The hyporheic zone is the interface beneath and adjacent to streams and rivers where surface water and groundwater interact. The hyporheic zone presents unique conditions for reaction of solutes from ...both surface water and groundwater, including reactions which depend upon mixing of source waters. Some models assume that hyporheic zones are well‐mixed and conceptualize the hyporheic zone as a surface water‐groundwater mixing zone. But what are the controls on and effects of hyporheic mixing? What specific mechanisms cause the relatively large (>∼1 m) mixing zones suggested by subsurface solute measurements? In this commentary, we explore the various processes that might enhance mixing in the hyporheic zone relative to deeper groundwater, and pose the question whether the substantial mixing suggested by field studies may be due to the combination of fluctuating boundary conditions and multiscale physical and chemical spatial heterogeneity. We encourage investigation of hyporheic mixing using numerical modeling and laboratory experiments to ultimately inform field investigations.
Plain Language Summary
The hyporheic zone is the area beneath and adjacent to streams and rivers where surface water and groundwater interact. The hyporheic zone presents unique conditions for reaction of pollutants from both surface water and groundwater, including reactions which depend upon mixing of these different source waters. This type of mixing is not well understood, yet potentially important for pollutant mitigation in watersheds. In this commentary, we explore the various processes that might enhance mixing in the hyporheic zone relative to deeper groundwater, and pose the question whether the substantial mixing observed by field studies may be due to the combination of fluctuating boundary conditions and multi‐scale physical and chemical spatial heterogeneity. We encourage investigation of hyporheic mixing using numerical modeling and laboratory experiments to ultimately inform field investigations.
Key Points
Field studies show large hyporheic mixing zones
Current theory cannot explain large field mixing zones
Sediment heterogeneity and surface water dynamics may explain mixing
Capsular contracture remains a challenging complication of implant-based aesthetic breast surgery despite improvements in implant design. The lowering of capsular contracture rates noted with the ...past use of polyurethane foam-covered implants has increased awareness of the importance of the biologic response at the interface between the implant surface and breast tissue. Emerging evidence indicates that much like the polyurethane foam, acellular dermal matrices alter the biologic response at the surface interface, resulting in a more vascular and less constrictive pattern of collagen deposition. This study reports on the authors' clinical experience using Strattice Reconstructive Tissue Matrix (LifeCell Corporation, Branchburg, N.J.) for the treatment of capsular contracture in patients with established capsules and for prevention in patients undergoing primary augmentation or augmentation/mastopexy. Of 80 patients (154 breasts) in whom Strattice was used, clinically significant contracture (Baker grade III/IV) occurred in three breasts (3.75 percent), all of which were in the treatment of previous contracture group. In addition, the authors noted two seromas requiring implant removal (both patients developed capsules, as mentioned above) and two hematomas requiring revision, for an overall failure rate of 6.25 percent for Strattice-assisted surgery. The data confirm that the use of Strattice significantly lowers the incidence of capsular contracture in the first 3.5 years after implant placement.
This study evaluated patients who underwent primary breast surgery within a single group practice from 1994 to 2009. Reoperations were divided by reoperation reason into total reoperations and ...implant-specific reoperations. The authors hypothesized that the implant-specific reoperation rate will provide the most accurate measurement of complications caused by the breast implant device.
A total of 812 patients received the same brand of breast implant for primary breast augmentation or augmentation/mastopexy. Safety and efficacy data were recorded and complication rates were calculated. Statistics were applied using Kaplan-Meier estimated cumulative incidence calculations.
This study included 482 patients with saline and 330 patients with silicone implants. The most common complications included capsular contracture, rippling, rupture, infection, and hematoma. A total of 8.2 percent of patients developed Baker grade III/IV capsular contracture by 6 years. The raw incidence of rippling was 7.1 percent, and the rate was significantly increased in underweight patients with subglandular saline implants (p = 0.045). The rate of total reoperation at 1 year was 14.2 percent. While a significantly increased rate of total reoperation was seen for silicone compared with saline implants (p < 0.01), no difference was seen in the rate of implant-specific reoperation for saline compared to silicone implants (p = 0.582).
The use of total reoperation rates as an indication of complications of breast implants can lead to both an overestimation of implant-related complications and the inaccurate conclusion that silicone implants result in higher complication rates than saline implants. The implant-specific reoperation rate may provide a more accurate incidence of implant complications than the total reoperation rate, which includes reoperations for factors unrelated to the implant.
Common in-stream geomorphic structures such as debris dams and steps can drive hyporheic exchange in streams. Exchange is important for ecological stream function, and restoring function is a goal of ...many stream restoration projects, yet the connection between in-stream geomorphic form, hydrogeologic setting, and hyporheic exchange remains inadequately characterized. We used the models HEC-RAS, MODFLOW, and MODPATH to simulate coupled surface and subsurface hydraulics in a gaining stream containing a single in-stream geomorphic structure and to systematically evaluate the impact of fundamental characteristics of the structure and its hydrogeologic setting on induced exchange. We also conducted a field study to support model results. Model results indicated that structure size, background groundwater discharge rate, and sediment hydraulic conductivity are the most important factors determining the magnitude of induced hyporheic exchange, followed by geomorphic structure type, depth to bedrock, and channel slope. Model results indicated channel-spanning structures were more effective at driving hyporheic flow than were partially spanning structures, and weirs were more effective than were steps. Across most structure types, downwelling flux rate increased linearly with structure size, yet hyporheic residence time exhibited nonlinear behavior, increasing quickly with size at low structure sizes and declining thereafter. Important trends in model results were observed at the field site and also interpreted using simple hydraulic theory, thereby supporting the modeling approach and clarifying underlying processes.
Runoff from parking lots during summer storms injects surges of hot water into receiving water bodies. We present temperature data collected near urban storm sewer outfalls in Blacksburg, Virginia, ...using arrays of sensors in a stream and a stormwater pond. Surges occurred roughly a dozen times per month, ranging up to 8.1...C with average duration 2 h in the stream and up to 11.2...C with average duration 7 h in the pond. Surges were larger in the pond due to a larger contributing watershed, no dilution by upstream water, and cool background temperatures near the outfall. Surges began abruptly, warming at rates averaging 0.2...C/min for periods of 5-20 min. Surges dissipated as they propagated into the water bodies, travelling further in the stream (>19 m) than the pond (~10 m) consistent with greater advection in the stream. Surges were largest and most frequent in the afternoon but occurred at all times of day and night. Stream surges exhibited two phases: an early high-temperature low-volume input from the storm sewer and a later low-temperature high-volume input from upstream. Surges at the pond did not exhibit two phases, consistent with inputs only from storm sewers. Surges are likely common in urban areas, and may cumulatively have consequences for aquatic organisms, biogeochemical process rates, and even human health. Such effects may be compounded by urban heat islands and climate change, so prevention or mitigation should be considered. (ProQuest: ... denotes formulae/symbols omitted.)
Fanconi anemia is a recessively inherited disease that is characterized by congenital abnormalities, bone marrow failure, and a predisposition to develop cancer, particularly squamous cell carcinomas ...(SCCs) in the head and neck and anogenital regions. Previous studies of Fanconi anemia SCCs, mainly from US patients, revealed the presence of high-risk human papillomavirus (HPV) DNA in 21 (84%) of 25 tumors analyzed. We examined a panel of 21 SCCs mainly from European Fanconi anemia patients (n = 19 FA patients; 16 head and neck squamous cell carcinomas HNSCCs, 2 esophageal SCCs, and 3 anogenital SCCs) for their clinical and molecular characteristics, including patterns of allelic loss, TP53 mutations, and the presence of HPV DNA by GP5+/6+ polymerase chain reaction. HPV DNA was detected in only two (10%) of 21 tumors (both anogenital SCCs) but in none of the 16 HNSCCs. Of the 18 tumors analyzed, 10 contained a TP53 mutation. The patterns of allelic loss were comparable to those generally found in sporadic SCCs. Our data show that HPV does not play a major role in squamous cell carcinogenesis in this cohort of Fanconi anemia patients and that the Fanconi anemia SCCs are genetically similar to sporadic SCCs despite having a different etiology.
We report the outcomes of 20 patients (12 men, 8 women, 21 feet) with Charcot neuro-arthropathy who underwent correction of deformities of the ankle and hindfoot using retrograde intramedullary nail ...arthrodesis. The mean age of the patients was 62.6 years (46 to 83); their mean BMI was 32.7 (15 to 47) and their median American Society of Anaesthetists score was 3 (2 to 4). All presented with severe deformities and 15 had chronic ulceration. All were treated with reconstructive surgery and seven underwent simultaneous midfoot fusion using a bolt, locking plate or a combination of both. At a mean follow-up of 26 months (8 to 54), limb salvage was achieved in all patients and 12 patients (80%) with ulceration achieved healing and all but one patient regained independent mobilisation. There was failure of fixation with a broken nail requiring revision surgery in one patient. Migration of distal locking screws occurred only when standard screws had been used but not with hydroxyapatite-coated screws. The mean American Academy of Orthopaedic Surgeons Foot and Ankle (AAOS-FAO) score improved from 50.7 (17 to 88) to 65.2 (22 to 88), (p = 0.015). The mean Short Form (SF)-36 Health Survey Physical Component Score improved from 25.2 (16.4 to 42.8) to 29.8 (17.7 to 44.2), (p = 0.003) and the mean Euroqol EQ‑5D‑5L score improved from 0.63 (0.51 to 0.78) to 0.67 (0.57 to 0.84), (p = 0.012). Single-stage correction of deformity using an intramedullary hindfoot arthrodesis nail is a good form of treatment for patients with severe Charcot hindfoot deformity, ulceration and instability provided a multidisciplinary care plan is delivered.
Hereditary Hemorrhagic Telangiectasia (HHT) is a rare inherited disorder characterized by development of mucocutaneous telangiectases and visceral organ arteriovenous malformations, which can lead to ...recurrent, spontaneous bleeding and development of iron deficiency anemia. The primary objective of this study was to ascertain the relationship between epistaxis severity scores (ESS), laboratory values, genotype, and phenotype in HHT. Our secondary objective was to assess efficacy of systemic antifibrinolytic therapy in reducing ESS in HHT. We conducted a retrospective review of patients seen at the UNC HHT Center from January 1, 2009 to February 28, 2015. ESS, demographics, and results of genetic testing were abstracted from the medical record. Response to antifibrinolytic therapy was evaluated by comparing pre-post ESS. One hundred and forty nine patients were eligible with 116 having genetic testing and 33 without. Age, hemoglobin and ferritin levels were predictive of ESS. Of the 116 patients that underwent genetic testing: 63 had an ACVRL1 mutation, 40 had an ENG mutation, 2 had a SMAD4 mutation, and 11 patients had no pathologic HHT genetic variation detected. Compared to patients without a detectable HHT-associated genetic variation, patients with a HHT-associated genetic variation had higher ESS scores (p < 0.05). Neither ESS nor genotype was predictive of pulmonary or brain AVMs. Twenty-four HHT patients with ESS > 4 were started on antifibrinolytic therapy (tranexamic acid or aminocaproic acid) and had a post-treatment ESS recorded. All patients had a decrease in ESS of > 0.71 (minimal meaningful difference), but patients taking antifibrinolytics displayed larger decreases. No patients on antifibrinolytics experienced a VTE with median follow up of 13 months. We demonstrate that the ESS correlates with age, hemoglobin and ferritin. Additionally, we demonstrate that HHT patients with genetic mutations have higher ESS scores. Our data demonstrate that antifibrinolytics are effective in decreasing epistaxis severity and safe with long-term use in HHT patients.
As robotic-assisted surgery (RAS) expands to smaller centres, platforms are shared between specialities. Healthcare providers must consider case volume and mix required to maintain quality and ...cost-effectiveness. This can be informed, in-part, by the volume-outcome relationship. We perform a systematic review to describe the volume-outcome relationship in intra-abdominal robotic-assisted surgery to report on suggested minimum volumes standards. A literature search of Medline, NICE Evidence Search, Health Technology Assessment Database and Cochrane Library using the terms: “robot*”, “surgery”, “volume” and “outcome” was performed. The included procedures were gynecological: hysterectomy, urological: partial and radical nephrectomy, cystectomy, prostatectomy, and general surgical: colectomy, esophagectomy. Hospital and surgeon volume measures and all reported outcomes were analysed. 41 studies, including 983,149 procedures, met the inclusion criteria. Study quality was assessed using the Newcastle–Ottawa Quality Assessment Scale and the retrieved data was synthesised in a narrative review. Significant volume-outcome relationships were described in relation to key outcome measures, including operative time, complications, positive margins, lymph node yield and cost. Annual surgeon and hospital volume thresholds were described. We concluded that in centres with an annual volume of fewer than 10 cases of a given procedure, having multiple surgeons performing these procedures led to worse outcomes and, therefore, opportunities should be sought to perform other complimentary robotic procedures or undertake joint cases.
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