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LETTERS TO THE EDITOR

Certainly, all of this deserves our continued attention and follow-up. We appreciate your thoughtful comments.

http://dx.doi.org/10.1016/j.jhsa.2014.12.010

REFERENCES

Ida K. Fox, MD Division of Plastic & Reconstructive Surgery Department of Surgery Washington University School of Medicine St. Louis, MO

1. Schneider LH. Opponensplasty using the extensor digiti minimi. J Bone Joint Surg Am. 1969;51(7):1297e1302. 2. Sammer DM, Chung KC. Tendon transfers: part I. Principles of transfer and transfers for radial nerve palsy. Plast Reconstr Surg. 2009;123(5):169ee77e.

Bunnell Technique and Bidirectional Barbed Suture for Flexor Tendon Repair To the Editor: Concerning the article of Jordan et al, “Biomechanical analysis of flexor tendon repair using knotted Kessler and Bunnell techniques and the knotless Bunnell technique,”1 I would like to make some remarks. Forces in knotted suture techniques are resisted by the knot and strand. To permit healing, prevention of gapping is essential. In functional aftercare, residual gapping cannot be tolerated. Residual gaps of 2 mm or greater not only increase rupture rates but also impair range of motion and must be viewed as a complication on a level with suture breakage or knot rupture.2e4 In the presented study, in which bidirectional suture material with barbs was placed circumferentially on its surface, it can be assumed that in the demonstrated knotless Bunnell technique one-half of tensile force is borne by the suture material and onehalf by the barbs’ resistance. The strength of a tendon repair depends largely on its effectiveness in transmitting axial tension into the tendon tissue. Under tension, the suture in nongrasping methods such as the Bunnell technique generates a purse-stringing effect.5 This leads to gapping but also to tendon shortening and impaired passage through annular ligaments. For this reason and to transfer the results into clinical relevance, it would be interesting to know at what force the barbs give up their resistance to start triggering the purse-stringing effect. Unless this purse-stringing effect of the Bunnell technique is prevented by using bidirectional barbed suture materials, this technique cannot be recommended for clinical practice.

http://dx.doi.org/10.1016/j.jhsa.2015.02.021 REFERENCES 1. Jordan MC, Schmidt K, Meffert RH, Hoelscher-Doht S. Biomechanical analysis of flexor tendon repair using knotted Kessler and Bunnell techniques and the knotless Bunnell technique. J Hand Surg Am. 2015;40(1):115e120. 2. Gelberman RH, Boyer MI, Brodt MD, Winters SC, Silva MJ. The effect of gap formation at the repair site on the strength and excursion of intrasynovial flexor tendons: an experimental study on the early stages of tendon-healing in dogs. J Bone Joint Surg Am. 1999;81(7): 975e982. 3. Zeplin PH, Henle M, Zahn RK, et al. Tensile strength of flexor tendon repair using barbed suture material in a dynamic ex vivo model. J Hand Microsurg. 2012;4(1):16e20. 4. Zeplin PH, Zahn RK, Meffert RH, Schmidt K. Biomechanical evaluation of flexor tendon repair using barbed suture material: a comparative ex vivo study. J Hand Surg Am. 2011;36(3): 446e449. 5. Rawson S, Cartmell S, Wong J. Suture techniques for tendon repair; a comparative review. Muscles Ligaments Tendons J. 2013;3(3): 220e228.

In Reply: We thank our former colleague and co-worker in this field for his valuable comment regarding our recently published work. Concerning the letter, we would like to state the following. To evaluate the mentioned “purse-string” effect, we tested a knotted Kessler repair (3-0 PDS; Ethicon, Somerville, NY), a knotted Bunnell repair (3-0 PDS), and a knotless Bunnell repair (3-0 Stratafix; Ethicon) under uniaxial load with a 20-mm/min distraction rate. Figure 1 shows the behavior of the different suture designs under tension. Performing the Bunnell repair using barbed suture material can help prevent the unfavorable purse-string effect under relevant load. Moreover, Kanz et al1 confirmed greater resistance to gap formation and lower displacement compared with

Philip H. Zeplin, MD, PhD Department of Operative Medicine Leipzig University Hospital and Medical School Leipzig, Germany

J Hand Surg Am.

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Vol. 40, April 2015

Bunnell technique and bidirectional barbed suture for flexor tendon repair.

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