The Surgical Edge
Step into the world where precision meets innovation. The Surgical Edge is your go-to medical podcast for in-depth reviews and insightful discussions on a wide range of medical conditions, diseases, and the latest advancements in surgical techniques and healthcare technology.
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The Surgical Edge
Beyond the Patch: The Complex Evolution of Surgical Mesh
We explore the surprisingly complex world of surgical mesh, examining how our understanding has evolved over time through sometimes difficult lessons.
• Surgical mesh serves as a specialized reinforcing material used primarily in hernia repairs
• Three main approaches to mesh placement: bridging defects, plugging defects, and augmenting repairs
• The plugging method has largely been abandoned due to complications including pain, migration, and organ erosion
• Net meshes allow tissue integration while sheet meshes become encapsulated by the body
• "Mesh shrinkage" is actually mesh contracture - the body's scar tissue contracting around the mesh
• Lightweight meshes with larger pores (>1mm) often perform better than heavyweight options
• Biological meshes provide a scaffold for the body's cells but have limitations and higher costs
• Newer slowly absorbable meshes exist but lack long-term data on effectiveness
• Placement matters significantly - extraperitoneal or sublay placement is generally preferred
• Surprisingly, simple lightweight synthetic meshes may offer the best balance of safety and effectiveness
Quick discussion and review of topics that interests you.
Welcome to the Deep Dive. Today we're getting into something well surprisingly complex Surgical mesh.
Speaker 2:Yeah, it really is.
Speaker 1:It's used in millions of people, often seen as the standard medical fix, but sometimes it's the source of some really serious problems.
Speaker 2:Absolutely.
Speaker 1:So we're going on a bit of a journey here, not just to figure out what mesh is, but how our whole understanding of it has like totally shifted over time, Often through some tough lessons revealing some pretty surprising things about what actually works best in the end.
Speaker 2:That's a great way to put it. We'll be looking at the different kinds of mesh, how they actually work with the body, or sometimes against it, and how the surgical approaches themselves have evolved.
Speaker 1:Based on the latest insights right.
Speaker 2:Exactly, We've dug into the sources and, honestly, there are details here, ongoing debates even that might make you rethink what you thought you knew about. Hernia repair.
Speaker 1:Yeah.
Speaker 2:It's definitely a field where learning is constant.
Speaker 1:Okay, let's dive in then. So surgical mesh, we hear about it all the time, right?
Speaker 2:Yeah.
Speaker 1:Especially with hernia. Repairs Seems straightforward. You'd think so, but what a lot of us maybe don't grasp is just how much is going on beneath the surface, how much has changed. So today we're really digging into that story. Let's start basic, though. Beyond just calling it a patch, what is surgical mesh?
Speaker 2:fundamentally, Okay, so think of it like a specialized kind of reinforcing material, like patching a hole, yes, but medical grade. It's a prosthetic material. Usually looks like a net or maybe a flat sheet and surgeons use it to basically strengthen a hernia repair, give it some backup.
Speaker 1:Right Reinforcement.
Speaker 2:Exactly Now. Historically, there were sort of three main ways surgeons thought about using it. The first was just bridging a defect.
Speaker 1:Okay.
Speaker 2:So you lay the mesh over the hernia hole like a patch, but crucially, you need a really generous overlap onto the strong tissue all around it. It needs to be tension-free.
Speaker 1:Got it Needs room.
Speaker 2:Then there was this other method, plugging a defect, and this is really important because it's changed. They literally push a sort of plug made of mesh into the hole into the hole itself yeah, and the third way, which is generally seen as the best approach now, is augmenting a repair augmenting meaning you first close the hole, the defect with sutures, stitch it up, then you add the mesh on top or underneath for extra reinforcement, again tension-free.
Speaker 1:Okay, that distinction bridging, plugging, augmenting feels really key, especially since you highlighted that plugging method. You said it's been largely abandoned. Why? What was the problem there?
Speaker 2:Ah, yes, that's a critical point and it really boils down to patient outcomes long-term problems With that plugging method, the body's healing response, you know, laying down collagen, yeah, scar tissue. Exactly. It often created this really dense, hard, fibrous mass around the mesh plug. Surgeons even gave it a name a meshoma.
Speaker 1:Meshoma wow.
Speaker 2:And this meshoma could become a major source of chronic, sometimes debilitating pain for patients.
Speaker 1:Just didn't feel right, just pain or other things too, oh other things too.
Speaker 2:Beyond the pain, it could lead to the mesh migrating, actually moving from where the surgeon put it, Moving what? Anywhere nearby really? And even worse, sometimes eroding into adjacent organs like the bowel or causing fistulas. These abnormal connections, Really serious stuff.
Speaker 1:Okay, so plugging was definitely problematic.
Speaker 2:Hugely. And just to add, for kind of similar reasons, just putting mesh edge to edge in the defect what they call an inlay without that proper overlap also not recommended. It just doesn't provide that durable, strong reinforcement you need long-term.
Speaker 1:Right, doesn't really add much strength if it's just edge to edge, okay. So how it's used and how it's not used anymore, that's super important. Now what about the mesh itself, the physical forms? Is it all just one type of sheet, or are there different basic structures?
Speaker 2:Good question. No, it's not all the same. Structurally, you can think of two main types net meshes and sheet meshes.
Speaker 1:Net versus sheet Okay.
Speaker 2:So net meshes are like woven or knitted Think of a net, basically and the key thing is they're porous. They have holes, not a hole. That's intentional. It allows your own body tissue native tissue to grow into the mesh between the strands, so over a few months it actually becomes integrated part of the body structure.
Speaker 1:Wow Okay.
Speaker 2:Initially. Yeah, they need fixing in place, Usually maybe with surgical glue or sutures or little tacks or staples. Some of those might dissolve over time, Some don't. But interestingly, in some specific repairs, like certain inguinal hernia repairs done from behind the abdominal wall, you might not need any fixation at all. The body's pressure just holds it.
Speaker 1:Fascinating. So that's nets. What about sheets?
Speaker 2:Sheet meshes are the opposite. Basically they're non-porous. Maybe they have some tiny perforations, but fundamentally they don't let tissue grow through them. So why haven't? Instead, the body tends to form a capsule of fibrous tissue around them like walling it off, Like scar tissue forming a barrier. Exactly, and because they don't integrate like the nets, sheet meshes always need really strong, permanent fixation, non-absorbable sutures or tacks to stop them from moving or migrating.
Speaker 1:OK, that's a fundamental difference. Then Porous nets integrate, non-porous sheets get walled off. What does that mean for how the body interacts with them, long term, for the patient experience?
Speaker 2:Well, it connects directly to the materials used. Most meshes today are synthetic polymers, plastics basically, usually polypropylene, polyester or PTFE polytetrafluoroethylene.
Speaker 1:Right the synthetic stuff.
Speaker 2:Yeah, sometimes they have extra coatings or additives, maybe an anti-adhesive barrier on one side, but the core material is typically one of those three.
Speaker 1:And do they behave differently? Polypropylene versus polyester versus PTFE?
Speaker 2:They do have different properties. Polypropylene is quite inert. It doesn't react much. It's hydrophobic, repels water and it's usually a monofilament, a single strand, which makes it harder for bacteria to sort of get a foothold, resists infection better, allows clean tissue in growth. Polyester is similar in some ways, but it's hydrophilic. It likes water and some believe this actually encourages tiny blood vessels, microvessels, to grow into it, maybe speeding up integration.
Speaker 1:And PTFE.
Speaker 2:PTFE usually comes as those flat sheets we mentioned. It's also very inert, but it's really resistant to both tissue ingrowth and forming adhesions, which sounds good, but it means it totally relies on that fixation to stay put. It won't integrate on its own.
Speaker 1:So mostly non-absorbable materials designed to get the body to build a strong barrier with them. Through that, tissue ingrowth Makes sense. Okay, now let's tackle something I hear a lot and it sounds kind of alarming Mesh shrinkage. People worry their mesh is shrinking inside them. What's actually going on there Is the mesh shrinking.
Speaker 2:Yeah, that term is really common, but it's a bit misleading, A misnomer actually.
Speaker 1:Okay.
Speaker 2:The mesh material itself doesn't really shrink. What is happening is something called mesh contracture.
Speaker 1:Contracture.
Speaker 2:Right. It's the fibrous tissue, the scar tissue that your body grows into, the mesh that naturally contracts over time. It's the body's healing process tightening up, not the implant shrinking.
Speaker 1:So it's the scar tissue pulling inward.
Speaker 2:Exactly, and this contraction can be a real problem. If that scar tissue tightens too much, the area the mesh covers effectively gets smaller.
Speaker 1:How much smaller.
Speaker 2:Our sources say it can contract an area by more than 50%, which means it might not cover the original hernia defect anymore, leading to the hernia coming back Recurrence 50%. Yeah.
Speaker 1:Wow, why does that happen? Why does the scar tissue contract so much sometimes?
Speaker 2:It seems related to the mesh design itself. Older meshes or meshes that are very dense they call them heavyweight meshes tend to provoke a much stronger inflammatory and fibrous reaction from the body.
Speaker 1:More reaction, more scar tissue.
Speaker 2:More scar tissue and that leads to more collagen contraction. The whole area gets stiffer, less flexible.
Speaker 1:So what does that feel like for the patient then, if this contracture is happening?
Speaker 2:Well, it can lead to the abdominal wall feeling stiff, less elastic. People might lose some mobility. They might feel a constant foreign body sensation, like something's pulling or just there.
Speaker 1:Uncomfortable.
Speaker 2:Definitely, and it can also be a significant cause of chronic pain. This whole understanding is why the thinking has shifted.
Speaker 1:Shifted how.
Speaker 2:Current opinion really favors meshes that are well lighter, thinner strands and, crucially, larger spaces or pores between those strands.
Speaker 1:Bigger holes in the net.
Speaker 2:Basically, yes. The ideal pore size is thought to be at least one millimeter in all directions. This seems to promote the in-growth of strong collagen, but collagen that's more elastic, less prone to that intense contraction.
Speaker 1:So better integration, less contraction.
Speaker 2:Less foreign body reaction, more flexibility in the abdominal wall and, ultimately, more comfort for the patient. It really does seem like those early meshes were, you know, trying too hard, over-engineered for pure strength, maybe forgetting about flexibility.
Speaker 1:That's fascinating. So less is more, in a way. Lighter mesh, bigger pores. It's almost counterintuitive. Now, beyond these synthetic options, you hear about biological meshes. What's the story there? Are they totally different?
Speaker 2:Completely different approach. Yeah, biological meshes aren't synthetic polymers. They're made from connective tissue that's been harvested, sterilized and had all the cells removed, decellularized.
Speaker 1:Harvested from where.
Speaker 2:Various sources Could be human skin, dermis, animal skin, cow heart lining, bovine pericardium, even pig intestine lining, porcine, intestinal submucosa. It's essentially using a natural tissue scaffold, a scaffold. What does it do? The theory is it provides this temporary framework sub mucosa.
Speaker 1:It's essentially using a natural tissue scaffold. A scaffold, what does it do?
Speaker 2:the theory is it provides this temporary framework. It encourages your body's own cells to move in blood vessels, fibroblasts, the cells that make collagen so the body rebuilds on top of it that's the idea. Your own cells populate the scaffold, lay down new collagen and, over time, your body's enzymes are supposed to break down the biological mesh implant, leaving behind your own newly formed, strong, fibrous tissue, eventually turning the repair into your own tissue.
Speaker 1:That sounds ideal in theory. Does it always work like that?
Speaker 2:Well, there's variability how quickly the mesh breaks down, how quickly the new collagen forms. It varies a lot between different products and it also really depends on the environment where it's placed in the body.
Speaker 1:What kind of environment?
Speaker 2:Infection is a big one. If the area is infected, some biological meshes break down much faster. They can weaken and fail before your body has had time to rebuild properly, leading to the hernia coming back early.
Speaker 1:So infection is a major issue for them.
Speaker 2:It can be, although some biological meshes have chemical cross-linking, which makes them more resistant to breaking down, even with infection. So there are nuances.
Speaker 1:So it sounds like their use is pretty specific and I've heard they're expensive. Is their role clear yet?
Speaker 2:They definitely have a role in certain complex situations, often where infection is a concern or synthetic mesh might not be suitable. But yes, they are considerably more expensive. And you're right, their exact sort of optimal place in routine honey repair is still being worked out. More long-term data is needed.
Speaker 1:Okay, so synthetic, biological? What about meshes designed to disappear, completely Absorbable ones?
Speaker 2:Right, there are synthetic absorbable meshes made from materials like polyglycolic acid or collagen-based ones, polyhydroxybutyrate, things like that.
Speaker 1:And where are they used?
Speaker 2:Their use is pretty limited, actually, mainly for very temporary situations, like temporary closure of the abdominal wall if it needs to be reopened soon, or maybe just adding a little short-term reinforcement to a suture line.
Speaker 1:Okay, temporary, so why not for a standard hernia repair? Wouldn't dissolving away be the perfect outcome? No foreign material left behind.
Speaker 2:You'd think so, but the problem is these standard absorbable meshes dissolve too quickly.
Speaker 1:Too fast.
Speaker 2:Yeah, they're gone before the body has laid down enough strong new collagen to actually hold the repair, so the hernia would just come back once the mesh disappears. They don't induce a strong enough long-term response. However, there's a newer category now Synthetic slowly absorbable meshes, sometimes called long-term absorbable.
Speaker 1:Slowly absorbable. How slow.
Speaker 2:Designed to degrade very gradually, maybe over many months, even a year or two. The idea there is that they stick around long enough to guide the formation of strong native collagen, a robust scar plate, and then disappear theoretically, leaving a permanent repair made of your own tissue.
Speaker 1:Okay, that sounds promising.
Speaker 2:Yeah.
Speaker 1:But is it proven?
Speaker 2:And that's the crucial point this is where it gets really interesting or maybe concerning, depending on your view, the long-term outcomes you know, five, 10 years down the line for repairs using these newer, slowly absorbable meshes. They are as yet unknown.
Speaker 1:Unknown. That feels like a pretty big asterisk.
Speaker 2:It is. It's an area of active development and research, but we don't have the long-term data yet to say for sure how they perform compared to the standard non-absorbable ones.
Speaker 1:Okay, so lots of unknowns there. Let's shift gears a bit. Placement matters, right, we talked about avoiding putting mesh in the defect, but what about putting it inside the abdomen, near the bowel and other organs? That seems risky.
Speaker 2:It absolutely is risky and it's a specific challenge Most standard meshes. If you place them right inside the peritoneal cavity next to your intestines, they tend to cause fibrosis, scarring and promote adhesions. Basically, the bowel can stick to the mesh.
Speaker 1:Which sounds bad.
Speaker 2:It can be very bad. It can lead to bowel obstruction, blockages, things like that. So this led to the development of special meshes called tissue-separating meshes.
Speaker 1:Designed for that specific spot.
Speaker 2:Exactly For intraperitoneal use. They usually have two very different sides. One side is sort of sticky or porous, designed to encourage tissue in growth and stick to the abdominal wall, the fascia or muscle side.
Speaker 1:Okay, sticks to the wall.
Speaker 2:And the other side is deliberately smooth or slippery, made from materials meant to prevent adhesions, so the bowel just glides over it and doesn't stick.
Speaker 1:What kind of slippery materials?
Speaker 2:Things like special cellulose collagen coatings or even a layer of that PTFE we mentioned earlier.
Speaker 1:But do they work perfectly?
Speaker 2:Ah, that's the catch. None of them are 100% effective. Adhesions can still form, even with these specialized meshes.
Speaker 1:So the risk isn't zero.
Speaker 2:Not at all. And because of that residual risk, intraperitoneal mesh placement, putting mesh inside the abdomen is still associated with those serious complications. We worried about Bowel obstruction, yes, but also the mesh eroding directly into the bowel or causing fistulas.
Speaker 1:Erosion and fistulas again. That sounds awful.
Speaker 2:It can be devastating, which leads to the next point.
Speaker 1:Which is.
Speaker 2:Precisely, surgeons now really try to avoid placing mesh inside the peritoneal cavity whenever possible. If there's a way to place it in a different layer of the abdominal wall, that's generally preferred.
Speaker 1:So it comes back to that idea of location, location, location.
Speaker 2:Absolutely. The strength of any mesh repair relies on getting good host tissue ingrowth. You need to lay it tension-free on a healthy, well-vascularized tissue bed and you need that generous overlap.
Speaker 1:Okay, so if intraperitoneal is avoided, what are the preferred spots? You mentioned different planes or layers.
Speaker 2:Right. Surgeons can place the mesh in several different tissue plans, whether they're doing open surgery or laparoscopic keyhole surgery.
Speaker 1:Let's run through them. You mentioned onlay before.
Speaker 2:Yes, onlay is on top of the main muscle layer, the fascia, but just underneath the skin and fat in the subcutaneous space.
Speaker 1:Pros and cons.
Speaker 2:Relatively straightforward to place, maybe, but the cons are significant. If the wound doesn't heal well, the mesh can become exposed and you often have to lift up big flaps of skin to get enough overlap, which can damage the skin's blood supply or lead to fluid collections called seromas.
Speaker 1:Okay, so onlay has risks, then inlay.
Speaker 2:Inlay is in the defect edge to edge. We already said that's not recommended. Doesn't add much strength.
Speaker 1:Right, skip that one. What about sublay?
Speaker 2:Sublay is a key one. This means placing the mesh underneath the main muscle layers of the abdominal wall, but still outside the peritoneum, outside the main abdominal cavity.
Speaker 1:Under the muscle. Why is that good?
Speaker 2:It has a big mechanical advantage. When your abdominal pressure increases, when you cough or lift something, that pressure actually pushes the mesh against the abdominal wall, helping to keep it flat and in place. It aids integration Generally preferred.
Speaker 1:Okay, pressure helps hold, it Makes sense. Then extraperitoneal Sounds similar.
Speaker 2:It is similar in concept. Extraperitoneal just means anywhere outside the peritoneal lining. Sublay is one type of extraperitoneal placement. It shares those advantages Mechanical benefit from pressure and, crucially, avoids contact with the bowel and the risks of intraperitoneal placement, also generally preferred.
Speaker 1:And lastly, intraperitoneal, which we know is inside the cavity.
Speaker 2:Inside the cavity next to the organs, avoided if possible, due to the adhesion and erosion risks.
Speaker 1:So, to sum up, placement, sublay or extraperitoneal seems to be the way to go whenever feasible.
Speaker 2:That's the current thinking.
Speaker 1:yes, Best combination of mechanical advantage and lower risk profile. Okay, beyond placement challenges, what are the other?
Speaker 2:big limitations surgeons run into with mesh. Two really stand out. First, as we touched on with biologicals, is infection.
Speaker 1:Still a big problem.
Speaker 2:Huge. If a synthetic mesh gets infected it almost always needs to be removed completely. That means another operation failure of the repair. It's a major complication. Sometimes maybe you can salvage it with aggressive cleaning, antibiotics, special vacuum dressings, but removal is often necessary.
Speaker 1:Infection is limitation one. What's two?
Speaker 2:Cost Plain and simple, Especially those biological meshes or the newer slowly absorbable ones or the complex tissue separating meshes for intraperitoneal use. They can be very expensive and that can be a barrier sometimes.
Speaker 1:Right Cost is always a factor.
Speaker 2:And this brings us to maybe the most counterintuitive takeaway from all the research and experience.
Speaker 1:Which is.
Speaker 2:Price or how new and fancy a mesh seems is not always a good indicator of how safe or effective it is.
Speaker 1:Really Newer isn't always better.
Speaker 2:It seems not in this case, the consensus. Now, looking at the long-term data, the complications, the patient outcomes, it points towards a simple, non-absorbable, large, poor synthetic mesh like that lightweight polypropylene we talked about as being generally the safest and most reliable implant for the majority of honey repairs.
Speaker 1:Wow, after all that complexity biologicals, absorbables, special coatings the best answer for most people might be the relatively simple, large pore synthetic net.
Speaker 2:That's what the evidence strongly suggests right now. It's quite a lesson in medical technology. Sometimes the tried and true refined over time actually holds up better than the complex newcomer.
Speaker 1:That is genuinely surprising. We've covered so much today the basic definition, how it's used, the different materials, from synthetic to biological to absorbable, the whole shrinkage versus contracture thing, placement strategies it's way more intricate than just hernia mesh.
Speaker 2:It really is more intricate than just hernia mesh. It really is. And seeing that evolution from those early heavy, over-engineered meshes and the failed plug concept to today's preference for these simple, lightweight, large pore designs, it shows how medicine learns and adapts, often based on figuring out what doesn't work or what causes problems long term.
Speaker 1:Yeah.
Speaker 2:And it leaves us with a really interesting question to ponder, especially thinking about those new, slowly absorbable meshes where the long term data just isn't in yet.
Speaker 1:That's the question.
Speaker 2:How do we balance that drive for innovation for the next best thing with what we've learned about the fundamentals, you know? How do we ensure that new developments truly offer better safety and long term comfort for patients and aren't just repeating old mistakes in a new guise? It's a constant balancing act in medicine.
