An approach to evaluating and benchmarking the mechanical behavior of a surgical mesh prototype designed for the repair of abdominal wall defects.

Ventral hernia repair is a common surgical procedure in abdominal surgery in which surgical mesh has become an essential tool to improve outcomes. To avoid recurrences the mesh needs to mimic the mechanical behavior of the abdominal wall. In this scenario the mechanical properties at the interface between the mesh and its surrounding tissue is critical for the performance of the device and, therefore, the success after surgery. We aimed to characterize and compare the mechanical behavior of the patented prototype mesh Spider and four commercial meshes at the mesh-tissue interface. The prototype mesh was designed based on the hypothesis that the best performance for a large-sized defect in a ventral hernia is obtained when the mesh presents an isotropic behavior. In contrast, commercial meshes presented significant anisotropic behavior. Mechanical properties of the meshes were characterized through uniaxial tensile tests. Longitudinal and transverse axes were defined for each mesh, and samples were cut in each axis orientation. Samples underwent uniaxial tensile testing, from which the elastic modulus in each axis was determined. The degree of anisotropy was calculated as the ratio between the elastic modulus in each axis. An in silico model of the ventral hernia defect was designed to simulate the mesh-tissue interface behavior via finite element method. Meshes were modeled by an hyperelastic orthotropic constitutive model, which allowed isotropic symmetry as particular case for the prototype mesh. Abdominal wall was modeled using a Neo-Hookean model. Once the simulations were launched, mesh-tissue interface behavior was evaluated through the difference between Von Mises stress values on either size of the interface, both on the external and the internal face of the mesh and abdominal wall. Mechanical response was anisotropic for all commercial meshes and isotropic for the Spider prototype. Among commercial, Ultrapro® was highly anisotropic. Tests revealed Gore-Tex® to be the stiffest, followed by Repol Angimesh®, Spider and Ultrapro®; Duramesh™  was found to be the most compliant. Concerning mesh-tissue behavior, simulation results revealed the Spider prototype and Duramesh™  to be the best; Spider due to its uniformity and lower stress difference thanks to its nearly isotropic behavior, and Duramesh™  due to its compliant behavior. Our results suggest that the compromise between stiffness and anisotropy must be considered in order to improve the mechanical performance of the meshes, bearing in mind that for large-sized ventral defects, nearly isotropic mesh ensures better performance.

Necrotising fasciitis of the lower limb due to perforated inguinal hernia.

Acute inguinal hernia complications (incarceration, strangulation) are relatively frequent conditions, especially in the elderly. Urgent surgery is the appropriate treatment if manual reduction is not achieved or strangulation or perforation is suspected. We present a 77-year-old patient with necrotising fasciitis of the lower limb as a consequence of extraperitoneal perforation of a sliding inguinal hernia. This devastating condition was diagnosed 20 h after the manual reduction of the hernia. Suspicion arose at the physical examination (crepitation, signs of cellulitis) and clinical deterioration of the patient, and was confirmed by computed tomography (CT) scanning. Urgent surgery was performed, including sigmoidectomy, debridement of the necrotic tissues of the medial and anterior thigh compartment, and fasciectomy, combined with optimal intensive care support. No signs of peritoneal or pelvic involvement were found. However, the comorbidities, advanced age and the progression of the disease led to fatal outcome. Early recognition of the complications of strangulated hernias is of vital importance for successful treatment in these cases, even if no signs of acute abdomen are present.

[Three prognostic scales; clinical utility and prediction of intrahospital survival in alcoholic hepatitis]. / Utilidad clínica y predicciónde supervivencia intrahospitalaria de 3 escalas pronósticas en hepatitis alcohólica.

BACKGROUND: Alcoholic hepatitis is a serious clinical problem; opportune detection is transcendental for treatment and survival improvement. The aim of this study was to evaluate clinical utility of in-hospital mortality prediction of 3 alcoholic hepatitis scores and to assess survival prediction fitting them to the best cut-off points. MATERIAL AND METHODS: Retrospective, observational study. All patients with diagnosis of alcoholic hepatitis from January 2002 to January 2005 were included.Clinical and laboratory variables were analyzed for the different prognostic scores (MELD, GAHS and the Discriminate Function Maddrey's index) calculation. Evaluation of clinical utility scores was done with ROC curves and expressed by c-statistics. After fitting best cut-off points, survival prediction was assessed by Kaplan-Meier's method. RESULTS: Of 120 patients with alcoholic hepatitis, 48 fulfilled the admission criteria. The c-statistics of MELD was of 0.72, GAHS 0.75 and Maddrey's index 0.64. Survival analysis of the 3 prognostic scales showed statistical significance (log rank < 0.05) with the adjusted cut-off point to our population. CONCLUSION: The prediction of in hospital survival of GAHS, MELD and Maddrey's index after fitting best cut-off points are similar. The clinical utility for in-hospital mortality prediction of GAHS and MELD are superior to Maddrey's index in this Mexican cohort.

[MELD or Maddrey?: comparison of two prognosis models in patients with alcohol toxic hepatitis]. / ¿MELD o Maddrey?: comparación de 2 modelos pronóstico en pacientes con hepatitis tóxica por alcohol.

BACKGROUND: The toxic hepatitis is the most common manifestation of acute liver disease in patient with alcohol. In these patients the discriminatory function index (DFI) > 32, has been associated with a mortality rate of up to 50%. MELD is a scale that has been recently validated as independent risk factors for death in patients who are candidates for liver transplantation. OBJECTIVES: To compare the usefulness in mortality score vs. MELD. Maddrey index of discrimination in patients with alcoholic hepatitis and analyze the factors in a cohort Mexican prognosis. MATERIALS AND METHODS: We evaluated the usefulness of MELD, compared with the index of discrimination Maddrey so retrospective in 67 hospitalized patients with alcoholic hepatitis in the Hospital Juárez in Mexico. RESULTS: The c-statistic for mDFI was 0.69 (CI 0.56-0.82) and to MELD was 0.73 (CI 0.61-0.86), sensitivity and specificity of DFI > 32 in 7 days to predict mortality was 100 and 7.1% , Respectively, and to meld > 21 sensitivity was 96% and specificity of 9.5%. The presence of encephalopathy > grade 2 and creatinine > 1.5 mg/dL was independent predictors of mortality. CONCLUSIONS: MELD > 21 calculated on admission, is equally useful for the mDFI for predicting mortality in patients with alcoholic hepatitis in the first week.

Cluster analysis application to Class I malocclusion.

The purpose of this study was to obtain Class I malocclusion statistical subtypes by applying cluster analysis techniques, to assess clinical and cephalometric characteristics from different clusters, and to analyse sex and age effects on grouping patterns. Four-hundred-and-sixteen Spanish patients (243 females, 173 males) with Class I osseous and dental malocclusion (4 degrees > ANB > 0 degrees) between 8 and 16 years of age, with no previous orthodontic treatment, were analysed. Cluster analysis was applied to the information provided by 20 variables both clinical and cephalometric (Ricketts' analysis) per patient. The grouped individuals were defined in a statistically significant manner by a greater lower incisive proclination, greater lower labial protrusion, less dental crowding, and less pogonion-NB distance. So, only the protrusive traits were statistically expressed in the cluster analysis. The grouping pattern in Class I malocclusion was shown in a more defined form at younger age levels and disappeared with age. The clustering pattern was very similar in Class I malocclusion males and females.

Rapid streptococcal antigen detection in experimental keratitis.

We assessed the role of commercially available immunodiagnostic procedures in comparison to Gram stain and culture in experimental bacterial keratitis. Rabbit corneas were inoculated with Streptococcus pneumoniae, S. pyogenes, S. faecalis, or Haemophilus influenzae. Corneal scrapings were processed before and during antibacterial therapy using a coagglutination assay to detect pneumococcal capsular antigen (Phadebact Pneumococcus test) and an enzyme immunoassay to detect group A streptococcal cell-wall antigen (TestPack Strep A test). In untreated infected eyes, both immunoassays were highly specific and as sensitive as Gram stain for detection of the respective microorganisms. For S. pneumoniae keratitis, the sensitivity of coagglutination was 82% and Gram stain, 73%. For S. pyogenes keratitis, the sensitivity of enzyme immunoassay was 100% and Gram stain, 62%. Immunoassays and Gram stain were less sensitive than culture during antibacterial therapy. Successful clinical application of the coagglutination assay in a patient with pneumococcal keratitis permitted early use of specific cephalosporin treatment.

Comparison of acridine orange and Gram stains in bacterial keratitis.

We assessed the comparative sensitivities of acridine orange and Gram stains in the examination of corneal scrapings using an experimental model of Pseudomonas aeruginosa keratitis. Acridine orange was more sensitive than Gram stain, requiring concentrations of about 10(4) colony-forming units/mg of corneal tissue compared to approximately 10(5) colony-forming units/mg. Our clinical experience with 21 consecutive cases of suspected microbial keratitis showed a similar diagnostic accuracy of acridine orange and Gram stain. Acridine orange accurately predicted culture results in 15 of 21 specimens (71%) compared to a diagnostic accuracy of 62% (13 of 21 specimens) for Gram stain.