Examining Hernia Mesh Options
The choice of using either synthetic or biologic mesh material is influenced by several factors. For extraperitoneal applications, the presence or absence and extent of bacterial contamination in the operative field is an initial consideration. In a clean case, synthetic mesh materials are usually the first choice. Current synthetic mesh available for extraperitoneal use includes mesh composed primarily of either polypropylene or polyester in a variety of configurations – either woven or unwoven, macroporous versus microporous, lightweight or heavyweight. Macroporous lightweight mesh material has theoretical advantages based on the concept that macroporous mesh incorporates into surrounding tissue through fluid and cellular transport across the mesh material that is facilitated by the large pore size minimizing fibrosis and foreign body reaction. Conversely, a dense fibrotic reaction, associated with heavyweight synthetic mesh, can manifest as a “scar plate” which can lead to less desirable clinical outcomes due to either stiffness or mesh shrinkage from contraction. The latter can contribute to chronic pain requiring mesh removal. Woven mesh material has been described as having increased surface area to facilitate tissue ingrowth compared to non-woven designs. The hydrophilic properties associated with polyester material are well described in comparison with polypropylene but the practical benefit is not well characterized.
Concern for synthetic mesh related complications increases along the continuum from a clean case to that of the grossly contaminated operative field. In the setting of high bacterial burden, synthetic mesh is associated with difficult to manage problems such as surgical site infection which can necessitate mesh removal if synthetic material is present (especially in the case of expanded polytetrafluoroethlyene (ePTFE)) which can only rarely be treated with local wound care or a wound vacuum to achieve the goal of tissue incorporation through granulation. As the bacterial burden increases most surgeons have some level of comfort opting for biologic products but the ideal or perfect biologic has yet to be developed. Even biologic mesh material is associated with problems in a grossly contaminated operative fields. Bacterial collagenase activity contributes to biologic mesh resorption such that the biologic material is rapidly degraded without cellular ingrowth leading to high recurrence rates. Accordingly, some biologic mesh materials are designed to be more resistant to bacterial collagenase activity through chemical cross-linking which minimizes or delays bacterial enzyme-mediated mesh degradation. However, biologic material that is extensively cross-linked may be disadvantageous due to the subsequent development of mesh stiffness and possibly enhanced scar plate formation.
On a practical level, just what material is in fact available at a particular hospital for the contaminated operative field is often affected by the exorbitant cost of biologic material. A limited shelf life for some products and the need for proper storage conditions (refrigeration) are just some of the disadvantages that limit the availability of many biologic products. The choice for biologic material is becoming increasingly convoluted and confusing since the number of products is extensive, ever increasing, and their constructs and tissue of origin and “proprietary” preparations vary.
Synthetic absorbable mesh has recently been developed that may also be of use in the contaminated or complex operative field. This material (Gore BioA™ tissue reinforcement) is composed of a web of bioabsorbable co-polymers that provide a matrix that facilitates cellular infiltration and tissue generation and is no longer present to any significant degree in approximately six months. Early clinical experience with this material has been promising for use as an only application in the contaminated operative field.
Comparative data to help guide clinical decision making comparing synthetic, biologic, and synthetic absorbable mesh materials have not yet emerged.