Effect of circumferential sutures on tensile and gap strength of repaired canine flexor tendons

Sixty-four dog cadaver flexor digitorum profundus tendons in zone 2 were lacerated and repaired with a simple or a cross-stitch peripheral circumferential suture in combination with two-, four-, or six-strand core sutures. The tensile and gap strengths were compared. The range of tensile strengths with the cross-stitch circumferential suture in combination with various core suture techniques (4.28–9.37 kgf) was significantly higher than the range of values for the simple circumferential suture and similar core suture techniques (1.70–4.98kgf). The tensile strength with two-strand core suture plus the cross-stitch circumferential suture (5.29kgf) was as great as that of the six-strand core suture plus the simple circumferential suture (4.98kgf). Increased gap strength values were also observed with the cross-stitch (1.11–3.19 kgf) compared to the simple (0.84 to 1.76 kgf) circumferential sutures. The cross-stitch circumferential suture had a mechanical advantage in flexor tendon repair compared to the simple circumferential suture. No benefits in any form have been received or will be received from any commercial party related directly or indirectly to the subject of this article. This study was supported in part by Grant No. 15953 from the Shriner's hospital for Crippled Children (USA)     

A biomechanical study of Tang's multiple locking techniques for flexor tendon repair

This study was designed to biomechanically compare Tang's multiple looped locking techniques with various suture techniques for flexor tendon repair in the hand. Fifty flexor digitorum profondus tendons taken from pig toes were used as models; The tendons were transected in the middle part of zone 2 defined as the area beneath bifurcation of the flexor digitorum superficialis tendons, and were repaired by five different suture methods: (1) modified Kessler, (2) Tsuge's suture, (3) double Kessler, (4) modified Kessler plus Tsuge, and (5) Tang's suture. The repaired tendons were placed in an Instron tensile testing machine to determine the tensile properties of the repair. 2 mm gap formation force and ultimate tensile strength were measured during the test. Maximal work to failure were calculated according to area under the load-displacement curve of the test. 2 mm gap formation force was 21.5 N for the Kessler, 20.6 N for the Tsuge, 31.6 N for double Kessler, 30.9 N for the Kessler plus Tsuge and 41.4 N for the Tang. Ultimate tensile strength was 23.5 N for the Kessler, 22.9 N for the Tsuge, 34.5 N for the Kessler plus Tsuge and 45.6 N for the Tang. Statistically, Tang's suture had the greatest gap formation force, ultimate strength and energy for failure among the five techniques (p < 0.01 or p < 0.001). Gap formation force, ultimate strength and energy to failure for double Kessler or the Kessler plus Tsuge were significantly greater than those for the Kessler or the Tsuge (p < 0.05 or < 0.01). The tendons repaired by Tang's method tolerated a significantly higher tensile load (133 to 198% of the other techniques) than the other methods. Among the methods tested, Tang's multiple looped locking suture provides sufficient gap resistance and tensile strength that may be able to withstand early active mobilization after primary flexor tendon repair.     

Biomechanical evaluation of flexor tendon repair techniques

Immediate active mobilization of repaired tendons is thought to be the most effective way to restore function of injured flexor tendons. Sixty human flexor digitorum profundus tendons were used to evaluate techniques for active tendon motion. The tendons were divided equally into six groups, and each group was assigned to one of the following techniques: Kessler core suture plus running peripheral suture, Kessler plus cross-stitch suture, Kessler plus Halsted suture, Tang core suture plus running peripheral suture, Tang plus cross-stitch suture, or Tang plus Halsted suture. Immediately after tendon repair, an Instron tensile testing machine was used to measure the 2-mm gap formation force, ultimate strength, elastic modulus, and energy to failure of the tendons repaired by these techniques. Ultimate strength, elastic modulus, and energy to failure were measured in load displacement curve. Results showed that the ultimate strength of the Tang plus Halsted or cross-stitch was, respectively, 116.8 +/- 9.6 N and 94.6 +/- 7.8 N; and 2-mm gap formation force was, respectively, 86.6 +/- 4.9 N and 71.9 +/- 5.1 N. The Tang plus Halsted or cross-stitch methods had a statistically significant increase in ultimate strength and 2-mm gap formation force as compared with the Kessler core suture or Tang plus running peripheral suture method. Elastic modulus and energy to failure of the Tang plus Halsted or cross-stitch suture were statistically higher than those of other techniques. The Tang plus cross-stitch or Tang plus Halsted sutures had the highest strength among the tested methods and are appropriate techniques for tendon repair in which the goal is immediate active tendon motion.     

Simplifying four-strand flexor tendon repair using double-stranded suture: a comparative ex vivo study on tensile strength and bulking

We have compared a simple four-strand flexor tendon repair, the single cross-stitch locked repair using a double-stranded suture (dsSCL) against two other four-strand repairs: the Pennington modified Kessler with double-stranded suture (dsPMK); and the cruciate cross-stitch locked repair with single-stranded suture (Modified Sandow). Thirty fresh frozen cadaveric flexor digitorum profundus tendons were transected and repaired with one of the core repair techniques using identical suture material and reinforced with identical peripheral sutures. Bulking at the repair site and tendon-suture junctions was measured. The tendons were subjected to linear load-to-failure testing. Results showed no significant difference in ultimate tensile strength between the Modified Sandow (36.8 N) and dsSCL (32.6 N) whereas the dsPMK was significantly weaker (26.8 N). There were no significant differences in 2 mm gap force, stiffness or bulk between the three repairs. We concluded that the simpler dsSCL repair is comparable to the modified Sandow repair in tensile strength, stiffness and bulking.     

几种屈肌腱缝合方法的即刻生物力学比较

目的比较几种临床常用肌腱缝合方法的即刻生物力学特性,为临床肌腱修复提供参考。方法成年AA白羽鸡爪60只,随机分为6组。锐刀横断Ⅱ区趾深屈肌肌腱,分别用改良Kessler法、改良Kessler加腱周连续缝合法、Cruciate法、滓下法,改良津下法,Tang法进行修复。缝合后立即取下肌腱进行拉伸—断裂测试。测定极限载荷、应变,计算出各组的肌腱韧度、极限拉伸强度、弹性模量和断裂功耗,并记录手术操作时间和断裂方式,进行统计学分析。结果Tang法组的极限载荷、极限拉伸强度、韧度和断裂功耗均大于其他五种方法（P〈0．05）,改良Kessler法的各组参数均小于其他五种方法（P〈0．05）。操作时间以改良Kessler法和Tsuge法最小（P〈0．05）。结论改良Kessler加腱周连续缝合法操作简单、强度可观、生物力学特性好、吻合端光滑,是临床中最常用的肌腱修复法。Tang法抗拉强度高,可以胜任术后早期功能锻炼,为一种可靠的肌腱修复方法。     

Biomechanical comparison of the simple running and cross-stitch epitenon sutures in achilles tendon repairs

BACKGROUND: Augmenting the strength of Achilles tendon repairs may allow for earlier active rehabilitation with less risk of adhesion formation and re-ruptures, leading to quicker and stronger healing. Building upon previous research that has (1) demonstrated strength gains in Achilles repairs upon addition of simple running epitenon sutures, and (2) shown the cross-stitch epitenon suture to be stronger than the simple running stitch in flexor tendons of the hand, this study compares use of these epitenon sutures in the Achilles tendon. MATERIALS AND METHODS: Ruptures were simulated in 7 matched pairs of fresh frozen human Achilles tendons and repaired with the two-tailed Krakow locking loop core technique using No. 2 nonabsorbable, braided, polyester suture. From each pair, one specimen was randomly selected to also receive the epitenon cross-stitch, the other receiving the simple running stitch. All epitenon repairs employed 4-0 nylon suture. Repaired tendons were loaded in tension to the point of failure on a Materials Testing Machine (MTS). RESULTS: Tendon repair augmented with the cross-stitch displayed a significant, 53% greater failure strength than those repaired with the simple running stitch. Increases in initial stiffness and resistance to 2-mm gap formation in the cross-stitch specimens were 3.1% and 3.6%, respectively. CONCLUSION: Gapping resistance and initial stiffness in Achilles tendon repairs were comparable between the cross-stitch and simple running stitch, but the cross-stitch significantly improved failure strength. CLINICAL RELEVANCE: Greater failure strength may translate clinically to lower rates of re-rupture and earlier mobilization following Achilles tendon repair.     

肌腱损伤修复后早期最大抗拉力与功耗变化的实验研究

目的 探讨鸡的趾深屈肌腱断伤后用改良Kessler法和Tsuge法修复后早期缝合1：3最大抗拉力和功耗变化的特点。方法 选用三黄鸡42只，分成2组：改良Kessler法缝合组和Tsuge法缝合组，每组各21只实验鸡。将鸡的右侧第2．4趾趾深屈肌腱切断后用上述方法缝合。分别于术后即刻、1、4,7、10、14、21d取材(7个时间组)。检测肌腱的最大抗拉力和达到最大力点的功耗。结果 最大抗拉力：改良Kessler法组在术后第10天降到最低点，术后14d恢复到术后即刻的水平。Tsuge法组在术后4d开始降低，术后21d还未恢复到即刻水平。达到最大力点的功耗：Tsuge法组在术后即刻和1d、7d比改良Kessler法组高；但在术后4d(Tsuge法组)和7d(改良Kessler法组)开始，就比术后即刻显著下降并持续到术后21d。结论 肌腱缝合后早期两种缝合方法的生物力学变化并不相同，对修复后的肌腱施加拉力直至拉断时所需的能量随术后时间的增加呈进行性下降。     

Tensile properties of suture methods for repair of partially lacerated human flexor tendon in vitro

The decision to treat zone II partially lacerated flexor tendons is challenging, because there can be justification for either repair or no repair, depending on the surgeon's assessment of the strength of the residual intact portion of the tendon. In this study tensile properties of various repair techniques were compared. Cadaveric human flexor tendons (n = 118) were lacerated to 75% of their cross-section and repaired with either a core suture method (Kessler, modified Kessler, Savage, Lee, augmented Becker, or Tsuge all finished with a circumferential running suture), an epitendinous suture alone (circumferential or partial), or the tendons were left unrepaired. Among the core suture methods there was no significant difference (p >.05) in maximum failure force (overall mean, 211.2 N; SD, 53.2) or force to produce a 1.5-mm gap (74.1 N; SD, 49.7). Likewise there was no significant difference (p >.05) in tendon stiffness (41.0 N/mm; SD, 14.0) or resistance to gap formation (52.3 N/mm; SD, 23.1). In comparison, repairs without the core suture, including unrepaired tendons, were significantly weaker (144.7 N, p <.001) and had a marginally lower stiffness (p =.04) but had a similar resistance to gap formation (43.5 N/mm).     

Suture techniques with high breaking strength and low gliding resistance: Experiments in the dog flexor digitorum profundus tendon

We studied the breaking strength and gliding resistance between the pulley and flexor tendon for various suture techniques. Canine flexor digitorum profundus tendons were transected and sutured using one of eight repair techniques: modified Kessler (MK); Tsuge (Tsuge); two variations of a double modified Kessler (DK1, DK2); combined modified Kessler-modified Tsuge (MKT); augmented Becker (Becker); Cruciate (Cruciate); and modified double Tsuge (DT). The force to produce a 1.5 mm gap, ultimate failure load, resistance to gap formation, and gliding resistance were measured. The force to produce a 1.5 mm gap and the ultimate breaking force were higher with the DK1, DK2, MKT, Becker, Cruciate, and DT repairs than they were with the MK and Tsuge repair, while the gliding resistance of the Becker was higher than that of the MK, DK1, DK2, MKT, Cruciate, and DT repairs. In addition to confirming that repair strength increases as the number of strands crossing the repair increases, we also found that these stronger repairs need not produce higher gliding resistance than less robust repairs.     

Suture techniques with high breaking strength and low gliding resistance: Experiments in the dog flexor digitorum profundus tendon

We studied the breaking strength and gliding resistance between the pulley and flexor tendon for various suture techniques. Canine flexor digitorum profundus tendons were transected and sutured using one of eight repair techniques: modified Kessler (MK); Tsuge (Tsuge); two variations of a double modified Kessler (DK1, DK2); combined modified Kessler-modified Tsuge (MKT); augmented Becker (Becker); Cruciate (Cruciate); and modified double Tsuge (DT). The force to produce a 1.5 mm gap, ultimate failure load, resistance to gap formation, and gliding resistance were measured. The force to produce a 1.5 mm gap and the ultimate breaking force were higher with the DK1, DK2, MKT, Becker, Cruciate, and DT repairs than they were with the MK and Tsuge repair, while the gliding resistance of the Becker was higher than that of the MK, DK1, DK2, MKT, Cruciate, and DT repairs. In addition to confirming that repair strength increases as the number of strands crossing the repair increases, we also found that these stronger repairs need not produce higher gliding resistance than less robust repairs.     

Suture techniques with high breaking strength and low gliding resistance: experiments in the dog flexor digitorum profundus tendon

We studied the breaking strength and gliding resistance between the pulley and flexor tendon for various suture techniques. Canine flexor digitorum profundus tendons were transected and sutured using one of eight repair techniques: modified Kessler (MK); Tsuge (Tsuge); two variations of a double modified Kessler (DK1, DK2); combined modified Kessler-modified Tsuge (MKT); augmented Becker (Becker); Cruciate (Cruciate); and modified double Tsuge (DT). The force to produce a 1.5 mm gap, ultimate failure load, resistance to gap formation, and gliding resistance were measured. The force to produce a 1.5 mm gap and the ultimate breaking force were higher with the DK1, DK2, MKT, Becker, Cruciate, and DT repairs than they were with the MK and Tsuge repair, while the gliding resistance of the Becker was higher than that of the MK, DK1, DK2, MKT. Cruciate, and UT repairs. In addition to confirming that repair strength increases as the number of strands crossing the repair increases, we also found that these stronger repairs need not produce higher gliding resistance than less robust repairs.     

Influence of core suture purchase length on strength of four-strand tendon repairs

PURPOSE: Recently the length of core suture purchase has been identified as a variable affecting the strength of tendon repairs. The influence of the length of the core suture purchase on the strength of multistrand locking and grasping suture repairs, however, has not been studied extensively in transversely lacerated tendons. We assessed the effects of the length of the core suture purchase on the strength of three 4-strand grasping or locking repair techniques. METHODS: Seventy-four fresh adult pig flexor tendons were cut transversely and repaired with 1 of 3 methods: double-modified Kessler, locking cruciate, and modified Savage. Each method was assessed using 2 different lengths of core suture purchase (1.0 and 0.4 cm). The tendons were subjected to a linear noncyclic load-to-failure test in a tensile testing machine. We recorded the forces required for gap formation, ultimate strength, stiffness of the tendon, and the mode of repair failure. RESULTS: The resistance to gap formation, the ultimate strength of all 3 repairs, and the stiffness of the tendons with the double-modified Kessler and modified Savage repairs decreased significantly as the length of core sutures decreased from 1.0 to 0.4 cm. Locking and grasping repairs had a similar decrease in strength when the purchase was decreased from 1.0 to 0.4 cm. All tendons with modified Savage repairs with 1.0-cm purchase failed by suture breakage and tendons with 0.4-cm purchase failed predominantly by pullout. CONCLUSIONS: The length of core suture purchase significantly affects the strength of these 4-strand tendon repairs. The forces required for gap formation and the ultimate failure of repairs with 0.4-cm purchase were 20% to 45% lower than those of the repairs with 1.0-cm purchase. Locking repairs did not show a greater capacity to offset the decrease in strength than grasping repairs when the length of core suture purchase was decreased from 1.0 to 0.4 cm. Our study indicates that the length of suture purchase directly influences the strength of both locking and grasping core tendon repair methods.     

The biomechanical assessment of gap formation after flexor tendon repair using partial interlocking cross-stitch peripheral sutures

The gap formation of five core plus peripheral suture techniques for flexor tendon repair was evaluated by cyclic load testing. Fifty pairs of dental roll tendon models were sutured using six-strand Pennington modified Kessler core suture with 4-0 Polypropylene. One-half or three-fourths circumferential interlocking cross-stitch, or three complete circumferential peripheral suture techniques were performed using 6-0 Polypropylene. An initial cyclic load of 10 N for 500 cycles was applied and increased by 5 N for an additional 500 cycles at each new load until rupture. The complete circumferential interlocking cross-stitch had the greatest fatigue strength. The partial circumferential cross-stitches resulted in significantly larger gap formations at both the repaired and unrepaired sides than the complete circumferential sutures, and were also associated with early rupture. The full circumference of the cut tendon must be sutured using an interlocking cross-stitch peripheral suture to improve strength and avoid gap formation.     

A comparative analysis of the biomechanical behaviour of five flexor tendon core sutures

Five core suture techniques were compared by static tensile testing in vitro. Fifty porcine tendons were used. The core sutures were performed with 3-0 or 4-0 braided polyester suture (Ticron) and the over-and-over running peripheral sutures with 6-0 monofilament polypropylene (Prolene). The core sutures were: (1) Pennington modified Kessler (3-0), (2) Double Pennington modified Kessler (3-0), (3) 4-strand Savage (3-0), (4) 4-strand Savage (4-0), and (5) 6-strand Savage (4-0). Repairs were compared as paired in regard to one variable: the number of core suture strands, the suture calibre, or the suture configuration. Biomechanical differences between the repair groups started during the linear region, with the yield force and stiffness increasing along with the number of core suture strands. All three variables influenced the strain at the yield point. Thus, the strength of the intact repair can be improved by modifying the core suture. In all repairs gap formation started near the yield point after failure of the peripheral suture. The yield force represents the strength of the intact repair composite and should be considered the strength of the tendon repair.     

Contribution of a locking cross-stitch to a modified kessler core suture: a new technique

We compared the gap-producing forces, ultimate tensile strength, and slip resistance of a new core suture technique and that of a modified Kessler suture in freshly harvested chicken tendons. Biomechanical trials were carried out using a tensile-strength testing machine. Our technique proved superior to the modified Kessler suture with respect to its ultimate tensile strength and slip resistance.     

Biomechanical testing of epitenon suture strength in Achilles tendon repairs

BACKGROUND: Recent evidence that early, active mobilization protocols after Achilles tendon repairs increase recovery speed and strength make operative repair strength critical to positive outcomes after Achilles tendon ruptures. While previous research has focused on core (tendon proper) repair techniques, no previous literature has reported testing of core repairs augmented with epitenon sutures, which have been shown to increase the strength of repairs of flexor tendons of the hand. METHODS: Five matched pairs of fresh frozen human Achilles tendons were tested with and without the addition of an epitenon suture to the core repair suture. All specimens were repaired using a No. 2 Ethibond Krakow locking loop core suture. The epitenon suture was added to one tendon randomly chosen from each pair, using a 4-0 nylon suture. All specimens were mounted on an MTS testing machine (MTS Systems Corp., Eden Prairie, MN) and loaded to failure, which was defined as a 1-cm gap formation. RESULTS: The addition of epitenon sutures significantly increased the force necessary to produce a 2-mm gap as compared to core sutures alone by 74%, and it increased the average load to failure by 119%. Also, initial tendon stiffness was 173% greater in tendons reinforced with epitenon sutures. CONCLUSIONS: This study demonstrates that greater resistance to gap formation, approximation of tissue ends, and tensile strength were achieved by the addition of an epitenon suture. Clinical relevance may improve healing by decreased gap formation at the repair site and a lower risk of adhesion formation.     

The effect of core suture flexor tendon repair techniques on gliding resistance during static cycle motion and load to failure: a human cadaver study

The purpose of this study was to describe a modification of the Massachusetts General Hospital (MMGH) tendon repair and to compare it with three other suture techniques. Twenty human flexor digitorum profundus (FDP) tendons were randomly assigned to the modified Pennington (MP) suture and the MMGH suture. These were compared to the modified Kessler (MK) and Massachusetts General Hospital (MGH) sutures, using data from a previous study. All tendons were repaired with a similar epitendinous stitch and core sutures of 4-0 FiberWire. There was no significant difference in the normalized gliding resistance within the two-strand or four-strand core repair groups. The MP suture had significantly higher 2 mm gap force and ultimate load to failure than the MK suture. The MMGH suture had significantly higher 2 mm gap force and maximum failure ultimate load than the MGH suture. All repairs failed by knot unravelling.     

Embedded cross-stitch suture: an alternative to current cross-stitch peripheral suture

The cross-stitch peripheral suture has good strength, but the large amount of exposed suture on the tendon surface has restricted its clinical usage. We report a method of embedded cross-stitch that incorporates cross-stitches into peripheral sutures and reduces the amount of exposed suture on the tendon surface. Thirty-three fresh pig flexor tendons were divided equally into three groups and repaired with cross-stitch, embedded cross-stitch, or modified Halsted sutures. The tendons were tested in an Instron tensile machine to assess the mechanical performance of these repairs. With an identical number of strands across the repair site, the gap formation and ultimate forces of the embedded cross-stitch method were statistically greater than those of the cross-stitch and modified Halsted methods. The embedded cross-stitch method also had significantly greater stiffness and energy to failure than the cross-stitch method. The embedded cross-stitch method, with little suture exposure on the tendon and sufficient strength, presents an alternative to the current cross-stitch peripheral repair.     

内置十字交叉法肌腱缝合技术的生物力学研究及其在Ⅶ区伸肌腱修复中的应用

目的 报道一种新的肌腱缝合方法——内置十字交叉法的生物力学特性,及其修复Ⅶ区伸肌腱损伤的初步临床应用结果。方法 本研究采用33根猪后足的肌腱作为实验材料,随机等分成3组,分别用十字交叉法、内置十字交叉法及Halsted法进行修复。用Instron材料力学测定仪测定修复后肌腱的2-mm间隙形成负荷、断裂负荷、刚度和断裂功耗。用内置十字交叉法临床修复Ⅶ区伸肌腱断裂21例,共56指,术后均采用保护性主被动活动相结合的锻炼计划。采用Strickland标准进行功能评价。结果 等速直线拉伸模式下,内置十字交叉法的2-mm间隙形成负荷为(49.2±5.6)N,断裂负荷为(68.3±6.3)N,刚度为(6.9±0.7)N/mm,断裂功耗为(0.79±0.07)J,均优于十字交叉法和Halsted法(P<0.05)。术后平均随访26个月,内置十字交叉法修复的Ⅶ区伸肌腱(56指)无一例发生断裂,根据Strickland TAM标准,优50指,良4指,可2指,优良率96.4%。结论 内置十字交叉法具备良好的生物力学强度,外露缝线少,能满足伸肌腱早期保护性主被动活动的需要,是伸肌腱修复的理想选择。     

Strength analysis and comparison of the Teno Fix Tendon Repair System with the two-strand modified Kessler repair in the Achilles tendon

BACKGROUND: Various options exist for repair of Achilles tendon ruptures, yet a method that consistently provides sufficient gap resistance to allow early mobilization remains elusive. This study compares the mechanical performance of a modified Kessler repair with that of the Teno Fix Tendon Repair System (Ortheon Medical, LLC) in matched pairs of cadaver Achilles tendons. METHODS: The two-strand modified Kessler repair was selected as the control construct on the basis of literature review and physician interviews which identified it among the many options as a popular method for repair of acutely ruptured Achilles tendons. Test specimens were harvested from matched pairs of cadaver ankles. The tendons were transected 3.5 cm proximal to the calcaneal insertion and repaired with either the two-strand modified Kessler suture construct or the Teno Fix Tendon Repair System. Assignment to the modified Kessler or Teno Fix group was done randomly for the first member of each pair. All test and control repairs were performed by the same author to reduce variability. Evaluation of the repairs consisted of tensile strength testing and measurement of the gap formation and peak stresses. RESULTS: Gap and peak stress for the two-strand modified Kessler repair were 0.30 +/- 0.15 N/mm2 and 1.03 +/- 0.51 N/mm2, respectively. For the Teno Fix repairs the mean gap and peak stress values were 0.80 +/- 0.46 N/mm2 and 1.19 +/- 0.12 N/mm2, respectively. The mean gap formation stress was significantly higher in the Teno Fix repairs than in the control repairs (p < .0005). There was no significant difference in peak strength between the repairs (p < .10). CONCLUSIONS: The Teno Fix repair was superior to the modified Kessler repair. In the Teno Fix repairs, the gap formation stress was 67% of the peak tensile stress. In comparison, in the modified Kessler repairs, the gap formation stress was 29% of the peak stress. This can be correlated to the elastic property of the modified Kessler suture and the initial tightening of the suture around the tendon fibers. The Teno Fix system is nonelastic and is fully tensioned during installation. This lends to a more gap resistant repair.