Estimating tropospheric and stratospheric winds using infrasound from explosions.

The receiver-to-source backazimuth of atmospheric infrasound signals is biased when cross-winds are present along the propagation path. Infrasound from 598 surface explosions from over 30 years in northern Finland is measured with high spatial resolution on an array 178 km almost due North. The array is situated in the classical shadow-zone distance from the explosions. However, strong infrasound is almost always observed, which is most plausibly due to partial reflections from stratospheric altitudes. The most probable propagation paths are subject to both tropospheric and stratospheric cross-winds, and the wave-propagation modelling in this study yields good correspondence between the observed backazimuth deviation and cross-winds from the European Centre for Medium-Range Weather Forecasts Reanalysis (ERA)-Interim reanalysis product. This study demonstrates that atmospheric cross-winds can be estimated directly from infrasound data using propagation time and backazimuth deviation observations. This study finds these cross-wind estimates to be in good agreement with the ERA-Interim reanalysis.

Contamination of 8.2 ka cold climate records by the Storegga tsunami in the Nordic Seas.

The 8200-year BP cooling event is reconstructed in part from sediments in the Norwegian and North Seas. Here we show that these sediments have been reworked by the Storegga tsunami - dated to the coldest decades of the 8.2 ka event. We simulate the maximum tsunami flow velocity to be 2-5 m/s on the shelf offshore western Norway and in the shallower North Sea, and up to about 1 m/s down to a water depth of 1000 m. We re-investigate sediment core MD95-2011 and found the cold-water foraminifera in the 8.2 ka layer to be re-deposited and 11,000 years of age. Oxygen isotopes of the recycled foraminifera might have led to an interpretation of a too large and dramatic climate cooling. Our simulations imply that large parts of the sea floor in the Norwegian and North Seas probably were reworked by currents during the Storegga tsunami.

A comparison of screw and suture button fixation in the management of adolescent ankle syndesmotic injuries.

Purpose: Ankle injuries involving the tibiofibular syndesmosis often necessitate operative fixation to restore stability to the ankle. Recent literature in the adult population has suggested that suture button fixation may be superior to screw fixation. There is little evidence as to which construct is preferable in the pediatric and adolescent population. This study investigates outcomes of suture button and screw fixation in adolescent ankle syndesmotic injuries. Methods: A retrospective matched cohort study over 10 years of pediatric patients who underwent ankle syndesmotic fixation at a large Level 1 Trauma Center was conducted. Both isolated syndesmotic injuries and ankle fractures with syndesmotic disruption were included. Preoperative variables collected include basic patient demographics, body mass index, and fracture type. Suture button and screw cohorts were matched based on age, race, sex, and open fracture utilizing propensity scores. Outcomes assessed include reoperation and implant failure. Results: A total of 44 cases of operative fixation of the ankle syndesmosis were identified with a mean age of 16 years. After matching cohorts based on age, sex, race, and open fracture status, there were 17 patients in the suture button and screw cohorts, respectively. Patients undergoing screw fixation had a six times greater risk of reoperation (p = 0.043) and 13 times greater risk of implant failure (p < 0.001). Out of six cases of reoperation in the screw cohort, five were unplanned. Conclusion: Our findings favor suture button fixation in operative management of adolescent tibiofibular syndesmotic injuries. Compared with screws, suture buttons are associated with lower risk of both reoperation and implant failure. Level of evidence: level III therapeutic.

Recurrent Infections After Percutaneous Pinning of a Proximal Radius and Ulna Fracture.

Elbow fractures in the pediatric population are an exceedingly common injury, comprising 5% to 10% of all pediatric fractures, with supracondylar fractures being the most common of the subset. Radial neck fractures are less frequent, comprising only 1% of all pediatric fractures. We provide a case report of a 7-year-old girl with a left radial neck and proximal ulna fracture. A 7-year-old girl presented to the emergency department after falling off a rock wall the day before. Imaging showed a left proximal ulna and proximal radial neck fracture. The patient underwent percutaneous reduction and fixation, complicated by subsequent infection requiring surgical débridement. The patient then developed a recurrent infection 1 year later, requiring repeat irrigation and débridement. The patient has since made a full recovery, returned to activities of daily living, and regained a full range of motion. Radial neck fractures have a low incidence and have been frequently associated with poor outcomes. The main mechanism by which these fractures occur is due to falling on an outstretched arm. Percutaneous pinning is often recommended after unsuccessful attempts at closed reduction because open reduction is often complicated by postoperative stiffness. As with any procedure that involves breaking the skin, there is a risk of infection. However, there is unclear evidence regarding ideal perioperative management to prevent postoperative infection.

Obesity Increases Time to Union in Surgically Treated Pediatric Fracture Patients.

INTRODUCTION: To determine whether obesity affects time to radiographic union in surgically treated pediatric extremity fractures. METHODS: A retrospective review of pediatric patients with extremity fractures at a Level 1 trauma center from 2010 to 2020. Those treated conservatively and patients with nonunions were excluded. Union was defined as radiographic evidence of bridging callus on all sides of the fracture and absence of the previous fracture line. RESULTS: Obese patients had a markedly increased time to union when compared with others, even when age, sex, fracture type, race, and ethnicity were controlled for. The mean time to union for obese and nonobese patients were 152 and 93.59 days, respectively (P < 0.001). Obese patients had 3.39 times increased odds of having increased time to union. Obese patients had 6.64 times increased odds of having fractures with delayed union of 4 months or greater (P < 0.001). CONCLUSIONS: There is a positive correlation between obesity and time to union in surgically treated pediatric fracture patients.

Global quieting of high-frequency seismic noise due to COVID-19 pandemic lockdown measures.

Human activity causes vibrations that propagate into the ground as high-frequency seismic waves. Measures to mitigate the coronavirus disease 2019 (COVID-19) pandemic caused widespread changes in human activity, leading to a months-long reduction in seismic noise of up to 50%. The 2020 seismic noise quiet period is the longest and most prominent global anthropogenic seismic noise reduction on record. Although the reduction is strongest at surface seismometers in populated areas, this seismic quiescence extends for many kilometers radially and hundreds of meters in depth. This quiet period provides an opportunity to detect subtle signals from subsurface seismic sources that would have been concealed in noisier times and to benchmark sources of anthropogenic noise. A strong correlation between seismic noise and independent measurements of human mobility suggests that seismology provides an absolute, real-time estimate of human activities.

Spine and Thoracic Height Measurements Have Excellent Interrater and Intrarater Reliability in Patients With Early Onset Scoliosis.

STUDY DESIGN: Reproducibility of measurements. OBJECTIVE: This study investigates the reliability and standard error of measurement of spine and thoracic height radiographic measurements in patients with early onset scoliosis (EOS). SUMMARY OF BACKGROUND DATA: Spine and thoracic height radiographic measurements are often used as a surrogate for pulmonary development in patients with EOS. There is limited literature validating the reliability of spine and thoracic height measurements in the EOS population. METHODS: Using pilot data, we determined measuring 49 unique radiographs would provide 80% power to obtain a 95% confidence interval (CI) width of 0.05 for the interclass correlation coefficients (ICCs). A random sampling strategy, stratified by underlying diagnosis from the Classification of Early Onset Scoliosis (C-EOS), was used to distribute the diagnoses in the study sample. Two attending pediatric spine surgeons, two pediatric orthopedic fellows, and two research assistants measured coronal spine (T1-S1) and thoracic (T1-T12) height on digital radiographs using imaging software (Surgimap; Nemaris, Inc, New York) on two separate occasions at least 3 weeks apart. Order of images was randomized for the second iteration. Linear mixed model regression analyses were used to estimate interrater and intrarater reliability. RESULTS: The study sample included subjects (N = 48) with idiopathic (N = 17, 35%), congenital (N = 16, 33%, 1 patient excluded), neuromuscular (N = 11, 23%), and syndromic (N = 4, 8%) scoliosis. Overall interrater reliability estimates for spine height (ICC: 0.894, 95% CI: 0.847-0.932) and thoracic height (ICC: 0.890, 95% CI: 0.844-0.929) were excellent. Intrarater reliability estimates for spine height (ICC: 0.906, 95% CI: 0.830-0.943) and thoracic height (ICC: 0.898, 95% CI: 0.817-0.938) were also excellent. CONCLUSION: There is excellent interrater and intrarater reliability for radiographic measurements of spine and thoracic height in the EOS population at our institution. LEVEL OF EVIDENCE: 2.

Joint seismic-infrasonic processing of recordings from a repeating source of atmospheric explosions.

A database has been established of seismic and infrasonic recordings from more than 100 well-constrained surface explosions, conducted by the Finnish military to destroy old ammunition. The recorded seismic signals are essentially identical and indicate that the variation in source location and magnitude is negligible. In contrast, the infrasonic arrivals on both seismic and infrasound sensors exhibit significant variation both with regard to the number of detected phases, phase travel times, and phase amplitudes, which would be attributable to atmospheric factors. This data set provides an excellent database for studies in sound propagation, infrasound array detection, and direction estimation.

Cross-correlation beamforming.

An areal distribution of sensors can be used for estimating the direction of incoming waves through beamforming. Beamforming may be implemented as a phase-shifting and stacking of data recorded on the different sensors (i.e., conventional beamforming). Alternatively, beamforming can be applied to cross-correlations between the waveforms on the different sensors. We derive a kernel for beamforming cross-correlated data and call it cross-correlation beamforming (CCBF). We point out that CCBF has slightly better resolution and aliasing characteristics than conventional beamforming. When auto-correlations are added to CCBF, the array response functions are the same as for conventional beamforming. We show numerically that CCBF is more resilient to non-coherent noise. Furthermore, we illustrate that with CCBF individual receiver-pairs can be removed to improve mapping to the slowness domain. An additional flexibility of CCBF is that cross-correlations can be time-windowed prior to beamforming, e.g., to remove the directionality of a scattered wavefield. The observations on synthetic data are confirmed with field data from the SPITS array (Svalbard). Both when beamforming an earthquake arrival and when beamforming ambient noise, CCBF focuses more of the energy to a central beam. Overall, the main advantage of CCBF is noise suppression and its flexibility to remove station pairs that deteriorate the signal-related beampower. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1007/s10950-016-9612-6) contains supplementary material, which is available to authorized users.

Effect of surgical treatment on mortality after acetabular fracture in the elderly: a multicenter study of 454 patients.

OBJECTIVES: Controversy exists regarding the effect of operative treatment on mortality after acetabular fracture in elderly patients. Our hypothesis was that operative treatment would confer a mortality benefit compared with nonoperative treatment even after adjusting for comorbidities associated with death. DESIGN: Retrospective study. SETTING: Three University Level I Trauma Centers. PATIENTS/PARTICIPANTS: All patients aged 60 years and older with acetabular fractures treated from 2002 to 2009 were included in the study. Four hundred fifty-four patients were identified with an average age of 74 years. Sixty-seven percent of the study group was male and 33% female. INTERVENTION: One of 4 treatments: nonoperative management with early mobilization, percutaneous reduction and fixation, open reduction and internal fixation, acute total hip arthroplasty. MAIN OUTCOME MEASUREMENTS: Kaplan-Meier survival curves were created, and Cox proportional hazards models were used to calculate unadjusted and adjusted hazard ratios (HRs) for covariates of interest. RESULTS: In contrast to previous smaller studies, the overall mortality was relatively low at 16% at 1 year [95% confidence interval (CI), 13-19]. Unadjusted survivorship curves suggested higher 1-year mortality rates for nonoperatively treated patients (21% vs. 13%, P < 0.001); however, nonoperative treatment was associated with other risk factors for higher mortality. By accounting for these patient risk factors, our final multivariate model of survival demonstrated no significant difference in hazard of death for nonoperative treatment (0.92, P = 0.6) nor for any of the 3 operative treatment subgroups (P range, 0.4-0.8). As expected, we did find a significantly increased hazard for factors such as the Charlson comorbidity index [HR, 1.25 per point (95% CI, 1.16-1.34)] and age [HR, 1.08 per year of age more than 70 years (95% CI, 1.05-1.11)]. In addition, associated fracture patterns (compared with elementary patterns) significantly increased the hazard of death with a ratio of 1.51 (95% CI, 1.10-2.06). CONCLUSIONS: The operative treatment of acetabular fractures does not increase or decrease mortality, once comorbidities are taken into account. The reasons for this are unknown. Regardless of the causes, the decision for operative versus nonoperative treatment of geriatric acetabular fractures should not be justified based on the concern for increased or decreased mortality alone. LEVEL OF EVIDENCE: Prognostic Level II. See Instructions for Authors for a complete description of levels of evidence.

Microbiological culture methods for pediatric musculoskeletal infection: a guideline for optimal use.

BACKGROUND: Culture results affect the diagnosis and treatment of children with musculoskeletal infection. To our knowledge, no previous large-scale study has assessed the relative value of culture methods employed during the evaluation of these conditions. The purpose of this study was to identify an optimal culture strategy for pediatric musculoskeletal infection. METHODS: Children with musculoskeletal infection were retrospectively studied to assess culture results from the infection site or blood; culture type, including aerobic, anaerobic, fungal, and acid-fast bacteria (AFB); antibiotic exposure history; and clinical history of children with positive culture results. RESULTS: We studied 869 children, including 353 with osteomyelitis, 199 with septic arthritis, forty-two with pyomyositis, and 275 with abscess. The 4537 cultures processed included 1303 aerobic, 903 anaerobic, 340 fungal, 289 AFB, and 1702 blood. Of 3004 specimens sent during initial work-up, positive results occurred in 677 of 1049 aerobic cultures (64.5%), 140 of 763 blood cultures (18.3%), eighteen of 722 anaerobic cultures (2.5%), five of 251 fungal cultures (2.0%), and two of 219 AFB cultures (0.9%). Staphylococcus aureus was the most common pathogen isolated, from 428 (50.7%) of 844 children for whom blood or infection-site culture material was sent (methicillin-resistant S. aureus, 252; and oxacillin-sensitive S. aureus, 176). Cultures were negative in 206 (29.0%) of the 710 children for whom culture material from the site of infection was sent. Children with true-positive anaerobic, fungal, or AFB cultures had a history of immunocompromise, penetrating inoculation, or failed primary treatment. Antibiotic exposure prior to culture-sample acquisition did not interfere with aerobic culture results from the site of infection. CONCLUSIONS: Our findings suggest that anaerobic, fungal, and AFB cultures should not be routinely performed during the initial evaluation of children with hematogenous musculoskeletal infection. These cultures should be performed for children with immunocompromise, clinical suspicion of penetrating inoculation, or failed primary treatment.

Functional outcomes in elderly patients with acetabular fractures treated with minimally invasive reduction and percutaneous fixation.

OBJECTIVES: To present the functional outcomes of elderly patients treated with percutaneous acetabular surgery and compare them with those treated with traditional open reduction and internal fixation in previously published series. DESIGN: Retrospective. SETTING: University level I trauma center. PATIENTS: All patients aged 60 and older treated with percutaneous screw fixation for acetabular fractures from 1994 to 2007 were included. Seventy-nine consecutive patients were identified. Thirty-six patients died before functional outcomes were obtained, leaving 43 patients and fractures in our study group. Functional outcomes were obtained in 35 of 43 (81.3%) patients at an average of 6.8 years after the index surgery. INTERVENTION: Minimally invasive reduction and percutaneous fixation of acetabular fractures. MAIN OUTCOME MEASUREMENT: Short musculoskeletal functional assessment and Harris Hip Score. RESULTS: One-year mortality was 13.9% (11 of 79). Average short musculoskeletal functional assessment dysfunction and bother indices were 23.3 and 21.3, respectively, in 24 patients who maintained their native hip. When compared with Short Musculoskeletal Functional Assessment data from 2 other series of patients treated with formal open reduction and internal fixation, no differences existed in the dysfunction (P = 0.49) or bother (P = 0.55) indices. Conversion to total hip arthroplasty occurred in 11 of 36 patients (30.6%). Average Harris Hip Scores in patients with their native hip was 77 (range, 33-100). In the 11 patients converted to total hip arthroplasty, average Short Musculoskeletal Functional Assessment dysfunction and bother indices were 24.3 and 23.9, respectively. No differences were found in the dysfunction (P = 0.93) or bother (P = 0.16) indices when compared with patients converted from open reduction and internal fixation to total hip arthroplasty. Average Harris Hip Score in patients converted to total hip arthroplasty was 83 (range, 68-92), and this was not significantly different from the best scores reported with acute total hip arthroplasty. CONCLUSIONS: Functional outcomes and rates of conversion to total hip arthroplasty of acetabular fractures in elderly patients treated with percutaneous reduction and fixation show no significant differences when compared with published series of patients treated with formal open reduction and internal fixation. LEVEL OF EVIDENCE: Therapeutic Level IV. See Instructions for Authors for a complete description of levels of evidence.

Elucidation of intracellular recycling pathways leading to exocytosis of the Fc receptor, FcRn, by using multifocal plane microscopy.

The intracellular events on the recycling pathway that lead from sorting endosomes to exocytosis at the plasma membrane are central to cellular function. However, despite intensive study, these processes are poorly characterized in spatial and dynamic terms. The primary reason for this is that, to date, it has not been possible to visualize rapidly moving intracellular compartments in three dimensions in cells. Here, we use a recently developed imaging setup in which multiple planes can be simultaneously imaged within the cell in conjunction with visualization of the plasma membrane plane by using total internal reflection fluorescence microscopy. This has allowed us to track and characterize intracellular events on the recycling pathway that lead to exocytosis of the MHC Class I-related receptor, FcRn. We observe both direct delivery of tubular and vesicular transport containers (TCs) from sorting endosomes to exocytic sites at the plasma membrane, and indirect pathways in which TCs that are not in proximity to sorting endosomes undergo exocytosis. TCs can also interact with different sorting endosomes before exocytosis. Our data provide insight into the intracellular events that precede exocytic fusion.