Breaking strength of barbed polypropylene sutures: rater-blinded, controlled comparison with nonbarbed sutures of various calibers

OBJECTIVES: To assess the strength of 2.0 barbed polypropylene suture, and, specifically, to determine the load required to break this suture, and to compare this with the strength of nonbarbed polypropylene suture. DESIGN: Rater-blinded, controlled trial. The individual responsible for setting up the experimental conditions was not blinded. SETTING: Biomechanics laboratory in an academic medical center. MATERIALS: This study did not include human subjects. Materials used included six 2.0 barbed polypropylene sutures and 3 each of 2.0, 3.0, 4.0, and 5.0 nonbarbed polypropylene sutures. Each suture was randomly selected from a different batch or box of similar sutures. INTERVENTION: Each suture was strung between 2 (top and bottom) cylinders and tied with a surgeon's knot. A tensile testing device was used to apply increasing force until the suture broke. Data were acquired through an analog-to-digital board on an IBM-compatible computer using commercially available software. MAIN OUTCOME MEASURES: Ultimate strength, stiffness, and elongation before suture rupture. RESULTS: Strength of the barbed sutures (mean SD] ultimate strength, 39.5 9.0] N) was intermediate between that of 2.0 (55.0 N) and 3.0 (36.4 N) nonbarbed sutures and was not significantly different from that of 3.0 nonbarbed sutures (P = .5). Barbed 2.0 polypropylene sutures differed significantly (P < .001) from each of the other types of nonbarbed sutures on measures of stiffness and elongation. Elongation of barbed sutures was closest to that of 3.0 nonbarbed sutures (P = .002). Stiffness of the barbed sutures (mean SD], 4.7 0.7] N/mm) was markedly in excess of that of any of the other suture types (P < .001). CONCLUSIONS: Barbed 2.0 polypropylene sutures seem to be at least as strong as 3.0 nonbarbed polypropylene sutures. As such, barbed sutures are significantly stronger than their rated strength, which has been stated as comparable to 4.0 nonbarbed sutures. This has implications for the long-term in vivo safety of barbed sutures.