A laparoscopic knot-tying device for minimally invasive cardiac surgery

ObJECTIVE: Intracorporeal suturing and knot tying can complicate, prolong or preclude minimally invasive surgical procedures, reducing their advantages over conventional approaches. An automated knot-tying device has been developed to speed suture fixation during minimally invasive cardiac surgery while retaining the desirable characteristics of conventional hand-tied surgeon's knots: holding strength and visual and haptic feedback. A rotating slotted disc (at the instrument's distal end) automates overhand throws, thereby eliminating the need to manually pass one suture end through a loop in the opposing end. The electronic actuation of this disc produces left or right overhand knots as desired by the operator. METHODS: To evaluate the effectiveness of this technology, seven surgeons with varying laparoscopic experience tied knots within a simulated minimally invasive setting, using both the automated knot-tying tool and conventional laparoscopic tools. Suture types were 2/0 braided and 4/0 monofilament. RESULTS: Mean knot-tying times were 246+/-116 s and 102+/-46 s for conventional and automated methods, respectively, showing an average 56% reduction in time per surgeon (p=0.003, paired t-test). The peak holding strength of each knot (the force required to break the suture or loosen the knot) was measured using tensile-testing equipment. These peak holding strengths were normalised by the ultimate tensile strength of each suture type (57.5 N and 22.1N for 2/0 braided and 4/0 monofilament, respectively). Mean normalised holding strengths for all knots were 68.2% and 71.8% of ultimate tensile strength for conventional and automated methods, respectively (p=0.914, paired t-test). CONCLUSIONS: Experimental data reveal that the automated suturing device has great potential for advancing minimally invasive surgery: it significantly reduced knot-tying times while providing equivalent or greater holding strength than conventionally tied knots.