Ultrasound biomicroscopy (UBM) and scanning acoustic microscopy (SAM) for the assessment of hernia mesh integration: a comparison to standard histology in an experimental model.

BACKGROUND: Mesh integration is a key parameter for reliable and safe hernia repair. So far, its assessment is based on histology obtained from rare second-look operations or experimental research. Therefore, non-invasive high-resolution imaging techniques would be of great value. Ultrasound biomicroscopy (UBM) and scanning acoustic microscopy (SAM) have shown potential in the imaging of hard and soft tissues. This experimental study compared the detection of mesh integration, foreign body reaction and scar formation in UBM/SAM with standard histology. MATERIALS AND METHODS: Ten titanized polypropylene meshes were implanted in rats in a model of onlay repair. 17 days postoperative animals were killed and samples were paraffin embedded for histology (H&E, Cresyl violet) or processed for postmortem UBM/SAM. The observation period was uneventful and meshes appeared well integrated. RESULTS: Relocation of neighboring cross-sectional levels could easily be achieved with the 40-MHz UBM and granulation tissue could be distinguished from adjacent muscle tissue layers. The spatial resolution of approximately 8 µm of the 200-MHz UBM system images was comparable to standard histology (2.5-5× magnification) and allowed a clear identification of mesh fibers and different tissue types, e.g., scar, fat, granulation, and muscle tissues, as well as vessels, abscedations, and foreign body giant cell clusters. CONCLUSION: This pilot study demonstrates the potential of high-frequency ultrasound to assess hernia mesh integration non-invasively. Although the methods lack cell-specific information, tissue integration could reliably be assessed. The possibility of conducting UBM in vivo advocates this method as a guidance tool for the indication of second-look operations and subsequent elaborate histological analyses.

Comparison of three separate antiadhesive barriers for intraperitoneal onlay mesh hernia repair in an experimental model.

BACKGROUND: Adhesion formation is a common adverse effect in intraperitoneal onlay mesh (IPOM) surgery. Different methods of adhesion prevention have been developed, including coated meshes and separate antiadhesive barriers (SABs). In this study one type of mesh was tested with different SABs, which were fixed to the sutured mesh using fibrin sealant. The primary aim was to compare adhesion prevention between different SABs. Secondary aims were the assessment of tissue integration and evaluation of SAB fixation with fibrin sealant. METHODS: Thirty-two rats were randomized to one of three treatment groups (SurgiWrap, Prevadh and Seprafilm) or a control group (no SAB). Animals were operated on with an open IPOM technique (8 per group). One macroporous polypropylene mesh per animal (2 × 2 cm) was fixed with four non-absorbable sutures. An antiadhesive barrier of 2·5 × 2·5 cm was fixed with fibrin sealant. After 30 days, adhesion formation, tissue integration, seroma formation, inflammation and vascularization were evaluated macroscopically and by histology. RESULTS: Prevadh and Seprafilm groups showed a significant reduction in adhesion formation compared with the control group. Tissue integration of the mesh was reduced in these groups. Fibrin sealant fixed the SAB to the mesh securely in all groups. CONCLUSION: Prevadh and Seprafilm are potent materials for the reduction of adhesion formation. A potential relationship between effective adhesion prevention and impaired tissue integration of the implant was observed. Fibrin sealant proved an excellent agent for SAB fixation.

Cyanoacrylate tissue sealant impairs tissue integration of macroporous mesh in experimental hernia repair.

BACKGROUND: Tissue sealants have been proposed as an alternative to permanent fixation devices in hernia repair with the aim of reducing perforation-associated complications and chronic pain. Sealants can be divided into three main categories: synthetic glues (e.g., cyanoacrylate based), biologic products (e.g., fibrin sealant), and genetically engineered polymer protein glues. The beneficial effects of fibrin sealant have been reported in both experimental and clinical hernia repair. However, data on cyanoacrylate glues for mesh sealing are limited. METHODS: In 20 Sprague-Dawley rats, two hernia defects (1.5 cm in diameter) per animal were created bilaterally in the midline of the abdominal wall. The peritoneum was spared. The lesions were left untreated for 10 days to achieve a chronic condition. Defects then were covered with TI-Mesh xl (2 x 2 cm), which was glued with Glubran-II. The time points of sacrifice were 17 days, 28 days, and 3 months. At autopsy, meshes were biomechanically tested, and histology was performed. RESULTS: Tissue integration of the meshes was impaired at all time points by impenetrable glue plaques. At application sites, the elasticity of the abdominal wall was significantly reduced because of nonresorbed, rigid glue residues. CONCLUSIONS: Mesh fixation by Glubran-II impairs tissue integration, elicits inflammation, and unfavorably alters the biomechanics of macroporous mesh and the abdominal wall.

Adverse effects of porcine small intestine submucosa implants in experimental ventral hernia repair.

BACKGROUND: Biomeshes made of porcine small intestine submucosa (SIS) have recently been suggested for repair of ventral hernia. A fully biodegradable combination of implant and fibrin sealant fixation was assessed in a new rat model with sutures serving as control. METHODS: In 10 Sprague-Dawley rats, two defects per animal were created in the abdominal wall left and right of the linea alba (1 cm in diameter), and the peritoneum was spared. The lesions were left untreated for 10 days to achieve a chronic condition and were then covered with SIS (2 x 2 cm), sealed or sutured (n = 10 per group). Randomization allowed sealant and sutures in one animal. Animals were killed on postoperative day 17, and implant sites were analyzed macroscopically, histologically, and microbiologically. RESULTS: Abscedation, encapsulation, and putrid seroma were observed in all samples, regardless of fixation technique. Histology revealed lytic necrosis and extensive inflammatory response of the surrounding tissue. Tissue samples obtained from three implant sites were positive for beta-hemolytic Streptococcus. SIS was not detectable after 17 days. CONCLUSIONS: Adverse effects were observed using SIS in an experimental model of ventral hernia and were not linked to fixation method or study design. Further experimental investigations on SIS are necessary before its clinical use in hernia repair.