Page 325 - Prevention and Treatment of Incisional Hernia- New Techniques and Materials

Discussion
In this case symptomatic bulging at the hernia repair site was caused by elongations of the mesh due to pore enlargement. Each mesh used for hernia repair has certain features that determine the mechanical properties. During normal daily activities, mesh material is exposed to stress subsequent to changes in intra-abdominal pressure. The intra-abdominal pressure can raise up to 100 mmHg during coughing and can reach 250 mmHg during vomiting or jumping(6, 7). When abdominal wall defects are repaired using a bridging technique the material has to withstand the tensile stress at the borders.
Normal daily activities require a tensile strength of 16 N/cm and strenuous activities a maximum tensile strength 42-47 N/cm(5, 8). Medium- weight and heavy-weight meshes made of polyester, polypropylene or (expanded) polytetra uoroethylene (ePTFE) provide the maximum tensile strength to prevent failure of the repair(5). In our patient polyester mesh was a valid choice for the rst repair with regard to the tensile strength. The elasticity of a mesh should correspond to the elasticity of the abdominal wall to prevent foreign body sensation or discomfort of sti ness. Biomechanical studies have shown low stretch properties of meshes, only up to 3.5% during normal daily activities due to the very large diameter of the laments(5). However, other biomechanical studies show that repetitive stress can change the tensile strength and stretches mesh materials(9). These studies did not test the polyester meshes, but in our case, elongation of polyester laments is clearly demonstrated.
Bulging is an important adverse e ect after abdominal wall repair. Incidences of bulging vary from 1.6% to 17.4%(2-4). Clinical distinction between recurrence and bulging of mesh is di cult(1-3). Di erentiation is therapeutically irrelevant in symptomatic patients, because both conditions surgical repair is indicated. Asymptomatic patients however do not require repair in the case of mesh bulging, except for cosmetic reasons. Radiologic imaging can be used to establish the right diagnosis. The use of CT-scans to distinguish between bulging or recurrence can be challenging because polypropylene meshes are visible lines with densities similar to adjacent muscle and can better be identi ed with ultrasound(10-12). When performing surgical repair for symptomatic bulging it is often not necessary to remove the implanted mesh, when incorporation is su cient. With open approach the
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Mesh expansion
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