As described before, the 2-0 V-Loc device is a single-ended unidirectional barbed suture with a welded loop at the end. There are 26 barbs per centimeter of material, and they are distributed circumferentially around the suture at 120° rotations with each barb 0.38 mm in length. Our barbed repair technique used 4 strands. The welded loop was not required for our repair method and so was cut off from the suture. The needle was passed through the tendon surface on one side, across the repair site and then out through the surface on the other side. Each pass was made through the midsubstance of the tendon, and they were made 2 mm apart from one another. This was repeated 4 times for each repair and the suture was cut flush to the tendon surface each time, so no barbs were present on the exposed tendon. To facilitate a solid, nonslip repair, each barbed suture strand was placed in an opposing direction to the one beside it. A core suture purchase of 10 mm was made for the barbed technique as well.
Repaired tendons were mechanically tested with a Zwick Z005 tensiometer (Zwick Z005, Ulm, Germany). To simulate the forces that act on an immobilized tendon during active flexion, the upper clamp of our material testing machine was set with a preload of 1.5N and an advancement rate of 20 mm per minute.33,34 These settings have been used previously in biomechanical tests on flexor tendons.19 The repaired tendons were secured tightly in the upper and lower sandpaper covered clamps before mechanical testing. There was no slippage of the tendon ends during testing.
A caliper with a preset of 2 mm was set up alongside the tensiometer. When a 2-mm gap at the repair site occurred during testing as measured by the caliper, the corresponding force that created this gap was recorded. The ultimate failure load of each repair was also recorded. This is the greatest force that occurs immediately before tendon repair failure. The mode of final failure (rupture or pullout) was also recorded.
A power analysis was carried out to determine the sample size in each arm of our study. This was based on maximum strength/ultimate force, and the study was powered to detect a 10N difference in maximum force. We performed a pilot study and results from this indicated that we required a minimum of 15 porcine tendons in each group for 0.80 power in the study to detect a significant difference of P < 0.05. Kolgomorov-Smirnov method was performed to determine the normality or otherwise of the data distribution. The 2-mm gap formation force and the maximum force were compared using Student’s t test with Welch correction. The difference in CSA between the 2 groups was compared using the Mann-Whitney test. Before analysis was carried out, log transformations of the maximum force, 2-mm gap formation force, and percentage change in CSA were performed. A P value of <0.05 was considered to be statistically significant.
The cause of repair failure for the barbed group was rupture in 12 cases and pullout in the remainder of the samples tested. For the Adelaide repair, there were 8 ruptures and 12 pullouts. Seven of the ruptures in the Adelaide group occurred at the knot. A repair failure was classified as a pullout if the suture strands pulled through the tendon without breaking. Rupture occurred when either the strands or knot broke. The maximum or ultimate force before repair failure can be seen in Table 1. There was no statistically significant difference between the 2 groups of tendon repairs (t test, P > 0.05).
The formation of a 2-mm gap at the repair site is widely regarded as a failed repair, and the force that caused a 2-mm gap at the repair site was measured in the 2 groups (Table 1). The results were extremely statistically significant (t test, P > 0.0001).
We have described a novel technique for flexor tendon repairs using a barbed suture device in which the directionality of the barbed suture is used to hold the repair. We found our barbed repair much easier and faster to perform and required fewer hand movements than the Adelaide repair. The barbed device was easier to handle than the polypropylene as we found that the barbs act as a grip. We also noticed that if technical errors were made during the barbed repair method, they were easy to rectify by pulling the suture out in the direction of the barbs. This is in contrast to more complex barbed suture repairs that have been described, where technical errors are not as easy to correct, as multiple suture passages of the suture within the tendon substance make it more difficult to extract the suture.6
We did not observe any significant difference in the tensile strengths of both repair methods as both repair methods failed at comparable forces. Gap formation is a common complication post flexor tendon repair that can adversely affect the end result and prolong tendon healing.37 There was a statistically significant difference in the 2-mm gap formation force required in the 2 groups. The barbed repair method was able to withstand more force than the traditional repair method before a 2-mm gap formed at the repair site. We did not pretension either material before repair so this may have had an effect on the gapping forces for the Adelaide group.38
Repaired flexor tendons should be able to pass freely through the flexor sheath. Repairs typically add bulk to the repair site due to bunching of the tendon ends and the presence of the knot and suture material. This increased CSA can impair tendon gliding and overall outcome.17 In our study, we found that the barbed suture group had a significantly reduced CSA than the Adelaide group. This would allow smoother gliding through the pulley system and could reduce the postoperative rupture rate.
A limitation of our study is that we used a caliper preset to 2 mm to calculate the 2-mm gap formation force. As distraction occurred at a rate of 20 mm/min, it was difficult to accurately assess the 2-mm gap formation force by visual estimation.
It would have been preferable to carry out our experiments using identical suture materials, as we directly compared a polybutester barbed suture to a polypropylene monofilament suture. Our biomechanical testing used a linear load to failure as one of the primary outcomes. To better replicate physiological conditions, it would have been interesting if angular tensile strengths or cyclical loading studies had been carried out.
The knotless barbed repair method we have described is a quick and easy technique that provides a strong repair without significantly increasing the bulk of the repair site. Our novel 4-strand knotless barbed technique had comparable tensile strength with a reduced CSA at the repair site in relation to the traditional 4-strand Adelaide repair. Furthermore, our barbed technique has no exposed barbs on the tendon surface, so there should be no attritional damage to the pulley system in vivo. The use of barbed devices for flexor tendon repairs shows promise, but further studies using animal models are warranted to examine their clinical applicability.
1. McDonald E, Gordon JA, Buckley JM, et al. Comparison of a multifilament stainless steel suture with FiberWire for flexor tendon repairs—an in vitro biomechanical study. J Hand Surg Eur Vol. 2013;38:418–423
2. Trail IA, Powell ES, Noble J. An evaluation of suture materials used in tendon surgery. J Hand Surg Br. 1989;14:422–427
3. Peltz TS, Haddad R, Scougall PJ, et al. Performance of a knotless four-strand flexor tendon repair with a unidirectional barbed suture device: a dynamic ex vivo comparison. J Hand Surg Eur Vol. 2014;39:30–39
4. Le SV, Chiu S, Meineke RC, et al. Number of suture throws and its impact on the biomechanical properties of the four-strand cruciate locked flexor tendon repair with FiberWire. J Hand Surg Eur. 2012;37:826–831
5. Momose T, Amadio PC, Zhao C, et al. The effect of knot location, suture material, and suture size on the gliding resistance of flexor tendons. J Biomed Mater Res. 2000;53:806–811
6. Parikh PM, Davison SP, Higgins JP. Barbed suture tenorrhaphy: an ex vivo biomechanical analysis. Plast Reconstr Surg. 2009;124:1551–1558
7. Rees L, Matthews A, Masouros SD, et al. Comparison of 1- and 2-knot, 4-strand, double-modified Kessler tendon repairs in a porcine model. J Hand Surg Am. 2009;34:705–709
8. Strick MJ, Filan SL, Hile M, et al. Adhesion formation after flexor tendon repair: a histologic and biomechanical comparison of 2- and 4-strand repairs in a chicken model. J Hand Surg Am. 2004;29:15–21
9. Manske PR, Lesker PA, Gelberman RH, et al. Intrinsic restoration of the flexor tendon surface in the nonhuman primate. J Hand Surg Am. 1985;10:632–637
10. Wong JK, Alyouha S, Kadler KE, et al. The cell biology of suturing tendons. Matrix Biol. 2010;29:525–536
11. McKenzie AR. An experimental multiple barbed suture for the long flexor tendons of the palm and fingers. Preliminary report. J Bone Joint Surg Br. 1967;49:440–447
12. Sulamanidze M. Evaluation of a novel technique for wound closure using a barbed suture. Plast Reconstr Surg. 2007;120:349–350; author reply 350
13. Zaruby J, Gingras K, Taylor J, et al. An in vivo comparison of barbed suture devices and conventional monofilament sutures for cosmetic skin closure: biomechanical wound strength and histology. Aesthet Surg J. 2011;31:232–240
14. Patri P, Beran C, Stjepanovic J, et al. V-loc, a new wound closure device for peritoneal closure—is it safe? A comparative study of different peritoneal closure systems. Surg Innov. 2011;18:145–149
15. Greenberg JA. The use of barbed sutures in obstetrics and gynecology. Rev Obstet Gynecol. 2010;3:82–91
16. Buschmann J, Müller A, Feldman K, et al. Small hook thread (Quill) and soft felt internal splint to increase the primary repair strength of lacerated rabbit Achilles tendons: biomechanical analysis and considerations for hand surgery. Clin Biomech (Bristol, Avon). 2011;26:626–631
17. Joyce CW, Whately KE, Chan JC, et al. Flexor tendon repair: a comparative study between a knotless barbed suture repair and a traditional four-strand monofilament suture repair. J Hand Surg Eur Vol. 2014;39:40–45
18. Marrero-Amadeo IC, Chauhan A, Warden SJ, et al. Flexor tendon repair with a knotless barbed suture: a comparative biomechanical study. J Hand Surg Am. 2011;36:1204–1208
19. McClellan WT, Schessler MJ, Ruch DS, et al. A knotless flexor tendon repair technique using a bidirectional barbed suture: an ex vivo comparison of three methods. Plast Reconstr Surg. 2011;128:322e–327e
20. Zeplin PH, Zahn RK, Meffert RH, et al. Biomechanical evaluation of flexor tendon repair using barbed suture material: a comparative ex vivo study. J Hand Surg Am. 2011;36:446–449
21. Sandow MJ, McMahon M. Active mobilisation following single cross grasp four-strand flexor tenorrhaphy (Adelaide repair). J Hand Surg Eur Vol. 2011;36:467–475
22. Cao Y, Zhu B, Xie RG, et al. Influence of core suture purchase length on strength of four-strand tendon repairs. J Hand Surg Am. 2006;31:107–112
23. Hausmann JT, Vekszler G, Bijak M, et al. Biomechanical comparison of modified Kessler and running suture repair in 3 different animal tendons and in human flexor tendons. J Hand Surg Am. 2009;34:93–101
24. Hirpara KM, Sullivan PJ, O’Sullivan ME. The effects of freezing on the tensile properties of repaired porcine flexor tendon. J Hand Surg Am. 2008;33:353–358
25. Mao WF, Wu YF, Zhou YL, et al. A study of the anatomy and repair strengths of porcine flexor and extensor tendons: are they appropriate experimental models? J Hand Surg Eur Vol. 2011;36:663–669
26. Rigó IZ, Haugstvedt JR, Ludvigsen P, et al. Comparison of modified Kessler and Yotsumoto-Dona suture: a biomechanical study on porcine tendons. J Plast Surg Hand Surg. 2012;46:313–317
27. Smith AM, Forder JA, Annapureddy SR, et al. The porcine forelimb as a model for human flexor tendon surgery. J Hand Surg Br. 2005;30:307–309
28. Viinikainen A, Göransson H, Huovinen K, et al. Material and knot properties of braided polyester (Ticron) and bioabsorbable poly-L/D-lactide (PLDLA) 96/4 sutures. J Mater Sci Mater Med. 2006;17:169–177
29. Peltz TS, Haddad R, Scougall PJ, et al. Influence of locking stitch size in a four-strand cross-locked cruciate flexor tendon repair. J Hand Surg Am. 2011;36:450–455
30. Greenberg JA, Clark RM. Advances in suture material for obstetric and gynecologic surgery. Rev Obstet Gynecol. 2009;2:146–158
31. Rashid RM, Sartori M, White LE, et al. Breaking strength of barbed polypropylene sutures: rater-blinded, controlled comparison with nonbarbed sutures of various calibers. Arch Dermatol. 2007;143:869–872
32. Villa MT, White LE, Lam M, et al. Barbed sutures: a review of the literature. Plast Reconstr Surg. 2008;121:102–108
33. Tang JB, Cao Y, Xie RG. Effects of tension direction on strength of tendon repair. J Hand Surg Am. 2001;26:1105–1110
34. Xie RG, Tang JB. Investigation of locking configurations for tendon repair. J Hand Surg Am. 2005;30:461–465
35. Barrie KA, Tomak SL, Cholewicki J, et al. Effect of suture locking and suture caliber on fatigue strength of flexor tendon repairs. J Hand Surg Am. 2000;26:340–346
36. Croog A, Goldstein R, Nasser P, et al. Comparative biomechanic performances of locked cruciate four-strand flexor tendon repairs in an ex vivo porcine model. J Hand Surg Am. 2007;32:225–232
37. Vanhees M, Thoreson AR, Larson DR, et al. The effect of suture preloading on the force to failure and gap formation after flexor tendon repair. J Hand Surg Am. 2013;38:56–61
38. Smith GH, Huntley JS, Anakwe RE, et al. Tensioning of Prolene reduces creep under cyclical load: relevance to a simple pre-operative manoeuvre. J Hand Surg Eur Vol. 2012;37:823–825