Secondary Logo

Journal Logo

Unhas Suture, A Novel Tendon Repair Technique

An In Vitro Experimental Study Comparing Unhas Suture and Bunnell Suture in Tensile Strength and Gap Formation

Yurianto, Henry, PhD; Saleh, Ruksal, PhD; Paturusi, Idrus A., PhD; Supriyadi, Wilhelmus, MD; Lee, Jansen, MD

doi: 10.1097/BTO.0000000000000304
Novel Research Methods and Models
Open

Purpose: Developing a simple and yet strong repair technique that allows smooth gliding of the tendon within the tendon sheath has remained a challenge to meet the biomechanical needs of early active rehabilitation. Our Objective was to compare Unhas and Bunnell suture technique in terms of strength and gap resistance in tendon repair.

Materials and Methods: Thirty feet of healthy roosters Gallus domesticus were harvested and assigned randomly into 2 groups of 15 feet each. The tendons were repaired using Unhas suture and Bunnell suture utilizing monofilament nylon 4-0. Every specimens were tested by using repaired tendon gap formation apparatus and then measured when it produced an initial gap and 2-mm gap at the repair site. The measurements were then analyzed for statistical significance.

Results: Significant difference in initial gap was detected between repaired tendon using Unhas suture and Bunnell suture. Two-millimeter gap forces were tested and Unhas suture group was also significantly higher compared with Bunnell suture group.

Conclusions: Unhas suture was proven to be able to resist gap forces either in initial gap or 2-mm gap compared with Bunnell suture

Clinical Relevance: Unhas suture may be a reliable alternative in tendon repair that provides tensile strength, gapping resistance and also provide easiness which can be performed with conventional suture material and less operating time.

Department of Orthopaedic and Traumatology, Dr. Wahidin Sudirohusodo General Hospital at Hasanuddin University, Makassar, Indonesia

The authors declare that they have nothing to disclose.

For reprint requests, or additional information and guidance on the techniques described in the article, please contact Jansen Lee, MD, at or by mail at Department of Orthopaedic and Traumatology, Dr. Wahidin Sudirohusodo General Hospital at University of Hasanuddin, Makassar 90245, Indonesia. You may inquire whether the author(s) will agree to phone conferences and/or visits regarding these techniques.

This is an open-access article distributed under the terms of the Creative Commons Attribution-Non Commercial-No Derivatives License 4.0 (CCBY-NC-ND), where it is permissible to download and share the work provided it is properly cited. The work cannot be changed in any way or used commercially without permission from the journal. http://creativecommons.org/licenses/by-nc-nd/4.0/

Since the ancient age, starting with eye needles, surgical suture and misrecognizing tendon as nerve ending with fearing consequences of suturing, development of tendon knowledge and repair technique has expanded.1–10 Starting with the invention of Bunnel suture for flexor tendon repair and facing the failure in primary flexor tendon repair due to adhesions,3,5,6 predominant opinion was that secondary tendon repair with grafting should be performed.7,8

Since the superior results presented by Verdan and Kleinert in primary flexor tendon repair,3,10 both experimental studies on flexor tendon injury, repair, and healing as well as clinical investigations have expanded the knowledge.11 However, the problem of restoring normal tendon gliding and hand function and primary end-to-end repair within the tendon sheath has not been overcome.12 Early controlled rehabilitation has improved the results after flexor tendon repair by decreasing adhesion formation, increasing repair strength, and improving the functional outcome.13,14 Later clinical investigations have shown that controlled active mobilization further improves the functional outcome.3,15–18

Today, the flexor tendon repair is considered a composite of the core suture and the peripheral suture.10,19,20 Both techniques have been developed to meet the biomechanical needs of early active rehabilitation. Stronger core suture techniques to withstand the forces of active motion have been developed usually by increasing the number of strands forming different types of multistrand repairs.21–23 However, multistrand repairs are technically demanding in clinical settings increasing tendon handling and requiring more surgical time, which limits their clinical use. Developing a simple and yet strong repair technique that allows smooth gliding of the tendon within the tendon sheath has remained a challenge.3

The ideal tendon repair would have high tensile strength and gap resistance but would minimize suture material on the tendon surface so as not to interfere with tendon gliding or healing. Efforts to develop such repairs have resulted in innovations as Strickland stressed 6 characteristics of an ideal tendon repair.24–26 Makassar, the largest city of Eastern Indonesia, bears a high burden of road traffic accidents, gangsters, and criminals. Tendon injuries cases are undeniably high and demands a practical tendon repair technique. Considering the limited resources, the author concluded that an ideal tendon repair must be affordable in addition to the criteria proposed by Strickland. There are variations of tendon repair available27,28 and the author has developed a new core suture technique which is called as Unhas suture named after University of Hasanuddin (Unhas), Makassar, Indonesia. The illustration of the suture is depicted in Figure 1.

FIGURE 1

FIGURE 1

Back to Top | Article Outline

MATERIALS AND METHODS

This study was conducted to compare Unhas and Bunnell suture technique in terms of strength and gap resistance in tendon repair on rooster (male chicken/Gallus domesticus) tendons. Chicken have been chosen as one of animal models to characterize flexor tendon injury in some researches.29–31

Back to Top | Article Outline

Specimen Preparation

Thirty feet of healthy roosters G. domesticus were used in this study in which the roosters were selected randomly with the age of 4 to 7 months and body weight ranging 1500 to 2000 g. The roosters were initially prepared by being bathed and their feet were cleaned. The roosters were then sacrificed and their feet were harvested for the study. The rest part of the roosters were used for other purposes. Longitudinal incision was performed on the third toe of each foot followed by identification of the flexor perforantus digitorum pedis profundus while the other tendons were cut off. In full extension, the tendon was marked 6-cm proximal from the insertion and then harvested from the mark made to the distal. Sharp incision was made in the middle of the harvested tendon. Any damaged or torn tendons, dry tendons, or exposed tendons for >8 hours after harvesting were excluded in this study.

Back to Top | Article Outline

Repair Technique

The specimens were assigned randomly into 2 groups of 15 feet each. The tendons from the first group were repaired using Bunnell suture and the second were Unhas suture. Core tendon repair was performed by using monofilament nylon 4-0 and peripheral suture using monofilament nylon 6-0.

Back to Top | Article Outline

Bunnell Suture

Bunnell suture is a classic intratendinous crisscross suture technique that transmits the stress directly across the juncture by the suture material and depends on the strength of the suture itself.26 The schematic illustration of Bunnel suture is depicted in Figure 2.

FIGURE 2

FIGURE 2

Back to Top | Article Outline

Unhas Suture

Unhas suture is a modified tendon repair technique adopted from Tsuge Method which is classified as 2-strand core suture with the knot placed on the surface of the tendon. The technique involves purchasing the needle in the center of tendon with the distance of 10 mm from the end of the tendon (A to B, C to D, G to H, and I to J) and secure locking loops with diameter of 2 mm (E to F and K to L) and sufficient depth (1/3 of the diameter of tendon) to ensure the optimal core sutures. The illustrations are depicted in Figure 3.

FIGURE 3

FIGURE 3

Back to Top | Article Outline

Peripheral Suture

Peripheral suture used in this study was a circumferential epitenon simple running suture of 6-0 monofilament nylon. The running suture loops were ~4 mm long (2 mm from bite to the cut tendon end) with the depth of ~1 to 1.5 mm. The illustration is depicted in Figure 4.

FIGURE 4

FIGURE 4

Back to Top | Article Outline

Biomechanical Testing

Every specimens were tested by using repaired tendon gap formation apparatus adapted from the previous study conducted by Zhao et al.32 Each of the repaired tendons end was mounted with custom-made clamps such that the repaired site is centrally located. The grip-to-grip distance was ~40 mm with the repair site centrally located. The upper part of the clamp was connected to load cell and actuator. The tendon was then pulled proximally by the actuator against the weight at the rate of 0.1 mm/s. Digital indicator A12 showed the force causing gap formation in kilogram force and then converted to Newton (1 kg force=9.8 N). The force was then measured when it produced an initial gap and 2-mm gap at the repair site. The tendon was kept moist by dropping 0.9% saline solution every several seconds through the testing procedures. The gap formation apparatus is shown in Figure 5 and the illustrations of specimen perparations to biomechanical testing are depicted in Figure 6.

FIGURE 5

FIGURE 5

FIGURE 6

FIGURE 6

Back to Top | Article Outline

Statistical Methods

Mann-Whitney test was used to compare the force causing the initial gap and 2-mm gap between repaired tendons using Bunnell suture and Unhas suture. In those cases, a level of P<0.05 was considered to be significant.

Back to Top | Article Outline

RESULTS

Seventeen roosters G. domesticus were sacrificed to obtain the specimens. A total of 30 specimens were used and 4 specimens were ineligible due to damaged tendon before distraction test. The mean (and SD) initial gap forces in repaired tendon using Unhas suture was 9.76±0.55 N and Bunnell suture was 9.16±0.66 N. The mean initial gap forces of repaired tendon using Unhas suture was significantly higher than that of Bunnell suture (P<0.05).

Two-millimeter gap forces tested with the result of Unhas suture group was 19.54±1.12 N and Bunnell suture group was 15.24±1.7 N. The statistical analysis between the 2 groups was significantly higher in Unhas suture group (P<0.05). The comparison of gap forces between Unhas suture and Bunnell suture is shown in Table 1.

TABLE 1

TABLE 1

Back to Top | Article Outline

DISCUSSION

The gap resistance and ultimate strength of repaired tendon are the primary parameters that define the mechanical properties of a surgical repair. Adequate mechanical strength is essential for a repair to resist gapping and failure. Maintaining a certain baseline tension on the core suture during surgery greatly benefits gap resistance.19,33 Peripheral suture could also significantly increase the strength of tendon repairs.19,20,34,35,39,40

Gap formation is one of the most frequent complications following tendon suture and postoperative rehabilitation in which it is believed as one of the major causes of adhesion formation after tendon repair,32,36–39 and the formation itself occurs during the first few weeks of tendon repair.32,37 If a gap could be detected when it was small, it might be possible to use modifications in the therapy.32 To prevent gap formation, strong and yet simple suture techniques has remained a challenge.

Since Tsuge technique requires looped suture or double arm suture which are not always available in every health service centers, Unhas suture simply uses the conventional suture material. Author defined Unhas suture as a simple intratendon sutures, parallel with the tendon collagen fibers, which carries stress of the repair away from the ends of the tendon. The nodes provide approximation of ends of tendon rupture, thus reducing the tendon gap formation so the tendon healing is guaranteed.

Unhas suture is believed to be closed to an ideal suture technique including repair strength, gapping resistance, maintaining glide, reducing tendon damage, minimizing adhesion formation, and also provide easiness which can be performed with conventional suture material and less operating time. In this study, Unhas suture was proven statistically significant in resisting gap forces compared with that of Bunnell suture. Locking loops in which the type of suture used to hold the tendon on either side in Unhas suture technique is superior compared with Bunnell suture technique which uses grasping loops.19,22,24 Locking loops provide better grasp of tendon fibers and prevent suture pullout. As grasping loops do not tighten around tendon fibers it would be expected that grasping repairs would fail by suture pullout with repetitive load.24,40

In Human, various studies had evaluated the forces to tendon during passive and active mobilization.41–43 Tendon forces up to 9 N were present during passive mobilization of the fingers.19,42,44 In this study, the mean initial gap forces in repaired tendon using Unhas suture was 9.76 N and using Bunnell suture was 9.16 N and the result was higher compared with the forces present during passive mobilization in which Unhas suture and Bunnell suture were assumed to be able to resist the gap formation in passive mobilization under supervision if applied in human tendon repair.

Tendon forces up to 35 N were present during active unresisted finger motion.19,42,44 According to Urbaniak and coauthors, an average tension in a human profundus tendon to be 14.7 N and found that tensile strength of tendon repair decreases to approximately one-fifth of its initial strength at first week. Taking into account of increased resistance from edema after surgery and a decrease in suture strength during initial weeks after repair.45 In this study, the mean 2-mm gap forces developed in repaired tendon using Unhas suture was 19.53 N and using Bunnell suture was 15.2 N. This value is above the average tension developed in a human profundus tendon but still needs further evaluation for adequacy in resisting forces developed during active motion.

There were limitations to this study. These values are estimated from experiments on rooster tendons and therefore requires further studies which included cadaveric studies and with the intact pulley system to support its use on clinical setting. Cyclic loading was not conducted and linier load to failure may not mimic physiological conditions.23,46,47 In this study, Nylon 4-0 was chosen due to the size of our tendon specimens and its use is supported by multiple researches both in vitro and in vivo.19 Possible of using other specimens, size, thread materials, and number of loops could be applied depends on the study design.

In summary, in the present in vitro study, Unhas suture technique was statistically significant higher in tensile strength and resisting gap formation compared with those of Bunnell suture.

Back to Top | Article Outline

REFERENCES

1. Mackenzie D. The history of sutures. Med Hist. 1973;17:58–168.
2. Deepak M, Subraramanian CS, Senthilvelan, et al. A prospectic randomised study on cosmetic outcome between simple suturing and mattress suturing in hernioplasty. Int J Modn Res Revs. 2014;2:418–420.
3. Viinikainen A. Development of a New Flexor Tendon Repair Technique Performed With Bioabsorbsorbable Poly-L/D-Lactide (PLDLA) 96/4 Suture: An Experimental Ex Vivo Study [Academic Dissertation] Helsinki: University of Helsinki; 2008.
4. Manske PR. History of flexor tendon repair. Hand Clin. 2005;21:123–127.
5. Strickland JW. Development of flexor tendon surgery: twenty-five years of progress. J Hand Surg Am. 2000;25:214–235.
6. Kotwal PP, Ansari MT. Zone 2 flexor tendon injuries: venturing into the no man’s land. Indian J Orthop. 2012;46:608–615.
7. Rawson S, Cartmell S, Wong J. Suture techniques for tendon repair: a comparative review. Muscles Ligaments Tendons J. 2013;3:220–228.
8. Adamson JE, Wilson JN. The history of flexor-tendon grafting. J Bone Joint Surg. 1961;43-A:709–716.
9. Verdan CE. Primary repair of flexor tendons. J Bone Joint Surg Am. 1960;42:647–657.
10. Singh R, Rymer B, Theobald P, et al. A review of current concepts in flexor tendon repair: physiology, biomechanics, surgical technique and rehabilitation. Orthop Rev. 2015;7:101–105.
11. Strickland JW. The scientific basis for advances in flexor tendon surgery. J Hand Ther. 2005;18:94–110.
12. Tang JB. Clinical outcomes associated with flexor tendon repair. Hand Clin. 2005;21:199–210.
13. Lister GD, Kleinert HE, Kutz JE, et al. Primary flexor tendon repair followed by immediate controlled mobilization. J Hand Surg. 1977;2:441–451.
14. Strickland JW, Glogovac SV. Digital function following flexor tendon repair in zone II: a comparison of immobilization and controlled passive motion techniques. J Hand Surg. 1980;5:537–543.
15. Cullen KW, Tolhurst P, Lang D, et al. Flexor tendon repair in zone 2 followed by controlled active mobilisation. J Hand Surg. 1989;14B:392–395.
16. Small JO, Brennen MD, Colville J. Early active mobilisation following flexor tendon repair in zone 2. J Hand Surg. 1989;14B:383–391.
17. Bainbridge LC, Robertson C, Gillies D, et al. A Comparison of post-operative mobilization of flexor tendon repairs with“passive flexion-active extension” and “controlled active motion” techniques. J Hand Surg. 1994;19B:517–521.
18. Baktir A, Türk CY, Kabak S, et al. Flexor tendon repair in zone 2 followed by early active mobilization. J Hand Surg. 1996;21B:624–628.
19. Tang JB, Xie RGTang JB, Amadio PC, Guimberteau JC, Chang J. Biomechanics of core and peripheral tendon repairs. Tendon Surgery of the Hand. Philadelphia: Elsevier Saunders; 2012:2035.
20. Merrell GA, Wolfe SW, Kacena WJ, et al. The effect of increased peripheral suture purchase on the strength of flexor tendon repairs. J Hand Surg Am. 2003;28:464–468.
21. Mishra V, Kuiper JH, Kelly CP. Influence of core suture material and peripheral repair technique on the strength of Kessler flexor tendon repair. J Hand Surg. 2003;28B:357–362.
22. Shaieb MD, Singer DI. Tensile strengths of various suture techniques. J Hand Surg. 1997;22B:764–767.
23. Barrie KA, Tomak SL, Cholewicki J, et al. The role of multiple strands and locking sutures on gap formation of flexor tendon repairs during cyclical loading. J Hand Surg. 2000a;25A:714–720.
24. Tanaka T, Amadia PC, Zhao CF, et al. Biomechanical properties of locking versus grasping suture. Summer Bioengineering Conference, Minnesota Orthopaedic Biomechanics Laboratory; Rochester, Minnesota, 2003;635–636.
25. Viinikainen A, Goransson H, Ryhanen J. Primary flexor tendon repair techniques. Scand J Surg. 2008;97:333–340.
26. Cannon DLCanale ST, Beaty JH. Flexor and extensor tendon injuries. Campbell’s Operative Orthopaedics, 12th ed. Philadelphia: Elsevier Mosby; 2013:3249.
27. Ryan JD. Principles and Techniques of Tendon Repair. Georgia: The Podiatry Institute; 2010. Available at: www.podiatryinstitute.com/pdfs/Update_2010/2010_52.pdf. Accessed January 15, 2016.
28. Sebastin SJ, Ho A, Karjalainen T, et al. History and evolution of the kessler repair. J Hand Surg. 2013;38A:552–561.
29. 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.
30. Lee H, Hou Z, Liu P, et al. An experimental study comparing active mobilization to passive flexion-active extension-active flexion after flexor tendon repair in zone 2. J Hand Surg Am. 2013;38:672–676.
31. Hast MW, Zuskow A, Soslowsky LJ. The role of animal models in tendon research. Bone Joint Res. 2014;3:193–202.
32. Zhao C, Amadio PC, Tanaka T, et al. Effect on gap size on gliding resistance after flexor tendon repair. J Bone Joint Surg Am. 2004;86A:2482–2488.
33. Beredjiklian PK. Biologic aspects of flexor tendon laceration and repair: current concepts review. J Bone Joint Surg Am. 2003;85A:539–550.
34. Uslu M, Isik C, Ozsahin M, et al. Flexor tendon repair: effect of core suture caliber with increased number of suture strands and peripheral sutures: a sheep model. Orthop Traumatol Surg Res. 2014;100:611–616.
35. Diao E, Hariharan JS, Soejima O, et al. Effect of peripheral suture depth on strength of tendon repairs. J Hand Surg Am. 1996;21:234–239.
36. Boyer MI, Gelberman RH, Burns ME, et al. Intrasynovial flexor tendon repair. an experimental study comparing low and high levels in vivo during rehabilitation in canines. J Bone Joint Surg Am. 2001;83:891–899.
37. Gelberman RH, Boyer MI, Brodt MD, et al. 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;81:975–982.
38. Ejeskär A, Irstam L. Elongation in profundus tendon repair: a clinical and radiological study. Scand J Plast Reconstr Surg. 1981;15:61–68.
39. Amadio PC. Friction of the gliding surface: implications for tendon surgery and rehabilitation. J Hand Ther. 2005;18:112–119.
40. Amis AASchuind F, An KN, Cooney WP III, Garcia-Elias M. The mechanical properties of finger flexor tendons and development of stronger tendon suturing techniques. Advances in the Biomechanics of the Hand and Wrist. New York: Springer Science+Business Media; 1994:41–57.
41. Kursa K, Lattanza L, Diao E, et al. In vivo flexor tendon forces increase with finger and wrist flexion during active finger flexion and extension. J Orthop Res. 2006;24:763–769.
42. Schuind F, Garcia-Elias M, Cooney WP III, et al. Flexor tendon forces: in vivo measurements. J Hand Surg Am. 1992;17:291–298.
43. 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.
44. An KNGuilak F, Butler DL, Goldstein SA, Moonet D. In vivo force and strain of tendon, ligament, and capsule. Functional Tissue Engineering. USA: Springer-Verlag; 2003:96–105.
45. Mitsunaga KA, Szabo RMWright HG. What is the best method of rehabilitation after felxor tendon repair in zone II: passive mobilization of early active motion? What is the best suture configuration for repair of flexor tendon lacerations? Evidence-Based Orthopaedics: The Best Answers to Clinical Questions, 1st ed. Philadelphia: Saunders Elsevier; 2009:91–103.
46. Choueka J, Heminger H, Mass DP. Cyclical testing of zone ii flexor tendon repairs. J Hand Surg Am. 2000;25:1127–1134.
47. Pruitt DL, Manske PR, Fink B. Cyclic stress analysis of flexor tendon repair. J Hand Surg Am. 1991;16:701–707.
Keywords:

unhas suture; tendon repair; tensile strength; gap formation

Copyright © 2019 Wolters Kluwer Health, Inc. All rights reserved