Effect of Manufacturing Conditions on Structural and Handling Properties of Braided Polyamide Suture

Suture performances include handling characteristics and knot mechanical properties. These performances depend mainly on frictional, flexural, and compressive forces. The interaction between these forces developed inside the suture knot governs the displacement mode and the deformability of the suture yarn inside the knot. In the present work, we studied the effect of manufacturing conditions on structural properties and handling characteristics. Obtained results show that manufacturing parameters have significant impact on slipperiness, flexibility, and compressibility. Consequently, suture performances widely depend on manufacturing parameters. We show that after a hot stretch step, suture structure becomes more uniform and compact. Furthermore, after this treatment, lateral deformation, friction force, and bending rigidity are reduced and knot performances are improved. INTRODUCTION A suture is defined as a thread that either holds adjacent cut surfaces of the wound or compresses blood vessels to stop bleeding [1]. Polyamide was the first synthetic suture available, and it is the most commonly used non absorbable material in dermatologic surgery. It is available in both monofilament and multifilament form. Monofilament sutures are made of a single strand of material. Because of their simplified structure, they encounter less resistance as they pass through tissue than multifilament suture material. Monofilament sutures tie down easily. However, because of their construction, extreme care must be taken when handling and tying these sutures. Crushing or crimping of this suture type can nick or create a weak spot in the strand. This may result in suture breakage. Braided multifilament sutures are commonly used in surgery because of their excellent flexibility and handling proprieties compared to monofilament. They consist of several filaments, or strands, braided together. The braided suture manufacturing processes are described in literature but the available data gives only some step details of these processes [1-3]. In the first step, filaments are coated with spin finish and braided together using a circular braiding machine. During a subsequent step, the spin finish is removed from the filaments by scouring. The suture is then hot stretched to manage its elongation, and annealed in a heated chamber for an extended period of time to relax the structure. Multifilament sutures may also be coated to help them pass smoothly through tissue and enhance handling characteristics. Coated multifilament sutures are well suited to intestinal procedures. The suture manufacture is finished by swaging a needle onto the suture, packaging the needle and suture and finally by sterilizing the package. In the literature, there are a lack of information concerning manufacturing conditions of braided polyamide suture and their impact on suture properties. Chesterfield et al. proposed varieties of braided structures that can be used as a suture, because they have improved flexibility and reduced roughness in suture surface [4]. In order to improve the mechanical properties of polyamide suture, Suryadevara et al. suggested a new method for drawing and annealing polyamide filaments which can be used as monofilament or braided suture [5]. Washington et al. developed a new technique for suture hot stretching [6]. They submitted ligatures to progressive stretch and successive steps of heat treatment. The developed device is composed by a series of rolls with incremented temperature and speed. They recommended this treatment to obtain more uniform and flexible sutures. However, they did not determine the impact of hot stretching conditions on handling characteristics of suture and knot performance. Sutures key properties include tensile strength during the critical wound healing period, knot security, knot slippage, ease of sterilization, foreign body response and handling characteristics [7, 8]. The handling characteristics of suture include pliability and the