In Vitro Loss of Tensile Strength and Elasticity of Five Absorbable Suture Materials in Sterile and Infected Canine Urine

Abstract

The loss of breaking strength and elasticity of five absorbable suture materials (polydioxanone [PDS-II], polyglycolic acid [PGA], polyglactin 910 [PG-910], polyglyconate [GTMC], and chromic gut) after in vitro incubation in sterile, Escherichia coli- and Proteus mirabilis-inoculated canine urine was studied. Biomechanical testing, in a controlled environment, was performed during the 28-day study period. Polydioxanone and chromic gut retained greater than 90% of their original strengths after 28 days of incubation in sterile urine and 87% of original strengths in E. coli-inoculated urine. Polyglyconate retained 24% and 18% of original strength, respectively, after incubation in sterile and E. coli-inoculated urine for 28 days. Polyglycolic acid and PG-910 retained less than 30% of original strength in sterile urine and only 7% in E. coli-inoculated urine after 21 days of incubation. In P. mirabilis-inoculated urine, loss of tensile strength and elongation was significant for all suture materials. Polyglycolic acid and PG-910 lost all strength after 24 hours of incubation. Polydioxanone lost all strength after 7 days of incubation, whereas GTMC retained 19% at day 7. Chromic gut retained 78% at day 7 and 16% after 21 days of incubation, however, the absence of normal phagocytic destruction of chromic gut in this in vitro study may have artificially elevated these values. In sterile urine with chemically modified pH, loss of strength and elongation was greater in alkaline urine than in neutral or acidic urine for all types of suture materials.

Measuring the strength of knotted suture materials

“…A knot-tensioning load or force is reported in few investigations reviewed (e.g. 1.5 kg [Rosin & Robinson, 1989], 1 N [Schiller et al, 1993], 7 N [Nilsson, 1982], and 9 N [Holmlund, 1974]). Results from a trial involving 10 surgeons tying sutures around synthetic tissue did not include values for the knot-tensioning loads, but in the subsequent investigation knots were tensioned with a force of 10 N (Annunziata et al, 1997).…”

“…In the cut-loop method a loop is formed as in the loop method, however the knotted suture loop is cut opposite the knot and each newly formed end is placed in a jaw of a tensile tester (Huber et al, 1999;Lewis, Milthorpe, & Bellenger, 1997;Rodeheaver, Green, Odum, Bussard, & Edlich, 1998;Rosin & Robinson, 1989;Schiller, Stone, & Gupta, 1993;Tera & Aberg, 1976a;Thacker et al, 1975). Although the load is applied to the patient's side, the cutloop technique usually measures knot slippage rather than knot strength, the measured values being affected by the length of the ears.…”

Tensile Strength of Absorbable Suture Materials: In Vitro Analysis of the Effects of pH and Bacteria

“…7,8 Bacteria such as Proteus spp should theoretically cause greater suture degradation through urease-splitting action to produce ammonia, which accelerate destruction of absorbable suture materials that undergo hydrolysis. 5,8 However, the data obtained from this study suggested slightly greater suture materials degradation in an E coli inoculated medium than a Proteus inoculated medium.…”

Sutures and general surgical implants

“…5 Polydioxanone Polydioxanone (PDS) or poly-p-dioxanone is a slowly absorbable monofilament suture composed of the polyester, poly (p-dioxanone). It is naturally degraded in the body by hydrolysis and has approximately 60% strength left at 14 days; absorption is completed between 60 and 90 days.…”

“…5 It is biologically inert and can easily be sterilized by autoclaving. Steel has the highest strength of any other suture material.…”