Functional assessment and tissue response of short- and long-term absorbable surgical meshes.

Within the last few years meshes have become essential for the temporary closure of the abdominal cavity to avoid the development of an intra-abdominal compartment syndrome. The interposition of a mesh as an inlay reduces the intra-abdominal pressure and improves markedly the blood circulation, particularly for the intestines and kidneys. Whereas non-absorbable meshes usually tend to produce fistulas in direct contact to the bowels, the interposition of short-term absorbable meshes result in large incisional hernias in almost all cases. In the following study we investigated the functional and histological consequences of a short-term absorbable mesh (polyglactin 910, Vicryl, loss of 50% of its mechanical stability within 3 weeks) and a long-term absorbable mesh (polylactide, LTS, preserved >50% of its mechanical stability for over 1 year). The mesh-modifications were both tested with the aid of three-dimensional stereography, tensiometry, light- (LM) and transmission electron microscopy (TEM) as well as morphometry after implantation intervals of 3, 7, 14, 21, 45, 90, 135 and 180 days in a standardised rat model. The PG-mesh initially revealed a pronounced inflammatory reaction and a significantly increased formation of connective tissue. The extensive arrangement of connective tissue in the interface mesh/recipient tissues correlated to an increased stiffness of the abdominal wall compared to the sham-group. However, a loss of mechanical stability and an increase of elasticity could be detected after 3 weeks of implantation which may be explained by the rapid absorption of the mesh material. In contrast to PG, the LTS-mesh indicated a decreased but persisting inflammatory reaction in the interface mesh-fibres/recipient tissues and a significantly reduced induction of connective tissue. Although, the formation of scar-tissue was diminished compared to PG the LTS-mesh preserved its mechanical stability after 180 days. The results indicate that the frequent development of incisional hernias with short-term absorbable meshes (PG) might be due to the decreased mechanical stability and dilatation of the newly formed connective tissue after 2-3 weeks. Moreover, extensive scar tissue development may promote adhesion formation. The implantation of the long-term absorbable LTS-mesh seems to be favourable with respect to its long-term mechanical stability and the decreased connective tissue formation.