Tuesday, February 27, 2018

Types of meshes for hernia repair

Hey everyone, I've just started surgery, and realised that I love the subject! The first topic I started reading was the most commonly read one: hernia!

I realised something very interesting- hernia repair using meshes is a pretty difficult thing to do, because you need to find the right mesh for a particular type of hernia. This is a very dry topic but an important one, so I've tried to add some tricks to remember stuff about meshes!

Q. What's a mesh?
A. A mesh is usually a sheet which has been perforated to make very tiny holes in it, hence it could either be a net or a flat sheet. A mesh is supposed to have a good overlap over the area of defect, and it's margins should cover greater than 2 cm but less than 5 cm of the area with defect.

Q. What are the functions of a mesh?
A. 1. Bridge a defect, to form a tension free patch over the area.
2. To plug a defect if it is small and overlap is hard to achieve.
3. ‎Augment a repair by reinforcing it with the support of this mesh.

Remember it as: BPA (Bridge, Plug, Augment).

Q. Does a mesh cause complications? Which ones?
A. Although an amazing treatment for hernia, it does have its set of complications.
- Mesh plugs can cause meshomas which is a plug of the mesh substance and collagen which will grow over it. -‎migration of the mesh from its original place
-‎ Erosion of surrounding organs
-‎ Fistula formation
-‎ Chronic pain

Remember it as: Growth of a meshoma, pushes upon the surrounding structures causing erosion, eventually it grows so much that the mesh is pushed away (migration), eventually it grows so much it forms a hole (fistula) which obviously causes pain!

Q. How does a mesh work?
A. Net meshes allow fibrous tissue to grow between its strands and become adherent. This integration happens within few months. The initial fixation hence is by means of absorbable material such as glue, sutures or staples.

On the other hand, sheet meshes do not allow such growth between its strands, but gets encapsulated with the fibrous tissue.

Types of Meshes:
1. Synthetic Polymers: polypropylene, polyester, polytetrafluoroethylene.
These are non absorbable and provoke little tissue reaction. As polypropylene has strong monofilament mesh they will have no antibacterial properties, hydrophobic in nature and the monofilament nature impedes growth. Polyester has braided filament mesh and is hydrophilic in nature which hence allows rapid vascular and cellular infiltration.

Features of synthetic meshes:
- Very strong
-‎ Provokes fibrous reaction
-‎ More heavy hence more tissue reaction
-‎ Mesh shrinkage causes progressive decrease in size of mesh over time, leading to tissue pain and hernia recurrence if the defect is not covered fully by shrunken mesh.

2. Biological Meshes: Materials used are usually human or animal dermis, bovine pericardium or porcine intestinal submucosa. These are sterilised, decellularised, non immunogenic connective tissue materials. It has a scaffold structure upon which enzymes work to break down the biological implant and replace and remodel with host fibrous tissue. It's expensive.

3. Absorbable Meshes: polyglycolic acid is a common material. It is for temporary abdominal wall closure.

4. Tissue Separation Meshes: Polycellulose and collagen are widely used. these are for intraperitoneal use, their one side is sticky and the other is slippery. These have good adhesion, with host tissue on parietal side of mesh using the sticky side, and the other side, the slippery one, needed to prevent adhesion is on the visceral side.

There are a lot of Polys here. Let's try remembering which one is under which type?

Ester, Propylene, Tetrafluoroethylene: sound like fake names, so will probably be synthetic!

Glycolic acid is used a lot in skincare products, especially soap. Soap is absorbable, hence a mesh made out of it will also be absorbable, right?

Cellulose and collagen used in the 4th type of mesh are naturally available materials. So can be definitely used for intraperitoneal procedures! Hence can be used in tissue separation!

FactFatigue: Meshes greater than 80 g/ sq m are called heavy meshes. Those less than 40 g/ sq m are called light meshes and are preferred in surgery.

Hope this was an interesting and easier way to remember hernia repair!

This awesome post was written by Devanshi Shah

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