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.     

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.     

Biomechanical evaluation of a four-strand modification of the Tang method of tendon repair

We report a four-strand modification of the Tang technique of tendon repair that uses fewer sutures and fewer knots on the tendon surface. This repair consists of four longitudinal and two horizontal strands that form a "U" configuration within the tendon made with a single looped suture. Thirty-four fresh pig flexor tendons were divided into 3 groups and repaired with the four-strand modified Tang method, a double-looped four-strand method or a double Kessler repair (four-strand). The tendons were subjected to a single cycle of load-to-failure test in a tensile testing machine. The initial force, 2-mm gap formation force and ultimate strength of the four-strand modified Tang repair were statistically identical to those of the double looped suture and were superior to those of the double Kessler repair. Ultimate strength was 43.4+/-4.3N for the four-strand modified Tang method, 45.2+/-4.0N for the double-looped method and 39.1+/-4.0N for the double Kessler repair. The four-strand modification of the Tang method appears to have strength sufficient for protected active finger motion. Given our preliminary clinical experience with this method, we recommend this new and simplified technique for clinical flexor tendon repairs.     

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.     

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。     

Influence of core suture material and peripheral repair technique on the strength of Kessler flexor tendon repair

The purpose of our study was to determine the most favourable combination of core suture material and peripheral repair technique for Kessler tendon repair. Thirty freshly thawed pig flexor tendons were repaired by a Kessler technique, either with braided polyester or monofilament nylon suture. A peripheral augmentation was done using one of the three techniques-running, cross-stitch and Halsted. All repairs were tested by cyclic loading, followed by load-to-failure. During cyclic loading six of the 15 tendons with a nylon core failed, but none with a braided polyester core. Irrespective of peripheral technique, the monofilament nylon core suture allowed early central cyclic gapping, resulting in failure of the repair. During load-to-failure testing, the running stitch proved weakest and the cross-stitch repair toughest.     

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).     

Dorsal-enhanced sutures improve tension resistance of tendon repair

Thirty-six fresh pig flexor tendons were repaired using either the modified Kessler method or the Tang method. Nine tendons from each group were tested in an Instron tensile testing machine with the tendons passing 90 degrees around a pulley. The other nine tendons from each group were pulled linearly by the testing machine. The 2 mm gap formation force of the tendons repaired with the modified Kessler and Tang methods and pulled at 90 degrees were 64%+/-5% and 79%+/-9% respectively of those forces recorded during linear testing. The ultimate strengths of tendons repaired by the modified Kessler and Tang methods and pulled at 90 degrees were 76%+/-6% and 81%+/-8% respectively of the forces measured during linear testing. The percentage gap formation and ultimate strength of the Tang method was significantly higher than that of the modified Kessler suture when the tendons were pulled around a pulley. This demonstrates that the Tang suture, with its main components in the dorsal part of the repaired tendon, has greater tension resistance capacity than conventional tendon sutures which are placed in the middle of the tendon. This study suggests that dorsally-enhanced multiple tendon sutures are better placed to sustain the tension generated during active finger flexion.     

四种与Kessler相关的屈肌腱缝合方法的生物力学研究

目的 研究四种与Kessler相关的屈肌腱缝合方法 对肌腱修复抗张强度的影响.方法 采用新鲜猪后肢跖深屈肌腱,将40根肌腱分为4组,每组10根,横行切断,以Kessler法、DoubleKessler法、Running suture法、Kessler+Running suture法缝合.检测缝合后肌腱2mm间隙形成的负荷、最大抗张强度,采用ANOVA法进行统计分析.结果 对于肌腱的横断伤,最大抗张强度DoubleKessler法Kessler+Running suture法Kessler法Running suture法. 2mm间隙形成的负荷Kessler+Running suture法Double Kessler法Rumming suture法Kessler法.结论 肌腱横行损伤修复时,采用强生3-0编织缝合线,Kessler+Running suture法能够满足临床早期功能锻炼的强度要求.     

Comparative biomechanic performances of locked cruciate four-strand flexor tendon repairs in an ex vivo porcine model

PURPOSE: To investigate the effects of 3 different locking configurations on repair strength when used in a cruciate four-strand repair. METHODS: Sixty fresh porcine flexor tendons were transected and repaired with cruciate four-strand core suture repairs with 3 different locking configurations: simple locks (a modification of the Pennigton method), circle locks, and cross locks. Half of the repairs in each locking group were reinforced with a peripheral suture. The tendon repairs were subjected to linear load-to-failure testing. Outcome measures were 2-mm gap force and ultimate tensile strength. RESULTS: The cross lock repair had significantly greater 2-mm gap force and ultimate tensile strength than the simple lock repair, both with and without a peripheral suture. The cross lock repair showed significantly greater 2-mm gap force without a peripheral suture and significantly greater ultimate tensile strength with a peripheral suture than the circle lock repair. With peripheral reinforcement, the cross lock cruciate repair had a mean 2-mm gap force of 92 N and ultimate tensile strength of 119 N. The cross lock cruciate repair consistently produced the strongest biomechanic performance in all outcome measures. CONCLUSIONS: Locking configuration influences the biomechanic performance of cruciate four-strand flexor tendon repairs. Our results suggest that the cruciate repair with cross locks is stronger than repairs with simple locks or circle locks. Whether the results of this ex vivo porcine linear model can be translated to the clinical arena is unknown, because the factors of tendon/sheath friction, tendon healing, and compromised tendon viability from the lock were not addressed.     

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)     

Effects of direction of tendon lacerations on strength of tendon repairs

PURPOSE: We compared the tensile strength of different repair configurations on tendons with oblique and transverse lacerations. METHOD: Seventy-two fresh pig flexor tendons were divided randomly and repaired using the modified Kessler, the cruciate, or the 4-strand Massachusetts General Hospital (MGH) repair methods. The tendons were lacerated either transversely or obliquely. They were repaired with conventional and oblique suture repairs. The 2-mm gap formation force and ultimate strength were determined as biomechanical performance for each repair. RESULTS: The gap formation and ultimate strength of the tendons vary with orientations of tendon lacerations and suture methods. In the tendons repaired with the modified Kessler or the cruciate methods, the 2-mm gap formation and ultimate strength of obliquely cut tendons were significantly lower than those of transversely cut tendons. The obliquely placed modified Kessler or cruciate sutures significantly improved the repair strength in the tendons with an oblique laceration. In the tendons repaired with the MGH method, no statistical differences were found in the repair strength of obliquely and transversely lacerated tendons. CONCLUSIONS: The direction of tendon lacerations affects strength of certain repair configurations. The nonlocking modified Kessler or the cruciate tendon repairs are weakened considerably when the tendon laceration is oblique but their mechanical performance is strengthened by re-orienting the repair strands to lie parallel to the laceration. The cross-locked configuration of the MGH repair is not affected by the obliquity of the tendon laceration.     

Repair strength of tendons of varying gliding curvature: a study in a curvilinear model

PURPOSE: This study was done to investigate changes in the strength of the repaired tendons by different curvatures of tendon motion arcs. METHOD: Forty-two fresh-frozen digital flexor tendons were divided into 4 groups and were repaired by the modified Kessler method with a running peripheral suture. The tendons were pulled over pulleys with tension at a fixed angle of 90 degrees, but radii of gliding curvature of the pulleys were set at 2.0, 1.5, and 1.0 cm in 3 groups, respectively. The tendons in the other group were subjected to linear tension. These tendons were tested in an Instron tensile machine to determine the 2-mm gap formation force and ultimate strength of the repairs. RESULTS: The 2-mm gap formation force of the tendons pulled over the curvature of a 2.0-, 1.0-, and 0.5-cm radius was, respectively, 69%, 61%, and 49% of that pulled linearly. The ultimate strength of the tendons over curvatures of 2.0-, 1.5-, and 1.0-cm radius was, respectively, 77%, 73%, and 63% of that of tendons pulled with linear tension. The gap formation force and ultimate strength were statistically the lowest in the tendons with a gliding radius of curvature of 1.0 cm. Both the gap formation force and the ultimate strength of tendon repairs decreased as the radius decreased. CONCLUSIONS: The curvature of tendon motion arcs affects the repair strength of the tendons. The findings suggest an increased likelihood of repair ruptures in the tendons that glide along curvatures over the sheaths, pulleys, or joints.     

Effects of tension direction on strength of tendon repair

We investigated changes of tensile strength in tendon repair according to tension direction. Thirty-six fresh-frozen digital flexor tendons were divided into 4 groups with 9 tendons each. The tendons were repaired by the modified Kessler method. Sutured tendons were pulled against pulleys at angles of 0 degrees, 30 degrees, 60 degrees, and 90 degrees to the direction of the pull of the testing machine in the 4 groups, respectively. The repaired tendons were tested in a tensile machine to determine 2-mm gap formation force and ultimate strength of the tendons. The 2-mm gap formation force and ultimate strength in the tendons pulled at 0 degrees were statistically higher than those in the tendons pulled at 30 degrees, 60 degrees, and 90 degrees. The 2-mm gap formation force of the tendons pulled at 30 degrees, 60 degrees, and 90 degrees was 86% +/- 10%, 73% +/- 9%, and 64% +/- 8% of that at 0 degrees, respectively. Ultimate strength of tendons pulled at 30 degrees, 60 degrees, and 90 degrees was 89% +/- 9%, 82% +/- 11%, and 76% +/- 8% of that at 0 degrees, respectively. Values of the 2-mm gap formation force and ultimate strength were statistically the lowest in the group with a pulling angle of 90 degrees. There was no statistically significant difference in repair strength between tendons tested at 0 degrees and those in the model without pulleys. The strength of tendon repair changed considerably according to direction of tension added to the tendons. The gap formation force and ultimate strength decreased as angles of tension increased. The results imply that a repaired tendon will be weakened as the finger is increasingly flexed. The decrease in repair strength should therefore be considered in planning a tendon suture to tolerate active finger flexion and a tendon motion protocol after primary tendon repair.     

Gliding characteristics and gap formation for locking and grasping tendon repairs: a biomechanical study in a human cadaver model

PURPOSE: The purpose of this study was to compare the frictional characteristics and mechanical properties of various locking and grasping suture techniques in a human in vitro model of flexor tendon repair. METHODS: Forty-five cadaveric human flexor digitorum profundus tendons were transected in zone II and repaired using 1 of 5 core suture methods (n = 9 per group): either grasping (modified grasping Kessler, modified Lee) or locking (Pennington, modified Pennington, locking Lee) loop suture techniques. All repairs used 4-0 Supramid looped core suture and an epitenon running suture of 6-0 nylon. Gliding resistance at the tendon-pulley interface was measured along with failure strength and gap formation. The force to produce 0.5-, 1.0-, 1.5-, and 2.0-mm gaps were measured. RESULTS: One of the locking repairs, the locking Lee, had a gliding resistance significantly higher than that of one of the grasping repairs (modified grasping Kessler) and the other 2 locking repairs (Pennington, modified Pennington) (p <.05). There was no significant difference between the other grasping (modified Kessler, modified Lee) and locking (Pennington, modified Pennington) suture configurations (p =.21). The maximum force of one of the locking repairs, the modified Pennington repair (48.0 N; standard deviation, 3.9) was significantly higher than the other locking and grasping repairs (p <.05). The force required to produce more than 1.5 mm of gap for the modified Pennington repair was also significantly higher than that for some of the other grasping (modified Kessler, modified Lee) and locking (Pennington) repairs (p <.05). CONCLUSIONS: The lack of significant difference in gliding resistance among the similarly designed modified grasping Kessler, Pennington, and modified Pennington repairs (overall mean, 0.87 N; standard deviation, 0.16) suggests that the locking loop configuration itself does not adversely affect tendon gliding resistance. The modified Pennington repair increased not only ultimate strength but also resistance to gap formation more than 1.5 mm.     

Optimizing biomechanical performance of the 4-strand cruciate flexor tendon repair

PURPOSE: The purpose of this study was to determine whether increasing the size of the locking loop increased the repair strength of the cruciate 4-strand suture technique and to quantify the biomechanical properties that various peripheral suture techniques provide in the cruciate 4-strand suture technique. METHODS: Fifty-six deep flexor tendons harvested from adult sheep hind limbs were divided randomly into 7 groups of 8. Four groups were repaired using the cruciate core technique without a peripheral suture. The locking loops were set using 10%, 25%, 33%, or 50% of the tendon width and loaded to failure using a distraction rate of 20 mm/min. The 3 groups of tendons then were repaired by using the established optimal locking loop size. These 3 groups were combined with a simple running, cross-stitch, or the interlocking horizontal mattress (IHM) peripheral suture. Repairs were tested to failure and the load at a 2-mm gap, load at failure, and stiffness were determined for all samples. RESULTS: Repairs with locking loops of 25% had the greatest biomechanical properties with load to 2-mm gap formation, load to failure, and stiffness of 10 N, 46.3 N, and 3.9 N/mm, respectively. Those with 33%, 50%, and 10% locking loops followed. Repairs with 10% locking loops failed owing to the suture cut out of the tendon. All other groups failed because of suture breakage. By using the cruciate core technique with a 25% locking loop the IHM/cruciate combination was markedly better than both the cross-stitch/cruciate and simple running/cruciate combinations. CONCLUSIONS: The ideal-sized bite of the locking loops for the cruciate repair is 25% of the tendon's width. Peripheral sutures are vital to the biomechanical properties of the repair. The IHM peripheral suture technique provided the greatest improvement in biomechanical properties.     

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。     

Core suture purchase affects strength of tendon repairs

PURPOSE: It generally is considered that a certain distance should be maintained between the site of the tendon-suture junction and the laceration level of the tendon. In this study we assessed how the length of core suture purchase may affect the repair strength of transversely cut tendons using a 2-strand modified Kessler method and a 4-strand circle-locking method. METHODS: Seventy-four fresh pig flexor tendons were transected. Fifty-eight tendons were divided into 4 groups and repaired with a 2-strand grasping repair technique with the core suture purchase in the tendon stump ranging from 0.4 to 1.2 cm. Sixteen tendons were repaired with a 4-strand circle-locking tendon-suture repair technique. The core suture purchase of these tendons was 0.4 and 1.0 cm, respectively. The tendons were subjected to a linear, noncyclic, load-to-failure test in a tensile testing machine. The forces measured for initial gap formation, 2-mm gap formation, and ultimate strength were recorded for each repair. RESULTS: The resistance to gap formation and ultimate strength of 2-strand grasping technique repairs increased significantly as the suture purchase increased from 0.4 to 0.7, 1.0, and 1.2 cm although strength remained constant from 0.7 to 1.2 cm. The strength of 4-strand circle-locking repairs with a suture purchase of 1.0 cm was statistically greater than that of the repairs with a suture purchase of 0.4 cm. CONCLUSIONS: For both the 2-strand grasping and 4-strand circle-locking repair methods, the length of core suture purchase significantly influences the resistance to 2-mm gap formation and the ultimate strength of repairs in transversely lacerated flexor tendons. We determined that the optimal length of purchase is between 0.7 and 1.0 cm and that increased length of purchase from 0.7 to 1.2 cm does not increase the strength of the repair. Core suture purchase length of 0.4 cm or less results in significantly weaker repairs.     

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.