenced diagnostic criteria, radiographic diagnosis of AVN following CR in DDH patients demonstrated only moderate agreement across surgeons. The addition of sequential radiographs did not improve cross-observer reliability, and while substantial agreement was seen within observers, the range of intraobserver kappa values was large. Level of Evidence: Level I—diagnostic study.

The 40Ar/39Ar dating method is among the most versatile of geochronometers, having the potential to date a broad variety of K-bearing materials spanning from the time of Earth’s formation into the historical realm. Measurements using modern noble-gas mass spectrometers are now producing 40Ar/39Ar dates with analytical uncertainties of ~0.1%, thereby providing precise time constraints for a wide range of geologic and extraterrestrial processes. Analyses of increasingly smaller subsamples have revealed age dispersion in many materials, including some minerals used as neutron fluence monitors. Accordingly, interpretive strategies are evolving to address observed dispersion in dates from a single sample. Moreover, inferring a geologically meaningful “age” from a measured “date” or set of dates is dependent on the geological problem being addressed and the salient assumptions associated with each set of data. We highlight requirements for collateral information that will better constrain the interpretation of 40Ar/39Ar data sets, including those associated with single-crystal fusion analyses, incremental heating experiments, and in situ analyses of microsampled domains. To ensure the utility and viability of published results, we emphasize previous recommendations for reporting 40Ar/39Ar data and the related essential metadata, with the amendment that data conform to evolving standards of being findable, accessible, interoperable, and reusable (FAIR) by both humans and computers. Our examples provide guidance for the presentation and interpretation of 40Ar/39Ar dates to maximize their interdisciplinary usage, reproducibility, and longevity.

The Pavlik harness (PH) is commonly used to treat infantile dislocated hips. However, significant variability exists in the duration of brace treatment after successful reduction of the dislocated hip. The purpose of this study was to evaluate the effect of prescribed time in brace on acetabular index (AI) at two years of age using a prospective, international, multicenter database.We retrospectively studied prospectively enrolled infants with at least 1 dislocated hip that were initially treated with a PH and had a recorded AI at 2-year follow-up. Subjects were treated at 1 of 2 institutions. Institution 1 used the PH until they observed normal radiographic acetabular development. Institution 2 followed a structured shorter brace treatment protocol. Hip dislocation was defined as30% femoral head coverage at rest on the pretreatment ultrasound or International Hip Dysplasia Institute (IHDI) grade III or IV on the pretreatment radiograph.Fifty-three hips met our inclusion criteria. Hips from Institution 1 were treated with a brace ×3 longer than hips from institution 2 (adjusted mean 8.9±1.3 vs. 2.6±0.2 mo) (P0.001). Institution 1 had an 88% success rate and institution 2 had an 85% success rate at achieving hip reduction (P=0.735). At 2-year follow-up, we observed no significant difference in AI between Institution 1 (adjusted mean 25.6±0.9 degrees) compared with Institution 2 (adjusted mean 23.5±0.8 degrees) (P=0.1). However, 19% of patients from Institution 1 and 44% of patients from Institution 2 were at or below the 50th percentile of previously published age-matched and sex-matched AI normal data (P=0.049). Also, 27% (7/26) of hips from Institution 1 had significant acetabular dysplasia (more than 2 SD from the mean), compared with a 22% (6/27) from Institution 2 (P=0.691). We found no correlation between age at initiation of bracing and AI at 2-year follow-up (P=0.071).The PH brace can successfully treat dislocated infant hips, however, prolonged brace treatment was not found to result in improved acetabular development at 2-year follow-up.Level III.

Isotopic analyses of natural samples suggest that the heavy noble gases (HNG; Ar, Kr, and Xe) in the mantle are dominated by components recycled by subduction ( Holland and Ballentine, 2006 , Kendrick et al., 2011 , Parai and Mukhopadhyay, 2018 , Smye et al., 2017 ). However, the mechanism of recycling is not clear: are they primarily trapped in pore spaces and inclusions, are the gases dissolved in the lattices of mineral phases, or are they located along grain boundaries? Serpentinite is a dominant volatile-bearing lithology in subducting plates, and experimental studies suggest that HNG may be highly soluble in serpentinite ( Jackson et al., 2015 , Zaikowski and Schaeffer, 1979 ). To understand its role in HNG recycling, the solubility of noble gases in natural serpentinite has been experimentally measured at pressures from 0.15 to 1.13 kbar. Measured solubilities for He, Ne, Ar, Kr, and Xe are 1.78 ⋅ 10−9, 1.35 ⋅ 10−10, 3.03 ⋅ 10−10, 1.25 ⋅ 10−9, and 3.29 ⋅ 10−9 mol ⋅ g−1 ⋅ bar−1 with an average relative error of 9%. The solubilities are relatively high, indicating that even if less than 1% of the initial HNG estimated to be in subducting serpentinite survives slab dehydration, there would be enough remaining to dominate the mantle HNG budget. That the MORB and OIB mantle sources retain any primordial Kr or Xe in the face of such a large potential slab flux suggests subduction zones extract most (but not all) HNG from the slab at shallow depths. Serpentinite fractionates the HNG, with solubilities increasing from Ar to Kr to Xe. Kr/Ar and Xe/Ar ratios in MORB are quite similar to those predicted for subducted serpentinite, consistent with most HNG in the MORB-source coming from subducted serpentinite, possibly in combination with marine sediments. HNG ratios in most EM1- and EM2-type OIBs can also be explained primarily by serpentinite recycling. A prominent exception is Iceland, which appears to require dominantly sediment recycling, with little or no serpentinite. HIMU OIBs have highly fractionated HNG ratios that cannot be explained by serpentinite recycling but are consistent with subduction of HNG in amphibole ( Chavrit et al., 2016 ).

Supplemental Digital Content is available in the text., Background: Closed reduction (CR) is a common treatment for infantile developmental dysplasia of the hip. The purpose of this observational, prospective, multicenter study was to determine the early outcomes following CR. Methods: Prospectively collected data from an international multicenter study group was analyzed for patients treated from 2010 to 2014. Baseline demographics, clinical exam, radiographic/ultrasonographic data, and history of previous orthotic treatment were assessed. At minimum 1-year follow-up, failure was defined as an IHDI grade 3 or 4 hip and/or need for open reduction. The incidence of avascular necrosis (AVN), residual dysplasia, and need for further surgery was assessed. Results: A total of 78 patients undergoing CR for 87 hips were evaluated with a median age at initial reduction of 8 months (range, 1 to 20 mo). Of these, 8 hips (9%) were unable to be closed reduced initially. At most recent follow-up (median 22 mo; range, 12 to 36 mo), 72/79 initially successful CRs (91%) remained stable. The likelihood of failure was unaffected by initial clinical reducibility of the hip (P=0.434), age at initial CR (P=0.897), or previous treatment in brace (P=0.222). Excluding those hips that failed initial CR, 18/72 hips (25%) developed AVN, and the risk of osteonecrosis was unaffected by prereduction reducibility of the hip (P=0.586), age at CR (P=0.745), presence of an ossific nucleus (P=0.496), or previous treatment in brace (P=0.662). Mean acetabular index on most recent radiographs was 25 degrees (±6 degrees), and was also unaffected by any of the above variables. During the follow-up period, 8/72 successfully closed reduced hips (11%) underwent acetabular and/or femoral osteotomy for residual dysplasia. Conclusions: Following an initially successful CR, 9% of hips failed reduction and 25% developed radiographic AVN at early-term follow-up. History of femoral head reducibility, previous orthotic bracing, and age at CR did not correlate with success or chances of developing AVN. Further follow-up of this prospective, multicenter cohort will be necessary to establish definitive success and complication rates following CR for infantile developmental dysplasia of the hip. Level of Evidence: Level II—prospective observational cohort.

Background Infants with dislocated irreducible (D/I) hips can be substantially harder to treat than infants with dislocated but reducible hips. The purpose of this study was to compare treatment methods and outcomes for infants with D/I hips in order to optimize management of this difficult patient cohort. Methods A multicenter prospective hip dysplasia study database was analyzed from 2010 to 2016. Infants aged below 6 months with clinically and radiologically confirmed D/I hips were included in the study. Teratological hips (syndromic/neuromuscular) were excluded. Results In total, 59 hips in 52 patients were included. All hips were clinically Ortolani negative and radiologically dislocated but irreducible on presentation and had at least 20 months of follow-up. Mean age at diagnosis was 1.9 months (range, 0.1 to 5.9 mo). There were 33 left hips, 12 right hips, and 14 bilateral hips (7 patients). In total, 48 of 59 hips were treated in Pavlik harness. The remainder were treated by alternative braces or primary closed or open reductions. Pavlik treatment was successful in 27 of 48 hips. Pavlik treatment was abandoned in 21 D/I hips, 3 due to femoral nerve palsy and the remainder due to failure to achieve reduction. There was no statistical correlation between Pavlik success and age at diagnosis (P=0.22), patient sex (P=0.61), or bilateral compared with unilateral D/I hips (P=0.07). Left hips were more likely to be successfully reduced in Pavlik harness than right hips (P=0.01). Five complications occurred: 3 patients developed femoral nerve palsy in Pavlik harness, while 2 patients developed avascular necrosis, both after failed Pavlik treatment and subsequent surgery. Conclusions Pavlik harness treatment has been demonstrated to be a safe and sensible first-line treatment for infants with D/I hips. Left hips were more likely to be successfully reduced in Pavlik harness than right hips, but age, sex, and bilaterality were not correlated. The outcomes demonstrated from this multicentre prospective database inform management of this complex patient cohort. Level of evidence Level II-prognostic study: less-quality prospective study.

Background: The Gait Outcomes Assessment List for children with Lower Limb Difference (GOAL-LD) is a patient and parent-reported outcome measure that incorporates the framework of the International Classification of Functioning, Disability, and Health. This prospective multicenter cohort study evaluates the validity and reliability of the GOAL-LD and the differences between parent and adolescent report. Method: One hundred thirty-seven pediatric patients aged over 5 years attending limb reconstruction clinics at the participating sites were assessed at baseline, and a self-selected cohort also completed an assessment 2 to 6 weeks later. Construct and criterion validity were assessed by comparing GOAL-LD scores with a measure of limb deformity complexity (LLRS-AIM) and the Pediatric Outcomes Data Collection Instrument, using Spearman correlation coefficients. Face and content validity were determined through ratings of item importance. Test-retest reliability was reported as an intraclass correlation coefficient and internal consistency using Cronbach α. Adolescent reports were compared with their parents using paired t tests. Results: The GOAL-LD demonstrated a moderate negative correlation with the LLRS-AIM (r=−0.40, P

The Boltysh impact structure formed 0.65 Ma after the K-Pg boundary, coincident with the Lower C29n hyperthermal., Both the Chicxulub and Boltysh impact events are associated with the K-Pg boundary. While Chicxulub is firmly linked to the end-Cretaceous mass extinction, the temporal relationship of the ~24-km-diameter Boltysh impact to these events is uncertain, although it is thought to have occurred 2 to 5 ka before the mass extinction. Here, we conduct the first direct geochronological comparison of Boltysh to the K-Pg boundary. Our 40Ar/39Ar age of 65.39 ± 0.14/0.16 Ma shows that the impact occurred ~0.65 Ma after the mass extinction. At that time, the climate was recovering from the effects of the Chicxulub impact and Deccan trap flood volcanism. This age shows that Boltysh has a close temporal association with the Lower C29n hyperthermal recorded by global sediment archives and in the Boltysh crater lake sediments. The temporal coincidence raises the possibility that even a small impact event could disrupt recovery of the Earth system from catastrophic events.

Purpose The acetabular index (AI) is a radiographic measure that guides surgical decision-making in developmental dysplasia of the hip (DDH). Two AI measurement methods are described; to the lateral edge of the acetabulum (AI-L) and to the lateral edge of the sourcil (AI-S). The purpose of this study was to determine the level of agreement between AI-L and AI-S on the diagnosis and degree of acetabular dysplasia in DDH. Methods A total of 35 patients treated for DDH with Pavlik harness were identified. The AI-L and AI-S were measured on radiographs (70 hips) at two and five years of age. AI-L and AI-S were then transformed relative to published normative data (tAI-L and tAI-S). Bland-Altman plots, linear regression and heat mapping were used to evaluate the agreement between tAI-L and tAI-S. Results There was poor agreement between tAI-S and tAI-L on the Bland-Altman plots with wide limits of agreement and no proportional bias. The two AI measurements were in agreement as to the presence and severity of dysplasia in only 63% of hips at two years of age and 81% at five years of age, leaving the remaining hips classified as various combinations of normal, mildly and severely dysplastic. Conclusion AI-L and AI-S have poor agreement on the presence or degree of acetabular dysplasia in DDH and cannot be used interchangeably. Clinicians are cautioned to prudently evaluate both measures of AI in surgical decision-making. Level of evidence I

40Ar–39Ar dating of glass shards from silicic tuffs of the Ellensburg Formation (NW, USA) interbedding basaltic lavas yielded accurate, precise, reproducible plateau and isochron ages that are within error at the 2σ level. The age-spectra have flat plateaus and the inverse isochrons have atmospheric 40Ar/36Ar at the 2σ level. Ages of 12.00 ± 0.24, 11.37 ± 0.15, 10.67 ± 0.21 and 10.70 ± 0.18 Ma are consistent with the stratigraphy of four of the dated layers; the age of 10.77 ± 0.18 Ma for a fifth layer is at odds with the stratigraphy. This discrepancy arises due to the effect of glass alteration that induced K- and Ar-loss. There is no evidence of excess 40Ar or 39Ar recoil. The new ages indirectly constrain the timing of eruption of the lavas above and below the ash beds. This demonstrates that volcanic glass from interbeds can be used as an additional tool for indirectly dating basaltic lava sequences, which is independent of the lavas and complementary to other materials. Considering the numerous studies in which volcanic glass failed to provide reliable 40Ar–39Ar ages, additional and supportive constraints are still needed to assess the validity of the ages from glass shards. Supplementary material: A1 – sample location, stratigraphic position and depositional environments; A2 – electron microprobe information with calibration and sample data; A3 – Ar isotopic data of blanks and samples, data reduction software, J values, criteria for age calculation and images of age spectra and inverse isochrons are available at https://doi.org/10.6084/m9.figshare.c.5077705

Traditional practical work for higher education in STEM subjects is under pressure from rising student numbers and adesired increase in active learning. Investing in more buildings and staff is financially challenging, while stretching existing resources affects outcomes, health, and participation. A more pragmatic approach is to embrace a less instrumentalist view of practical work in physical spaces and instead adopt a critical post-humanist approach which mixes both humanity and technology to achieve a sum greater than the parts, not bound by the limits of either. We share the experiences of leading UK exponents of non-traditional laboratories in the four main categories of simulation, virtual laboratories, real-asynchronous, and real- synchronous activities, as well as experts in scaling digital education initiatives for university-wide adoption. We foreshadow opportunities, challenges and potential solutions to increasing the opportunity for active learning by students studying at traditional campuses, via the complementary addition of non-traditional practical work.

Co-auteur étranger; International audience; doi: 10.7185/geochemlet.2028 lower mantle upper mantle OIB MORB outer core Low 3 He/ 22 Ne High 3 He/ 4 He Co re C on tr ib ut io n This study investigates metal-silicate partitioning of neon (D Ne) under the likely conditions of early Earth's core formation: up to 16 GPa, ∼ 3000 K and an oxygen fugacity near IW-2 (2 log units below the Iron-Wüstite buffer). We find that the D Ne coefficients range between 10 −2 and 10 −1. These partition coefficients are only one of the controlling factors of noble gas distributions within the early Earth: because, even if D He and D Ne are low (∼10 −4), there may have been sufficient noble gases present in the mantle to supply a significant quantity of He and Ne to the core. Assuming gas-melt equilibrium of the molten proto-Earth with a nebular gas composition and con-comitant metal-silicate differentiation, the core would have inherited and maintained throughout Earth's history high 3 He/ 4 He ratios and low 3 He/ 22 Ne ratios (

The Kalkarindji flood basalt province of northern Australia erupted in the mid-Cambrian. Today, the province consists of scattered volcanic and intrusive suites, the largest being the Antrim Plateau Volcanics (APV) in Northern Territory. Accurate dating of the Kalkarindji flood basalt province has proved challenging, with previous studies focused on minor volcanic rocks and intrusive dykes in Northern Territory and Western Australia. These previously published data, corrected to the same decay constants, range from 512.8 to 509.6 ± 2.5 Ma [2σ], placing the Kalkarindji flood basalt province in apparent synchronicity with the Cambrian Stage 4–5 biotic crisis at 510 ± 1 Ma. This study utilizes 40Ar/39Ar dating of basalts from the APV to accurately date the major volcanic eruptions in this province. The results yield an age of 508.0–498.3 ± 5.5 Ma [2σ], indicating that the APV is younger than the intrusive rocks. These dates allude to a relative timing discrepancy, where intrusive activity in the North Australian Craton preceded the eruption of the APV as the last magmatic activity in the region. The determination of these largest eruptions to be later than 510 Ma effectively disassociates the Kalkarindji lavas from being a major cause of the 510 Ma biotic crisis, but cannot definitively discount any deleterious effects on the fragile Cambrian ecosystem. Supplementary material: 40Ar/39Ar analysis data tables, XRF geochemical data, alteration study and photomicrographs of all five samples are available at: https://doi.org/10.6084/m9.figshare.c.4176674

Background Avascular necrosis (AVN) is a significant and potentially devastating complication following the treatment of developmental dysplasia of the hip (DDH). The reported rate of AVN following closed reduction for DDH ranges from 4 to 60%, and the resultant influence on hip development remains unclear. Purpose A systematic review of the literature was undertaken to evaluate the frequency of AVN after more than 5 years of follow-up in children that underwent closed reduction at younger than 2-years of age for DDH. Methods The search strategy was formulated with key-concepts and keywords identified using the patient problem, intervention, comparison and outcome process. Searches were undertaken using Pubmed, Scopus and Web of Science up to and including May, 2016 to identify potential studies. Results A total of seven papers met the a priori inclusion and exclusion criteria of this review. The overall rate of significant AVN in 441 patients (538 hips) was 10% at a mean length of follow-up of 7.6 years (5–18.8) following closed reduction. This finding can be used to inform the feasibility of future intervention studies, and act as a baseline for which surgeons to compare their results to a ‘standard’.

Purpose The ability to monitor and study developmental dysplasia of the hip (DDH) requires validated radiographic outcome measures. The sourcil method of acetabular index measurement (AI-S) has not yet been shown to be a reliable measure of acetabular dysplasia in a DDH population, despite its widespread use. The aims of this study were to test the reliability of the AI-S method in a DDH population, and to compare the reliability of the AI-S method with that of the classic lateral edge method (AI-L). Methods From an institutional database, standardized anteroposterior hip radiographs were obtained from a cohort of 35 female patients (70 hips) at two and five years of age who had been treated nonoperatively for DDH. Three observers independently measured the acetabular index using the AI-L and AI-S methods on all 70 hips at two time points, four weeks apart. Results The inter-rater reliability intraclass correlation coefficient (ICC) for the AI-L and AI-S methods was between good and excellent at 0.94 (confidence interval (CI) 0.89 to 0.96) and 0.91 (CI 0.87 to 0.94), respectively. The ICCs for intra-rater reliability for the AI-L method were excellent at 0.93 (CI 0.90 to 0.95), 0.95 (CI 0.93 to 0.97) and 0.95 (CI 0.94 to 0.97) for raters 1, 2 and 3, respectively. The ICCs for intra-rater reliability for the AI-S method were between good and excellent at 0.91 (CI 0.87 to 0.93), 0.93 (CI 0.90 to 0.95) and 0.90 (CI 0.86 to 0.93) for raters 1, 2 and 3 respectively. Conclusion Both AI-S and AI-L methods are equally reliable radiographic measures of DDH. Level of Evidence Level III (diagnostic)

Syngenetic inclusions of yimengite K (Cr, Ti, Mg, Fe, Al)12O19, a potassium member of the magnetoplumbite mineral group, have been recorded in an octahedral macrodiamond from the Sese kimberlite (50 km south of Masvingo, Zimbabwe). One yimengite inclusion carries lamellae of chromite suggesting peridotitic diamond paragenesis. The diamond and inclusions were studied in situ in a plate polished parallel to (011). Cathodoluminescence (CL) imaging has shown blue colour and octahedral zonation of the diamond, lack of cracks and the location of five yimengites in different growth zones. Nitrogen (N) contents (at. ppm) in the diamond determined by Fourier transform infrared spectroscopy (FTIR) steadily decrease from 576 (core) to 146 (rim). N aggregation (%1aB) is correspondingly 40% in the core and 30% in the rim. Hydrogen (H) content is high in the core, moderate in the intermediate and very high in the rim zones. Four yimengites were dated using the laser 40Ar/39Ar method. Three inclusions yielded total gas ages that agree with, or are younger than, or within error of, the Sese kimberlite eruption age (538±11 Ma) but may be compromised by gas loss. One inclusion, with the highest tapped interface gas yield, gave a total gas age of 892±21 Ma that is a likely minimum yimengite age. Time–T °C constraints from N aggregation systematics give a range of possible ages from kimberlite eruption date back to Archean and do not resolve the variable results of the 40Ar/39Ar dating. Compared with the published chemistry of yimengite from kimberlites, inclusions from the Sese diamond contain higher Al, Mg, and Sr and have lower concentration of Fe3+. The chondrite-normalised REE pattern of the yimengite shows enrichment in LREE and depletion in HREE, but LREE/HREE fractionations are lower than for lindsleyite–mathiasite series mantle titanates and rather similar to the REE concentrations in kimberlite and lamproite rocks. It is suggested that Sese yimengite formed in the lithospheric mantle from metasomatism of chrome spinel by a fluid rich in Ti, K, Ba and LREE.

Virtual Learning Environments (VLEs) are becoming commonplace in Higher Education. Amongst the latest VLE developments is the design and use of Virtual Microscopes (VMs) that allow for viewing and manipulation of online images by multiple students. Although students are found to be generally satisfied with the use of VMs, it is yet not known what teaching and learning conditions better support their use and lead to enhanced learning outcomes. The aim of this paper is to compare the usage patterns and perceptions of two different cohorts of undergraduate students that made use of the VM in blended and online only learning conditions respectively, and draw conclusions about the pedagogy that better supports teaching and learning with VMs. Data collected from a survey with 139 students and 11 semistructured interviews revealed that blended learning better caters for students' engagement and satisfaction due to the systematic use of the VM in course design, its complementary use with a physical microscope, and the ongoing provision of tutors' support and guidance. Equally good perceived learning gains were reported by both blended and online only students. Implications for the design of learning environments around virtual microscopy are discussed.

Purpose: The aim of this study is to evaluate foot deformities and anomalies present in congenital limb deficiencies (CLDs). We sought to define the relationship between the type of limb deficiency and foot posture, patterns of ray deficiencies, and association between tarsal coalition (TC) and ball-and-socket ankle. Materials and Methods: This is a single institution, retrospective radiograph, and medical record review of patients with CLD, comprising congenital femoral deficiency (CFD), tibial hemimelia (TH), and fibular hemimelia (FH) from January 2000 to January 2019. Data extracted included patient demographics, predicted leg length discrepancy, associated deformities and anomalies, and specifics of the foot deformity. Surgical procedures were recorded. Data were reported using descriptive statistics. Fisher's exact test analyses of contingency tables were used for the exploratory components of this study. Results: Eighty-one patients with 97 limb deficiencies were identified (16 – CFD, 18 – TH, and 63 – FH). Isolated CFD was not associated with foot and ankle deformity and TH was associated with an equinocavovarus foot in all limbs. In FH, an equinocavovarus deformity was present in 15/63 (24%) feet, most requiring foot surgery. Of 48 patients with FH and absent rays, two lacked lateral rays, whereas the remainder missed one or more intermediate rays. TC was unrelated to the presence of ball-and-socket ankle. Conclusions: This study demonstrates heterogeneity in the spectrum of foot and ankle deformity in CLD, particularly in FH. Recognition of this phenotypic variation is critical for surgeons to formulate a comprehensive treatment plan and ensure optimal functional outcomes. Level of Evidence: IV.

Background The use of competency-based training is increasing in medical education as it offers individualized learning opportunities to master required skills. Inherent to this method of teaching is the need for standardized and objective assessments of skill mastery. In orthopaedic surgery, educational programs have focused on surgical skills with lesser emphasis on nonoperative techniques. Accordingly, formal evaluation tools specific to Pavlik Harness application do not exist, despite its widespread use and potential complications from inappropriate application. This study sought to develop a reliable and valid evaluation tool based on international expert consensus to standardize and evaluate Pavlik Harness application for developmental dysplasia of the hip. Methods Consensus was sought from 10 content experts using Delphi methodology. Resulting items formed the Objective Structured Assessment of Technical Skill (OSATS). Thirty-five participants were selected into 3 a priori groups (expert, intermediate and novice) based on Pavlik Harness experience. On 2 occasions, 3 content experts assessed randomized and deidentified videotapes of each participant applying a Pavlik Harness to an infant model using the OSATS and global rating scales (GRS). The reliability and validity of the OSATS was determined with intraclass (ICC) and Pearson correlations and analysis of variance (ANOVA). Results Consensus was obtained after 2 rounds of structured surveying and resulted in a 25-item OSATS. The reliability of the OSATS was excellent with an ICC of 0.96 for interrater and 0.98 for test-retest reliability. Construct validity was excellent with high correlations between OSATS and GRS (>0.90). In addition, the OSATS discriminated between expert, intermediate, and novice users. Conclusions We have developed a competency-based evaluation tool for Pavlik Harness application based on consensus from international experts. The OSATS has been shown to be a reliable and valid method for assessing Pavlik Harness application that can discriminate between expert, intermediate, and novice users. Level of evidence Level II.

Background The Pavlik harness is the most common initial treatment for developmental dysplasia of the hip worldwide. During treatment, parents are required to re-apply the harness at home. Teaching parents how to apply the harness is therefore paramount to success. While simulated learning for medical training is commonplace, it has not yet been trialed in teaching parents how to apply a Pavlik harness. Methods A group of parents underwent a simulated learning module for Pavlik harness application. Parents were evaluated pre- and post-exposure and at one month after testing. A validated objective structured assessment of technical skill (OSATS) and a global rating scale (GRS) specific to Pavlik harness application were used for evaluation. A control group of parents was also tested at both time points. A clinical expert group was used to determine competency. ANOVA and t tests were used to assess differences between groups and over time. Results Parent scores on the OSATS improved to the level of expert clinicians both immediately post-intervention and at retention testing. However, on the GRS, only half were considered competent due to their inability to achieve the required hip positions. The control group did not improve nor were they considered competent. Conclusions The use of a simulated learning module improves both the confidence and skill level of parents in the application of the Pavlik harness. However, the challenges parents face in understanding the more detailed subtleties of medical care suggest that they still require an appropriate level of supervision by clinicians to ensure effective treatment.

Background: The use of a brace has been shown to be an effective treatment for hip dislocation in infants; however, previous studies of such treatment have been single-center or retrospective. The purpose of the current study was to evaluate the success rate for brace use in the treatment of infant hip dislocation in an international, multicenter, prospective cohort, and to identify the variables associated with brace failure. Methods: All dislocations were verified with use of ultrasound or radiography prior to the initiation of treatment, and patients were followed prospectively for a minimum of 18 months. Successful treatment was defined as the use of a brace that resulted in a clinically and radiographically reduced hip, without surgical intervention. The Mann-Whitney test, chi-square analysis, and Fisher exact test were used to identify risk factors for brace failure. A multivariate logistic regression model was used to determine the probability of brace failure according to the risk factors identified. Results: Brace treatment was successful in 162 (79%) of the 204 dislocated hips in this series. Six variables were found to be significant risk factors for failure: developing femoral nerve palsy during brace treatment (p = 0.001), treatment with a static brace (p < 0.001), an initially irreducible hip (p < 0.001), treatment initiated after the age of 7 weeks (p = 0.005), a right hip dislocation (p = 0.006), and a Graf-IV hip (p = 0.02). Hips with no risk factors had a 3% probability of failure, whereas hips with 4 or 5 risk factors had a 100% probability of failure. Conclusions: These data provide valuable information for patient families and their providers regarding the important variables that influence successful brace treatment for dislocated hips in infants. Level of Evidence: Prognostic Level I. See Instructions for Authors for a complete description of levels of evidence.

Background: Simulation-based learning is increasingly prevalent in many surgical training programs, as medical education moves toward competency-based curricula. In orthopaedic surgery, developmental dysplasia of the hip is a commonly treated condition, where the standard of care for patients less than six months of age is an orthotic device such as the Pavlik harness. However, despite widespread use of the Pavlik harness and the potential complications that may arise from inappropriate application, we know of no previously described formal training curriculum for Pavlik harness application. Methods: We developed a video and model-based simulation learning module for Pavlik harness application. Two novice groups (residents and allied health professionals) were exposed to the module and, at pre-intervention, post-intervention, and retention testing, were evaluated on their ability to apply a Pavlik harness to the model. Evaluations were completed using a previously validated Objective Structured Assessment of Technical Skills (OSATS) and a global rating scale (GRS) specific to Pavlik harness application. A control group that did not undergo the module was also evaluated at two time points to determine if exposure to the Pavlik harness alone would affect skill acquisition. All groups were compared with a group of clinical experts, whose scores were used as a competency benchmark. Statistical analysis of skill acquisition and retention was conducted using t tests and analysis of variance (ANOVA). Results: Exposure to the learning module improved resident and allied health professionals’ competency in applying a Pavlik harness (p < 0.05) to the level of the expert clinicians, and this level of competency was retained one month after exposure to the module. Control subjects who were not exposed to the module did not improve, nor did they achieve competency. Conclusions: The simulation-based learning module was shown to be an effective tool for teaching the application of a Pavlik harness, and learners demonstrated retainable skills post-intervention. This learning module can form the cornerstone of formal teaching of Pavlik harness application for developmental dysplasia of the hip.

Tibial hemimelia is a rare, debilitating and often sporadic congenital deficiency. In syndromic cases, mutations of a Sonic hedgehog (SHH) enhancer have been identified. Here we describe an ~5 kb deletion within the SHH repressor GLI3 in two patients with bilateral tibial hemimelia. This deletion results in a truncated GLI3 protein that lacks a DNA-binding domain and cannot repress hedgehog signaling. These findings strengthen the concept that tibial hemimelia arises because of failure to restrict SHH activity to the posterior aspect of the limb bud.

Children differ markedly from adults in their response to trauma. They sustain predictable injuries from typical mechanisms based upon their age and activity profile. They have been shown to have different patterns of injury when sustaining single bone trauma, pelvic fractures and spinal injuries. The microscopic structure of a child's bone is different creating an environment for unique fracture types including those of the physis. The biological healing response differs and children often have the capacity for significant remodelling. Due to the unique anatomy and physiology of a child, the management of severe trauma and multiple injuries is different to that of an adult. Continuing growth and development always need to be taken into account and will have a bearing on the management plan. The long-term outcome, from both a functional and psychological standpoint, is of great concern as these patients have potentially so much time ahead of them. It is important to be aware of all these differences to ensure that assessment, diagnosis, initial and definitive management, rehabilitation and follow up are optimal for each injured child.

The 40Ar/39Ar ages of metamorphic micas that crystallized at high temperatures are commonly interpreted as cooling ages, with grains considered to have lost 40Ar via thermally-driven diffusion into the grain boundary network. Recently reported laser-ablation data suggest that the spatial distribution of Ar in metamorphic micas does not always conform to the patterns predicted by diffusion theory and that despite high metamorphic temperatures, argon was not removed efficiently from the local system during metamorphic evolution. In the Western Gneiss Region (WGR), Norway, felsic gneisses preserve microtextural evidence for the breakdown of phengite to biotite and plagioclase symplectites during near isothermal decompression from c. 20–25 to c. 8–12 kbar at ~700°C. These samples provide an ideal natural laboratory to assess whether the complete replacement of one K-bearing mineral by another at high temperatures completely ‘resets’ the Ar clock, or whether there is some inheritance of 40Ar in the neo-crystallized phase. The timing of the high-temperature portion of the WGR metamorphic cycle has been well constrained in previous studies. However, the timing of cooling following the overprint is still much debated. In-situ laser ablation spot dating in phengite, biotite-plagioclase symplectites and coarser, texturally later biotite yielded 40Ar/39Ar ages that span much of the metamorphic cycle. Together these data show that despite residence at temperatures of ~700°C, Ar is not completely removed by diffusive loss or during metamorphic recrystallization. Instead, Ar released during phengite breakdown appears to be partially reincorporated into the newly crystallizing biotite and plagioclase (or is trapped in fluid inclusions in those phases) within a close system. Our data show that the microtextural and petrographic evolution of the sample being dated provides a critical framework in which local 40Ar recycling can be tracked, thus potentially allowing 40Ar/39Ar dates to be linked more accurately to metamorphic history.

Developmental dysplasia of the hip (DDH), if left untreated in the young child, is known to result in early-onset hip dysfunction. Labral and chondral pathology manifests in the young adult and often results in an accelerated need for joint replacement due to the altered weight-bearing mechanics of the femoral head in a shallow acetabulum. Acetabular reorientation procedures, such as the Salter innominate osteotomy, are performed for DDH in the skeletally immature patient in order to acutely correct anterolateral acetabular deficiency by rotating the acetabular fragment about the symphysis pubis. The Salter innominate osteotomy therefore restores hip stability and may be used in combination with an open reduction and capsulorrhaphy, and/or with femoral osteotomies, as necessary. The improvement of the hip joint mechanics has also been found to induce remodeling of the acetabulum with continued growth of the child, leading to improved clinical outcomes.

Osteotomy of the proximal femur has been used to correct deformity associated with slipped capital femoral epiphysis (SCFE) for more than 50 years. Southwick described an osteotomy “through the lesser trochanter” in 1963 and reported his results in later publications. Current concepts are similar to the flexion osteotomy in the intertrochanteric region, described by Imhauser in 1973. The principal indications are for the management of moderate to severe, symptomatic deformity of the proximal femur, after healing of SCFE. The components of flexion-valgus intertrochanteric osteotomy (FVIT) for SCFE deformity include combinations of flexion and valgus. Biomechanical modelling by Rab, axial imaging and clinical studies support flexion as being the key component of deformity correction with a small degree of valgus usually required. The evolution of fixation for FVIT in SCFE has included simple plates, compression plates, blade plates and locking plates. Accompanying procedures may include surgical hip dislocation (SHD) and additional surgery for femoro-acetabular impingement (FAI) at the time of FVIT or as a staged procedure. FVIT for moderate to severe deformity of the proximal femur after healing of a SCFE is a technically demanding procedure. However, FVIT can relieve pain, improve gait and function and preserve the native hip until a more suitable age for arthroplasty.

Hip pain with mechanical snapping is a common symptom with a wide-ranging differential diagnosis, including both extra and intra-articular etiologies. Femoroischial impingement should also be considered since many cases of recalcitrant hip pain may be misdiagnosed cases of this form of impingement. To the best of our knowledge, femoroischial impingement was first described by Johnson in 19771. He hypothesized that superior and medial migration of the lesser trochanter as a result of degenerative changes, posttraumatic changes, or surgery causes a decrease in the distance from the lesser trochanter to the ischium, thus leading to painful impingement. His report included three cases that were limited to older patients: there were two cases with a malpositioned total hip prosthesis and one case with degenerative changes prior to arthroplasty. Subsequent reports have involved only adult patients2-5. Quadratus femoris muscle tears have also been described as an unusual cause of hip pain6-8, and they have been reported in cases of femoroischial impingement3,5. They affect women much more frequently than men3,5, and they may or may not include a history of trauma or surgery9. The pain may radiate to the legs, which may be related to the proximity of the sciatic nerve4,10. Anti-inflammatory medications have been used with variable results as a first-line treatment3-5. Lesser trochanteric resection has been advocated in recalcitrant cases1,2,5. To our knowledge, we present the first documented case of primary femoroischial impingement as a cause of snapping hip syndrome in a fourteen-year-old girl. This diagnosis should be considered in the investigation of snapping hip syndrome as a readily identifiable and treatable cause of hip pain. We offer …

Light noble gas (He–Ne–Ar) solubility has been experimentally determined in a range of materials with six-member, tetrahedral ring structures: beryl, cordierite, tourmaline, antigorite, muscovite, F-phlogopite, actinolite, and pargasite. Helium solubility in these materials is relatively high, 4 × 10 −10 to 3 × 10 −7 mol g −1 bar −1 , which is ∼100 to 100,000× greater than He solubility in olivine, pyroxene, or spinel. Helium solubility broadly correlates with the topology of ring structures within different minerals. Distinctive He–Ne–Ar solubility patterns are associated with the different ring structure topologies. Combined, these observations suggest ring structures have a strong influence on noble gas solubility in materials and could facilitate the recycling of noble gases, along with other volatiles (i.e., water, chlorine, and fluorine), into the mantle. Measurements of Ne and Ar solubility in antigorite, however, are highly variable and correlated with each other, suggesting multiple factors contribute the solubility of noble gases in serpentine-rich materials.

Mass-balance calculations indicate that a massive amount of δ 13 C-depleted carbon was released into the early Danian atmosphere in volumes comparable with the younger Paleocene–Eocene Thermal Maximum (PETM). This Danian hyperthermal event (the Dan-C2) has been documented from the fill of the Boltysh meteorite crater, Ukraine. Palynofloras recovered from the Boltysh crater fill show a trend from mesic forest to savannah ecosystem dominance on a millennial scale across the hyperthermal inception with no abrupt compositional shift. This longer-term trend is overprinted by moisture availability oscillations reflecting orbital forcing. Forcing is not directly tracked by the oscillations, which are composed of mesic forest and savannah palynofloras separated by rapid critical transitions. The absence of an ecological collapse at the Dan-C2 indicates that plant ecosystems experienced dominant forcing from orbital cyclicity, rather than a stochastic temperature rise.

Major volatile contents (H 2 O, CO 2 , F, Cl, and S) and 40 Ar/ 39 Ar ages have been determined in variably degassed rhyolite obsidians from Pleistocene–Holocene aged subaerial and subglacial eruption environments from the Torfajokull volcanic center and the monogenetic volcano at Prestahnukur (Iceland). Icelandic subglacial rhyolites preserve residual H 2 O contents of 0.08–0.69 wt.%, undetectable CO 2 , 840–1780 ppm F, 430–2000 ppm Cl and 6–45 ppm S. Most subglacial obsidians have degassed volatile signatures at the time of their eruption under ice. One eruption (Blahnukur, Torfajokull) showed H 2 O contents which exceed those expected for quenching at atmospheric pressures (up to 0.69 wt.% H 2 O) and are consistent with eruption at ~40 kbar of pressure or equivalent to under ~450 m of ice. Altered and microcrystalline groundmass in some subglacial rhyolites yield variable volatile contents that are likely the result of micro-scale variability and the presence of alteration products. Two subaerial rhyolite obsidians gave low volatile contents consistent with quenching at the surface. New 40 Ar/ 39 Ar ages were determined on the subglacially erupted rhyolites and provide broad constraints on the timing and frequency of glacio-volcanism during the Pleistocene. Three subglacial eruptions at Torfajokull yielded ages of 108 ±22 ka (Blahnukur), 255 ±20 ka (Habarmur) and 236 ±7 ka (Haskerðingur) which fit into a range of previously determined ages at Torfajokull of 67–384 ka. A new age of 132 ±19 ka was determined for the monogenetic subglacial eruption at Prestahnukur. Holocene-aged subaerial volcanic glass produced no ages due to large amounts of air-derived 40 Ar (84–93%). Preliminary apparent 40 Ar/ 39 Ar ages from the limited feldspar phenocrysts available in these crystal-poor samples yield erroneous apparent plateau ages far older than eruption ages suggesting a homogenously distributed excess Ar component. Disturbances to the 40 Ar/ 39 Ar geochronometer are correlated with a heterogeneous distribution of volatiles in glass and linked to hydration (e.g., Kaldaklofsfjoll), mild alteration (e.g., Habarmur) and alteration and/or recrystallization of glass (e.g., Blahnukur). Our observations indicate however, that unaltered, subglacially erupted glasses that are partially to wholly degassed are promising materials for the application of the 40 Ar/ 39 Ar geochronometer. The precision to which we can date these young glassy samples currently limits the use of 40 Ar/ 39 Ar geochronometer as a tool for understanding the exact timing and duration of glaciovolcanism in the recent past.

Background Postoperative imaging for operatively treated developmental dislocation of the hip typically uses computed tomography or a magnetic resonance imaging (MRI). Neither imaging modality offers the ability to intervene intraoperatively. The 3-dimensional (3D) C-arm provides an attractive alternative providing immediate intraoperative feedback on the quality of a hip reduction. Our primary research question was to determine whether 3D fluoroscopy could assess hip position after closed reduction and spica casting. Secondary questions included whether reduction was maintained postoperatively when compared with postoperative MRI, and to determine the radiation dose received by the infant. Methods We retrospectively identified 16 patients from 2010 to 2013 who underwent closed reduction and spica casting for a developmentally dislocated hip who underwent both intraoperative 3D fluoroscopy and postoperative MRI imaging. Scans were retrieved and assessed by a blinded pediatric orthopaedic fellow. Assessment of hip reduction was graded based on the modified Shenton line of the pelvis in axial plane images. Effective radiation doses between imaging modalities were compared using an anthropomorphic phantom. Results All hips were reduced on 3D fluoroscopic images. Comparing the intraoperative 3D scans with the postoperative MRI images all 16 hips were in the same position. At 12 weeks all hips were reduced and no signs of subluxation were identified on the plain anteroposterior radiograph. 3D fluoroscopy achieved the lowest effective dose of radiation per study measuring 0.3 mSv compared with 0.5 mSv for low-dose CT and 0.48 mSv for 60 seconds of live fluoroscopy. Conclusions Accurate assessment of the quality of hip reduction is possible in the axial plane using 3D fluoroscopy with no significant loss of reduction in the early postoperative period. When comparing the effective radiation exposure to limited-cut computed tomography protocols, 3D fluoroscopy offers a low-dose alternative that may facilitate cost savings and early discharge. Level of evidence Diagnostic studies-investigating a diagnostic test; study of nonconsecutive patients with consistently applied gold standard; level III.

Distraction osteogenesis for brachymetacarpia has been described in several small case series and single case reports, but the rehabilitation required to optimize outcomes has not been reported. We present a case report describing the hand rehabilitation program of a 13-year-old girl with congenital brachymetacarpia who underwent distraction osteogenesis of the third metacarpal. Intense weekly hand therapy including desensitization, scar massage, range of motion exercises and splinting was essential up to 28 weeks postoperatively to address the progressive changes in the anatomical structures. At final follow-up, she had full active range of motion, no functional deficits in grasp or in-hand manipulation skills and resumed her participation in competitive baton twirling. Patient and family satisfaction with outcome was high. However, better education regarding the progressive symptoms with distraction and daily challenges of wearing an external fixator would have improved the overall experience. With a strong family commitment to rehabilitation and thorough patient education, distraction osteogenesis for brachymetacarpia has the potential to improve functional and aesthetic outcome in the hand. V.

40Ar/39Ar thermochronology is commonly used to constrain the rates and times of cooling in exhumed metamorphic terranes, with ages usually linked to temperature via Dodson's closure temperature (TC) formulation. Whilst many metamorphic 40Ar/39Ar data are consistent with the timing of crystallisation or cooling within a chronological framework defined by other, higher temperature, chronometers, other 40Ar/39Ar data are more difficult to interpret. We report white mica and biotite single grain fusion and laser ablation 40Ar/39Ar ages from felsic gneisses from the Western Gneiss Region, Norway. The rocks record isothermal decompression from peak eclogite-facies conditions (white mica stable) to amphibolite-facies conditions (biotite stable) at c. 700 °C. White mica and biotite yield dispersed single grain fusion dates from 416 to 373 Ma and 437 to 360 Ma respectively. In-situ laser ablation analyses provide a similar range, with white mica spot ages ranging from 424 to 370 Ma and biotite spot ages ranging from 437 to 370 Ma. The dates span the duration of the metamorphic cycle suggested by previous studies, and cannot be reconciled with the results of simple models of Ar loss by diffusion during cooling. Samples that show evidence for different physical processes, such as the chemical breakdown of white mica, partial melting, and fluid ingress, generated different age populations to samples that did not experience or record obvious petrological evidence for these processes. Samples that record significant recrystallization and deformation yielded younger white mica (but older biotite) single grain fusion ages than more pristine samples. Amphibolite-facies gneisses that preserve evidence for significant partial melting generated younger biotite ages than samples that recorded evidence for significant hydration. Our data support other reported observations that high-temperature metamorphic mica 40Ar/39Ar dates cannot be assumed to record the timing of cooling through a specific temperature window. Careful assessment of the petrographic context of the dated minerals and consideration of their post-crystallisation history may provide a more robust insight into whether ‘age’ links to ‘stage’ in a temporally meaningful way.

Helium partitioning between olivine, orthopyroxene, clinopyroxene, and spinel and basaltic melt has been experimentally determined under upper mantle melting conditions (up to 20 kbar and 1450 °C). Under the conditions explored, helium partition coefficients are similar in all minerals investigated ( K d He ∼ 10 − 4 ), suggesting He is evenly distributed between the minerals of spinel peridotite. This is in contrast to most incompatible elements, which are concentrated in clinopyroxene in spinel peridotite. The studied minerals have different concentrations of point defects, but similar He solubility, providing no evidence for He partitioning onto specific defects sites (e.g. cation vacancies). Upper limits on the partition coefficients for Ne and Ar have also been determined, constraining these elements to be moderately to highly incompatible in olivine at the conditions of spinel peridotite melting ( 10 − 2 and 10 − 3 , respectively). Helium partitioning in peridotite minerals varies little within the range of temperatures, pressures, and mineral compositions explored in this study. Reported partition coefficients, in combination with previous work, suggest that moderate to high degree mantle melting is not an efficient mechanism for increasing (U+Th)/He, (U+Th)/Ne, or K/Ar of the depleted mantle (DMM) through time, and consequently, supports the argument that recycling of oceanic crust is largely responsible for the relatively strong radiogenic noble gas signatures in the depleted mantle. Mantle residues with lowered (U+Th)/He, (U+Th)/Ne, and K/Ar may be produced through large extents of melting, but concentrations of noble gases will be low, unless noble gas solubility in solids deviate from Henryʼs Law at high fugacity.

The noble gas geochemistry of different types of terrestrial diamond including coated stones, alluvial diamonds, framesites, carbonados and impact diamonds yields a wealth of information on the sources of volatiles responsible for diamond formation. We present an illustrated compilation of published analyses of noble gases in different types of natural diamond. Noble gases in diamond record primary signatures from the mantle indicative of their integrated sources, and, the contribution of different metasomatic agents including subducting fluids and kimberlitic melt sampled during diamond growth. In addition, they show evidence of secondary processes such as resorption. Most data are available for coated stones, which trap abundant volatile-rich microscopic inclusions in their rims. While the coated stones are dominated by Mid-Oceanic-Ridge-Basalt (MORB) type noble gas signatures, the other diamond types contain predominantly crustal and atmospheric components although some mantle gases may be present, the latter indicated in elevated 20 Ne/ 22 Ne and/or 129 Xe/ 132 Xe ratios relative to atmospheric values. Some alluvial diamonds have very high 3 He/ 4 He that may represent the presence of a solar component trapped during their formation, but are just as likely to be the result of cosmogenic 3 He implantation during their prolonged residence at the Earth's surface. Oceanic-Island-Basalt (OIB) type noble gases occur in nanometer sized inclusions in metamorphic diamond from Kazakhstan, yet their significance as a fingerprint of mantle processes is not fully understood. Implanted noble gases occur near the outer surfaces of individual crystals, and are generally not a major hindrance for the study of mantle signatures, except for polycrystalline diamond like framesites with small grain size. Some diamonds including the polycrystalline carbonados, are dominated by crustal noble gases with no discernible mantle component evidenced by very low 3 He/ 4 He and 20 Ne/ 22 Ne ratios, and very high 21 Ne/ 22 Ne and 131,134,136 Xe/ 132 Xe ratios. In many diamonds, variations in both concentration and isotopic composition within samples from the same geographical location require complex diamond growth. For example, coated stones of Zaire trap noble gases from multiple sources and different generations of diamond growth. Thus noble gas studies have the potential to record major processes during the complex growth histories of natural diamond and also to provide valuable information about the sub-continental mantle. Noble gas signatures may be affected by diffusive losses, notably in some framesites. Lastly, we discuss the future trend and scope of noble gas studies in diamond combining noble gas analyses with other elements including trace elements and halogens, and in situ 40 Ar– 39 Ar age determinations to constrain the entrapment and diamond growth age. A key to greater understanding lies in systematic pre-analytical sample characterisation and treatment. This includes core-rim separation for coated stones, removal of the outer 25 μm to remove implanted gases, analysis of fluid inclusion density, and characterised heterogeneity using optical microscope to identify resorption and alteration.

International audience; The observed escape of the primordial helium isotope, 3He, from the Earth's interior indicates that primordial helium survived the energetic process of planetary accretion and has been trapped within the Earth to the present day. Two distinct reservoirs in the Earth's interior have been invoked to account for variations in the 3He=4He ratio observed at the surface in ocean basalts: a conventional depleted mantle source and a deep, still enigmatic, source that must have been isolated from processing throughout Earth history. The Earth's iron-based core has not been considered a potential helium source because partitioning of helium into metal liquid has been assumed to be negligible. Here we determine helium partitioning in experiments between molten silicates and iron-rich metal liquids at conditions up to 16 GPa and 3,000 K. Analyses of the samples by ultraviolet laser ablation mass spectrometry yield metal-silicate helium partition coefficients that range between 4:7 10-3 and 1:7 10-2 and suggest that significant quantities of helium may reside in the core. Based on estimated concentrations of primordial helium,we conclude that the early core could have incorporated enough helium to supply deep-rooted plumes enriched in 3He throughout the age of the Earth.

The extent to which intracrystalline microtextures influence the diffusion of radiogenic Ar within alkali feldspars from slowly cooled igneous rocks is a long standing question in thermochronology. By combining high-resolution electron microscopy with in-situ UV-laser ablation microprobe 40 Ar/ 39 Ar analysis the interplay of microtextures with isotope ages can be studied directly, enabling some of the assumptions underlying 40 Ar/ 39 Ar thermochronological techniques to be tested and allowing deduction of thermochronological and geological histories. However, there are numerous potential mechanisms by which a sample can be damaged and its Ar-isotope system disturbed by such microscopy techniques. To test this hypothesis, perthitic alkali feldspars from the 270–280 Ma Dartmoor Granite, UK, and gem-quality orthoclase from Itrongay, Madagascar (~ 470 Ma) were polished with colloidal silica or etched with hydrofluoric acid and irradiated with electrons and Ga + ions. The accelerating voltages and currents used were typical of those for electron beam imaging by scanning electron microscopy, X-ray analysis and mapping by electron probe, and for extraction of foils using the focused ion beam technique. No disturbance to the Ar-isotope system was observed for Ga + ion irradiation, or for low-resolution SEM imaging, but electron irradiation of small areas for long durations, as occurs during extended high-magnification SEM imaging, was found to disturb the Ar-isotope system over hundreds of micrometre sized areas by the addition of K and atmospheric Ar, producing anomalously young apparent 40 Ar/ 39 Ar ages. The best explanation for this age disturbance is electromigration of K and implantation of atmospheric Ar during sample charging.

Carbon isotope and palynological analysis of the fine-grained organic carbon–rich lacustrine sediments that filled the Cretaceous-Paleogene (K-Pg) boundary–age Boltysh impact crater (Ukraine) preserve a uniquely complete and detailed record of a negative carbon isotope excursion in an expanded section of the early Danian that we estimate lasted as long as ∼340 k.y. Palynological assemblages recovered through the excursion reflect the increasing dominance of thermophylic Normapolles species, indicating an increasingly warm and dry climate, while those recovered below and above the excursion reflect a cooler and wetter climate. The record of a transient warming event (hyperthermal) in the early Danian at Boltysh has strong similarities with the Dan-C2 hyperthermal event recorded in marine sediments in Tethys and the Atlantic Ocean, and suggests that there were profound environmental changes occurring on a global scale shortly after the K-Pg boundary.

Spatially resolved argon isotope measurements have been performed on neutron-irradiated samples of NW Africa (NWA) 4797. Shock heating of NWA 4797 completely melted and vesiculated precursor igneous plagioclase, which cooled to an assemblage of plagioclase crystals with interstitial glasses of variable composition (Ca/K ratios). Using a focused ultraviolet laser beam, is has been possible to distinguish between argon isotopic signatures from groundmass minerals (igneous olivine + pyroxene), plagioclase and a shock vein. This study focuses on the potential for this meteorite to shed light on shock ages of shergottites. Apparent 40Ar/39Ar ages of groundmass minerals show that there are large amounts of excess argon in this phase, yielding a wide range of calculated ages from 690 ± 30 Ma to several apparent ages older than 4.5 Ga. A traverse of laser-probe extractions across the 1 mm-diameter shock vein in NWA 4797 yielded apparent 40Ar/39Ar ages younger than the groundmass. A signature of the Martian atmosphere, identified by 40Ar/36Ar ratios of 1600-1900, was not found in the NWA 4797 shock vein. This is distinct from other shergottites where the products of shock melting contain a nearly pure sample of Martian atmosphere. We attribute this to a distinct formation mechanism, and hence gas-trapping mechanism, of the NWA 4797 shock vein. We undertook 44 analyses of plagioclase areas identified by SEM analysis. Ages ranged from 45 ± 27 to 3771 ± 109 Ma and yield an average age of 375 ± 77 Ma, considerably younger than ages obtained in this study from either the groundmass or the shock vein. A plot of age v. 37Ar/39Ar for plagioclase showed a continuum of ages from the oldest to youngest ages measured. Older ages are correlated with higher Ca/K ratios of plagioclase, indicating contamination from groundmass minerals rich in excess argon. The youngest ages correlate to plagioclase extractions with the lowest Ca/K ratios, interpreted to have crystallized from a nearly pure plagioclase melt with contributions from a K-rich mesostasis. We see no evidence for multiple shock events in NWA 4797. Rather, we favour the interpretation that the cosmic-ray exposure (CRE) age of 3.0 ± 0.5 Ma, obtained on NWA 4797 in this study using cosmogenic 38Ar, approximates the timing of shock melting in this meteorite.

How noble gases are recycled from the atmosphere back into the mantle has been unclear. High-pressure experiments demonstrate that noble gases are highly soluble in an important hydrous mineral in altered oceanic crust, suggesting that subduction of this type of crust may be a significant pathway for noble gas flux back into the mantle.

Sedimentary rocks filling the Boltysh meteorite crater preserve an expanded record of post Cretaceous–Palaeogene (K/Pg) event vegetation destruction and subsequent floral recolonization. A post-destruction barren zone is succeeded by a fern spore spike recording the initial recovery vegetation. The Boltysh fern spore spike is divisible into two phases. Phase 1 is characterized by low abundances of fern spores, whereas the overlying Phase 2 has high fern spore abundances and contains common palm pollen. Comparison of the Boltysh Phase 2 fern spore spike with other palynological records shows strong similarities to the immediately post K/Pg boundary record of the Western Interior, North America. Variation in the composition of the Boltysh palynofloras has been used to define four moisture availability cycles between the K/Pg boundary and the Dan-C2 negative carbon isotope excursion, a period of some 300 kyr. Early post K/Pg event vegetation community recovery followed a common seral successional pathway at rates seen in large igneous provinces, although enhanced by high moisture availability. Continued succession to the first true swamp community was at a considerably slower tempo. The post K/Pg event vegetation recovery was therefore retarded by lack of moisture availability, extending the apparent period of recovery.

We investigated exterior and interior subsamples from the Martian shergottite meteorites Allan Hills (ALH) A77005 and Roberts Massif (RBT) 04261 for secondary minerals, oxygen isotopes, Ar-Ar, and noble gas signatures. Electron microprobe investigations revealed that RBT 04261 does not contain any visible alteration even in its most exterior fractures, whereas fracture fillings in ALHA77005 penetrate into the meteorite up to 300 μm, beyond which the fractures are devoid of secondary minerals. Light noble gases seem to be almost unaffected by terrestrially induced alteration in both meteorites. Thus, a shock metamorphic overprint of 30–35 GPa can be deduced from the helium measurements in RBT 04261. Oxygen isotopes also seem unaffected by terrestrially weathering and variations can easily be reconciled with the differences in modal mineralogy of the exterior and interior subsamples. The measurements on irradiated samples (Ar-Ar) showed a clear Martian atmospheric contribution in ALHA77005, but this is less apparent in our sample of RBT 04261. Exterior and interior subsamples show slight differences in apparent ages, but the overall results are very similar between the two. In contrast, krypton and xenon are severely affected by terrestrial contamination, demonstrating the ubiquitous presence of elementally fractionated air in RBT 04261. Although seemingly contradictory, our results indicate that RBT 04261 was more affected by contamination than ALHA77005. We conclude that irrespective of on which planet the alteration occurred, exposure of Martian rocks to atmosphere (or brine) introduces noble gases with signatures elementally fractionated relative to the respective atmospheric composition into the rock, and relationships of that process with oxygen isotopes or mineralogical observations are not straightforward.

40Ar/39Ar dating of metamorphic white mica is commonly used to elucidate the timing of cooling and/or exhumation of metamorphic terranes. In theory, so long as the dated mineral originally crystallised above its closure temperature, the yielded 40Ar/39Ar ages should not vary significantly within or between samples, and should vary only due to grain size (~ 3 Ma variation depending on the estimated cooling rate). Infra-red laser single grain fusion and ultra-violet laser spot muscovite and/or phengite data from mafic eclogite bodies and their host gneisses in the Nordfjord region of the Western Gneiss Complex (WGC), Norway, show that the ages yielded both within and between white micas from the same mafic eclogite sample vary by up to 284 Ma. Ages yielded within the same pelitic gneiss sample vary by up to 28 Ma. Overall the 40Ar/39Ar phengite dates from mafic eclogites range from ~ 750 to 440 Ma and are significantly older than the previously reported 405–400 Ma U–Pb zircon age constraining peak metamorphism in the Nordfjord WGC. The felsic host gneiss samples, which recrystalised during a post-peak, exhumation-related, amphibolite-facies overprint, yield single grain fusion and laser spot 40Ar/39Ar white mica dates spanning ~ 420 to 385 Ma, encompassing previous estimates of the timing of the entire metamorphic cycle. These data suggest that Ar is heterogeneously distributed both within grains and between grains on the cm to sub-mm scale in all samples, and imply restricted Ar transport and inefficient removal during the metamorphic cycle. Open system (zero grain boundary Ar concentration) behaviour is an inherent assumption in the commonly applied closure temperature formulation, but unless this can be demonstrated, linking 40Ar/39Ar ages to temperature is no longer trivial. The high spatial and chronological precision afforded by UV laser ablation mean that intra-grain Ar concentration distributions may be used to assess open vs. closed system behaviour. The data presented here suggest that open system behaviour cannot be assumed in metamorphic systems, even those in which the pressure, temperature and time conditions in theory allow for efficient diffusion during the metamorphic cycle. High spatial resolution 40Ar/39Ar data and robust comparison with numerical models of open system behaviour provide the greatest future potential for unravelling the complexities of metamorphic exhumation timescales.

This chapter aims to summarise the best available evidence for decision making in treating children with developmental dysplasia of the hip. While the treatment of DDH is not without risk, it is universally accepted that the clinician should do what is necessary to achieve and maintain a gentle, concentric and stable reduction. Several challenges became apparent during the preparation of this chapter. Many of the studies are retrospective case series with suboptimal methodology, small numbers and inconsistent treatment methods. Radiological appearance (using the Severin classification and scores to identify the pattern of growth disturbance) are consistently used as surrogates for poor outcome. There are several aspects in the treatment of DDH where uncertainties remain. We hope that this chapter will help guide the surgeon through these controversies.

Noble-gas geochemistry is an important tool for understanding planetary processes from accretion to mantle dynamics and atmospheric formation1,2,3,4. Central to much of the modelling of such processes is the crystal–melt partitioning of noble gases during mantle melting, magma ascent and near-surface degassing5. Geochemists have traditionally considered the ‘inert’ noble gases to be extremely incompatible elements, with almost 100 per cent extraction efficiency from the solid phase during melting processes. Previously published experimental data on partitioning between crystalline silicates and melts has, however, suggested that noble gases approach compatible behaviour, and a significant proportion should therefore remain in the mantle during melt extraction5,6,7,8. Here we present experimental data to show that noble gases are more incompatible than previously demonstrated, but not necessarily to the extent assumed or required by geochemical models. Independent atomistic computer simulations indicate that noble gases can be considered as species of ‘zero charge’ incorporated at crystal lattice sites. Together with the lattice strain model9,10, this provides a theoretical framework with which to model noble-gas geochemistry as a function of residual mantle mineralogy.

The relative incompatibility of Ar and K are fundamental parameters in understanding the degassing history of the mantle. Clinopyroxene is the main host for K in most of the upper mantle, playing an important role in controlling the K/Ar ratio of residual mantle and the subsequent time-integrated evolution of 40Ar/36Ar ratios. Clinopyroxene also contributes to the bulk Ar partition coefficient that controls the Ar degassing rate during mantle melting. The partitioning of Ar and K between clinopyroxene and quenched silicate melt has been experimentally determined from 1 to 8 GPa for the bulk compositions Ab80Di20 (80 mol% albite-20 mol% diopside) and Ab20Di80 with an ultraviolet laser ablation microprobe (UVLAMP) technique for Ar analysis and the ion microprobe for K. Data for Kr (UVLAMP) and Rb (ion probe) have also been determined to evaluate the role of crystal lattice sites in controlling partitioning. By excluding crystal analyses that show evidence of glass contamination, we find relatively constant Ar partition coefficients (DAr) of 2.6 × 10-4 to 3.9 × 10-4 for the Ab80Di20 system at pressures from 2 to 8 GPa. In the Ab20Di80 system, DAr shows similar low values of 7.0 × 10-5 and 3.0 × 10-4 at 1 to 3 GPa. All these values are several orders of magnitude lower than previous measurements on separated crystal-glass pairs. DK is 10 to 50 times greater than DRb for all experiments, and both elements follow parallel trends with increasing pressure, although these trends are significantly different in each system studied. The DK values for clinopyroxene are at least an order of magnitude greater than DAr under all conditions investigated here, but DAr appears to show more consistent behavior between the two systems than K or Rb. The partitioning behavior of K and Rb can be explained in terms of combined pressure, temperature, and crystal chemistry effects that result in changes for the size of the clinopyroxene M2 site. In the Ab20Di80 system, where clinopyroxene is diopside rich at all pressures, DK and DRb increase with pressure (and temperature) in an analogous fashion to the well-documented behavior of Na. For the Ab80Di20 system, the jadeite content of the clinopyroxene increase from 22 to 75 mol% with pressure resulting in a contraction of the M2 site. This has the effect of discriminating against the large K+ and Rb+ ions, thereby countering the effect of increasing pressure. As a consequence Dk and DRb do not increase with pressure in this system. In contrast to the alkalis (Na, K, and Rb), DKr values are similar to DAr despite a large difference in atomic radius. This lack of discrimination (and the constant DAr over a range of crystal compositions) is also consistent with incorporation of these heavier noble gases at crystal lattice sites and a predicted consequence of their neutrality or "zero charge." Combined with published DAr values for olivine, our results confirm that magma generation is an efficient mechanism for the removal of Ar from the uppermost 200 km of the mantle, and that K/Ar ratios in the residuum are controlled by the amount of clinopyroxene. Generally, Ar is more compatible than K during mantle melting because DAr for olivine is similar to Dk for clinopyroxene. As a result, residual mantle that has experienced variable amounts of melt extraction may show considerable variability in time-integrated 36Ar/40Ar. Copyright © 2002 Elsevier Science Ltd.

Jurassic dykes ( c . 182 Ma) are widespread across the Falkland Islands and exhibit considerable geochemical variability. Orthopyroxene-bearing NW–SE-oriented quartz-tholeiite dykes underwent fractional crystallization at >1 GPa, and major element constraints suggest that they were derived by melting of a pyroxenite-rich source. They have eNd 182 in the range −6 to −11 and 87 Sr/ 86 Sr 182 >0.710 and therefore require an old lithospheric component in their source. A suite of basaltic-andesites and andesites exhibit geochemical compositions transitional between Ferrar and Karoo magma types, and are similar to those seen in the KwaZulu-Natal region of southern Africa and the Theron Mountains of Antarctica. Olivine-phyric intrusions equilibrated at 182 1.6–3.6 and 87 Sr/ 86 Sr 182 0.7036–0.7058) that require limited interaction with old continental lithosphere. A suite of plagioclase-phyric intrusions with 87 Sr/ 86 Sr 182 c . 0.7035 and eNd 182 c . +4, and low Th/Ta and La/Ta ratios ( c . 1 and c . 15, respectively) also largely escaped interaction with the lithosphere. These isotopically depleted intrusions were probably emplaced synchronously with Gondwana fragmentation and the formation of new oceanic lithosphere. Estimates of mantle potential temperature from olivine equilibration temperatures do not provide unequivocal evidence for the presence of a plume thermal anomaly beneath the Falkland Islands at 182 Ma. Supplementary materials: Mineralogical data, XRF major and trace element data and Ar-Ar results for Falkland Islands intrusions are available at http://www.geolsoc.org.uk/sup18873.