Global rates and patterns of channel migration in river deltas.

River deltas are dynamic systems whose channels can widen, narrow, migrate, avulse, and bifurcate to form new channel networks through time. With hundreds of millions of people living on these globally ubiquitous systems, it is critically important to understand and predict how delta channel networks will evolve over time. Although much work has been done to understand drivers of channel migration on the individual channel scale, a global-scale analysis of the current state of delta morphological change has not been attempted. In this study, we present a methodology for the automatic extraction of channel migration vectors from remotely sensed imagery by combining deep learning and principles from particle image velocimetry (PIV). This methodology is implemented on 48 river delta systems to create a global dataset of decadal-scale delta channel migration. By comparing delta channel migration distributions with a variety of known external forcings, we find that global patterns of channel migration can largely be reconciled with the level of fluvial forcing acting on the delta, sediment flux magnitude, and frequency of flood events. An understanding of modern rates and patterns of channel migration in river deltas is critical for successfully predicting future changes to delta systems and for informing decision makers striving for deltaic resilience.

Application of Circumferential Compression Device (Binder) in Pelvic Injuries: Room for Improvement.

INTRODUCTION: The use of a noninvasive pelvic circumferential compression device (PCCD) to achieve pelvic stabilization by both decreasing pelvic volume and limiting inter-fragmentary motion has become commonplace, and is a well-established component of Advanced Trauma Life Support (ATLS) protocol in the treatment of pelvic ring injuries. The purpose of this study was to evaluate the following: 1) how consistently a PCCD was placed on patients who arrived at our hospital with unstable pelvic ring injuries; 2) if they were placed in a timely manner; and 3) if hemodynamic instability influenced their use. METHODS: We performed an institutional review board-approved retrospective study on 112 consecutive unstable pelvic ring injuries, managed over a two-year period at our Level I trauma center. Our hospital electronic medical records were used to review EMT, physician, nurses', operative notes and radiographic images, to obtain information on the injury and PCCD application. The injuries were classified by an orthopaedic trauma surgeon and a senior orthopaedic resident. Proper application of a pelvic binder using a sheet is demonstrated. RESULTS: Only 47% of unstable pelvic fractures received PCCD placement, despite being the standard of care according to ATLS. Lateral compression mechanism pelvic injuries received PCCDs in 33% of cases, while anterior posterior compression (APC) and vertical shear (VS) injuries had applications in 63% of cases. Most of these PCCD devices were applied after imaging (72%). Hemodynamic instability did not influence PCCD application. CONCLUSION: PCCD placement was missed in many (37%) of APC and VS mechanism injuries, where their application could have been critical to providing stability. Furthermore, to provide rapid stability, pelvic circumferential compression devices should be applied after secondary examination, rather than after receiving imaging results. Better education on timing and technique of PCCD placement at our institution is required to improve treatment of pelvic ring injuries.

Effect of Pelvic Binder Placement on OTA Classification of Pelvic Ring Injuries Using Computed Tomography. Does It Mask the Injury?

OBJECTIVES: To assess the diagnostic sensitivity of computed tomography (CT) in patients with an unstable pelvic ring injury after application of a pelvic binder. DESIGN: An institutional review board approved retrospective study from 2003 to 2010. SETTING: Level 1 trauma center. PATIENTS: Inclusion criteria were patients in our trauma database with AO/OTA B or C type pelvic ring injury, which first had an anterior-posterior pelvic x-ray followed by application of a pelvic circumferential compression device (PCCD), then a CT, and a fluoroscopic stress examination under anesthesia (FEUA) (used as gold standard). Of 867 patients, 43 met the inclusion criteria. INTERVENTION: A senior Orthopaedic Resident and Trauma Attendings assessed x-rays, CTs, and FEUAs. Binomial test was used to compare imaging against final diagnosis. RESULTS: In Anterior Posterior Compression/Vertical Shear (OTA 61-B1, 61-B3.1, 61-C) injury patterns, prebinder x-rays were diagnostic in 69.4% (CI, 51.9%-83.7%) of cases, compared with 50% (CI, 32.9%-67.1%) with CT + PCCD. The x-ray was superior to CT + PCCD for identification of the anterior pelvic injury (McNemar exact P = 0.0352). If x-ray and CT + PCCD were viewed in tandem, 83.3% (CI, 67.2%-93.6%) of classifications were in agreement with the FEUA. For lateral compression mechanisms, the binder did not effect of the sensitivity of the CT except in the open book component of an lateral compression 3 (61-B3.2) mechanism. CONCLUSIONS: The placement of a pelvic binder has the potential to mask the severity of unstable pelvic ring injuries when relying only on CT for diagnosis. Fluoroscopic manual pelvic stress examination under anesthesia is an essential adjunct when a binder is placed before imaging. LEVEL OF EVIDENCE: Diagnostic level III. See Instructions for Authors for a complete description of levels of evidence.

Mid-Pleistocene climate transition drives net mass loss from rapidly uplifting St. Elias Mountains, Alaska.

Erosion, sediment production, and routing on a tectonically active continental margin reflect both tectonic and climatic processes; partitioning the relative importance of these processes remains controversial. Gulf of Alaska contains a preserved sedimentary record of the Yakutat Terrane collision with North America. Because tectonic convergence in the coastal St. Elias orogen has been roughly constant for 6 My, variations in its eroded sediments preserved in the offshore Surveyor Fan constrain a budget of tectonic material influx, erosion, and sediment output. Seismically imaged sediment volumes calibrated with chronologies derived from Integrated Ocean Drilling Program boreholes show that erosion accelerated in response to Northern Hemisphere glacial intensification (∼ 2.7 Ma) and that the 900-km-long Surveyor Channel inception appears to correlate with this event. However, tectonic influx exceeded integrated sediment efflux over the interval 2.8-1.2 Ma. Volumetric erosion accelerated following the onset of quasi-periodic (∼ 100-ky) glacial cycles in the mid-Pleistocene climate transition (1.2-0.7 Ma). Since then, erosion and transport of material out of the orogen has outpaced tectonic influx by 50-80%. Such a rapid net mass loss explains apparent increases in exhumation rates inferred onshore from exposure dates and mapped out-of-sequence fault patterns. The 1.2-My mass budget imbalance must relax back toward equilibrium in balance with tectonic influx over the timescale of orogenic wedge response (millions of years). The St. Elias Range provides a key example of how active orogenic systems respond to transient mass fluxes, and of the possible influence of climate-driven erosive processes that diverge from equilibrium on the million-year scale.

Sentinel lymph node biopsy in contralateral prophylactic mastectomy: are we overtreating? Experience at a tertiary care hospital.

OBJECTIVE: Use of routine sentinel lymph node biopsy (SLNB) in contralateral prophylactic mastectomy (CPM) is controversial. This retrospective study was undertaken to determine the frequency of SLNB in CPM at a community hospital and its utility as a guide to patient decision making. METHODS: Between 2007 and 2009, 170 patients underwent CPM at a suburban, tertiary care facility. The CPM was either immediate or delayed, or was for ipsilateral recurrent breast cancer. Thirty-seven (21.8%) of 170 patients had SLNB performed with CPM. The mastectomy specimens underwent standard pathologic evaluation by using intraoperative touch preparation cytology and postoperative hematoxylin and eosin staining and immunohistochemistry. RESULTS: No patients who underwent SLNB had positive nodes on touch preparation or final hematoxylin and eosin staining (0/37 [0%]). Fourteen (8.2%) of 37 patients had additional nodes identified in the specimens. These were either axillary tail or intramammary nodes. The median number of SLNs removed was 2 (range, 1-5), none of these were positive. There were 3 incidental cancers diagnosed on final pathology. Two invasive cancers (T1a and grade I) and 1 ductal carcinoma in situ were identified. SLNB was only performed on the patient with DCIS. Neither SLNB nor subsequent axillary lymph node dissection was performed in the invasive cancers. CONCLUSIONS: SLNB was performed in 37 (21.8%) of patients who underwent CPM in a community hospital. Only 3 (1.76%) of 170 patients who underwent CPM had findings on final pathology that would have justified axillary staging. This correlates with other published data regarding SLNB in CPM. Because SLNB is associated with significant morbidity, guidelines for SLNB in prophylactic mastectomy need to be established so to avoid overtreatment.