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Editorial Commentary: What’s Knot to Like? In the Biomechanics Laboratory, Knotless Shoulder Anchors Hold Their Own
Editorial Commentary: What’s Knot to Like? In the Biomechanics Laboratory, Knotless Shoulder Anchors Hold Their Own Robert A. Pedowitz, M.D., Ph.D.
Abstract: Arthroscopic knot tying remains challenging, and the knots are a weak link for many repair constructs. Knotless strategies continue to evolve, and in some cases, these methods enhance biomechanical repair characteristics. The associated impact on clinical outcomes remains unknown.
See related article on page 2954
A
rthroscopic knot tying is a difficult skill to master. Even for experienced arthroscopic surgeons, knot quality is inconsistent, with a substantial percentage of inadequate knots observed when tested objectively.1,2 Obvious solutions include effective training paradigms, repeated benchtop practice, and fastidious attention to technical consistency during arthroscopic surgery. An alternative strategy is development of fixation methods and surgical techniques that do not rely on arthroscopic knot tying for construct biomechanical performance. The article “Remplissage Using Interconnected Knotless Anchors: Superior Biomechanical Properties to a Knotted Technique?” by Funakoshi, Hartzler, Stewien, and Burkhart3 presents biomechanical support for a specific knotless remplissage technique for anterior shoulder instability in the setting of a Hill-Sachs defect. In this benchtop study, the authors compared a 2-anchor knotted double-pulley repair with a 2-anchor knotless double-pulley repair for infraspinatus tenodesis. Although there were no differences between the groups in gap formation during the 100-N cyclic loading protocol, the knotless repair had significantly higher yield
University of California, Los Angeles The author reports the following potential conflicts of interest or sources of funding: R.A.P. is a consultant for Virtamed and chair of the Fundamentals of Arthroscopic Surgery Training (FAST) Program for AANA/AAOS/ABOS. Full ICMJE author disclosure forms are available for this article online, as supplementary material. Ó 2018 by the Arthroscopy Association of North America 0749-8063/181060/$36.00 https://doi.org/10.1016/j.arthro.2018.08.024
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strength and load to failure than the knotted constructs. The mode of failure in the knotted constructs was generally knot slippage or suture failure, whereas the knotless constructs failed by tendon tear or anchor pullout. Funakoshi et al. should be congratulated for a well-designed biomechanical study with clear questions, solid methodology, and a concise analysis. Will this construct enhance clinical outcomes? Maybe, maybe knot. To put the study in proper context, we should consider a few relevant factors. First, this study used knotless anchors with an internal locking splice mechanism that has unique biomechanical characteristics. Therefore, the study findings cannot be extrapolated to other knotless strategies. Funakoshi et al.3 appropriately disclose their relevant financial conflicts of interest and the research support provided by the maker of these anchors and the associated sutures. Although it is hard to measure the impact of such financial factors on the study findings, at least readers are made aware. The repair procedures were performed in an open manner, with other soft-tissue structures removed. These are idealized (non-arthroscopic) conditions, which are good from the perspective of study design and construct consistency. However, we do not know whether, or how much, construct strength and consistency would be affected by arthroscopic delivery. It was particularly interesting that gap formation with cyclic loading was not statistically different for the 2 repair constructs. In both groups, gap formation was below the clinically relevant threshold as defined by the authors. I found this surprising. Perhaps 100 N of cyclic load was insufficient to show a construct difference. Of
Arthroscopy: The Journal of Arthroscopic and Related Surgery, Vol 34, No 11 (November), 2018: pp 2960-2961
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EDITORIAL COMMENTARY
greater relevance, we can’t be sure that a 100-N infraspinatus load is relevant to postoperative clinical conditions. We also don’t know if early postoperative patients ever subject the repair to the loads required for construct yield and ultimate failure in the current study. Perhaps such loads would be seen with a later dislocation event. By that time (hopefully), the remplissage would have healed, making implant choice relatively unimportant. Food for thought. Finally, these repairs were performed in the absence of a Hill-Sachs lesion. This was a good study decision from the perspective of biomechanical consistency. But what if clinical bone deficiency causes the bone-anchor interface to become the weak link, as opposed to the sutures and knots? In that case, knotless wouldn’t make much of a difference in the setting of a large Hill-Sachs lesion. It will be interesting to scrutinize clinical outcomes of arthroscopic repair using this knotless implant strategy to understand differences in remplissage healing rates and repair failure modalities compared with knotted approaches.
In summary, Funakoshi et al.3 have shown biomechanical advantages of a unique knotless remplissage construct compared with an analogous repair with knots. If a knotless technique can do the job as well as or better than arthroscopic knot tying, why knot? I look forward to the clinical results!
References 1. Hanypsiak BT, DeLong JM, Simmons L, Lowe W, Burkhart S. Knot strength varies widely among expert arthroscopists. Am J Sports Med 2014;42:1978-1984. 2. Pedowitz RA, Nicandri GT, Angelo RL, Ryu RK, Gallagher AG. Objective assessment of knot-tying proficiency with the fundamentals of arthroscopic surgery training program workstation and knot tester. Arthroscopy 2015;31:1872-1879. 3. Funakoshi T, Hartzler R, Stewien E, Burkhart S. Remplissage using interconnected knotless anchors: Superior biomechanical properties to a knotted technique? Arthroscopy 2018;34:2954-2959.
Abstract: Arthroscopic knot tying remains challenging, and the knots are a weak link for many repair constructs. Knotless strategies continue to evolve, and in some cases, these methods enhance biomechanical repair characteristics. The associated impact on clinical outcomes remains unknown.
See related article on page 2954
A
rthroscopic knot tying is a difficult skill to master. Even for experienced arthroscopic surgeons, knot quality is inconsistent, with a substantial percentage of inadequate knots observed when tested objectively.1,2 Obvious solutions include effective training paradigms, repeated benchtop practice, and fastidious attention to technical consistency during arthroscopic surgery. An alternative strategy is development of fixation methods and surgical techniques that do not rely on arthroscopic knot tying for construct biomechanical performance. The article “Remplissage Using Interconnected Knotless Anchors: Superior Biomechanical Properties to a Knotted Technique?” by Funakoshi, Hartzler, Stewien, and Burkhart3 presents biomechanical support for a specific knotless remplissage technique for anterior shoulder instability in the setting of a Hill-Sachs defect. In this benchtop study, the authors compared a 2-anchor knotted double-pulley repair with a 2-anchor knotless double-pulley repair for infraspinatus tenodesis. Although there were no differences between the groups in gap formation during the 100-N cyclic loading protocol, the knotless repair had significantly higher yield
University of California, Los Angeles The author reports the following potential conflicts of interest or sources of funding: R.A.P. is a consultant for Virtamed and chair of the Fundamentals of Arthroscopic Surgery Training (FAST) Program for AANA/AAOS/ABOS. Full ICMJE author disclosure forms are available for this article online, as supplementary material. Ó 2018 by the Arthroscopy Association of North America 0749-8063/181060/$36.00 https://doi.org/10.1016/j.arthro.2018.08.024
2960
strength and load to failure than the knotted constructs. The mode of failure in the knotted constructs was generally knot slippage or suture failure, whereas the knotless constructs failed by tendon tear or anchor pullout. Funakoshi et al. should be congratulated for a well-designed biomechanical study with clear questions, solid methodology, and a concise analysis. Will this construct enhance clinical outcomes? Maybe, maybe knot. To put the study in proper context, we should consider a few relevant factors. First, this study used knotless anchors with an internal locking splice mechanism that has unique biomechanical characteristics. Therefore, the study findings cannot be extrapolated to other knotless strategies. Funakoshi et al.3 appropriately disclose their relevant financial conflicts of interest and the research support provided by the maker of these anchors and the associated sutures. Although it is hard to measure the impact of such financial factors on the study findings, at least readers are made aware. The repair procedures were performed in an open manner, with other soft-tissue structures removed. These are idealized (non-arthroscopic) conditions, which are good from the perspective of study design and construct consistency. However, we do not know whether, or how much, construct strength and consistency would be affected by arthroscopic delivery. It was particularly interesting that gap formation with cyclic loading was not statistically different for the 2 repair constructs. In both groups, gap formation was below the clinically relevant threshold as defined by the authors. I found this surprising. Perhaps 100 N of cyclic load was insufficient to show a construct difference. Of
Arthroscopy: The Journal of Arthroscopic and Related Surgery, Vol 34, No 11 (November), 2018: pp 2960-2961
2961
EDITORIAL COMMENTARY
greater relevance, we can’t be sure that a 100-N infraspinatus load is relevant to postoperative clinical conditions. We also don’t know if early postoperative patients ever subject the repair to the loads required for construct yield and ultimate failure in the current study. Perhaps such loads would be seen with a later dislocation event. By that time (hopefully), the remplissage would have healed, making implant choice relatively unimportant. Food for thought. Finally, these repairs were performed in the absence of a Hill-Sachs lesion. This was a good study decision from the perspective of biomechanical consistency. But what if clinical bone deficiency causes the bone-anchor interface to become the weak link, as opposed to the sutures and knots? In that case, knotless wouldn’t make much of a difference in the setting of a large Hill-Sachs lesion. It will be interesting to scrutinize clinical outcomes of arthroscopic repair using this knotless implant strategy to understand differences in remplissage healing rates and repair failure modalities compared with knotted approaches.
In summary, Funakoshi et al.3 have shown biomechanical advantages of a unique knotless remplissage construct compared with an analogous repair with knots. If a knotless technique can do the job as well as or better than arthroscopic knot tying, why knot? I look forward to the clinical results!
References 1. Hanypsiak BT, DeLong JM, Simmons L, Lowe W, Burkhart S. Knot strength varies widely among expert arthroscopists. Am J Sports Med 2014;42:1978-1984. 2. Pedowitz RA, Nicandri GT, Angelo RL, Ryu RK, Gallagher AG. Objective assessment of knot-tying proficiency with the fundamentals of arthroscopic surgery training program workstation and knot tester. Arthroscopy 2015;31:1872-1879. 3. Funakoshi T, Hartzler R, Stewien E, Burkhart S. Remplissage using interconnected knotless anchors: Superior biomechanical properties to a knotted technique? Arthroscopy 2018;34:2954-2959.