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.     

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.     

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).     

Biomechanical testing of epitenon suture strength in Achilles tendon repairs

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

The biomechanical analysis of a tendon fixation device for flexor tendon repair

PURPOSE: Stainless steel suture is high in tensile strength but is not widely used in flexor tendon repair because of difficulty with handling and knot tying. The purpose of this study was to examine the biomechanical characteristics of the single-strand multifilament stainless steel Teno Fix device (Ortheon Medical, Winter Park, FL) designed for zone II flexor digitorum profundus (FDP) tendon repair. METHODS: Sixty cadaveric flexor tendons were transected and randomized to receive a Teno Fix or 4-stranded (3-0 or 4-0 braided polyester) suture repair; all repairs were tested with and without a 5-0 monofilament polypropylene circumferential epitendinous suture. By using a material testing system all tendons were tested to failure in tension using a linear model with a loading rate of 1 mm/s. Stiffness, force, and energy at both 2-mm gap and peak force were calculated from the resulting force-displacement curves. RESULTS: The 2-mm gapping force was significantly greater for the Teno Fix and the 3-0 repairs than for the 4-0 repairs. The energy absorbed up to 2-mm gap was significantly greater for the Teno Fix, however, than for all suture repairs both with and without a circumferential suture. There was no statistically significant difference in peak force or energy absorbed at peak force between the Teno Fix and suture repairs; the average gap at peak force for all repairs was 5.2 mm. The addition of a circumferential suture increased the 2-mm gapping and peak forces of the Teno Fix repair to 54.5 N and 66.7 N, respectively. CONCLUSIONS: Increased strength and energy absorbed at 2-mm gap and ease of installation makes the Teno Fix a promising repair method.     

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.     

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.     

Tensioning of Prolene reduces creep under cyclical load: relevance to a simple pre-operative manoeuvre

A longitudinal stretch or 'pre-tensioning' is a method employed by some surgeons to improve the handling characteristics of a suture. We used a tensile tester to assess the effect of pre-tensioning on the mechanical properties of two suture materials (3-0 Prolene and 3-0 Ethibond) commonly used for flexor tendon repair. A cyclical loading programme was used to simulate an early rehabilitation regime. All sutures were subsequently tested to failure (for ultimate tensile strength). The pre-tensioned Prolene sutures showed significantly less creep after cyclical loading in comparison to controls. Conversely pre-tensioning had no measurable effect on the deformation of Ethibond by creep. There was no effect on ultimate tensile strength for either material. The propensity of Prolene to creep (and thereby form a 'gap' in tendon repairs) can be reduced by pre-tensioning.     

Biomechanical comparison of double grasping repair versus cross-locked cruciate flexor tendon repair

Purpose

This study was conducted to compare the in vitro biomechanical properties of tensile strength and gap resistance of a double grasping loop (DGL) flexor tendon repair with the established four-strand cross-locked cruciate (CLC) flexor tendon repair, both with an interlocking horizontal mattress (IHM) epitendinous suture. The hypothesis is that the DGL-IHM method which utilizes two looped core sutures, grasping and locking loops, and a single intralesional knot will have greater strength and increased gap resistance than the CLC-IHM method.

Methods

Forty porcine tendons were evenly assigned to either the DGL-IHM or CLC-IHM group. The tendon repair strength, 2-mm gap force and load to failure, was measured under a constant rate of distraction. The stiffness of tendon repair was calculated and the method of repair failure was analyzed.

Results

The CLC-IHM group exhibited a statistically significant greater resistance to gapping, a statistically significant higher load to 2-mm gapping (62.0 N), and load to failure (99.7 N) than the DGL-IHM group (37.1 N and 75.1 N, respectively). Ninety percent of CLC-IHM failures were a result of knot failure whereas 30 % of the DGL-IHM group exhibited knot failure.

Conclusions

This study demonstrates that the CLC-IHM flexor tendon repair method better resists gapping and has a greater tensile strength compared to the experimental DGL-IHM method. The authors believe that while the DGL-IHM provides double the number of sutures at the repair site per needle pass, this configuration does not adequately secure the loop suture to the tendon, resulting in a high percentage of suture pullout and inability to tolerate loads as high as those of the CLC-IHM group.     

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.     

Biomechanical analysis of knotless flexor tendon repair using large-diameter unidirection barbed suture

Purpose

In traditional flexor tendon repairs, suture knots can be sites of weakness, impair tendon healing, stimulate an inflammatory response, and increase the bulk of the tendon repair. Because of this, there has been an increased interest in knotless flexor tendon repair using barbed suture. Since knots are not required, it may be possible to increase the strength of the tendon repair by using a large-diameter barbed suture. The purpose of this study was to biomechanically compare a traditional four-strand tendon repair using 3-0 braided polyester with a similar knotless four-strand tendon repair using 0 unidirectional barbed suture.

Methods

Twenty-two matched cadaveric flexor digitorum profundus tendons were lacerated and assigned to repair by a four-strand modified Kirchmayr–Kessler technique using 3-0 braided polyester (n = 11) or knotless four-strand modified Kirchmayr–Kessler repair using 0 unidirectional barbed suture (n = 11). Repaired tendons were linearly distracted to failure at 20 mm/min after 1 N preload. Maximum load and load at 2-mm gap formation were recorded. Maximum load and load at 2-mm gap formation were compared with the Student’s t test, and p values ≤ 0.05 were considered significant.

Results

The mean maximum load of the barbed, knotless suture repair was higher than that of the traditional repair (52 vs. 42 N). There was no difference between the two groups in the mean load required to produce a 2-mm gap.

Conclusions

The four-strand knotless tendon repairs using a large-diameter unidirectional barbed suture were stronger than the traditional four-strand repairs using 3-0 braided polyester, and had similar 2-mm gap resistance.     

Bone suture anchors versus the pullout button for repair of distal profundus tendon injuries: a comparison of strength in human cadaveric hands.

Avulsion or distal tendon laceration of flexor digitorum profundus (FDP) is classically repaired to the base of the distal phalanx via a pullout suture over a button. Bone suture anchors, used extensively in other surgical areas, have recently been proposed for reattachment of the FDP to the distal phalanx. The FDP tendons of the index, long, and ring fingers in 9 fresh frozen cadeveric hands were randomized to 1 of 3 repair techniques after simulated distal avulsion injuries. These were the pullout button using 3-0 monofilament nylon in a 2-strand Bunnell suture pattern, the 1.8 mm Mini QuickAnchor (Mitek Products, Norwood, MA) using 3-0 braided polyester in a 2-strand Bunnell suture pattern, and the Mitek micro anchor using 3-0 braided polyester with a modified 4-strand Becker suture pattern. Nine specimens were loaded to failure, noting maximum load and mode of failure. The 1.3 mm Micro QuickAnchor (Mitek) technique (69.6 +/- 10.8 N) was significantly stronger than the pullout button (43.3 +/- 4.8 N) or the Mini anchor technique (44.6 +/- 12.7 N). The Micro bone suture anchor provides a stronger tendon to bone repair than the pullout button or the Mini anchor. Given the disadvantages of the pullout button, the Micro bone suture anchor with the modified Becker technique is worth consideration as an alternative method to repair distal FDP avulsions.     

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

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

In vitro cyclic tensile testing of combined peripheral and core flexor tenorrhaphy suture techniques

Early tenorrhaphy mobilization increases repair site strength and decreases adhesions. Preliminary unpublished data suggest that early active mobilization improves clinical outcome compared with traditional passive motion protocols. We loaded cadaver flexor profundus tendon repairs to 8.0 kg (78.4 N) for up to 5,000 cycles to simulate the loads and cycle number of our active flexor tendon rehabilitation protocol. 3-0 Ethibond (Ethicon, Somerville, NJ) and 6-0 Prolene (Surgi-pro; US Surgical, Norwalk, CT) were used for core and peripheral sutures, respectively. Four different groups were tested: 2-strand Tajima core suture with either a running interlocking (2R) or a Silfverski?ld cross-stitch (2S) peripheral suture and 4-strand Tajima plus horizontal mattress core suture with either a running interlocking (4R) or a Silfverski?ld peripheral suture (4S). Repairs failed in the suture midsubstance or at the knot. There was considerable variability within groups and no significant difference in the number of cycles to failure between the 2R, 4R, and 2S repairs, which failed after 2 +/- 2, 304 +/- 249, and 560 +/- 987 cycles, respectively. All 4S repairs were intact after 5,000 cycles. Our data suggest that flexor tenorrhaphy with the 4S repair can withstand the cyclic loads we estimate would be present during an active rehabilitation protocol.     

Part II: Biomechanical assessment for a footprint-restoring transosseous-equivalent rotator cuff repair technique compared with a double-row repair technique

We hypothesized that a transosseous-equivalent repair would demonstrate improved tensile strength and gap formation between the tendon and tuberosity when compared with a double-row technique. In 6 fresh-frozen human shoulders, a transosseous-equivalent rotator cuff repair was performed: a suture limb from each of two medial anchors was bridged over the tendon and fixed laterally with an interference screw. In 6 contralateral matched-pair specimens, a double-row repair was performed. For all repairs, a materials testing machine was used to load each repair cyclically from 10 N to 180 N for 30 cycles; each repair underwent tensile testing to measure failure loads at a deformation rate of 1 mm/sec. Gap formation between the tendon edge and insertion was measured with a video digitizing system. The mean ultimate load to failure was significantly greater for the transosseous-equivalent technique (443.0 +/- 87.8 N) compared with the double-row technique (299.2 +/- 52.5 N) (P = .043). Gap formation during cyclic loading was not significantly different between the transosseous-equivalent and double-row techniques, with mean values of 3.74 +/- 1.51 mm and 3.79 +/- 0.68 mm, respectively (P = .95). Stiffness for all cycles was not statistically different between the two constructs (P > .40). The transosseous-equivalent rotator cuff repair technique improves ultimate failure loads when compared with a double-row technique. Gap formation is similar for both techniques. A transosseous-equivalent repair helps restore footprint dimensions and provides a stronger repair than the double-row technique, which may help optimize healing biology.     

Effect of core suture technique and type on the gliding resistance during cyclic motion following flexor tendon repair: A cadaveric study

We investigated the effects of two suture techniques using three suture types in a human model in vitro. We obtained 60 flexor digitorum profundus (FDP) tendons from cadavers and measured the gliding resistance during 1,000 cycles of simulated flexion–extension motion and load to failure of six groups: the modified Kessler (MK) repair using 3‐0 coated, braided polyester (Ethibond, Ethicon, Somerville, NJ), 3‐0 coated, braided polyester/monofilament polyethylene composite (FiberWire®; Arthrex, Naples, FL), or 4‐0 FiberWire; and the Massachusetts General Hospital (MGH) repair using 3‐0 Ethibond, 3‐0 FiberWire, or 4‐0 FiberWire. The 3‐0 Ethibond MGH suture had significantly higher ultimate load to failure than the 3‐0 or 4‐0 FiberWire MK suture. The 3‐0 and 4‐0 FiberWire MGH sutures had significantly higher load to failure than the three MK groups. The gliding resistances of the three MGH groups were significantly higher than that of the three corresponding MK groups. The MGH repair had more gliding resistance than an MK repair, even when comparing large diameter suture in the MK repair with smaller diameter suture in the MGH repair. In this study, suture technique was more important in predicting repair load to failure and gliding resistance than the nature or caliber of the suture material that was used. © 2010 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 28:1475–1481, 2010     

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.     

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.     

The resistance of a four- and eight-strand suture technique to gap formation during tensile testing: an experimental study of repaired canine flexor tendons after 10 days of in vivo healing

There is a high incidence of gap formation at the repair site following tendon repair. Our goal was to determine the resistance of a 4- and an 8-strand suture technique to gap formation during tensile testing. We hypothesized that the 8-strand repair would sustain higher force levels at the onset of 1- and 3-mm gaps than the 4- strand repair. Twenty-two canine flexor tendons were transected, repaired, and tested to failure after 10 days of in vivo healing. Tests were recorded using a 60-Hz video system that allowed frame-by-frame playback for assessment of gap formation. The 8-strand repairs sustained 80% higher force at a gap of 1 mm than the 4-strand repairs (average force, 70 vs 39 N), but the force sustained at a gap of 3 mm did not differ between groups (35 N for both groups). For both repair types, a 1-mm gap typically occurred near the point of ultimate (maximum) force while a 3-mm gap occurred after the ultimate force. We conclude that the 8-strand repair is significantly more resistant to initial gapping during ex vivo tensile testing than the 4-strand repair but that the two repairs are equally susceptible to rupture if a gap of 3 mm or greater forms.     

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.