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Background: Over the years, reticular prostheses have undergone changes in their structure and composition to give rise to today's partially absorbable lightweight meshes. This study was designed to assess the biological and biomechanical behavior of these prostheses to establish whether they offer any advantages over nonabsorbable lightweight polypropylene prostheses., Materials and Methods: 7 x 5 cm defects were created in the anterior abdominal wall of New Zealand White rabbits and repaired by securing different prostheses to the edges of the defect with a running 4/0 polypropylene suture. The lightweight biomaterials compared were two nonabsorbable meshes: Parietene and Optilene elastic, and two partially absorbable prostheses: Vypro II and Ultrapro. At 14 and 90 days postimplant, tissue/prosthesis specimens were subjected to histological, immunohistochemical, shrinkage, and biomechanical analyses., Results: Adhesion formation on the peritoneum-facing surface of the meshes was significantly less extensive in the meshes with absorbable components at 90 days postimplant. The newly formed tissue around the prosthetic filaments was comprised of collagen fibers, fibroblasts, blood vessels, and macrophages. The partially absorbable meshes showed higher macrophage proportions (due to remnants of absorbable material and their structure) than the nonabsorbable meshes at 90 days, although differences were not significant. At 90 days postimplant, similar tensile strengths were recorded for all the implants., Conclusions: All the prosthetic materials induced good host tissue ingrowth, with no significant differences in tensile strength observed. Our findings suggest that partially absorbable lightweight prostheses could offer advantages over nonabsorbable lightweight meshes since less foreign material persists in the recipient, improving abdominal wall compliance.

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.