Journal of Biomedical Materials Research, Vol. 20, (1986) John Wiley & Sons, Inc.

Transcription

1 Journal of Biomedical Materials Research, Vol. 20, (1986) John Wiley & Sons, Inc.

2 862 Characterization of morphologic and mechanical properties of surgical mesh fabrics C. C. Chu, B. Pourdeyhimi,* and L. Welch Department of Design and Environmental Analysis, Martha Van Rensselaer Hall, Cornell University, lthaca, Ny The objective of this study is to use standard testing methods to characterize the currently available synthetic mesh fabrics in terms of their chemical, physical, mechanical, and morphologic properties. Three commonly used surgical mesh fabrics, Mersilene (Ethicon), Marlex (Davol), and Teflon (USCI), were used, and the tests reveal that they differ from one another chemically as well as configurationally. The experiment included an identification of the structure of the yarn and fabrics; a measurement of the porosity, pore size and shape; and a determination of tensile and bursting strength, flexural rigidity, and wrinkle recovery. A wide variation in structure and performance was observed among the three mesh fabrics. Mersilene mesh fabrics have the highest relative porosity, while Marlex and Teflon meshes have an equivalent, but lower value. Marlex meshes have the highest tensile and bursting strength followed by Teflon and Mersilene meshes. All three meshes have one common strength characteristic - a distinctive difference in tensile strength between the wale and course directions. Marlex mesh fabrics exhibit an immense flexural rigidity and poor wrinkle recovery, due mainly to the monofilament structure of the yarn. Mersilene and Teflon mesh fabrics have similar but considerably lower, flexural rigidity than Marlex. Thus, it is evident that the chemical nature of the constituent fibers, as well as the yarn and fabric structure, have a great effect on the performance of the resulting mesh fabrics. The availability of this characterization data can serve as the basis for a surgeon s selection of the most appropriate commercial surgical mesh fabric for each case, as well as to provide a foundation for the subsequent comparison of their in vivo performance. INTRODUCTION Defects of the body s tissues are the direct result of the radical resection of a cancer tumor, congenital lesions, infection and subsequent necrosis and debridement, violent crimes, accidents, or large hernias. Attempts to close these large defects are essential to save the patient s life, as well as to restore normal body functions. For those large defects lacking adequate tissue to *Current address: Department of Textiles and Consumer Economics, University of Maryland, College Park, MD Dr. B. Pourdeyhimi s name was omitted as the second author of the article by C.C. Chu, B. Pourdeyhimi, and L. Welch in the October 1985 issue (Journal of Biomedical Materials Research, Volume 19, Number 8 pp ). Please note the correction on this page.

3 863 permit primary repair, it is highly desirable to use materials of either a synthetic or a natural origin to reinforce tenuous aponeurotic closures and/or to bridge large defects in the abdominal or chest wall. A wide variety of biological and synthetic materials has been used to repair the defected body wall. Biological materials include autologous, homologous, and heterologous transplants of fascia lata, skin or dermis, and dura mater.i4 Synthetic materials include tantalum, stainless steel, polyamide (nylon), polyester (Dacron), polytetrafluoroethylene (Teflon), polypropylene (Marlex), and carbon fiber^.^-'^ These synthetic materials are fabricated in either a woven or knitted structure, and exhibit various levels of porosity and strength. Despite almost a century of experimentation, the use of such materials remains ~nsatisfactory,~,'~ and new products are continually being developed and promoted. Among the synthetic materials, metallic meshes have been shown to become work-hardened, inflexible, friable, and fragmented with time.2,3,1e They may protrude through the skin or erode into adjacent tissue or blood vessels. The plastic meshes are more successful, but still exhibit various problems. Mersilene meshes produce good results in tissue repair, but often produce seromas as the most common c~mplication.'~ Meshes made of Teflon are generally satisfactory, particularly in the presence of infection, but have "too much stretch"" and do not stimulate sufficient fibroplasia to be incorporated into the ti~sue.~ Meshes made of Marlex, the most commonly used, have the lowest frequency of related complications.20 However, they are relatively stiff and occasionally injures the underlying abdominal viscera.21 Long-term complications associated with Marlex mesh, such as mesh extrusion and/or en tric fistulae following coverage by split-thickness skin, have been reported.22 In addition, all the above plastic meshes share one common disadvantage- they must be removed in most cases if infection develops. To facilitate a better understanding of the failure modes of surgical meshes, in terms of their properties, and to aid the development of new and better surgical meshes, it is important to evaluate the properties of the currently used meshes systematically and quantitatively. Thus, the purpose of this study is to characterize all currently available synthetic mesh materials in terms of their chemical, physical, mechanical, and morphologic properties.

4 864 Figure 2, of the article by Frank DeLustro, Richard A. Condell, Mai Anh Nguyen, and John M. McPherson in the January issue was inadvertently misprinted (Journal of Biomedical Materials Research, Volume 20, Number 1 pp ). It is as follows: 2.5 ELISA Results (Absorbance at 414nm) r Serum Dilution (1: ) Figure 2. Sera were obtained on day 39 from guinea pigs implanted with collagen devices and examined in the ELISA for antibodies to their respective implant material. Results are expressed as the mean absorbance value obtained for each group (n = 7-8) Intact Collagen, -..- Collastat, --_-- Koken Atelocollagen, Gelfoam, Avitene -- Gax Collagen, - zc1.

5 865 Dr. H.D. Wagner's first initial and his address were omitted from the article by B. Pourdeyhimi and H. D. Wagner in the March issue (Journal of Biomedical Maferials Research, Volume 20, Number 3 pp ). Please note the corrections on the following page. On the correlation between the failure of vascular grafts and their structural and material properties: A critical analysis B. Pourdeyhirni* Department of Design and Environmental Analysis, New York State College of Human Ecology, Cornell University, Ithaca, New York H- D. Wagner** Sibley School of Mechanical and Aerospece Engineering, Cornell university, lthaca, NY A statistical investigation of reported vascular graft failures over a period of 30 years is undertaken. The most important causes of graft failure are underlined, as well as the time to failure and relative frequency of each failure mechanism. This brings out the need for a critical review of the properties of basic textile structures used in today's vascular prosthetic grafts. The physiologic and structural factors which contribute to mechanical failure of arteries and arteryhmplant composite systems are analyzed. The importance of obtaining the complete set of time-dependent elastic constants of the artery-which is viewed as an anisotropic material-is pointed out. Future research areas important for characterizing the mechanical behavior of artery/ implant systems are suggested, with the aim of establishing rational standards for prosthesis evaluation. INTRODUCTION With the widespread use of synthetic arterial grafts, complications inherent to these prostheses are being reported with increasing frequency. It should be noted that the true incidence of failure of arterial grafts is believed to be significantly greater than that reported in the literature.' Although there has been some concern about the suboptimal vascular surgery being performed in this countryi2 not sufficient emphasis has been placed on identifying those inherent features of the vascular grafts that could contribute to'their long term success or short term failure. Today, complete rational standards for evaluating the performance of such prostheses are not established. It is hoped that this article will help achieve that end. What follows is an explanation of the type of materials and textile structures used, a discussion of the causes of failure, and an analysis of graft failure data reported.in the literature. It is shown that the failure of vascular grafts may be analyzed using Weibull statistics. * Correspondence address: Department of Textiles and Consumer Economics, University of Maryland, College Park, MD **Current address: Department of Materials Research Weizmann Institute of Science, Rehovot 76100, Israel.