Материал: surgical knot tying manual covidien

suture is minimal until about the 60th day post-implantation and essentially complete within six months.

Another innovation in the development of monofilament synthetic absorbable sutures has been the production of Glycomer 631, a terpolymer composed of glycolide (60%), trimethylene carbonate (26%), and dioxanone (14%) (Biosyn™). The Biosyn™ suture has many distinct advantages over the braided synthetic absorbable sutures.17 First, this monofilament suture is significantly stronger than the braided synthetic absorbable suture over four weeks of implantation. It maintains approximately

75% of its USP tensile strength at two weeks and 40% at three weeks postimplant. Absorption is complete between 90 to 110 days. Due to it’s construction,

Monofilament suture potentiates less bacterial infection than does the braided suture. The handling characteristic of this monofilament suture is superior to the braided suture because it encounters lower drag forces in the tissue than does the braided suture.

The latest innovation in the development of monofilament absorbable sutures has been the rapidly absorbing Caprosyn™ suture. Caprosyn™ monofilament synthetic

17

III. scientific basis for the selection of surgical sutures (cont’d)

absorbable sutures are prepared from Polyglytone™ 6211 synthetic polyester which is composed of glycolide, caprolactone, trimethylene carbonate, and lactide. Implantation studies in animals indicate that Caprosyn™ suture retains a minimum of 50-60% USP knot strength at five days post implantation, and a minimum of 20-30% of knot strength at 10 days post implantation. All of its tensile strength is essentially lost by 21 days post implantation.

We recently have compared the biomechanical performance of Caprosyn™ suture to that of Chromic Gut suture.18 The biomechanical performance studies included quantitative measurements of wound security, strength loss, mass loss, potentiation of infection, tissue drag, knot security, knot rundown, as well as suture stiffness. Both Caprosyn™ and Chromic Gut sutures provided comparable resistance to wound disruption. Prior to implantation, suture loops of Caprosyn™ had a significantly greater mean breaking strength than suture loops of Chromic Gut. Three weeks after implantation of these absorbable suture loops, the sutures had no appreciable strength. The rate of loss of suture mass of these two sutures was similar. As expected, Chromic Gut sutures potentiated significantly more infection than did the Caprosyn™ sutures.

18

The handling properties of the Caprosyn™ sutures were far superior to those of the Chromic Gut sutures. The smooth surface of the Caprosyn™ sutures encountered lower drag forces than did the Chromic Gut sutures. Furthermore, it was much easier to reposition the Caprosyn™ knotted sutures than the knotted Chromic Gut sutures. In the case of Chromic Gut sutures, it was not possible to reposition a two-throw granny knot. These biomechanical performance studies demonstrated the superior performance of synthetic Caprosyn™ sutures compared to Chromic Gut sutures and provide compelling evidence of why Caprosyn™ sutures are an excellent alternative to Chromic Gut sutures.

The direct correlation of molecular weight and breaking strength of the synthetic absorbable sutures with both in vivo and in vitro incubation implies a similar mechanism of degradation. Because in vitro incubation provides only a buffered aqueous environment, the chemical degradation of these sutures appears to be by non-enzymatic hydrolysis of the ester bonds. Hydrolysis would be expected to proceed until small, soluble products are formed, then dissolved, and removed

from the implant site. In contrast, the gut or collagen suture, being a proteinaceous substance, is degraded primarily by the action of proteolytic enzymes.

19

III. scientific basis for the selection of surgical sutures (cont’d)

A distinction must be made between the rate of absorption and the rate of tensile strength loss of the suture material. The terms rate of absorption and rate of tensile strength loss are not interchangeable. Although the rate of absorption is of some importance with regard to late suture complications, such as sinus tracts and granulomas, the rate of tensile strength loss is of much greater importance to the surgeon considering the primary function of the suture, maintaining tissue approximation during healing.

When considering an absorbable suture’s tensile strength in vivo, we recommend that the manufacturer provide specific measurements of its holding capacity, rather than the percentage retained of its initial tensile strength. The United States Pharmacopoeia (USP) has set tensile strength standards for synthetic absorbable suture material. If the manufacturers were to use these standards to describe maintenance of tensile strength, the surgeon would have a valid clinical perspective to judge suture performance. Some manufacturers persist in reporting maintenance of the tensile strength of their suture in tissue by referring only to the percentage retained of its initial tensile strength, making comparisons between

20

sutures difficult. The need to use USP standards in reporting is particularly important when there are marked differences in the initial tensile strengths of the synthetic sutures. For example, the initial tensile strength of Biosyn™ is 43% stronger than that of polydioxanone. At two weeks, the Biosyn™ suture is approximately 30% stronger.

21