Editing Mesh

== '''Mesh classification''' ==

=== '''Desirable characteristics''' ===

** Chemically inert
** Resistant to mechanical stress while retaining compliance
*** >1.6N tensile strength
** Sterilizable and resists infection
** Non-carcinogenic
** Minimal inflammatory reaction or adhesions to viscera
** Hypo-allergenic
** Inexpensive
** Good incorporation into tissues
*** Mimics tissues it's replacing/reinforcing
*** Medium weight 
*** Large pores - facilitating tissue ingrowth and resisting infection
*** Doesn't contract

=== '''Considerations for use''' ===

** Position
** Whether in contact with viscera 
** Risk/presence of infection

=== '''Descriptive classifications''' ===

** '''Weight of the material'''
*** Lightweight mesh is generally described as <40g/m<sup>2</sup> (arbitrary)
**** Can fail/fracture
*** Medium: 40-60g/m<sup>2</sup> 
*** Intermediate: 60-75g/m<sup>2</sup> 
*** Heavy: >75g/m<sup>2</sup>
**** More rigid
**** Reduced abdominal wall compliance
**** Possible chronic pain
*** Controversial whether this impacts outcomes
**** Recent RCT showed less pain and recurrence two years after TEP with heavyweight mesh
**** RCT showed better outcomes for ventral repairs with lighter meshes
**** Lightweight mesh is generally favoured since it seems to cause slightly fewer mesh-related issues
** '''Pore size'''
*** May relate to ability to clear infections - larger pores are more resistant to infection
*** Large pores allow tissue ingrowth, which is good for extra-peritoneal use but not good for intra-peritoneal
*** Inversely related to weight of mesh
** Water angle (hydrophobic or hydrophilic)
** Whether there is an anti-adhesive barrier present
** Material
*** Synthetic non-absorbable
*** Synthetic absorbable
*** Biologic (derived from biological tissue)

== '''Synthetic non-absorbable''' ==

* '''Materials'''
** '''Polyester'''
*** Composed of polyethylene terephthalate
*** Hydrophilic, heavyweight, macroporous mesh
*** Comparable complication rates to other products when placed in pre-peritoneal space
*** Appropriate for extraperitoneal use
*** Infected polyester mesh generally requires at least partial removal - areas that are well-incorporated at time of removal can be left behind
** '''Polypropylene'''
*** Hydrophobic macro-porous mesh
*** Allows the ingrowth of native fibroblasts and incorporation into surrounding fascia
*** Semi-rigid, somewhat flexible, and porous
*** Lightweight polypropylene meshes often have an absorbable component of Vicryl or Monocryl which provides initial handling stability
*** Appropriate for extraperitoneal use
*** Tend to be the best for mesh salvage
** '''Expanded polytetrafluoroethylene (ePTFE)'''
*** More expensive
*** Non-adherent to bowel in micro-porous form
*** Can be made in composite-type form - micro-porous on the visceral side and macro-porous on the abdominal wall side to promote tissue ingrowth
*** Impermeable to fluid
*** Not incorporated into native tissue like polypropylene
*** Does not allow skin grafting on top
*** When it is infected, it almost always needs to be removed
** '''Composite'''
*** ePTFE on the visceral surface, polypropylene on the abdominal wall surface
**** Variable rates of contraction, so can cause buckling of the mesh
*** There are also combinations of synthetic meshes with biologic coatings

== '''Synthetic absorbable''' ==

* Materials
** Polyglactin (Vicryl)
*** Can be placed in any plane typically used for repair, ideally with soft tissue coverage anterior to the mesh
*** Hydrolyses completely in 8-9 weeks - rapidly-absorbable
*** Comes in slowly-resorbable forms too
*** Generally avoid using in contaminated situations

== '''Biologic and biosynthetic''' ==

* '''Function'''
** Largely composed of acellular matrix
** Provide a matrix for neovascularisation and native collagen deposition
** Function best as a fascial reinforcement rather than as a bridge or interposition repair
** Enthusiasm waning for these somewhat - prone to late formation of weaknesses and bulges, and eventual hernia recurrence
* '''Classification'''
** Source material
** Post-harvesting processing techniques
** Sterilisation techniques
** Materials
*** Human dermis
*** Porcine dermis
*** Bovine fetal dermis
*** Porcine intestine
* '''Brands'''
** Bio-A
*** 67% PGA and 33% TMC
*** Polyfilament, microporous
*** Expected to absorb in 6-7 months
** Phasix
*** Knitted monofilament mesh scaffold of P4HB (poly-4-hydroxybutyrate)
*** Biologically-derived, fully resorbable in 12-18 months
*** Essentially a polymerised version of butyrate, which means it takes 12-18 months to hydrolyse
** Biodesign grafts including rectopexy
*** Porcine intestinal submucosa scaffold
* '''Indications'''
** Advantage in infected or contaminated fields - but long-term outcomes questionable here
** Can be used for coverage of viscera as part of a planned hernia with eventual skin graft on top

== '''Specific meshes''' ==

* Monofilament polypropylene flat sheet - 15x10cm
* Parietene DS  - composite polypropylene and absorbable collagen film. Comes in 12cm or 15cm round, or 15x10/20x15/25x20/30x20cm sizes.
* ProGrip - composite polyester and absorbable polylactic acid microgrip
* Parietex - composite patch of polyester and absorbable hydrophilic collagen film - comes in 4.6, 6.6 and 8.6 sizes
* Symbotex
* Ventralex ST - polypropylene with hydrogel posterior layer, for intra-peritoneal placement. Comes in 4.3, 6.4 and 8cm sizes.
* Ventralex - polypropylene/ePTFE, for pre-peritoneal placement.
* ProLite - polypropylene. ProLite Ultra is low-weight polypropylene.
* Bard 3D Max - knitted polypropylene pre-formed mesh
* UltraPro - macroporous partially-absorbable - polypropylene/monocryl - monocryl added to make it 'stiffer' and less flimsy - commonly 6x11cm

== Choice of mesh ==

* European Hernia Society Guidelines on use of mesh
* Grade 1 - no risk factors for infection or contamination - use whatever you choose
* Grade 2 - risk factors for infection but no contamination - whatever you choose, but could consider biologic
* Grade 3 - potentially contaminated e.g. stoma, violation of GIT - biologic mesh generally recommended
* Grade 4 - infected - biologic



[[Category:Operating theatre]]