Page 112 - Postoperative Intra-Abdominal Adhesions- New insights in prevention and consequences

Chapter 6
Discussion
The current study analyzed five different meshes in terms of adhesion formation, incorporation, and shrinkage after 30 and 90 days. For these three parameters Parietex Composite mesh demonstrated the best long-term results compared with all other meshes. The biological non-crosslinked mesh Strattice showed little adhesion formation and moderate shrinkage, but poor incorporation.
Adhesions are formed during the inflammatory phase in the first seven days after surgery [24]. This period is followed by the proliferation phase until about day 30, when some regression is observed, whereas the remaining adhesions become more organized to fibrous and vascularised tissue. In general, previous opinion maintained that this succeeding phase of remodelling was temporary and that inert scar tissue was finally formed. However, findings recently have shown that even after months to years, macrophages, fibroblasts, mononuclear cells and neovascularisation can be identified in abdominal adhesion tissue suggesting a dynamic and ongoing process of remodelling [25-27]. This is supported by our study showing major alterations in the results after 90 days compared with 30 days. The amount of adhesion formation to the Strattice and the Prolene mesh was significantly diminished, whereas the extent of adhesions to the Surgisis mesh increased at 90 days.
The fact that the anti-adhesive collagen layer of the Parietex Composite mesh is absorbed within 30 days is not congruent with our findings that very few adhesions occur on this mesh even on the long term[28]. These data support recent long-term studies in which Parietex Composite resulted in minimal adhesion formation[29, 30]. The mechanism of this phenomenon is not completely understood, but perhaps the formation of a new mesothelial layer plays a pivotal role in this process. Histological examination of tissue samples after hematoxylin and eosin supports this hypothesis showing a new mesothelial layer on the Parietex Composite and Strattice mesh. On Permacol mesh a new mesothelial layer was alternating with a small fibrous layer, the latter most probably the result of adhesion formation.
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