Original Research

In Vitro and In Situ Characterization of Arthroscopic Loop Security and Knot Security of Braided Polyblend Sutures: A Biomechanical Study

Am J Orthop. 2015 April;44(4):176-182

References

1. Burkhart SS, Wirth MA, Simonich M, Salem D, Lanctot D, Athanasiou K. Knot security in simple sliding knots and its relationship to rotator cuff repair: how secure must the knot be? Arthroscopy. 2000;16(2):202-207.

2. Burkhart SS, Wirth MA, Simonich M, Salem D, Lanctot D, Athanasiou K. Loop security as a determinant of tissue fixation security. Arthroscopy. 1998;14(7):773-776.

3. Elkousy H, Hammerman SM, Edwards TB, et al. The arthroscopic square knot: a biomechanical comparison with open and arthroscopic knots. Arthroscopy. 2006;22(7):736-741.

4. Elkousy HA, Sekiya JK, Stabile KJ, McMahon PJ. A biomechanical comparison of arthroscopic sliding and sliding-locking knots. Arthroscopy. 2005;21(2):204-210.

5. Ilahi OA, Younas SA, Alexander J, Noble PC. Cyclic testing of arthroscopic knot security. Arthroscopy. 2004;20(1):62-68.

6. Loutzenheiser TD, Harryman DT 2nd, Ziegler DW, Yung SW. Optimizing arthroscopic knots using braided or monofilament suture. Arthroscopy. 1998;14(1):57-65.

7. Chan KC, Burkhart SS, Thiagarajan P, Goh JC. Optimization of stacked half-hitch knots for arthroscopic surgery. Arthroscopy. 2001;17(7):752-759.

8. Lee TQ, Matsuura PA, Fogolin RP, Lin AC, Kim D, McMahon PJ. Arthroscopic suture tying: a comparison of knot types and suture materials. Arthroscopy. 2001;17(4):348-352.

9. Mishra DK, Cannon WD Jr, Lucas DJ, Belzer JP. Elongation of arthroscopically tied knots. Am J Sports Med. 1997;25(1):113-117.

10. Kim SH, Ha KI, Kim SH, Kim JS. Significance of the internal locking mechanism for loop security enhancement in the arthroscopic knot. Arthroscopy. 2001;17(8):850-855.

11. Weston PV. A new clinch knot. Obstet Gynecol. 1991;78(1):144-147.

12. Lo IK, Burkhart SS, Chan KC, Athanasiou K. Arthroscopic knots: determining the optimal balance of loop security and knot security. Arthroscopy. 2004;20(5):489-502.

13. Lo IK, Burkhart SS, Athanasiou K. Abrasion resistance of two types of nonabsorbable braided suture. Arthroscopy. 2004;20(4):407-413.

14. De Beer JF, van Rooyen K, Boezaart AP. Nicky’s knot—a new slip knot for arthroscopic surgery. Arthroscopy. 1998;14(1):109-110.

15. Loutzenheiser TD, Harryman DT 2nd, Yung SW, France MP, Sidles JA. Optimizing arthroscopic knots. Arthroscopy. 1995;11(2):199-206.

16. Wetzler MJ, Bartolozzi AR, Gillespie MJ, et al. Fatigue properties of suture anchors in anterior shoulder reconstructions: Mitek GII. Arthroscopy. 1996;12(6):687-693.

17. Barber FA, Herbert MA, Beavis RC. Cyclic load and failure behavior of arthroscopic knots and high strength sutures. Arthroscopy. 2009;25(2):192-199.

18. Richmond JC. A comparison of ultrasonic suture welding and traditional knot tying. Am J Sports Med. 200;29(3):297-299.

19. James JD, Wu MM, Batra EK, Rodeheaver GT, Edlich RF. Technical considerations in manual and instrument tying techniques. J Emerg Med. 1992;10(4):469-480.

20. Batra EK, Franz DA, Towler MA, et al. Influence of emergency physician’s tying technique on knot security. J Emerg Med. 1992;10(3):309-316.

21. Livermore RW, Chong AC, Prohaska DJ, Cooke FW, Jones TL. Knot security, loop security and elongation of braided polyblend sutures used for arthroscopic knots. Am J Orthop. 2010;39(12):569-576.

22. Tera H, Aberg C. The strength of suture knots after one week in vivo. Acta Chir Scand. 1976;142(4):301-307.

23. Babetty Z, Sümer A, Altintaş S, Ergüney S, Göksel S. Changes in knot-holding capacity of sliding knots in vivo and tissue reaction. Arch Surg. 1998;133(7):727-734.

24. Milia MJ, Peindl RD, Connor PM. Arthroscopic knot tying: the role of instrumentation in achieving knot security. Arthroscopy. 2005;21(1):69-76.

25. Lieurance RK, Pflaster DS, Abbott D, Nottage WM. Failure characteristics of various arthroscopically tied knots. Clin Orthop. 2003;(408):311-318.

26. Abbi G, Espinoza L, Odell T, Mahar A, Pedowitz R. Evaluation of 5 knots and 2 suture materials for arthroscopic rotator cuff repair: very strong sutures can still slip. Arthroscopy. 2006;22(1):38-43.

27. Wüst DM, Meyer DC, Favre P, Gerber C. Mechanical and handling properties of braided polyblend polyethylene sutures in comparison to braided polyester and monofilament polydioxanone sutures. Arthroscopy. 2006;22(11):1146-1153.

28. Mahar AT, Moezzi DM, Serra-Hsu F, Pedowitz RA. Comparison and performance characteristics of 3 different knots when tied with 2 suture materials used for shoulder arthroscopy. Arthroscopy. 2006;22(6):614.e1-e2.

For the in situ condition, the same test parameters were used, except that each combination of the suture loop was preloaded to 6 N and soaked in physiologic solution bath (human blood plasma) at 37°C (body temperature) for 24 hours before testing in an effort to simulate the aqueous medium in vivo after surgery. The in situ tests were performed under physiologic solution maintained at 37°C to approximate postoperative physical conditions.

Statistical Analysis

Means and standard deviations of the knot security and loop security achieved by the surgeons (different experience levels) were calculated for each test configuration and each test condition. These values were used to determine the statistical relevance of the difference in arthroscopic loop security and knot security in each configuration. One-way analysis of variance (ANOVA) performed with SPSS Version 19.0 software (SPSS, Chicago, Illinois) with the least significant difference (LSD) multiple comparisons post hoc analysis was used to determine if any observed differences between the types of braided polyblend sutures, the types of sliding knots, the test conditions (in vitro, in situ), and the levels of surgeon experience were significant for each knot configuration. The level of significance of differences was set at P < .001.

Results

Figure 4 shows the mean maximum clinical failure load (3 mm of displacement) of different arthroscopic knot configurations for different braided polyblend sutures by surgeons of different levels of experience. In the comparison of biomechanical performance (knot and loop security) under in vitro and in situ conditions, no significant difference was detected when Ultrabraid suture material was used, regardless of surgeon experience, for all knot configurations. For surgeon B, there was no significant difference between in vitro and in situ conditions for any knot configurations or suture materials. When Orthocord suture material was used, Weston knots tied by surgeon A, and static surgeon’s knots by surgeons A and C, resulted in a significant difference between the in vitro and in situ conditions. When ForceFiber suture material was used, only Weston knots and Tennessee slider knots by surgeon A had a significant difference between in vitro and in situ conditions. Weston knots by surgeon A exhibited a significant difference between in vitro and in situ conditions, except when Ultrabraid suture material was used.

Surgeon C’s Tennessee slider knots with all polyblend sutures showed significantly lower loads at clinical failure compared with all the other knot configurations and with knots tied by the other 2 surgeons under both in vitro and in situ conditions. Overall, knots tied by surgeon B had higher clinical failure load than knots tied by the other 2 surgeons.

Figure 5 shows the mean ultimate failure load (complete structural failure) of different arthroscopic knot configurations for different braided polyblend sutures by surgeons of different levels of experience. Knots tied with Orthocord suture material had the overall lower ultimate failure load compared with other suture materials, whereas knots tied with Ultrabraid suture material had the overall highest ultimate failure load. However, the ultimate failure loads for all the knots tied using any suture material, regardless of surgeon experience, were more than 61 N, which is the estimated minimum required ultimate load per suture during a maximum muscle contraction.¹

Figure 6 shows the percentage of knot slipping at constant clinical failure load. Orthocord and Fiberwire suture materials had the lowest incidence of knot slippage. Surgeon C had complete knot slippage at constant clinical failure load using ForceFiber with the Weston knot and Ultrabraid with the Tennessee slider knot. When using Ultrabraid or ForceFiber, surgeons A and C had at least 2 knots slip for all knot configurations.

Discussion

Optimization of knot security for any given knot configuration, suture material, and surgeon experience level during arthroscopic knot tying is crucial.^1-10 Our study results showed that, under single LTF test scenarios, there was a significant difference between in vitro and in situ conditions with respect to both knot configuration and surgeon experience level, except when Ultrabraid suture material was used. Arthroscopic sliding knots are lockable or nonlockable.^7,12 With lockable sliding knots, slippage may be prevented by tensioning the wrapping limb, which distorts the post in the distal part of the knot, resulting in a kink in the post, thereby increasing the internal interference that increases the resistance of the knot from backing off. With nonlockable sliding knots, slippage may be prevented by the tight grip of the wrappings around the initial post.⁷ The static surgeon’s knot and the Tennessee slider knot are nonlockable, whereas the Weston knot is a distal lockable sliding knot. Compared with nonlockable sliding knots, lockable sliding knots cause less suture loop enlargement. In 1976, Tera and Aberg²² studied the strength of knotted thread for 12 different types of suture knots combined with 11 types of suture material. They conducted their study 1 week after suture material was inserted into the subcutaneous tissue of rabbits. Their results show a greater propensity for certain suture materials to slip when tested in an aqueous environment. In 1998, Babetty and colleagues²³ used Wistar rats to compare the in vivo strength, knot efficiency, and knot security of 4 types of sliding knots and to assess tissue reaction as a result of knot configuration, knot volume, and suture size. They found that 4/0 knots lost more strength than 2/0 knots did, and they concluded that the tissue response to all the knots, except 2/0 nylon, was similar. They indicated that the inflammatory sheath volume varied with knot volume, suture size, and knot configuration. Our results agree with observations that exposure to an aqueous environment alters the force to clinical failure of comparable suture and knot configurations.