Page 36 - International guidelines for groin hernia management

Hernia

Evidence in literature mesh-related complications. Due to manufacturing process,
Various factors may impact mesh-related complica- textile meshes often have considerable anisotropy with
tions. 366–379 These factors have been identified from human different mechanical properties when stressed vertically or
anatomy studies, studies of mesh-related failures, numer- horizontally. Therefore, any measurement of strength and
ous preclinical tests in animal species, and in vitro tests. elasticity is strongly affected by the setting of the test
procedure (e.g., tensile strength tested on mesh strips or by
• Material reduction can decrease mesh-related compli-
puncture test, width of the mesh sample, or distinct direc-
cation risk; larger pore flat meshes have a lower risk of
tions of the mesh fibers in the test unit). As a result, the
mesh-related complications than do small-pore flat
strength and elasticity of anisotropic meshes cannot be
meshes. expressed as a single number. 373, 379 Current data on
• A tensile strength [ 16 N/cm 2 is unnecessary for physiological biomechanical requirements are flawed and
meshes used in groin hernia repair. 373, 377, 380
only provide rough estimates for the mesh’s mechanical
• Shrinkage and stiffness of flexible meshes is affected
characteristics. In groin hernia repair, the tensile strength of
by scar tissue. Smaller inter-filament distances and 2
meshes does not need to be [ 16 N/cm, but it is unknown
pores have an increased risk of bridging by scar whether a minimum strength requirement exists. For con-
tissue. 366, 378
struction of a mesh a monofilamental polypropylene com-
• For mechanical stress, mesh deformation lengthwise is
position is recommended, as multifilamental meshes tend
linked to pore-size reduction. Therefore, prevention of 387
to show a higher infection potential. Mesh shrinkage is
pore collapse to avoid bridging scars requires high
seen as a consequence of the contracting scar tissue in the
structural load stability of the textile mesh area. Depending of the local inflammatory activity
construction. 381–386
and the amount of scar, it is found in a range from 20% up
• Plugs, when compared with flat meshes, have higher 388
to 90% in the so-called meshoma. Preclinical studies
risks of extensive fibrosis and are more likely to
show that high structural stability may help to reduce mesh
stimulate an intense inflammatory reaction, thereby 381
shrinkage.
resulting in nonconforming biomechanical
366, 382 Pore size and effective porosity
properties.
One mesh classification focuses on the risk for mesh
Mechanical properties infection and separates meshes with pores \ 10 lm (high
Characterization and classification of in vivo mesh mate- risk for infection) from those with pores [ 75 lm (low
rials must account for functional and biological outcomes. risk). 370 Another classification stratifies by risk for fibrotic
Modifications of polymers will result in substantially dif- bridging (defined as pores completely filled by scar), sep-
ferent biological responses. Any attempt to stratify meshes’ arating large-pore meshes ([ 1 mm, effective poros-
impact on surgical outcomes has to consider the complex ity [ 0%) from small-pore meshes (\ 1 mm, effective
interplay between the polymer, the textile structure with porosity = 0%). 366 Small-pore constructions have a higher
fiber, the total amount of material, the porosity, the con- risk for fibrotic bridging, whereas large-pore constructions
figuration of textile bindings, the implant location, and the have a lower risk. A pore size [ 1.0 mm defines ‘‘large-
mechanical strain placed upon the implant. None of these pore-size’’ but there is no consensus on this definition.
parameters in isolation are able to predict the inflammatory Some guidelines use a definition for large-pore-size
and fibrotic tissue response and classify meshes across all as [ 1.5 mm. 241 For the newer meshes, larger pore size is

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