Degradation of an ultrasonically welded device for surgical suture holding

A biodegradable ultrasonically welded device has for the first time been developed for in-body sutures that eliminates the need for surgical knotting. The device comprises two parts that fit together, with a suture inserted between them. Ultrasonic welding is then used to secure the suture by welding the two parts together. The device was manufactured from three biodegradable polymers: Poly(L-lactide-co-D,L-lactide) [PLDLA]; Poly(L-lactide-co-glycolide) [PLGA]; Poly(L-lactide) [PLLA]. All devices were degraded through immersion in phosphate buffer solution at a temperature of 37°C ± 2°C. Knotted sutures on their own were also subject to degradation testing. The devices and knotted sutures were mechanically tested at week zero and after 1, 3 and 6 weeks of degradation. Mechanically testing was undertaken to measure the pull-out strength of sutures from the device. PLGA is not suitable for the device, where a significant reduction in failure force was seen after 3 weeks of degradation. By week 6 the mean failure force (±SD) for PLGA was 74.9 ± 23.4 N, which was significantly less than the use of a suture knot on its own, with a mean failure force of 153.2 ± 37.2 N. PLDLA and PLLA were found to be promising materials, with only a small reduction in mean failure force after 6 weeks of degradation. At week 6 there was no significant difference between the mean failure force of PLDLA, PLLA or the suture knot, with mean failure forces of 152.6 ± 15.0, 128.8 ± 35.0 and 153.2 ± 37.2 N, respectively.