Synthetic bioabsorbable

Polydioxanone (PDS) is completely elirninated from the body upon absorption. The mechanism of polydioxanone degradation is similar to that observed for other synthetic bioabsorbable polymers. Polydioxanone degradation in vitro was affected by gamma irradiation dosage but not substantially by the presence of enzymes (39). The strength loss and absorption of braided PDS, but not monofilament PDS, implanted in infected wounds, however, was significantly greater than in noninfected wounds. 

About two decades ago, most bioabsorbable polymers were natural polymers or derivatives thereof Scientific interest in totally synthetic bioabsorbable polymers has grown considerably since the early seventies because of their relatively low tissue reaction and because of their more predictable in vitro and in vivo properties as compared with the natural materials. Bioabsorbable polymers can be classified into three major groups soluble, solubilizable, and depolymerizable. The structural features and possible mode of bioabsorption of these polymers are outlined as follows. 

M.W.King,Y.Marois,G.R.Marinov,J.P.Delagoutte and R.Guidoin, Monitoring the inflammatory response and rate of resorption of partially resorbable bicomponent fibers. Proceedings of ASTM Symposium on Synthetic Bioabsorbable Polymers for Implants, Kansas City, MO, USA, 16-17 Nov. 1999, p. 8. 

K. Gorona, S. Gogolewski, Novel biodegradable polyurethanes for medical applications, in Synthetic Bioabsorbable Polymers for Implants, ed. by C.M. Agrawal, J.E. Parr, S.T. Lin (ASTM special technical publication, UK, 2000), pp. 39-57... 

Synthetic, bioabsorbable sutures available today are listed in Table 8.9, together with their chemical structure. As can be seen, they are composed of copolymers, except for PGA and poly-p-dioxanone. One of the monomers in the copolymers of aU sutures is glycolide. The surface of most multifilament sutures is coated to permit easy tissue passage, precise knot placement, and smooth tie-down. The coating materials applied include calcium stearate, poly(E-caprolactone) (PCL), PGLA (30 70), and poly(CL-co-GA). The characteristics of these bioabsorbable sutures are briefly described below. 

As demonstrated in this chapter, a variety of bioabsorbable polymers, both natural and synthetic, have been investigated as surgical materials and devices. Sutures have the largest market share among the synthetic bioabsorbable polymer used in medicine. Since different types of monofilament and multifilament sutures with... 

Sakuma, K., Iguchi, A., Ikada, Y., Tabayashi, K. Closure of the pericardium using synthetic bioabsorbable polymers. Ann. Thorac. Surg. 80, 1835-1840 (2005)... 

Barrows, T.H. (1991) Synthetic bioabsorbable polymers, in M. Szycher (ed.), High Performance Biomaterials, Technomic Publ., Lancaster PA, pp. 243-257. Benicewicz, B.C. and Hopper, P.K. (1991) Polymers for absorbable surgical sutures-Part II. J. Bioact. Comp. Polym. 6, 64-95. 

Marois Y, Zhang Z, Vert M, Deng X, Lenz RW, Guidoin R (2000) In Mauli Agrawal C, Parr JE, Lin ST (eds) Synthetic bioabsorbable polymers for implants. American Society for Testing and Materials, West Conshohocken, p 12... 

PGA was used to produce the first example of bioabsorbable synthetic suture threads under the commercial name of Dexon, although the mechanical strength of such devices decreased in a short period of time (2-4 weeks) (Ratner, 2004), limiting the application of this polymer. In order to improve PGA mechanical characteristics, PGA and PLA copolymers were realized PLA is hydrophobic and limits water uptake, slowing the hydrolysis mechanism... 

Anti-adhesive materials have been developed to prevent tissue adhesion by providing a physical barrier between an injured site and the adjacent tissues. Although several non-absorbable synthetic materials such as silicone and PTFE have been shown to be effective, bioabsorbable materials are preferred because of the lack of necessity of secondary surgery to remove non-absorbable materials and the lack of need to consider long-term biocompatibihty such as encapsulation of the material, which will also evoke tissue adhesion. Moreover, non-absorbable synthetic materials have been shown to form adhesions on long-term application [99]. A wide variety of substances and materials have been used over the years. Commercially available anti-adhesive products are summarized in Table 8.7. 

Non-bioabsorbable sutures are defined by their resistance to degradation by living tissues. They are most useful in percutaneous closures. Synthetic, non-bioabsorbable, monofilament sutures include nylon, polypropylene, and polybutester sutures, while synthetic, non-bioabsorbable, multifilament (braided) sutures are composed of nylon and polyester. Polybutester, developed in 2000, is a block copolymer that contains butylene terephthalate and telramethylene ether glycol. Metallic fibers such as steel fibers are also used extensively for suturing. 

This type of copolymer is prepared as A-B-A block copolymers in a 2 1 GA trimethylene carbonate (TMC) ratio, with a GA-TMC center block (B) and pure GA end blocks (A). These materials have better flexibility than pure PGA and are absorbed in approximately 7 months. This copolymer was developed to combine the predictable in vivo performance of a synthetic absorbable suture with the handling characteristics of a monofilament suture. The copolymer has a high initial tensile strength (greater than that of polydioxanone) and retains 81 % of its strength at day 14, 59 % at day 28, and 30 % at week 6. This suture is easier to handle and has greater knot security than the three bioabsorbable sutures mentioned above. 

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