A Conservative Numerical Method for the Cahn–Hilliard Equation with Generalized Mobilities on Curved Surfaces in Three-Dimensional Space

In this paper, we develop a conservative numerical method for the Cahn– Hilliard equation with generalized mobilities on curved surfaces in three-dimensional space. We use an unconditionally gradient stable nonlinear splitting numerical scheme and solve the resulting system of implicit discrete equations on a discrete narrow band domain by using a Jacobi-type iteration. For the domain boundary cells, we use the trilinear interpolation using the closest point method. The proposing numerical algorithm is computationally efficient because we can use the standard finite difference Laplacian scheme on three-dimensional Cartesian narrow band mesh instead of discrete Laplace–Beltrami operator on triangulated curved surfaces. In particular, we employ a mass conserving correction scheme, which enforces conservation of total mass. We perform numerical experiments on the various curved surfaces such as sphere, torus, bunny, cube, and cylinder to demonstrate the performance and effectiveness of the proposed method. We also present the dynamics of the CH equation with constant and space-dependent mobilities on the curved surfaces.     

Improving Outcomes in Hernia Repair by the Use of Light Meshes—A Comparison of Different Implant Constructions Based on a Critical Appraisal of the Literature

Background Despite convincing advantages offered by meshes, their use in hernia surgery remains controversial because of fears concerning the long-term effects of their implantation. To improve biocompatibility, a large variety of newly developed light meshes has been introduced to the market. This overview of the literature aimed to establish whether absolute material reduction (g per implanted mesh), use of absorbable components, and coating by inert materials are evidence-based ways to improve biocompatibility of meshes. Method A review of the current English and German language literature on the outcome of groin und incisional hernia mesh repair was performed. Both basic research and clinical trials were used as sources of data. Meta-analyses and randomized controlled trials were given priority and were referred to whenever possible. Results Operative technique was an independent prognostic factor for the clinical outcome. Mesh construction and composition as characterized by pore size and filament structure appeared to be more important determinants of foreign body reaction after implantation than absolute material reduction of 1 g or more per implant. No data exist about an oncogenic effect of alloplastic materials in humans, but disturbed fertility in animal studies remains an issue of concern and should be further investigated. Conclusions According to data from current randomized controlled trials and retrospective studies, light meshes seem to have some advantages with respect to postoperative pain and foreign body sensation. However, their use is associated with increased recurrence rates. Light meshes offer no advantages with respect to alleviating severe chronic groin pain. At the same time, experimental data reveal that material composition and mesh structure may significantly affect foreign body reaction.     

How Did the Number and Type of Injuries in Patients Presenting to a Regional Level I Trauma Center Change During the COVID-19 Pandemic with a Stay-at-home Order?

BackgroundDuring a pandemic, it is paramount to understand volume changes in Level I trauma so that with appropriate planning and reallocation of resources, these facilities can maintain and even improve life-saving capabilities. Evaluating nonaccidental and accidental trauma can highlight potential areas of improvement in societal behavior and hospital preparedness. These critical questions were proposed to better understand how healthcare leaders might adjust surgeon and team coverage of trauma services as well as prepare from a system standpoint what resources will be needed during a pandemic or similar crisis to maintain services.Questions/purposes(1) How did the total observed number of trauma activations, defined as patients who meet mechanism of injury requirements which trigger the notification and aggregation of the trauma team upon entering the emergency department, change during a pandemic and stay-at-home order? (2) How did the proportion of major mechanisms of traumatic injury change during this time period? (3) How did the proportion and absolute numbers of accidental versus nonaccidental traumatic injury in children and adults change during this time period?MethodsThis was a retrospective study of trauma activations at a Level I trauma center in New Orleans, LA, USA, using trauma registry data of all patients presenting to the trauma center from 2017 to 2020. The number of trauma activations during a government mandated coronavirus 2019 (COVID-19) stay-at-home order (from March 20, 2020 to May 14, 2020) was compared with the expected number of activations for the same time period from 2017 to 2019, called “predicted period”. The expected number (predicted period) was assumed based on the linear trend of trauma activations seen in the prior 3 years (2017 to 2019) for the same date range (March 20, 2020 to May 14, 2020). To define the total number of traumatic injuries, account for proportion changes, and evaluate fluctuation in accidental verses nonaccidental trauma, variables including type of traumatic injury (blunt, penetrating, and thermal), and mechanism of injury (gunshot wound, fall, knife wound, motor vehicle collision, assault, burns) were collected for each patient.ResultsThere were fewer total trauma activations during the stay-at-home period than during the predicted period (372 versus 532 [95% CI 77 to 122]; p = 0.016). The proportion of penetrating trauma among total activations was greater during the stay-at-home period than during the predicted period (35% [129 of 372] versus 26% [141 of 532]; p = 0.01), while the proportion of blunt trauma was lower during the stay-at-home period than during the predicted period (63 % [236 of 372] versus 71% [376 of 532]; p = 0.02). The proportion of gunshot wounds in relation to total activations was greater during the stay-at-home period than expected (26% [97 of 372] versus 18% [96 of 532]; p = 0.004). There were fewer motor vehicle collisions in relation to total activations during the stay-at-home period than expected (42% [156 of 372] versus 49% [263 of 532]; p = 0.03). Among total trauma activations, the stay-at-home period had a lower proportion of accidental injuries than the predicted period (55% [203 of 372] versus 61% [326 of 532]; p = 0.05), and there was a greater proportion of nonaccidental injuries than the predicted period (37% [137 of 372] versus 27% [143 of 532]; p < 0.001). In adults, the stay-at-home period had a greater proportion of nonaccidental injuries than the predicted period (38% [123 of 328] versus 26% [123 of 466]; p < 0.001). There was no difference between the stay-at-home period and predicted period in nonaccidental and accidental injuries among children.ConclusionData from the trauma registry at our region’s only Level I trauma center indicate that a stay-at-home order during the COVID-19 pandemic was associated with a 70% reduction in the number of traumatic injuries, and the types of injuries shifted from more accidental blunt trauma to more nonaccidental penetrating trauma. Non-accidental trauma, including gunshot wounds, increased during this period, which suggest community awareness, crisis de-escalation strategies, and programs need to be created to address violence in the community. Understanding these changes allows for adjustments in staffing schedules. Surgeons and trauma teams could allow for longer shifts between changeover, decreasing viral exposure because the volume of work would be lower. Understanding the shift in injury could also lead to a change in specialists covering call. With the often limited availability of orthopaedic trauma-trained surgeons who can perform life-saving pelvis and acetabular surgery, this data may be used to mitigate exposure of these surgeons during pandemic situations.Level of EvidenceLevel III, therapeutic study.     

When Should We Order a CT Scan and When Should We Rely on the Results to Diagnose an Acute Appendicitis?

OBJECTIVE: The objective of this study was to retrospectively analyze the last 100 consecutive emergency appendectomies performed in the authors' institution, which is a community-based teaching hospital, and look at the accuracy of the CT scan in the diagnosis of acute appendicitis. DESIGN: Retrospective clinical study. SETTING: A 600-bed community-based teaching hospital. METHODS: The last 100 consecutive emergency appendectomies, which were performed at New York Methodist Hospital in 2004, were retrospectively analyzed. The collected data included the demographics of the patients, relevant history, physical examination, laboratory and radiological tests, and pathology results. The statistical analyses were performed using the JMP version 3.2 software (SAS Institute Inc., Cary, North Carolina). An alpha value of 0.05 was used in all statistical analyses, and p values were considered as being statistically significant at or below the alpha value of 0.05. RESULTS: There was no statistically significant correlation between the acute appendicitis and some of the typical presenting symptoms and signs of acute appendicitis (rebound tenderness, low-grade fever, elevated white blood cell count, and anorexia). The sensitivity, specificity, positive predictive value, and negative predictive value of the CT scan in this retrospective analysis were 96%, 75%, 98.5%, and 50%, respectively, with an overall efficiency of 95%. However, the sensitivity, specificity, positive predictive value, and negative predictive value of the CT scan increased after reevaluation of the false-positive, false-negative, and inconclusive CT results by an experienced radiologist in a blind fashion (97%, 100%, 100%, and 71%, respectively). The correlation between the CT scan and the pathology result was statistically significant when the CT result was positive or negative (p = 0.0001). CONCLUSION: The CT scan is indicated when the clinical presentation is equivocal, and it will be helpful if the result is positive or interpreted as negative only by an experienced radiology attending.     

Evaluation of the possibility to assess bone age on the basis of DXA derived hand scans—preliminary results

The classical method of skeletal age assessment is based on the recognition of changes in the radiographic appearance of the maturity indicators in hand-wrist radiographs by comparison with a reference atlas. The purpose of this study was the evaluation of the possibility to assess bone age using a less invasive method such as dual-energy X-ray absorptiometry (DXA). Bone ages of 50 children free of any chronic diseases (5–18 years old) and ten with multihormonal pituitary deficiency (MPD) (8–20 years old) were assessed using an Expert-XL densitometer. Hand scans and classical hand-wrist radiographs were evaluated by two independent observers for bone age by visual comparison with reference standards of skeletal development published in the atlas. The precision errors of duplicate bone age ratings were low both for radiographs (<1%) and DXA hand scans (<0.9%). A high degree of agreement between bone age ratings done by two observers was assessed by intraclass correlation coefficients. The same bone age based on radiographs and DXA hand scans was assessed in 44 of 60 cases (73.3%); in 16 cases the differences between bone age were no higher than 0.5 year. No significant difference between mean bone age based on radiographs and DXA hand scans was observed (P>0.05). Moreover, there was a very strong correlation between bone age results (r=0.998; r ²=0.996; P<0.0001), indicating agreement of bone age assessments based on DXA and radiographic images. Remarkable differences (up to 3 years) between bone age and chronological age were observed in healthy subjects, probably reflecting the effect of the secular trend towards earlier maturation or alterations in pubertal development. The study indicates that evaluation of skeletal maturity using DXA images is less invasive (up to 8 µSv) than radiography, giving results comparable to the classical method.