EXPERIMENTAL STUDY Mechanical testing of different knot types using high-performance suture material M. H. Baums • Ch. Sachs • T. Kostuj • K. Schmidt-Horlohe ´ • W. Schultz • H.-M. Klinger Received: 13 May 2013 / Accepted: 3 October 2013 Ó Springer-Verlag Berlin Heidelberg 2013 Abstract Purpose This laboratory study aimed to evaluate the loop security, knot security, cyclic loading resistance and load- to-failure rate of three different knot types with establish- ing a new experimental set-up. Additionally, the mode of failure of each knot was evaluated. Methods With the use of nonabsorbable, braided poly- ethylene sutures, USP size No. 2 [Hi-Fi Ò ; ConMed Lin- vatec], the arthroscopic knot types Dines, SMC as well as the surgeon’s knot were tested using a material testing machine. The knots were tied openly as well as arthro- scopically. The set-up enables testing of knot configura- tions while eliminating friction between knot loop and its suspension points. Including all test procedures, a total of 216 knots were tested. Results All openly tied knot types and ten of each type of arthroscopically tied knots resisted against cyclic loading of 1,000 cycles. With subsequent load-to-failure testing, openly tied knot types achieved significantly higher values of tensile strength than arthroscopically tied knots. Regarding clinical failure, defined as an elongation of 3 mm, Dines knot reached highest loop as well as knot security. Knot slippage was the most common failure mechanism at an elongation of 3 mm, whereas suture breakage was evaluated most at an elongation of 6 mm. Conclusions The new experimental set-up confirms the loop security of arthroscopic knot types. Using a knot pusher clinically is a key factor to attain this as compared to openly hand-tied techniques. The Dines knot presented the highest reliability. It may provide a secure tissue healing during rehabilitation and consequently can be recommended for clinical application. Keywords Suture knots Á Biomechanics Á Ultra-high molecular weight polyethylene Á Cyclic loading Á Security Introduction Suture–knot configurations are an essential basis for post- operative tissue healing. In this context, the knot itself, irrespective of its configuration or suture material, is the weakest link [29]. In the quest for stable, simple knots coupled with the growing popularity of arthroscopic pro- cedures, the spectrum of knot styles is constantly expand- ing [3]. Therefore, knot configurations should be tested prior to clinical application, specifically in conjunction with new suture materials [26]. Testing should be carried out under conditions that most closely approximate the in vivo setting and take the laws of physics into account to gain significant findings. Moreover, the effect of different knot-tying techniques should be addressed [10]. However, the in vivo conditions have not been suffi- ciently simulated to date [19], and laws of physics often were disregarded in using a fixed experimental set-up. In addition, the effect of knot tying using open and M. H. Baums (&) Á Ch. Sachs Á W. Schultz Á H.-M. Klinger Department of Orthopaedic Surgery, University of Go ¨ttingen Medical Centre (UMG), Georg-August-University, Robert-Koch-Str. 40, 37099 Go ¨ttingen, Germany e-mail: mbaums@t-online.de T. Kostuj Department of Orthopaedics, Trauma Surgery and Rheumatology, Katholisches Krankenhaus Dortmund-West, Dortmund, Germany K. Schmidt-Horlohe ´ Department of Trauma and Orthopaedic Surgery, Trauma Center Frankfurt/Main, Frankfurt, Germany 123 Knee Surg Sports Traumatol Arthrosc DOI 10.1007/s00167-013-2711-9