Degradation, infection and heat effects on polypropylene mesh for pelvic implantation: what was known and when it was known
Many properties of polypropylene mesh that are causative in producing the complications that our patients are experiencing were published in the literature prior to the marketing of most currently used mesh configurations and mesh kits. These factors were not sufficiently taken into account prior to the sale of these products for use in patients. This report indicates when this information was available to both mesh kit manufacturers and the Food and Drug Administration.
KeywordsPolypropylene Mesh Degradation Heat Infection
There has been a lack of dissemination of information regarding many of the characteristics of polypropylene mesh especially the many factors which are implicated in the complications that our patients experience postoperatively. The first polypropylene mesh kit cleared by the US Food and Drug Administration (FDA) for implantation was that used in the transvaginal tape (TVT®) procedure for the treatment of stress incontinence. This clearance was granted in 1998. Previously in 1996, a woven polyester mesh kit was cleared and further meshes and mesh kits meshes were granted clearance in the ensuing years. All FDA information regarding clearance for marketing dates is available at http://www.fda.gov/MedicalDevices/default.htm. I will concentrate here on those factors known to influence the behavior of mesh in vivo until 2003, when many more new mesh kits were cleared by the FDA. Heat effects and degradation will be summarized.
Any implanted device must not be physically modified by tissue fluids, be chemically inert, not incite an inflammatory or foreign body cell response, be non-carcinogenic, not produce allergic reactions, stand up to mechanical stress, be fabricated in form required at low cost and be capable of sterilization .
PP monofilament suture had high tensile strength, good flexibility and resistance to fatigue along with good knot retention along with being inert with excellent chemical resistance .
One hundred bacteria were enough to cause infection of a multfilament suture and monofilament suture withstood infection .
Monofilament suture is better than multifilament suture in wound infections .
Granulation formation related to friction between tissue and implant .
Immobile bacteria propagate inside multifilament suture and this plays a role in the spread of infection .
Bacteria are protected in interstices of material .
Bacterial adherence to multifilament suture 5-8 times greater than monofilament suture as documented with SEM .
Pore size is important for tissue incorporation .
Bacteria are protected in interstices from phagocytosis since leukocytes cannot readily enter the small pores of multifilament suture which supports infection and may result in sustained and prolonged infection [10, 11].
Multifilament sutures harbor bacteria at 70 days after implantation as shown with SEM .
Heat exposed PP releases biologically active degradation products affecting normal metabolic events .
Degradation of PP suture known as seen with SEM .
Immediately upon insertion of a mesh there is a race to the mesh surface between bacteria and host defense cells .
Bacteria adhere more to hydrophobic surfaces and produce a biofilm which further protects them from phagocytosis and antibiotics .
Multifilament mesh with a histiocytic reaction and unstable fixation which promotes infection .
Bacteria migrate along synthetic polymeric fibers .
Bacteria adhere to biomaterials using a biofilm .
PP mesh shrinks 30-50% after 4 weeks .
A multifilament mesh must be removed with infection .
Surface roughness promotes wicking of bacteria .
Ten bacterial colony forming units are enough to infect 15% of multifilament meshes .
Bacterial colonization found in 33% of explanted meshes .
IVS® FDA Clearance Letter Dated April 4, 2001
The extent of bacterial adherence depends on the mesh surface area. Multifilament meshes have a 205% increase in surface area compared to monofilament meshes. This may explain infection months to years after implantation .
An abundance of information was available for both the FDA and mesh manufacturers prior to the FDA clearance of most meshes. Many publications detailed degradation mechanisms including heat exposure during manufacture and bacterial colonization of the polypropylene used in pelvic repair meshes.
Conflicts of interest
Paid consultant, American Medical Systems; expert testimony in mesh litigation.
This article is distributed under the terms of the Creative Commons Attribution Noncommercial License which permits any noncommercial use, distribution, and reproduction in any medium, provided the original author(s) and source are credited.
- 4.Van Winkle W, Jr HJC, Barker E, Hines D, Nichols W (1975) Effect of suture materials on healing skin wounds. Surgery 140:933–7Google Scholar
- 10.Osterburg B (1983) Influence of capillary multifilament sutures on the antibacterial action of inflammatory cells in infected wounds. Acta Chir Scand 149:751–7Google Scholar
- 11.Osterburg B (1983) Enclosure of bacteria within capillary multifilament sutures as protection against leukocytes. Acta Chir Scand 149:663–8Google Scholar
- 20.Gl B, Go PM, van Mameren H (1996) Foreign body reactions to monofilament and braided polypropylene mesh used as preperitoneal implants in pigs. Eur J Surg 162:823–5Google Scholar
- 25.Merritt K, Chang CC (1999) Tissue colonization from implantable biomaterials with low numbers of bacteria. J Biomed Mater Res 5:185–203Google Scholar
- 29.Klinge U, Junge K, Spellerburg B, Piroth C, Klosterhalfen B, Schumpelick V (2002) Do multifilament allopolastic meshes increase the infection rate? Analysis of the polymeric surface, the bacterial adherence and the in vivo consequences in a rat model. J Biomed Mater Res 63:765–71PubMedCrossRefGoogle Scholar