Uncertainty reduction in residual stress measurements by an optimised inverse solution using nonconsecutive polynomials

Many destructive methods for measuring residual stresses such as the slittingmethod require an inverse analysis to solve the problem. The accuracy of theresult as well as an uncertainty component (the model uncertainty) dependson the basis functions used in the inverse solution. The use of a series expan-sion as the basis functions for the inverse solution was analysed in a previouswork for the particular case where functions orders grew consecutively. Thepresent work presents a new estimation of the model uncertainty and a newimproved methodology to select the final basis functions for the case wherethe basis is composed of polynomials. Including nonconsecutive polynomialorders in the basis generates a larger space of possible solutions to be evaluatedand allows the possibility to include higher-order polynomials. The paperincludes a comparison with two other inverse analyses methodologies appliedto synthetically generated data. With the new methodology, the final error isreduced and the uncertainty estimation improved

Outcomes and Risk Score for Distal Pancreatectomy with Celiac Axis Resection (DP-CAR): An International Multicenter Analysis

Background: Distal pancreatectomy with celiac axis resection (DP-CAR) is a treatment option for selected patients with pancreatic cancer involving the celiac axis. A recent multicenter European study reported a 90-day mortality rate of 16%, highlighting the importance of patient selection. The authors constructed a risk score to predict 90-day mortality and assessed oncologic outcomes. Methods: This multicenter retrospective cohort study investigated patients undergoing DP-CAR at 20 European centers from 12 countries (model design 2000–2016) and three very-high-volume international centers in the United States and Japan (model validation 2004–2017). The area under receiver operator curve (AUC) and calibration plots were used for validation of the 90-day mortality risk model. Secondary outcomes included resection margin status, adjuvant therapy, and survival. Results: For 191 DP-CAR patients, the 90-day mortality rate was 5.5% (95 confidence interval [CI], 2.2–11%) at 5 high-volume (≥ 1 DP-CAR/year) and 18% (95 CI, 9–30%) at 18 low-volume DP-CAR centers (P = 0.015). A risk score with age, sex, body mass index (BMI), American Society of Anesthesiologists (ASA) score, multivisceral resection, open versus minimally invasive surgery, and low- versus high-volume center performed well in both the design and validation cohorts (AUC, 0.79 vs 0.74; P = 0.642). For 174 patients with pancreatic ductal adenocarcinoma, the R0 resection rate was 60%, neoadjuvant and adjuvant therapies were applied for respectively 69% and 67% of the patients, and the median overall survival period was 19 months (95 CI, 15–25 months). Conclusions: When performed for selected patients at high-volume centers, DP-CAR is associated with acceptable 90-day mortality and overall survival. The authors propose a 90-day mortality risk score to improve patient selection and outcomes, with DP-CAR volume as the dominant predictor

Incidence and risk factors for incisional hernia and recurrence: retrospective analysis of the French national database

International audiencePurposeTo determine the rate of incisional hernia (IH) repair and risk factors for IH repair after laparotomy.MethodsThis population‐based study used data extracted from the French (PMSI) database. All patients who had undergone a laparotomy in 2010, their hospital visits from 2010‒2015, and patients who underwent a first IH repair in 2013 were included. Risk factors identified previously included: age, gender, high blood pressure (HBP), obesity, diabetes and chronic obstructive pulmonary disease (COPD).ResultsAmong the 431 619 patients who underwent a laparotomy in 2010, 5% underwent IH repair between 2010 and 2015. A high‐risk list of the most frequent surgical procedures (>100) with a significant risk of IH repair (>10% at 5 years) was established including 71 863 patients (17%, 65 procedures). Overall IH repair rate from the list was 17%. Gastrointestinal (GI) surgery represented 89% of procedures with the majority of patients (72%) undergoing lower GI tract surgery. IH repair rate was 56% at 1 year and 79% at 2 years. Risk factors for IH repair included obesity (31% vs. 15%, p<0.001), COPD (20% vs. 15%), HBP (19% vs. 15%) and diabetes (19% vs. 16%). Even for recurrence after IH repair, obesity was the main risk factor (19% vs. 13%, p<0.001)ConclusionFrom the PMSI database, the real rate of IH repair after laparotomy was 5%, increasing to 17% after digestive surgery. Obesity was the main risk factor with an IH repair rate of 31% after digestive surgery. Because of the important medico‐economic consequences, prevention of IH after laparotomy in high‐risk patients should be considered

Uncertainty reduction in residual stress measurements by an optimised inverse solution using nonconsecutive polynomials

Many destructive methods for measuring residual stresses such as the slitting method require an inverse analysis to solve the problem. The accuracy of the result as well as an uncertainty component (the model uncertainty) depends on the basis functions used in the inverse solution. The use of a series expansion as the basis functions for the inverse solution was analysed in a previous work for the particular case where functions orders grew consecutively. The present work presents a new estimation of the model uncertainty and a new improved methodology to select the final basis functions for the case where the basis is composed of polynomials. Including nonconsecutive polynomial orders in the basis generates a larger space of possible solutions to be evaluated and allows the possibility to include higher-order polynomials. The paper includes a comparison with two other inverse analyses methodologies applied to synthetically generated data. With the new methodology, the final error is reduced and the uncertainty estimation improved

Hepatic venous pressure gradient after portal vein embolization: An accurate predictor of future liver remnant hypertrophy

[DOI:\hrefhttps://dx.doi.org/10.1016/j.surg.2018.03.01410.1016/j.surg.2018.03.014] [PubMed:\hrefhttps://www.ncbi.nlm.nih.gov/pubmed/2975346129753461]The impact of portal hemodynamic variations after portal vein embolization on liver regeneration remains unknown. We studied the correlation between the parameters of hepatic venous pressure measured before and after portal vein embolization and future hypertrophy of the liver remnant after portal vein embolization.\ Between 2014 and 2017, we reviewed patients who were eligible for major hepatectomy and who had portal vein embolization. Patients had undergone simultaneous measurement of portal venous pressure and hepatic venous pressure gradient before and after portal vein embolization by direct puncture of portal vein and inferior vena cava. We assessed these parameters to predict future liver remnant hypertrophy.\ Twenty-six patients were included. After portal vein embolization, median portal venous pressure (range) increased from 15 (9-24) to 19 (10-27) mm Hg and hepatic venous pressure gradient increased from 5 (0-12) to 8 (0-14) mm Hg. Median future liver remnant volume (range) was 513 (299-933) mL before portal vein embolization versus 724 (499-1279) mL 3 weeks after portal vein embolization, representing a 35% (7.4-83.6) median hypertrophy. Post-portal vein embolization hepatic venous pressure gradient was the most accurate parameter to predict failure of future liver remnant to reach a 30% hypertrophy (c-statistic: 0.882 [95% CI: 0.727-1.000], P < 0.001). A cut-off value of post-portal vein embolization hepatic venous pressure gradient of 8 mm Hg showed a sensitivity of 91% (95% CI: 57%-99%), specificity of 80% (95% CI: 52%-96%), positive predictive value of 77% (95% CI: 46%-95%) and negative predictive value of 92.3% (95% CI: 64.0%-99.8%). On multivariate analysis, post-portal vein embolization hepatic venous pressure gradient and previous chemotherapy were identified as predictors of impaired future liver remnant hypertrophy.\ Post-portal vein embolization hepatic venous pressure gradient is a simple and reproducible tool which accurately predicts future liver remnant hypertrophy after portal vein embolization and allows early detection of patients who may benefit from more aggressive procedures inducing future liver remnant hypertrophy. (Surgery 2018;143:1-2.)