Page 37 - International guidelines for groin hernia management

Hernia

usually associated with reduced amount of material. Key question
Importantly, pore size measurement is not accurate if
looking only at length or width in one dimension, ignoring KQ10.b Which mesh characteristics with impact on clin-
the geometry of the pore. However, a technique does exist ical outcome should be considered?

to provide an accurate measurement of the critical pore Evidence in literature
sizes, which can avoid fibrotic bridging. 371 Therefore, Meshes in open and laparoscopic repair
studies using only the designation ‘‘small pore’’ or ‘‘large Overall, 23 RCTs relate mesh material to some clinical
pore’’ have inherent limitations unless they use the tech- outcomes. 147, 164, 170, 182, 392–410 Eight of those 23 RCTs
371
nique described by Mu ¨hl or an equivalent. did not find significant differences. However, all the trials
Amount of material are small and are too underpowered to detect any differ-
2
The weight of a mesh in g/m has been used to classify the ences of practical concern. Therefore, the lack of any sig-
devices in groups of higher or lower inflammation, foreign- nificant difference does not automatically imply equality of
body reaction, risk for infection and fibrosis. 366, 370 Cor- the compared meshes with regard to the observed outcome,
respondingly sub-grouping of meshes by weight has been and thus provide no arguments against a possible impact of
proposed. 372, 373 However, mesh weight is strongly affec- the mesh material for outcome. 15 RCTs confirmed an
ted by the specific density of the chosen polymer, e.g., impact of the material on outcome. There is strong evi-
polyvinylidene fluoride (PVDF) has a specific density of dence that mesh selection can change clinical outcomes
1.77 g/cm 3 and is therefore considerably heavier than (e.g. foreign-body sensation, chronic pain, sperm motil-
3 389
3
polypropylene (0.91 g/cm ) or polyester (1.38 g/cm ). ity 411 and recurrence). The effect of mesh selection on risk/
Therefore, the overall weight of meshes might vary con- benefit ratios for individual patients has yet to be defined.
siderably despite comparable mesh construction. 390 Fur- Large-pore size meshes
thermore, the use just of weight without considering the Currently, no distinction is made between large-pore-size
porosity is inappropriate to be able to predict the tissue and lightweight meshes. Research to date has focused
response. Meshes with very small pores induced remark- mainly on mesh weight. Only one study compared a mesh
ably increased inflammation despite reduced weight. 391 with 3–4 mm to a 1-mm mesh in Lichtenstein technique. 412
Thus, weight alone is an inappropriate parameter for mesh A significant difference with regard to chronic pain was not
classification in hernia surgery. observed. However, preclinical studies suggest that meshes
with larger pores ([ 1 mm) positively influence integration
Conclusion into adjacent tissue. 381, 413, 414
Lightweight meshes
A single classification system that considers all relevant The so-called lightweight meshes (LWM) are typically
risk factors for all kind of complications, e.g. pain, infec- defined as mesh constructs with large-pore size and
tion, recurrence, or operative complications is difficult if reduced weight. However, lightweight meshes with small
not impossible to develop. Thus HerniaSurge recommends pores are also available. 390 Considering the major impact
that surgeons be acquainted with the fact that every specific of pore size on tissue reaction, comparisons of meshes with
device has its specific risk pattern, which is strongly different weight have to include only materials with similar
affected by the surgical procedure and the patient’s pore sizes. There are only a small number of studies on this
biology. issue, which compare different outcomes of only large-pore

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