Arthroscopic knot tying: The role of instrumentation in achieving knot security

Purpose: To determine the role of arthroscopic knot-tying instrumentation in achieving knot security. Type of study: Biomechanical study. Methods: The security achieved by 3 different commercially available knot-tying instruments using No. 2 braided suture and a standardized knot configuration was compared. Instrumentation included (1) a single-hole knot pusher, (2) a cannulated double-diameter knot pusher, and (3) a mechanical end-splitting knot tightener. Hand-tied knots served as controls. Testing included both cyclic loading and load to failure parameters using the Bionix 858 (MTS Inc, Eden Prairie, MN) and Instron Mini 44 (Instron, Canton, MA) materials testing systems, respectively. An experienced arthroscopic shoulder surgeon and a less experienced junior-level orthopaedic resident surgeon performed tying. Results: Knot displacement after cyclic loading was smallest for the mechanical end-splitting knot tightener (average, 0.054 mm) and did not differ statistically from hand-tied knots (average, 0.058 mm). Knots tied with this device also withstood the greatest load to failure (average, 126.0 N) and were statistically similar to hand-tied knots (average, 134.1 N). The single-hole pusher had an average cyclic loading displacement of 0.095 mm and failed at 108.6 N. The cannulated double-diameter pushers had an average cyclic loading displacement of 0.106 mm and failed at 93.1 N. Both were statistically less secure than hand-tied knots or those tied with the end-splitting tightener. Investigator experience did not affect knot security with those tied by the mechanical end-splitting tightener or hand-tied knots. Conclusions: The end-splitting tightener provided the most secure arthroscopic knots that were statistically as secure as those tied by hand for both investigators. The knot-tying instrument used in arthroscopic shoulder surgery may be an important consideration with potential clinical implications based on knot security. Clinical relevance: The specific knot tying instrument that is selected for use in arthroscopic shoulder surgery may play an important role in the degree of ultimate knot security achieved in suture repair.