Pelvic Mesh Surgery - “good enough” is just not good enough

As new cases come to light highlighting the traumatic complications from vaginal mesh surgery in the UK, Professor of Tissue Engineering, Sheila MacNeil explains the need for better materials.

Prof Sheila MacNeil

Pelvic prolapse is a difficult area to treat. Patients struggle to make their concerns known and even some of the clinicians interviewed regularly seem to suggest that the operation works well if you simply know what you’re doing - this isn’t the case.Where we are now in the treatment of stress urinary incontinence and pelvic organ prolapse is that surgeons are probably doing the right operation but with a suboptimal material.

The polypropylene meshes currently being used in the pelvic floor were never tested for their performance in this very demanding environment. These meshes were used for hernia repair.

When implanting mesh to repair an abdominal hernia you need quite a strong material with big gaps between the fibres, which the patient’s own muscle grows into. When you get it right, the repair you achieve is better than if you didn’t use mesh.

However, initial meshes did produce complications. It is worth noting that there was at least a decade of modifying these meshes for hernia repair, essentially reducing the amount of bulk polypropylene per area to reduce the inflammatory response they initiated in the body. In fact, some of the early meshes were actually withdrawn because of clinical side effects. When manufacturers began to produce lighter meshes there was less inflammation, less contraction and less pain.

Surgeons also found that they had better results if they inserted the current polypropylene mesh directly on the muscle wound bed (where there is a rich blood supply) and that the tissue grew into the mesh very successfully. However, in the medical device industry it’s important to develop your material or implant to do the job you want it to do in that specific site in the body.

Following on from the success with hernia repairs, manufacturers produced versions of this mesh for surgeons to use in the pelvic floor, often inserting the material through the vagina. We know that the use of mesh here can cause sustained inflammation, more so in some patients than others. We also know that these very stiff inelastic meshes copes poorly with the physical forces experienced in the pelvic floor. Basically if you bounce up and down on a polypropylene mesh it will distort irreversibly and when it does it can actually cut through the patient’s tissues. As more severe side effects were found with these meshes, a few researchers and clinicians began to look critically at what was going on.

The first key bit of data came from researchers in New Zealand (Poul Nielson) who measured the forces that occur within the vagina when normal healthy volunteers exercise and found that, surprisingly, the biggest increases in pressure occurred in response to involuntary actions such as coughing, sneezing and even laughing, which are all the occasions that cause women with stress urinary incontinence to leak urine. The pressures that developed within the vagina were greater than those which developed in the abdomen

Then in 2013 a urogynaecologist in Leuven; Professor Jan de Prest, showed that sheep implanted with polypropylene mesh tolerated it well when it was in the abdomen but showed persistent inflammation when the same material was implanted in the vagina, mimicking what happens when it is used in women. Indeed in three out of the 10 sheep in the first study, the material eroded through the vaginal tissues. This study was the first to show that you couldn’t just take a mesh that worked well in the abdomen and assume it would work well in the vagina.

When the polypropylene meshes were introduced clinically the onus on reporting problems was left with the manufacturers. Which just didn’t happen.

This sorry state of affairs means that even to this day women are struggling to get GPs and surgeons to believe the extent of the complications they are suffering and the real incidence of severe complications, which often require further surgery to try and remove the mesh, has been underreported until fairly recently.

For all but a handful of researchers and surgeons worldwide who are close enough to the problem to know, another consequence of this has been that there has been very little research into improving on these materials or developing new materials.

When experienced urogynaecologists still find that this material produces poor results in an unacceptable number of patients then surely it’s time to say that we need better materials.

Prof. Sheila Macneil

A few manufacturers have made some modifications to the materials, making them softer and in some cases coating them to see if they can improve the body’s response to them. However, for as long as manufacturers and surgeons are saying there isn’t a problem then this makes it challenging to develop the new materials that are so badly needed.

Over the last six years our group in Sheffield have been developing new materials starting from a blank sheet of paper and designing materials that will be mechanically appropriate for use in the pelvic floor and are well tolerated. We have been very fortunate to have funding from the UK and European urology associations as they know of the need to develop better materials.

However, when it comes to seeking funding from non-specialist research organisations, the problems of urinary stress incontinence and pelvic organ prolapse are not viewed as important alongside bids for research funding for cancer and heart disease for example.

In October 2017 with Royal Society funding there will be a workshop in London on on-going research from the UK, Europe, America and Australia focusing on developing materials specifically for use in the pelvic floor. This is long overdue.

When experienced urogynaecologists still find that this material produces poor results in an unacceptable number of patients then surely it’s time to say that we need better materials.

The cloak of silence over the actual incidence and severity of side-effects means there has been comparatively little research to develop better materials for patients during all this time. Our group consists of surgeons who treat women with stress urinary incontinence and who have the very difficult job of trying to remove meshes that are causing pain and scientists who are developing materials with appropriate strength and elasticity to perform well in the pelvic floor.
We are not just developing strong and flexible materials, but ones that also release the female hormone oestrogen, which helps stimulate new blood vessels in the area and new tissue formation. We are also exploring using cells derived from the patient’s abdominal fat to be introduced into the body with the support material to assist in the repair of the weakened tissues of the pelvis.

Given the current shocking state of affairs it’s really depressing that we and others haven’t already produced next-generation improved materials for use in the pelvic floor. When surgeons remove the polypropylene mesh they currently have no good alternative material to put in place.

Why are we in this state?
Well when companies and even some surgeons downplay the problem it’s very difficult for researchers to find the funding to develop the next generation of materials that will help surgeons treat woman with stress urinary incontinence and pelvic organ prolapse and not lead to horrific side effects.

This has to change. Women deserve to be treated with better materials designed for use in the pelvic floor –this is a situation where “ good enough” is simply not good enough.

Sheila MacNeil, Professor of Tissue Engineering, Department of Materials Science and Engineering at The University of Sheffield