The effect of flexor tendon repair bulk on tendon gliding during simulated active motion: an in vitro comparison of two-strand and six-strand techniques

The gliding function of 2-strand (Tajima) and 6-strand (Savage) techniques of flexor tendon repair were compared in an in vitro biomechanical model. Stainless steel beads were inserted directly into the metacarpals, phalanges, and flexor digitorum profundus tendons of 22 human cadaver specimens. The FDP tendons were loaded from 5 to 25 N using a pneumatic actuator. The angular rotation and tendon excursion of the cadaver specimens were measured radiographically. The gliding function of the repairs was compared with core suture only, core suture plus epitenon repair, and sheath repair. There was no significant difference in angular rotation or linear excursion between the 2-strand and 6-strand techniques of flexor tendon repair. The addition of the epitendinous suture to the core suture improved the angular rotation and linear excursion for the 2-strand technique. Although the 6-strand repair tended to increase the repair site bulk more than the conventional 2-strand technique, the gliding function of the repair techniques was equivalent.     

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 analysis of the modified Tsuge suture technique for repair of flexor tendon lacerations

Thirty-six flexor tendons from fresh frozen cadavers were randomized to three types of repairs: a Kessler-Tajima, a 4-strand modified Tsuge, and a 6-strand modified Tsuge. All repairs were accompanied by a standard epitendinous suture. The repaired tendons were then tested to initial gap and ultimate failure in an Instron machine. The average forces to ultimate failure were 31.8 N (SD, 8.8), 48.4 N (SD, 10.7), and 64.2 N (SD, 11.0) respectively. The 6-strand modified Tsuge suture was significantly stronger than the other repairs and the 4-strand modified Tsuge was significantly stronger than the 2-strand Kessler-Tajima. The 6-strand and 4-strand modified Tsuge repairs appear strong enough to withstand the forces generated during early active range of motion flexor tendon rehabilitation protocols. Clinical trials are required to evaluate the usefulness of these repairs.     

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.     

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.     

Biomechanic comparison of the Teno Fix tendon repair device with the cruciate and modified Kessler techniques

PURPOSE: To compare the mechanical behavior of a novel internal tendon repair device with commonly used 2-strand and 4-strand repair techniques for zone II flexor tendon lacerations. METHODS: Thirty cadaveric flexor digitorum profundus tendons were randomized to 1 of 3 core sutures: (1) cruciate locked 4-strand technique, (2) modified Kessler 2-strand core suture technique, or (3) Teno Fix multifilament wire tendon repair device. Each repair was tested in the load control setting on a Instron controller coupled to an MTS materials testing machine load frame by using an incremental cyclic linear loading protocol. A differential variable reluctance transducer was used to record displacement across the repair site. Cyclic force (n-cycles) to 1-mm gap and repair failure was recorded using serial digital photography. RESULTS: There was no significant difference in differential variable reluctance transducer displacement between the cruciate, modified Kessler, and Teno Fix repairs. The cruciate repair had greater resistance to visual 1-mm repair-site gap formation and repair-site failure when compared with the Kessler and Teno Fix repairs. No significant difference was found between the modified Kessler repair and the Teno Fix repair. In all specimens, the epitenon suture failed before the core suture. Repair failure occurred by suture rupture in the 7 cruciate specimens that failed, with evidence of gap formation before failure. Seven of 10 modified Kessler repairs failed by suture rupture. All of the Teno Fix repairs failed by pullout of the metal anchor. CONCLUSIONS: The Teno Fix repair system did not confer a mechanical advantage over the locked cruciate or modified Kessler suture techniques for zone II lacerations in cadaveric flexor tendons during cyclic loading in a linear testing model. This information may help to define safe boundaries for postoperative rehabilitation when using this internal tendon repair device.     

Zone II tendon repairs augmented with autogenous dorsal tendon graft: a biomechanical analysis

We investigated the biomechanical properties of a new technique for tendon repair that reinforces a standard suture with an autogenous tendon graft. A dynamic in situ testing apparatus was used to test 40 flexor digitorum profundus tendons harvested from fresh-frozen cadaver hands. The tendons were cut and repaired using 1 of 4 suture techniques: 2-strand modified Kessler, 4-strand modified Kessler, 6-strand modified Savage, and 2-strand modified Kessler augmented with autogenous dorsal tendon graft. The augmented repair uses 1 slip of the flexor digitorum superficialis tendon secured to the dorsal surface of the repair site with a continuous stitch. Ultimate tensile strength, resistance to gap formation, and work of flexion were measured simultaneously on an in situ tensile testing apparatus. No significant difference in tensile strength was found between the augmented repair and the 6-strand Savage repair. The augmented repair and the 6-strand Savage repair showed significantly greater ultimate tensile strength than the 2- and 4-strand repairs. The augmented repair had significantly greater resistance to 2 mm gap formation than the other 3 repairs. We were unable to show a significant difference in work of flexion between the repairs with the numbers tested (n = 10). Our findings suggest that the augmented repair is strong enough to tolerate the projected forces generated during active motion without dehiscence or gap formation at the repair site.     

Biomechanical analysis of the cruciate four-strand flexor tendon repair

The purpose of this study was to develop and test in vitro a new flexor tendon suture technique that was simple and easy to perform, yet strong enough to withstand the projected forces of an in vivo active motion rehabilitation protocol. Forty human cadaveric flexor digitorum profundus tendons were divided and repaired using 1 of 4 suture techniques (the modified Kessler, the Strickland, the modified 4-strand Savage, and the Cruciate 4-strand repairs). Each repair was tested using a slow-test machine and displacement control at 2 mm/s. Force applied, the resultant gap, and ultimate tensile strength were recorded and statistical comparisons were performed using a two-tailed Student's t-test with level of significance set at p = .05. The Cruciate suture technique was demonstrated to be nearly twice as strong to 2-mm gap formation (44 N) compared with the Kessler, Strickland, and Savage repairs. Ultimate tensile strength was also significantly stronger for the Cruciate technique (56 N) than the Kessler, Strickland, or Savage repairs. The technique was significantly faster to perform than the Savage or Strickland repairs and was comparable in repair time to the 2-stranded Kessler repair. The design of the new suture technique allowed the tendon repair to be completed with the ease and speed of a 2-strand technique, but bestowed on the repair strength that exceeded current 4-strand techniques.     

Adhesion formation after flexor tendon repair: a histologic and biomechanical comparison of 2- and 4-strand repairs in a chicken model

PURPOSE: Both increased handling and increased bulk at the repair site have been hypothesized as affecting adhesion formation and gliding after tendon repair. Tendons repaired with 2- and 4-strand techniques were compared using both biomechanical and histopathologic measurements to determine the influence of increasing strand number on adhesion formation and gliding. METHODS: The flexor digitorum profundus tendon of the right middle toe of 80 broiler chickens was cut and then repaired with either a single (2-strand) or double (4-strand) modified Kessler core suture, followed by a running epitendinous suture. The limb was immobilized after surgery. Birds were killed at either 3 days or 4 weeks after tendon repair and adhesion formation measured using either biomechanical testing or quantitative and qualitative histology. For biomechanical testing, the tendon was pulled free of the sheath and a force versus displacement curve was generated. Comparisons of peak force and work to peak were made. Histologic specimens were examined by a pathologist blinded to the treatment group who scored the length and density of adhesions and made qualitative observations. RESULTS: Both biomechanical and histologic data showed expected differences in adhesion formation for early (3 days) and late (4 weeks) healing but no significant differences between 2- and 4-strand repairs. Biomechanical testing of 4-week specimens showed a nonsignificant tendency toward greater work required to break adhesions in 4-strand repairs. CONCLUSIONS: Adhesion formation and gliding resistance of tendons after 2- or 4-strand modified Kessler core suture were not significantly different, which suggests that simply increasing the number of strands crossing a repair does not necessarily result in more adhesions or resistance in this model.     

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.     

The role of multiple strands and locking sutures on gap formation of flexor tendon repairs during cyclical loading

The purpose of this study was to delineate the contribution of increasing suture strands and locking repair design in the prevention of gap formation using a cadaveric model for linear cyclical loading. Forty flexor digitorum profundus tendons were lacerated and repaired using locked and nonlocked variations of a 4- and 8-strand flexor tendon repair. An incremental cyclical loading protocol from 25 N to 65 N was used. Comparison of the amount of Newton-cycles to reach 1, 2, 3, and 4 mm of gap and the Newton-cycles withstood before failure was performed using 2-way ANOVA. The 8-strand repairs demonstrated significantly increased fatigue strength compared with the 4-strand repairs, but the number of strands crossing the repair site did not significantly affect gap resistance. The locked repairs demonstrated a significant increase in gap resistance to 1 and 2 mm compared with the nonlocked repairs, but the difference was not sustained at higher load cycles. There was no association between gap resistance and fatigue strength. We conclude that an increase in the number of strands significantly increases the fatigue strength of a tendon repair but does not alter its gap resistance to cyclic loading. Locking of the repair does provide additional gap resistance at the relatively low cyclical loads anticipated during the early healing period using an active motion rehabilitation protocol.     

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.     

Flexor tendon repair in zone II with 6-strand techniques and early active mobilization

PURPOSE: There are many biomechanic studies of 6-strand suture techniques for active mobilization, but few reports have described the clinical outcome in zone II flexor tendon lacerations. We discuss the clinical results of zone II flexor tendon repair using 2 of these techniques followed by controlled early active mobilization. METHODS: Six-strand sutures using the number 1 technique by Yoshizu or a triple-looped suture technique were used to repair flexor tendons in 27 fingers from 21 consecutive patients. Fingers were mobilized by combining active extension and passive or active flexion in a protective splint for the first 3 weeks after surgery. The follow-up period averaged 13 months. RESULTS: Based on the original Strickland criteria, the results were excellent in 17 fingers, good in 9, and fair in 1. The average flexion was 62 degrees for distal interphalangeal joints and 91 degrees for proximal interphalangeal joints. None of the repaired tendons ruptured. CONCLUSIONS: The 6-strand flexor tendon suture technique followed by controlled active mobilization protected with a dorsal splint is safe, produces no ruptures, and achieves very good results in zone II flexor tendon laceration repair. TYPE OF STUDY/LEVEL OF EVIDENCE: Therapeutic, Level II.     

Repair of zone II flexor digitorum profundus lacerations using varying suture sizes: a comparative biomechanical study

PURPOSE: To compare the maximum tensile load, change in work of flexion, and gapping at the repair site after zone II flexor digitorum profundus tendon repairs using 2-0, 3-0, and 4-0 braided polyester 4-strand locked cruciate repair technique in fresh-frozen cadaveric hands with standard 6-0 suture epitenon repairs, to determine which suture size is the best for a core repair. METHODS: A randomized study was designed using 41 tendons from 15 fresh-frozen cadaveric hands. We included only the flexor digitorum profundus tendons from the index, middle, and ring fingers to minimize variation between digits. Core suture size was randomized for each finger. A sharp laceration through the flexor digitorum profundus in zone II was made and a 4-strand locked cruciate braided polyester core stitch was performed along with a locked epitenon stitch. Cyclic loading was performed for 1,000 cycles. For each tendon the mean work of flexion (before/after zone II repair) and maximum tensile load were measured using a custom-designed tensiometer, as was gapping before maximum tensile loading. RESULTS: Mean gaps after 1,000 load-unload cycles to 3.9 N of pulp pinch did not approach the clinically significant limit of 3 mm in each group. By using a regression model, we found that the prerepair and postrepair comparisons for mean work of flexion to a 3.9-N pulp pinch showed the greatest change in work of flexion for 2-0 braided polyester. Statistical significance was found between 2-0 braided polyester and 3-0 or 4-0 braided polyester; however, the work of flexion between the 3-0 and 4-0 polyester was not clinically significant. The highest maximum tensile load was obtained with suture size 2-0 braided polyester. The maximal tensile load statistically showed 2-0 braided polyester to be stronger than 4-0 braided polyester but we found no statistically significant difference between 3-0 and 2-0 braided polyester or between 3-0 and 4-0 braided polyester. CONCLUSIONS: In this cadaveric study we found that increasing locking cruciate suture caliber from 4-0 to 2-0 increased maximum tensile strength but also caused increased work of flexion. Gapping was not affected by suture caliber. There was no significant difference in strength or mean change in work of flexion between 3-0 or 4-0 braided polyester sutures.     

Comparative biomechanical performances of 4-strand core suture repairs for zone II flexor tendon lacerations

To compare the biomechanical performances of six 4-strand flexor tendon repairs at zone II, we used an in situ testing model in 54 cadaver profundus tendons. The techniques studied were the modified Becker, modified double Tsuge, Lee, locked cruciate, Robertson, and Strickland. Prerepair and postrepair comparisons for work of flexion to a 3.9-N pulp pinch (equal to 12.6 N tendon force) showed the greatest interference to gliding in the modified Becker repair and the least in the modified double Tsuge repair. Mean gaps after 1,000 load-unload cycles to a 3.9-N pulp pinch did not approach the clinically important limit of 3 mm in all groups. Ultimate tensile strength was highest in the modified Becker (69.4 +/- 8.2 N) but not significantly higher than the modified double Tsuge (60.3 +/-15.3 N) and locked cruciate (64.1 +/- 16.2 N). In all repair groups the mean pulp pinch forces upon failure were well above values recommended for active mobilization protocols that use external load guides. The locked cruciate, modified double Tsuge, and modified Becker repairs were strong enough for an early active motion protocol after surgery. Locked cruciate and modified double Tsuge were easier to perform and provided less interference to tendon gliding than the modified Becker repair.     

A biomechanical comparison of multistrand flexor tendon repairs using an in situ testing model

An in situ testing model was used to evaluate the performance of zone II flexor tendon repairs and to compare the biomechanical properties of 4-strand repairs with 2- and 6-strand repairs. Fifty digits from human cadaveric hands were mounted in a custom apparatus for in situ tensile testing. Intratendinous metallic markers were placed so that gap formation could be determined by fluoroscopy during tensile testing. Three 4-strand repairs (the 4-strand Kessler, the cruciate, and a locked modification of the cruciate repair) were compared with the 2-strand Kessler and the 6-strand Savage repairs. Ultimate tensile strength, load at 2-, 3-, and 4-mm gap formation, and work of flexion were determined. Work of flexion, while increased for the multistrand repairs, did not show a statistically significant correlation with the number of strands crossing the repair site. The tensile strength of the 6-strand repair was significantly greater than each of the 2- or 4-strand repairs. The tensile strength of all 4-strand repairs was significantly greater than the 2-strand repair. The 6-strand repair and the 2 cruciate repairs demonstrated a statistically increased resistance to gap formation compared with the 2-strand Kessler repair, but notably there was no statistically significant difference in gap resistance between the 2and 4-strand Kessler repairs. This in situ tensiletesting protocol demonstrated that 4- and 6-strand repairs have adequate initial strength to withstand the projected forces of early active motion protocols. Three of the 4 multistrand repairs demonstrated improved gap resistance compared with the 2-strand repair. The presence of the second suture in the Kessler configuration significantly increases its strength but not its gap resistance.     

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.     

Flexor tendon suture methods: a quantitative analysis of suture material within the repair site

This study compared the cross-sectional area and volume occupied by suture material at the repair site in three common methods of flexor tendon repair. A total of 51 human cadaveric tendons were studied. Zone II flexor digitorum profundus tendon lacerations were created and then repaired using the techniques described by Kessler, Tajima, and Savage. Quantitative cross-sectional area and volumetric measurements of suture material within each repair site were determined using a digital image analysis system. The Tajima repair occupied 27% of the tendon area at the repair site, while the Savage and Kessler repairs occupied 18% and 2%, respectively.     

Evaluation of suture caliber in flexor tendon repair

This biomechanical study investigated the effect of suture caliber variation on tensile strength in 3 types of 2-strand flexor tendon repairs. Each type of repair was constructed with 5-0, 4-0, 3-0, and 2-0 braided polyester suture. Linear distraction was performed on 120 repaired human cadaveric flexor digitorum profundus tendons until tensile failure occurred. Ten trials of each repair construct were tested. Analysis of variance revealed significant main effects of caliber and technique. Mean repair strength increased as suture caliber increased. A 4-0 suture was 66% stronger than a 5-0 suture, a 3-0 suture was 52% stronger than a 4-0 suture, and a 2-0 suture was 51% stronger than a 3-0 suture. The technique effected repair strength only with the larger 2-0 and 3-0 suture calibers, which tested the technique's capacity to hold the tendon.     

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.