Sutures poly

The prolonged retention of breaking strength of poly(p-dioxanone) suture is accompanied by a somew hat slow er rate of absorption than that reported for polyglactin 910 suture or polyglycolic acid suture. Poly(p-dioxanone) suture w as found to be essentially completely absorbed from the rat muscle by 180 days versus 60 to 90 days for polyglactin 910 and more than 120 days for polyglycolic acid suture, w hen similarly tested. 

The inherent flexibility of poly(p-dioxanone) allows it to be fabricated into a monofilament fiber useful for all sizes of sutures. Poly(j>dioxanone) suture has greater pliability than poly(propylene) suture and can provide substantial strength when compared to most other monofilament sutures. 

Vinyl alcohol does not exist as a monomer, but Herrmann and Haehnel (1) were able to obtain the desired product poly(vinyl alcohol) [9002-89-5] (PVA), by polymerizing vinyl acetate and then hydrolyzing the resultant poly(vinyl acetate). This process is employed for the commercial production of PVA even now. The principal concern of the discoverers was development of a suture for surgical operations the fiber then obtained was not suited for clothing use (2). 

Noncrystalline aromatic polycarbonates (qv) and polyesters (polyarylates) and alloys of polycarbonate with other thermoplastics are considered elsewhere, as are aHphatic polyesters derived from natural or biological sources such as poly(3-hydroxybutyrate), poly(glycoHde), or poly(lactide) these, too, are separately covered (see Polymers, environmentally degradable Sutures). Thermoplastic elastomers derived from poly(ester—ether) block copolymers such as PBT/PTMEG-T [82662-36-0] and known by commercial names such as Hytrel and Riteflex are included here in the section on poly(butylene terephthalate). Specific polymers are dealt with largely in order of volume, which puts PET first by virtue of its enormous market volume in bottie resin. 

Lubricious Coatings for Biomaterials. Coatings of poly(ethylene oxide) when dry are tactile. If brought into contact with water, the poly(ethylene oxide) hydates rapidly and forms a lubricious coating. This type of technology is of great interest for biomedical devices introduced into the human body, such as catheters and endotracheal tubes, and for sutures (114—117). 

In order to achieve the desired fiber properties, the two monomers were copolymerized so the final product was a block copolymer of the ABA type, where A was pure polyglycoHde and B, a random copolymer of mostly poly (trimethylene carbonate). The selected composition was about 30—40% poly (trimethylene carbonate). This suture reportedly has exceUent flexibiHty and superior in vivo tensile strength retention compared to polyglycoHde. It has been absorbed without adverse reaction ia about seven months (43). MetaboHsm studies show that the route of excretion for the trimethylene carbonate moiety is somewhat different from the glycolate moiety. Most of the glycolate is excreted by urine whereas most of the carbonate is excreted by expired CO2 and uriae. 

Copolymers of S-caprolactone and L-lactide are elastomeric when prepared from 25% S-caprolactone and 75% L-lactide, and rigid when prepared from 10% S-caprolactone and 90% L-lactide (47). Blends of poly-DL-lactide and polycaprolactone polymers are another way to achieve unique elastomeric properties. Copolymers of S-caprolactone and glycoHde have been evaluated in fiber form as potential absorbable sutures. Strong, flexible monofilaments have been produced which maintain 11—37% of initial tensile strength after two weeks in vivo (48). 

Common biodegradable polymers for medical devices are constructed from synthetic linear aliphatic polyesters. One material commonly used for internal sutures is poly(glycolic acid) (PGA). PGA is synthesized from the dimer of glycolic acid (Fig. 13.1.l). 1... 

Meanwhile Ethicon (and others) developed alternative absorbable surgical sutures, based, for example, on copolymers of polyglycolide with poly-L-lactide or poly(trimethylene carbonate), and on polydioxanone, and on poly(e-oxycaproate), and also on copolymers of these with polyglycolide or with each other. These different structures made it possible to provide fibres with different rates of absorption, with different degrees of stiffness or flexibility, and for use in monofilaments, braided multifilaments, and other yam structures, as required for different surgical operations. 

This field has been well reviewed by B. J. Tighe.(82) The polymers, for the most part, are polyesters. Poly(glycolic acid) (83) is widely used in sutures under the trade name of DEXON. Poly(lactic acid) is also used.(84) A copolymer of 92/8 mole percent poly(glycolic acid)/poly(lactic acid) (85,86) is another alternative. 

The same annealed braids were also subjected to in vivo BSR testing. The results are shown in Figure 1 for both the poly(L-lactide) and 95/5 poly(L-lactide-co-glycolide). These data showed that during the first 4-5 months, both sutures retained... 

Figure 2. In vivo breaking strength retention of Poly(i lactide) compared with commercial absorbable surgical sutures.

Polymers are also used as sutures. Fighters and other athletes have used poly(alpha-cyanoacrylates), super glues, to quickly stop blood flow in surface cuts. Today, super glue is also used for, in place of or along with, more traditional polymeric suture threads for selected surface wounds, internal surgery, and retinal and corneal surgery. The alpha-cyanoacrylate polymers (structure 19.22) undergo anionic polymerization in the presence of water. More about sutures is explained in Section 19.6. 

G. Laroche, Y. Marois, R. Guidoin, M.W. King, L. Martin, T. How, Y. Douville, Poly-vinylidene fluoride (PVDF) as a biomaterial From polymeric raw material to monofilament vascular suture, J. Biomed. Mater. Res. 29(12) (1995) 1525-1536. 

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