The biology of hernias and the abdominal wall

Animal model of chronic abdominal hernia in rabbit

PURPOSE

To create a feasible animal model of hernia that should be reliable to test the different types of mesh and/or surgical technique.

METHODS

Thirty six male New Zealand albino rabbits were submitted to surgical procedure to provoke a standard hole in the abdominal wall. A metallic frame measuring 3 cm length and 1 cm width was allocated longitudinally on the umbilicus scar and the comprehensive three squared centimeters area was resected. A continuous 4.0 polyamide was performed to closure the subcutaneous and skin.

RESULTS

During three weeks a score of signals/symptoms was performed to evaluate the wound and clinical conditions. No death or severe complications occurred. In the 3rd week the hernia ring and visceral adhesions were evaluated. Soft omental adherences were present in the hernial sac in all animals. The area of hernia ring ranged from 32.1+/-5.5 to 35.6+/-3.1 squared centimeter and the maximum was 39 cm(2) and the minimum was 30 cm(2). The model results in protrusion which was similar to a human incisional hernia with hernia sac, visceral adhesions and fibrous healing ring.

CONCLUSION

The model was more reliable to test further techniques or mesh on hernia repair.

Incisional ventral hernias: review of the literature and recommendations regarding the grading and technique of repair

Despite advances in surgical technique and prosthetic technologies, the risks for recurrence and infection are high following the repair of incisional ventral hernias. High-quality data suggest that all ventral hernia repairs should be reinforced with prosthetic repair materials. The current standard for reinforced hernia repair is synthetic mesh, which can reduce the risk for recurrence in many patients. However, permanent synthetic mesh can pose a serious clinical problem in the setting of infection. Assessing patients' risk for wound infection and other surgical-site occurrences, therefore, is an outstanding need. To our knowledge, there currently exists no consensus in the literature regarding the accurate assessment of risk of surgical-site occurrences in association with or the appropriate techniques for the repair of incisional ventral hernias. This article proposes a novel hernia grading system based on risk factor characteristics of the patient and the wound. Using this system, surgeons may better assess each patient's risk for surgical-site occurrences and thereby select the appropriate surgical technique, repair material, and overall clinical approach for the patient. A generalized approach and technical considerations for the repair of incisional ventral hernias are outlined, including the appropriate use of component separation and the growing role of biologic repair materials.

Fibroplasia after polypropylene mesh implantation for abdominal wall hernia repair in rats

PURPOSE

This study assessed the collagen deposition and correlated it with local inflammatory responses to evaluate the length of time required for fibroplasia when polypropylene meshes are used to repair incisional abdominal wall hernias in rats.

METHODS

Thirty-six male Wistar rats underwent longitudinal resection of a peritoneal and musculoaponeurotic tissue segment (3x2 cm) of the abdominal wall followed by defect reconstruction with polypropylene mesh bridging over aponeurosis. The animals were divided into 6 groups according to the time points for the analysis of fibroplasia: 1, 2, 3, 7, 21 and 30 days post-implantation. Animals were sacrificed at each time point, and the site where the polypropylene mesh was implanted was evaluated histologically to assess inflammatory response and percentage of collagen using computer-assisted videomorphometry.

RESULTS

Total collagen was found at the mesh site on the 3rd day post-implantation, and increased progressively on all subsequent days up to the 21st day, when it reached its highest percentage (p<0.001). Type III collagen increased progressively from the 3rd to the 21st days, when it reached its highest percentage (p<0.001); on the 30th day, it decreased significantly (p>0.001). Type I collagen was first found between the 7th and 21st days; it reached its highest percentage on the 21st day and then remained stable until the 30th day. The type I to type III collagen ratio increased significantly and progressively up to the 30th day (p<0.001). Neutrophils were found at the mesh site from the 1st to the 21st day post-implantation. Macrophages, giant cells and lymphocytes were seen on the 2nd day. Thirty days after mesh implantation, neutrophils disappeared, but the percentages of macrophages, giant cells and lymphocytes remained stable (p<0.001).

CONCLUSIONS

This study showed that total collagen was first seen on the 3rd day post-implantation, with a higher percentage of type I collagen at the last observational time point. The prolonged healing inflammatory response and the persistence of chronic inflammation surrounding to the mesh did not affect the length of time required for fibroplasia.

Looking past the lump: genetic aspects of inguinal hernia in children

Inguinal hernia is associated with a multitude of genetic syndromes. Disorders of the microfibril, elastin, collagen, and the glycosaminoglycan component of the extracellular matrix can result in an increase in the likelihood of inguinal hernia. In addition, inguinal hernia may be the presenting feature of disorders of sexual differentiation. Inguinal hernia of unknown etiology also occurs more commonly in several other groups of genetic diseases including chromosomal disorders, microdeletion disorders such as 22q11.2 microdeletion, and in single gene disorders. We review the genetics of connective tissue formation and focus on a series of genetic conditions that may present with or are characterized by a higher risk of inguinal hernia. A comprehensive review of the literature aims to provide a diagnostic framework to aid in the identification of patients with inguinal hernia as part of underlying genetic disease.

Primary mesh augmentation with fibrin glue for abdominal wall closure--investigations on a biomechanical model

BACKGROUND

The occurrence of incisional hernias after various types of abdominal procedures and incisions continues to be a problem. A number of studies conducted for diverse risk groups have identified a beneficial role for the prophylactic use of mesh augmentation. To what extent this affects the stability of a suture was tested in our biomechanical model.

MATERIALS AND METHODS

To that effect, we compared three groups, carrying out six measurements in each case: (1) single suture in a muscle specimen, (2) suture and additional reinforcement with fibrin glue, and (3) suture and additional reinforcement with a mesh fixed with fibrin glue (Tissucol, Tisseel; with an overlap of 2 cm to all sides).

RESULTS

The single suture conferred a tensile strength, which in our model, was just above the prescribed maximum abdominal pressure of 32 N (37.3 N). The additional use of fibrin glue did not have any significant impact on this result (41.8 N). Only through mesh augmentation with fibrin glue was it possible to achieve a significantly greater tensile strength (64.5 N, p = 0.003).

CONCLUSIONS

The prophylactic use of meshes for stabilization of laparotomy closures appears to be effective. Adequate mesh fixation can be achieved with fibrin glue alone. Further experimental studies and in particular randomized clinical trials are needed to demonstrate proof of the long-term advantages of mesh augmentation in risk groups.

Mesh repair of common abdominal hernias: a review on experimental and clinical studies

Results on hernia surgery from numerous centers confirm that tensionless repair with various meshes reduces the complication rates and the frequency of recurrences. Some evidence on incisional hernias suggests, however, that the use of mesh seems to transfer the onset of recurrences by several years. Persistent pain and other discomfort is also an unpleasant complication of otherwise successful surgery in a number of patients. Thus, improved, slowly degrading, mesh materials, with strong connective tissue-inducing action, might be more optimal for hernia surgery. Accumulating evidence also suggests that recurrent hernias appear in patients having inherited weakness of connective tissues. Numerous tissue specific collagens, in addition to the classical fibrillar I-III collagens and numerous substrate specific matrix proteinases, have recently been described in biochemical literature, and their roles as possible causes of tissue weakness are discussed.