Optimizing Achilles tendon repair: effect of epitendinous suture augmentation on the strength of achilles tendon repairs

BACKGROUND: Epitendinous suture augmentation has been shown to increase gap resistance and overall strength in flexor tendon repairs of the hand. The purpose of this study was to evaluate the effect of various suture augmentation techniques in Achilles tendon repair. MATERIALS AND METHODS: Eighteen fresh-frozen cadaveric Achilles tendons were transected and repaired with a 4-strand Krackow core stitch. Suture augmentation was performed with 3 figure-of-eight stitches in 6 specimens and a running cross-stitch weave in 6 specimens. The other 6 specimens were not augmented. Each tendon was loaded to failure on an MTS. Force to failure (defined as peak force or force at 5 mm gapping), gapping resistance, stiffness, and elongation were compared. RESULTS: Force to failure (p < 0.001), stiffness (p < 0.01) and gapping resistance (p < 0.05) were increased by suture augmentation. Additionally failure force and gapping resistance for the cross-stitch augmentation was higher than the figure-of-eight augmentation (p < 0.05). CONCLUSION: Cross-stitch augmentation of Achilles tendon repair yields a stronger and stiffer repair with greater resistance to gapping. CLINICAL RELEVANCE: Achilles tendon repairs augmented with a cross stitch weave will be able to withstand substantially higher forces than non-augmented repairs.     

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.     

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.     

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.     

Isobutyl cyanoacrylate as a soft tissue adhesive. An in vitro study in the rabbit Achilles tendon

Cyanoacrylates (CAs) are biodegradable, bacteriostatic, and hemostatic adhesives. CAs have been used in medical applications, but with adverse effects, including excessive inflammatory reaction and neural toxicity. Isobutyl CA (ICA) appears more biocompatible, with a long half-life that may be ideal for a soft tissue adhesive. The rabbit Achilles tendon was chosen to test (ICA), and a special muscle-freezing clamp to test this model was designed. The tendons were sharply cut 2 cm proximal to their insertion and repaired in four groups. They were tested to failure on an Instron machine. The breaking strength of the repairs was then noted. Also, the breaking strength of several suture materials was tested. Four Achilles tendon repair groups were evaluated: ICA alone 9.03 newtons (NTS); 4-0 silk Kessler stitch, mean 12.9 NTS; Kessler stitch plus three simple stitches, mean 23.0 NTS; and a combination of (a) and (c)--i.e., suture and adhesive, mean 40.2 NTS. The intact Achilles tendon was tested with an average breaking strength of 317 NTS. The muscle-freezing clamp facilitated reasonable testing of this tendon repair. ICA alone exhibits reasonable strength in vitro and in combination with suture provides a stronger initial repair than either suture or adhesive alone.     

Tensile strength of a new suture for fixation of tendon grafts when using a weave technique

PURPOSE: To evaluate a new corner stitch construct for tendon graft or tendon transfer fixation and compare the tensile strength with a conventional central cross-suture design in human cadaver tendons. METHODS: Flexor digitorum profundus tendons of the index, middle, and ring fingers (48 total) were used as recipients and palmaris longus, extensor indicis proprius, and extensor digitorum communis tendons of the index finger (48 total) were used as grafts from 16 fresh-frozen human cadaver hands. We compared the cross-stitch technique with a new corner stitch technique in tendon repairs made with 1, 2, or 3 weaves (8 per group). Tendons were sutured at each weave with either 2 full-thickness cross-stitches or 4 partial-thickness corner stitches of 4-0 nylon. Mattress sutures also were placed through the free tendon end for each repair type. The tensile strength of the tendon-graft composite was measured with a materials testing machine. RESULTS: The tensile strength of the repairs increased significantly with the number of weaves. When 2 or 3 weaves were used with the corner stitch or when 3 weaves were used with the cross-stitch, the repairs were significantly stronger. Although no significant difference in strength to failure was noted when comparing cross and corner stitches with equivalent numbers of weaves, qualitatively there was a difference in mode of failure with the 3-weave corner stitches failing primarily by intrasubstance tendon failure and the 3-weave cross-stitch repairs failing by tendon pullout. CONCLUSIONS: The corner stitch is as strong as conventional cross-stitch repairs and its superficial placement may be more favorable to tendon blood supply. This repair may be advantageous for clinical applications.     

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.     

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.     

Effect of suture locking and suture caliber on fatigue strength of flexor tendon repairs

The objectives of this cadaveric study were 2-fold: to determine the effect of different locking configurations on the cyclical fatigue strength of flexor tendon repairs and to assess the differences between each repair when a 3-0 or 4-0 suture is used. One hundred twenty flexor digitorum profundus tendons were cut and repaired using nonlocked, simple locked, and cross-stitch locked variations of 2- and 4-strand flexor tendon repairs. Using an incremental cyclical loading protocol we performed 10 trials of each repair with both 3-0 and 4-0 sutures and analyzed the number of Newton-cycles to failure using a 3-way ANOVA. The use of a 3-0 suture led to a 2- to 3-fold increase in fatigue strength in all repairs tested and the fatigue strength of the 4-strand repairs was significantly greater than the 2-strand repairs. All repairs performed with 4-0 suture failed by suture rupture. Of the 3-0 suture repairs, the three 2-strand repairs and the 4-strand cross-stitch locked repair failed by suture rupture. In contrast, 6 of 10 of the 4-strand simple locked and nonlocked repairs failed by suture pullout. There was no significant difference in fatigue strength between the 2 locked and the nonlocked 2-strand repairs using either 3-0 or 4-0 suture. There also was no significant difference in holding capacity or fatigue strength between the simple locked or nonlocked 4-strand repairs. However, the 4-strand cross-stitch locked repair with a 3-0 suture had significantly improved fatigue strength and holding capacity compared with the other repairs tested. Based on the consistently inferior biomechanical performance of 4-0 suture, we recommend that 3-0 suture be considered for 2- or 4-strand tendon repairs when early active motion is planned. The orientation of the transverse and longitudinal components of simple locked repairs did not significantly influence their holding capacity or fatigue strength. The cross-stitch type of locked repair provides better holding capacity and fatigue strength compared with simple locked or nonlocked 4-stranded flexor tendon repairs.     

A biomechanical study of Achilles tendon repair augmentation using GraftJacket matrix

BACKGROUND: Ruptured Achilles tendons benefit from primary repair by decreasing re-rupture rates and allowing earlier range of motion. A stronger repair might allow for more aggressive rehabilitation decreasing postoperative stiffness, calf atrophy, and repair site gapping. The hypothesis of this study was that human dermal allograft augmentation of an Achilles repair would significantly increase repair strength and stiffness. This study evaluated strength and stiffness of an Achilles tendon repair augmented with a human dermal allograft (GraftJacket). MATERIALS AND METHODS: Eight matched pairs of human cadaver legs were used. Simulated Achilles tendon ruptures were created 4 cm proximal to the calcaneal insertion. All tendons were repaired with a Krackow locking loop stitch. One of each matched pair was augmented with GraftJacket. Each construct was pre-loaded at 10 N and cyclically loaded (20 cycles) from 2 N to 30 N at a rate of 5 N/sec on an Instron machine. This was followed by testing to failure at a displacement rate of 6 mm/sec. RESULTS: The ultimate failure load in the control group was 217 N +/- 31 compared to 455 N +/- 76.5 in the GraftJacket group (p < 0.001). The mean stiffness in the control group was 4.3 +/- 0.83 N/mm which was significantly less than the 12.99 +/- 5.34; N/mm in the GraftJacket group (p = 0.002). CONCLUSION: The augmentation of an Achilles tendon repair with GraftJacket significantly increased repair strength and stiffness. CLINICAL SIGNIFICANCE: These findings suggest that a GraftJacket augmented Achilles tendon repair could acutely withstand a more aggressive rehabilitation program, potentially decreasing ankle stiffness and allowing earlier return to full activities.     

Flexor tendon repairs: the impact of fiberwire on grasping and locking core sutures

PURPOSE: Immediate surgical repair and early mobilization are essential in preventing adhesion formation and finger stiffness. A new polyethylene-based, braided suture material, Fiberwire (Arthrex, Naples, FL), touting increased strength, presents the potential for stronger repairs and, therefore, earlier active motion after surgery with a greater safety margin. The purpose of this biomechanic study was to investigate the differences in gap formation, tensile strength, and mode of failure for 2 distinct repair techniques using nylon, Ethibond (Ethicon, Somerville, NJ), and Fiberwire. METHODS: Human cadaver flexor tendons were harvested and repaired in a randomized fashion with either the Strickland or Massachusetts General Hospital (MGH) repairs using either nylon, Ethibond, or Fiberwire. Twelve tendons per group were repaired for each combination of material and method. During load-to-failure testing, 2-mm gap force and maximum tensile strength were statistically analyzed. RESULTS: Strickland repairs failed by suture pull-out in 74% of repairs, whereas 99% of the MGH repairs failed by suture breakage. For MGH repairs, Fiberwire suture provided significantly more tensile strength than Ethibond and nylon. For Strickland repairs, where the mode of failure was more often by suture pull-out rather than breakage, differences between type of suture were not significant. When comparing repair techniques using Fiberwire, the MGH repair was significantly stronger than the Strickland repair. CONCLUSIONS: Biomechanic testing shows that Fiberwire outperforms both Ethibond and nylon suture when using a locked flexor tendon repair suture (MGH repair) but not when using a grasping-type, nonlocking repair (Strickland 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。     

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.     

Increased suture embedment in tendons: an effective method to improve repair strength

We evaluated the effect of length of suture embedment within tendons on the tensile strength of repaired tendons. Thirty fresh pig flexor tendons were divided into three groups and subjected to repairs with the Halsted tendon sutures in which 1/3, 1/2, and 2/3 of the length of the longitudinal sutures was embedded within the tendons. The repaired tendons were pulled to complete failure by an Instron tensile testing machine. The 2 mm gap-formation force, ultimate strength, stiffness, and energy to failure were greatest when 2/3 of the suture length was embedded within the tendon. The results indicate that suture embedment is an important contributor to the tensile properties of the repair, and that increase in length of suture embedment is an effective way to strengthen tendon 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.     

Cyclic loading of Achilles tendon repairs: a comparison of polyester and polyblend suture

BACKGROUND: Early functional rehabilitation is widely used after open suture repair of the Achilles tendon. To our knowledge, no previous studies have assessed gap formation from cyclic loading and subsequent failure loads of simulated Achilles tendon repairs. A synthetic (polyblend) suture has been introduced for tendon repairs with reportedly greater strength than polyester suture. This stronger, stiffer suture material may provide stronger repairs with less elongation of the tendon repair. METHODS: Simulated Achilles tendon ruptures in bovine Achilles tendon were repaired with a four-strand Krackow suture technique using No. 2 polyester suture. Specimens were loaded for 3,000 cycles at maximal loads of 50, 75, 100, or 125 N, and gap formation at the repair site was continuously measured. After cyclic loading, each specimen was loaded to failure. Identical repairs were performed with number 2 polyblend suture and cyclically loaded to 75 N for 3,000 cycles. All specimens were loaded to failure. RESULTS: Cyclically loading polyester suture repairs to 50, 75, 100, or 125 N for 3,000 cycles resulted in mean gapping at the repair site of 3.0 +/- 0.8, 4.9 +/- 1.0, 7.2 +/- 0.9, and 7.9 +/- 0.8 mm, respectively. Cyclically loading the polyblend suture repairs for 3,000 cycles at 75 N, resulted in 3.3 +/- 0.3 mm of gap formation at the repair site, significantly less than polyester suture repairs (p < 0.001). The mean load to failure for polyester suture repair was 222 +/- 19 N and for polyblend suture repair was 582 +/- 49 N, a statistically significant difference (p < 0.001). Gap formation at 100, 1,000, and 2,000 cycles, as a percentage of total gap formation at 3,000 cycles, was 64.3%, 87.5%, and 95.4% for polyester suture and 45.8%, 78.5%, and 90.1% for polyblend repairs. All specimens in all groups failed at the knots during load-to-failure testing. CONCLUSIONS: Cyclic loading of simulated Achilles tendon repairs using a Krackow, four-core polyester suture technique showed progressive gap formation with increasing load. All repairs failed at the knot, and suture pull-out from tendon was not observed. Polyblend suture repair, when compared to identical repairs with braided polyester suture, resulted in a 260% higher load to failure and 33% less gap formation at the repair site after 3,000 cycles. CLINICAL RELEVANCE: The use of polyblend suture in a four-stranded Krackow configuration provides stronger repairs with less gap formation, which may provide increased security during early functional rehabilitation.     

The effect of increased peripheral suture purchase on the strength of flexor tendon repairs

PURPOSE: Previous studies have hypothesized unequal load sharing between peripheral and core sutures in flexor tendon repairs. Most commonly peripheral sutures are placed very near the repair site and characteristically fail before the core strands. We hypothesized that placement of the peripheral sutures farther from the repair site would better optimize load sharing and resist suture pullout, yielding a stronger overall repair. METHODS: To test the hypothesis we developed a mathematical model of the load sharing between core and peripheral sutures. By using this model we predicted that placement of peripheral sutures 2 mm from the repair site would optimize the balance of load between core and peripheral sutures. We then divided and repaired 27 flexor digitorum profundus tendons in 6 ways (core plus peripheral or peripheral sutures only at 1 mm, 2 mm, or 3 mm from the repair site). Tendons were clamped to a custom-built linear loading machine and distracted to failure. RESULTS: There was a clinically and statistically significant increase in strength with an increased distance of the peripheral suture from the repair site showing that core sutures augmented by a 2-mm peripheral repair were stronger than those performed with 1-mm peripheral repairs (50.8 vs 37.1 N). CONCLUSIONS: A peripheral stitch placement approximately 2 mm from the repair site represents a simple modification that can significantly increase the ultimate strength of flexor tendon repairs.     

Mechanical characteristics of cross-stitch epitenon suture in association with various two-strand core sutures: a biomechanical study using canine cadaver tendons

The purpose of this study was to investigate the ultimate tensile strength and stiffness of the cross-stitch epitenon suture technique in association with three different two-strand core suture techniques (the modified Kessler, Tsuge, and two-strand Savage). Twenty-four canine cadaver flexor profundus tendons were lacerated and repaired by one of the following techniques: the cross-stitch (Group 1), the modified Kessler with cross-stitch (Group 2), the Tsuge with cross-stitch (Group 3), and the two-strand Savage with cross-stitch (Group 4). Ultimate strength was determined with a tensile testing machine and stiffness was recorded by a video dimension analyser system. The ultimate strength of Group 2 (5.704 kgf) was significantly greater than that of the other techniques, followed by Group 4 (4.608 kgf), Group 3 (3.568 kgf), and Group 1 (2.935 kgf). The stiffness of Group 2 (495.8 kgf/m) was significantly greater than that of the other techniques, followed by Group 4 (369.7 kgf/m), Group 3 (225.7 kgf/m), and Group 1 (200.1 kgf/m). These results may be helpful to surgeons in deciding which core suture technique to use in association with the cross-stitch epitenon suture.     

A biomechanical analysis of suture materials and their influence on a four-strand flexor tendon repair

PURPOSE: Flexor tendon repair strength depends on the suture technique and the suture material used. Configurations that incorporate locking loops prevent sutures from pulling through the tendon but typically fail because of suture breakage. The choice of suture material therefore influences repair strength. This study investigated the mechanical properties of 5 nonabsorbable 4-0 suture materials (monofilament nylon, monofilament polypropylene, braided polyester, braided stainless steel wire, and braided polyethylene) and evaluated their performance when used in a locking 4-strand flexor tendon repair configuration. METHODS: Five samples of 2 strands of each suture type were tested mechanically to determine the material stiffness and ultimate load. In addition, 50 fresh porcine flexor tendons were divided and repaired with each of the 5 suture materials using a 4-strand single-cross technique. Gap force, ultimate strength, and stiffness were measured to compare biomechanical performance. RESULTS: All repairs failed by suture rupture at the locking loop. Fibrewire and stainless-steel sutures and repairs were significantly stronger and stiffer than the other suture types. The results for Prolene and Ethibond were similar in the tendon repair groups with respect to gap and ultimate forces although Ethibond provided significantly increased repair stiffness. Nylon sutures and repairs consistently produced the poorest mechanical performance in all outcome measures. CONCLUSIONS: Suture material strongly influences the biomechanical performance of multistrand tendon repairs and is an important consideration for the surgeon. Fibrewire and stainless steel are the most biomechanically suitable suture materials for flexor tendon repair whereas nylon is the least suitable. Further developments in suture materials are important for advancements in flexor tendon repair strength.     

Cyclical testing of zone II flexor tendon repairs

Kessler, Strickland, or modified Becker repairs, all augmented with a running circumferential epitenon suture, were performed for simulated zone II flexor tendon lacerations in the index, long, and ring fingers of 12 fresh-frozen cadaveric specimens. Each hand was tested with a tensiometer built for curvilinear testing of human flexor tendons in an intact hand. Each tendon was cycled 100 times, then examined for gapping before testing to failure. Maximum load to failure, including tendon load and pinch force, was recorded for each tendon. We propose that combining the advantages of cyclical testing and a curvilinear model is the most effective way of testing flexor tendon repairs capable of undergoing an early active motion protocol. None of the repaired tendons failed during the cyclic portion of testing. The average gapping after cycling for the 3 suture techniques was 0.12 +/- 0.35 mm for the Kessler technique, 0. 00 +/- 0.00 mm for the Strickland technique, and 0.19 +/- 0.26 mm for the modified Becker technique. The maximum tendon loads to failure were 33.8 +/- 6.8 N for the Kessler technique, 30.4 +/- 5.64 N for the Strickland technique, and 76.3 +/- 9.02 N for the modified Becker technique. There was a statistically significant difference between the modified Becker repair and the other 2 repairs for maximum tendon load and pinch force to failure. The results of this study show that all 3 tendon repair techniques can withstand forces reported with passive motion, but only the modified Becker repair allows sufficient strength above those forces that are estimated for active motion during tendon healing.