Implementation of a new constitutive model for abdominal muscles

BACKGROUND AND OBJECTIVE

Abdominal hernia repair is one of the most often performed surgical procedures worldwide. Numerical simulations of the abdominal wall mechanics can be a valuable tool to devise actions aimed at preventing hernia formation. A first step towards this goal is the development of consistent constitutive models for the tissues that form the human abdominal wall. In this study we propose, for each of the tissues involved, a new formulation of the so-called transversely isotropic hyperelastic model (TIHM).

METHODS

We propose a new TIHM for the human abdominal wall tissues and we present a systemic view of the methodology that we have implemented in the present study. First we consider the mathematical background of the TIHM. The novelty of our formulation is that both the isotropic and the fiber contributions to the strain energy function are characterized exclusively by polynomial convex functions of certain invariant quantities. Then, we provide a detailed description on how the constitutive model is implemented into an open source finite element (FE) software. In our approach we use the specific interface provided by the MFront software to incorporate our TIHM formulation into the Code Aster FE solver. For each of the tissues considered, the values of the TIHM constants are adjusted by means of a numerical simulation of previous experimental data from tensile tests.

RESULTS

We studied the following abdominal wall tissues: linea alba, rectus sheath, external oblique muscle, internal oblique muscle, transversus abdominis muscle and rectus abdominis muscle. Our formulation closely reproduces tensile test data for each tissue in the corresponding FE numerical simulation.

CONCLUSIONS

The new TIHM formulation is suitable for a future numerical investigation of the abdominal wall, which will in turn help us to assess the best zone to practice a colostomy. The methodology implemented in the present study can be easily extended in the future to develop and implement a TIHM for active muscles and/or a different type of constitutive model which might be suitable to characterize other tissues of biomedical interest.

Laparoscopic IPOM repair of an acquired abdominal intercostal hernia

Acquired abdominal intercostal hernia (AAIH) is an infrequent occurrence whereby intra-abdominal contents herniate into intercostal space directly from the peritoneal cavity through an acquired defect in the abdominal wall musculature and fascia. These hernias are difficult to diagnose and should always be suspected when a chest wall swelling occur after major or minor trauma. Surgical repair is warranted in symptomatic patients. The majority of AAIHs are repaired through an open approach using tension-free mesh, with significant recurrence risk. Recently, laparoscopic and robot-assisted repairs have been proposed. We discuss a 49-year-old man presented through outpatient setting with a 5-year history of ongoing left subcostal discomfort and a reducible lump. His history included a workplace accident 5 years ago. Contrast-enhanced abdominal CT confirmed AAIH with omentum herniation into the sac. A successful laparoscopic repair with intraperitoneal onlay mesh technique using composite mesh was performed.

[Cholelithiasis: complications and rehabilitation]

The results of laparoscopic cholecystectomy, conducted in 71 patients, suffering cholelithiasis, were analyzed. In early postoperative period an acute cholangitis have occurred in 2 (2.8%) patients, an acute pancreatitis--in 1 (1.4%), postoperative infiltrate--in 14(19.7%), suppuration of postoperative cicatrix--in 6 (8.4%); late compli- cations as a kind of postcholecystectomy syndrome was observed in 29 (40.8%) patients, and abdominal hernia--in 3 (4.2%).

Strangulated ileal trans-coloanal-anastomotic hernia: A complication of Altemeier’s procedure previously never reported

A postoperative complication after Altemeier operation, so far never reported, is described in a 42 years old mentally disabled patient with external full thickness rectal prolapse who usually had prolonged straining at defecation. After 6 d from perineal rectosigmoidectomy, the patient, was discharged free of complications. Four days later he was readmitted in emergency for strangulated perineal trans-anastomotic ileal hernia that occurred at home during efforts to defecate. The clinical feature required an emergency operation for repositioning the ileal loops into the abdomen, resection of the necrotic ileum, and end colostomy. The outcome of the second operation was free of complication and the patient was discharged on the 6^th postoperative day. In conclusion, after Altemeier operation prolonged straining at defecation should be carefully avoided

Double-mesh technique for correction of abdominal hernia following mammary reconstruction carried out with bipedicled TRAM flap and the primary closing of the donor area by using a single polypropylene mesh

BACKGROUND

Mammary reconstruction by using the transverse myocutaneous flap of the abdominal straight muscle (TRAM) is still an option well accepted in many parts of the world. However, bipedicled TRAM flaps are associated with greater morbidity of the abdominal donor area. The aim of this study was to describe an efficient technique for correcting the delayed defects of the abdominal wall following mammary reconstruction carried out with bipedicled TRAM flaps by using two polypropylene prostheses overlapped in different anatomical planes.

METHODS

At Hospital Estadual Sumaré at Universidade Estadual de Campinas, 18 women who underwent unilateral mammary reconstruction with bipedicled TRAM flaps and immediate fixation of two rectangular flaps of polypropylene mesh on the donor area were assessed. Later on, three patients (16.7%) presented with deformity of the anterolateral abdominal wall in the donor area. Each of these herniations was corrected by fixing two polypropylene meshes in different anatomical planes: the first mesh, which was bigger and preperitoneal, was fixed from the costal borders until the pubis; the second mesh was fixed from the external oblique muscle to the contralateral external oblique muscle, remaking the median line.

RESULTS

All patients were followed up for at least 18 months, without any signs of relapse, abdominal asymmetry, or chronic pain and with satisfactory functional results.

CONCLUSION

The correction of delayed deformities of the abdominal wall after mammary reconstruction with bipedicled TRAM flaps using double mesh was carried out in an effective and secure way, providing an interesting surgical option for mastologists and plastic and general surgeons.

[The surgical treatment of the incarcerated hernia]

The treatment results of 1540 patients with the incarcerated hernias of various localization were analyzed. It was revealed, that treatment results depend not only of the patient's age and concomitant diseases and operating time but the choice of surgical access and the type of intestinal anastomosis. The main postoperative negative factor proved to be the increase of the intraabdominal pressure, which severely impairs the lung ventilation. The factor can be excluded by using the prosthetic methods of hernioplasty, though.

[Comparative assessment of national and foreign endoprostheses for hernioplasty]

The used foreign endoprostheses have redundant strength, and great number and stiffness of implanted material might be a cause of complications and result in patients' discomfort associated with decreased mobility of the anterior abdominal wall. Less material consumption of endoprostheses results in increased porosity and less thickness facilitating rapid integration of the grid into the elastic and strong connective tissue scar. Company "Lintex" has developed and produced endoprostheses from polypropylene and polyvinylenfluoride monothreads in heavy, standard and light version, which allows their choice with a glance to the particular surgical situation.

A comparative biomechanical evaluation of hernia mesh fixation by fibrin sealant

BACKGROUND

The atraumatic fixation of meshes by fibrin sealant (FS) has been established for both open and laparoscopic techniques of hernia repair. This study was performed to evaluate the use of FS in hernia mesh fixation with different polymerization speed (thrombin concentrations), using commercial hernia meshes, and in two techniques, transabdominal preperitoneal mesh placement (TAPP) and intraperitoneal mesh placement (IPOM).

MATERIALS AND METHODS

A median laparotomy was performed in a pig model and hernia meshes were placed in IPOM and TAPP techniques. After mesh fixation with FS using thrombin concentrations of 4 and 500 IU/mL, maximum shear force before failure was measured at 5, 60, and 120 min.

RESULTS

At both thrombin concentrations and in all meshes in which the technique was used, the TAPP method tended to show higher maximum force levels at failure than did the IPOM method. In both TAPP and IPOM techniques and in all meshes, the 4 IU/mL thrombin concentration FS was superior to the 500 IU/mL thrombin concentration sealant.

CONCLUSIONS

Although both thrombin concentrations are suitable for mesh fixation, lower concentrations allow slower polymerization and better sealant diffusion leading to higher maximum force levels at failure. The TAPP method was biomechanically superior to the IPOM method. There were no major differences between mesh products.

Effect of Straining on the Lower Esophageal Sphincter: Identification of the “Straining-Esophageal Reflex” and Its Role in Gastroesophageal Competence Mechanism

The lower esophagus is intra-abdominal and exposed to intra-abdominal pressure (IAP) variations that may lead to gastroesophageal reflux (GER). We investigated the hypothesis that the lower esophageal sphincter (LES) undergoes phasic contraction on IAP increase, with a resulting inhibition of the stress GER. The study comprised 17 subjects (age 42.3 +/- 8.7 SD yr, 10 men, 7 women) who were scheduled for surgical repair of abdominal hernia. The patients had no swallowing problems. The electromyographic (EMG) activity of the LES and pressure within the LES were recorded at rest and during increased IAP (coughing, straining). The recording was repeated after LES anesthetization or saline infiltration. The LES EMG at rest showed regular slow waves (SWs), superimposed on or followed by random action potentials (APs). Coughing or straining induced increase of the SWs parameters and also of the APs; although the increase with straining was less than with coughing, the difference was insignificant. Coughing or straining increased the LES pressure significantly (p < .05, p < .05, respectively). Ten minutes after LES anesthetization, coughing or straining did not produce significant LES EMG or pressure changes, while saline infiltration of LES caused LES response similar to preinjection. Thus, coughing and straining effected an increase of the LES EMG activity and pressure, an action presumably mediated through a reflex that we call the "straining-esophageal reflex." This reflex seems to be evoked during increased intra-abdominal pressure and to effect LES contraction, thus, sharing with other factors in prevention of gastroesophageal reflux.

[Origin of abdominal herniae--anatomical aspects]

Based on anatomical background authors review the current knowledge on mechanisms and anatomical predisposes causing abdominal herniations. They are giving a brief summary of limitations of potential spaces involved into dislocation of abdominal visceral through natural spaces. Authors try to join anatomical knowledge with clinical information what might be useful in understanding of the patomechanism of these surgical disorders.

Internal herniation as a major cause of intestinal obstruction

OBJECTIVES

To evaluate internal herniation as a rare cause of intestinal obstruction.

MATERIALS AND METHODS

Files of 18 cases, operated due to internal herniation between 2000 and 2006 at Selcuk University, Meram School of Medicine, General Surgery Department, were reviewed retrospectively. Sixteen patients (88.8%) were male (mean age: 58.2 years; range: 42-67) and 2 were female (mean age: 56.5 years; range: 52-61).Cases were grouped according to the location of internal herniation, and the clinical findings and applied treatment strategies were evaluated.

RESULTS

All patients were taken into surgical operation after preoperative preparations were completed. Findings were as follows: 6 cases of paraduodenal internal herniation, 4 of internal herniation through a defect in the terminal mesoileum, 2 of herniation through a defect in the falciform ligament, 2 of herniation through a defect in the omentum majus, 1 of herniation to the recessus over the bladder, 2 of herniation through a defect in the transverse mesocolon and 1 iatrogenically caused internal herniation through a defect in the mesojejunum.

CONCLUSION

In an adult patient with findings of intestinal obstruction, diagnosis is difficult. Most cases presented to date are incidental findings during laparotomy, and surgical treatment is necessary.

Bursting strength evaluation in an experimental model of incisional hernia

Incisional hernias occur in up to 11 per cent of patients undergoing abdominal surgery. Up to 50 per cent of these patients with hernias will require repeat operative procedures. Management of these hernias have focused primarily on tensile strength of the mesh material, have not addressed currently used materials, and have not compared the strength of these repairs with each other. Forty-nine adult Sprague-Dawley rats had an incisional hernia created by removing a portion of their abdominal wall that was then repaired primarily, using either a composite mesh, Dual mesh (Gore-Tex), or polypropylene mesh. Six weeks after the repair, the rats were euthanized. Hydrostatic distension of the abdominal cavity was performed to compare bursting strength of each repair. Wound tensile strength was assessed and compared. Tissue samples were also taken to compare repair types for incorporation of prosthetic materials. The gross weight of the animals subjected to hydrostatic distention was equivalent between groups, as was the volume required prior to failure of the repair. There was a trend toward improved tensile strength of the Prolene mesh repair, which had a lower average inflammatory and fibrosis score on histology. Overall, the type of mesh used for repair does not seem to impact significantly the strength of the repair when assessed 6 weeks postoperatively. Choice of prosthetic material to repair the hernia should be made based on economics and handling characteristics alone. Prolene mesh has satisfactory strength with the least amount of inflammation and fibrosis.

Internal hernia through the broad ligament presenting with acute on chronic intestinal obstruction: A case report

BACKGROUND

Internal hernias are rare. Their occurrence through the broad ligament is one of the rarest forms. We present a report of a 45 year Nigerian female with acute on chronic intestinal obstruction due to an internal hernia of the broad ligament.

METHODS

Patients case notes and a review of relevant literature using manual library and Medline search was used.

RESULTS

A 45-year-old multiparous woman presented with a ten-year history of features of partial intestinal obstruction, and no previous abdominal surgery. Examination revealed right iliac fossa tenderness and a plain abdominal radiograph showed air fluid levels. Conservative management was not successful and laparatomy confirmed an internal hernia of the right broad ligament which was repaired with satisfactory outcome.

CONCLUSION

This report is to highlight the fact that though rare, internal hernia should be considered in the differential diagnosis of intestinal obstruction.

Incarcerated Spigelian hernia: a case report

BACKGROUND

Spigelian hernia is a rare partial abdominal wall defect in the transversus abdominus aponeurosis or Spigelian fascia. We here report the case of a patient with incarcerated greater omentum in a Spigelian hernia.

CASE REPORT

The patient presented with a six-hour history of nausea, constant abdominal pain, and a palpable mass in the left lower quadrant. Abdominal computed tomography revealed that omentum was strangulated in a Spigelian hernia that was successfully treated by plug and mesh repair. No recurrence has been observed during three-year follow-up.

CONCLUSIONS

In our case, plug and mesh repair was a safe and effective method of repairing an incarcerated Spigelian hernia with durability through three years of follow-up.

Late sigmoid colon internal herniation into the jejuno-jejunostomy mesenteric defect after laparoscopic Roux-en-Y gastric bypass

A 49-year-old female with morbid obesity (BMI 42) underwent laparoscopic Roux-en-Y gastric bypass (LRYGBP). 10 months after the operation, she presented to the hospital with intermittent mid-abdominal pain. An internal hernia of the sigmoid colon through a mesenteric defect of the jejuno-jejunostomy was found. Although small bowel internal herniation has been widely documented, the finding of large bowel internal herniation has not been previously reported. Maintaining a high index of suspicion and a low threshold for urgent intervention are required when evaluating patients with vague abdominal complaints after LRYGBP.

Smoking is a risk factor for incisional hernia

HYPOTHESIS

A number of risk factors for incisional hernia have been identified, but the pathogenesis remains unclear. Based on previous findings of smoking as a risk factor for wound complications and recurrence of groin hernia, we studied whether smoking is associated with incisional hernia.

DESIGN

Cohort study. Clinical follow-up study for incisional hernia 33 to 57 months following laparotomy for gastrointestinal disease. Variables predictive for incisional hernia were assessed by multiple regression analysis.

SETTING

Department of Surgery, Bispebjerg Hospital, University of Copenhagen, Copenhagen, Denmark.

PATIENTS

All 916 patients undergoing laparotomy from 1997 through 1998. Surgeons performed clinical examination in 310 patients; patients who failed to meet for examination, died, or were lost to follow-up were excluded.

MAIN OUTCOME MEASURES

Thirty-four variables related to patient history, preoperative clinical condition, operative severity and findings, and the surgeon's training.

RESULTS

The incidence of incisional hernia was 26% (81/310). Smokers had a 4-fold higher risk of incisional hernia (odds ratio [OR], 3.93 [95% confidence interval (CI), 1.82-8.49]) independent of other risk factors and confounders. Relaparotomy was the strongest factor associated with hernia (OR, 5.89 [95% CI, 1.78-19.48]). Other risk factors were postoperative wound complications (OR, 3.91 [95% CI, 1.99-7.66]), age (OR, 1.04 [95% CI, 1.02-1.06]), and male sex (OR, 2.17 [95% CI, 1.21-3.91]).

CONCLUSION

Smoking is a significant risk factor for incisional hernia in line with relaparotomy, postoperative wound complications, older age, and male sex.

Hernia surgery in the South American woodlands: A surgical adventure in Argentina

BACKGROUND

Because of the socioeconomic conditions existing today in Argentina, I decided to operate on hernias and incisional hernias among the poorest population in their living environment.

METHODS

To achieve this, I organized a group of 19 people, including resident surgeons and technicians, transferring everything in order to set up three surgical rooms in an old house, in the worst surgical environment, in the middle of the woodlands in the northeast tropical part of our country. It was like war-trench surgery but in peacetime. We successfully operated on 83 cases with different techniques in 4 days, in a trip that lasted a week.

RESULTS

After 18 months, there is not even one complication or recurrence.

CONCLUSIONS

Because of this experience, I must remark that the patients' immunity-cicatricial condition is essential to success.