Strength Of Flexor Tendon Repair Research Articles

Effect of loading speed on gap resistance and tensile strength of flexor tendon repair under cyclic loading test

Postoperative digit motion is important for the functional recovery of injured tendons. To date, it is unknown whether the loading speed impacts the biomechanical properties of a repaired tendon. This study investigated the effect of loading speed on the gap resistance and tensile strength of tendon repairs. One hundred porcine flexor tendons were repaired with two core sutures, 4-strand modified Kessler and double Q, and cyclically loaded at the speeds of 10, 40, 80, 160, and 320 mm/min. The number of tendons that formed an initial or 2 mm gap at the repair site during cyclic loading, stiffness at the 1st and 20th loading cycles, gap size between tendon ends when cyclic loading ended, and the ultimate strength were recorded. Under the lowest loading speed, the tendons repaired with the 4-strand modified Kessler suture developed significantly larger gaps and smaller stiffness than those with a greater loading speed. The loading speed did not affect the maximum strength of both tendon repairs. The findings suggest that very slow motion promotes gap formation of tendon repair with inferior gap resistance. The rate corresponds to regular hand action or the tendon core suture possessing a strong gap resistance increases the safety margin during early active finger movement. Our findings help to guide the exercise regimens after tendon surgery.

Biomechanical Analysis of Zone 2 Flexor Tendon Repair With a Coupler Device Versus Locking Cruciate Core Suture

To compare flexor tendon repair strength and speed between a tendon coupler and a standard-core suture in a cadaver model. In 5 matched-pair fresh cadaver hands, we cut the flexor digitorum profundus tendon of each finger in zone 2 and assigned 20 tendons to both the coupler and the suture groups. Coupler repair was with low-profile stainless steel staple plates in each tendon stump, bridged by polyethylene thread. Suture repair was performed using an 8-strand locking-cruciate technique with 4-0 looped, multifilament, polyamide suture. One surgeon with the Subspecialty Certificate in Surgery of the Hand performed all repairs. Via a load generator, each flexor digitorum profundus was loaded at 5 to 10 N and cycled through flexion just short of tip-to-palm and full extension at 0.2 Hz for 2,000 cycles to simulate 6 weeks of rehabilitation. We recorded repair gapping at predetermined cycle intervals. Our primary outcome was repair gapping at 2,000 cycles. Tendons that had not catastrophically failed by 2,000 cycles were loaded to failure on a servohydraulic frame at 1 mm/s. Tendon repair gapping was similar between coupled and sutured tendons at 2,000 cycles. Tendons repaired with the coupler had higher residual load to failure than sutured tendons. Mean coupler repair time was 4 times faster than suture repair. Zone 2 flexor repair with a coupler withstood simulated early active motion in fresh cadavers. Residual load to failure and repair speed were better with the coupler. This tendon coupler may eventually be an option for strong, reproducible, rapid flexor tendon repair.

Effect of Cyclic Loading on the Strength of Flexor Tendon Repair in Vitro Study

Background: The initial strength of the repair depends on the material properties and knot security of the sutures as well as on the holding capacity of the suture grip of the tendon. Objective: Detecting the effect of cyclic loading on the strength of flexor tendon repair using 6 strand Tang suture experimentally. Materials and Methods: In the present ex vivo study of 50 sheep flexor tendons, six strand Tang suture technique was used: Twenty five repairs were subjected to cyclic tensile testing, and twenty five repairs were subjected to static tensile testing using 4/0 polypropylene simple suture material + epitendinous continuous running sutures using 5/0 polypropylene suture material. Results: The results of the study showed that 44 % survival at 41.7 N cyclic testing, without evidence of significant gap formation or rupture and the breaking force on continuous loading mean 55.95 N. The Tang suture method provided much more sufficient gap resistance and tensile strength able to withstand early active mobilization after primary flexor tendon repair. Conclusion: The Tang suture method provided sufficient gap resistance and tensile strength able to withstand early active mobilization after primary flexor tendon repair. There were some disadvantages regarding to time consuming during surgery and difficult to use in pediatrics and small tendons.

Tensile Strength of Flexor Tendon Repair Using Barbed Suture Material in a Dynamic Ex Vivo Model

The purpose of this study was to compare two sutures; a knotted polydioxane with a knotless barbed in a 4-strand Kirchmayr-Kessler suture technique. Human flexor digitorum tendons were separated into four groups. Group 1 - polydioxane; Group 2 - barbed suture; Group 3 and 4 - same as group 1 and 2 with an additional peripheral running suture. In each group the repaired tendons were subjected to linear and cyclical loads. No difference in maximum tensile strength after linear and cyclical force could be detected between the knotted polydioxane suture and the knotless barbed suture. On linear force tests an additional circumferential repair increased the maximum tensile strength of both sutures. Cyclical force loading did not lead to a reduction of maximum strength. Following linear and cyclical loading the 4-strand barbed suture achieved maximum tensile strengths comparable to the 4-strand repair using the polydioxane suture. Barbed suture repair may offer the advantage of knotless suture techniques.

Flexor Tendon Repair With Looped Suture: 1 Versus 2 Knots

To assess the strength of flexor tendon repair with looped suture. We hypothesized that, after passing the intact looped suture in the desired repair configuration, splitting the loop and tying 2 independent knots would increase the strength of flexor tendon repair. Thirty-two flexor tendons were harvested and were sharply transected in zone II. The tendons were repaired with a 4-strand core suture repair using 3-0 looped nonabsorbable nylon suture. The harvested tendons were randomly assigned and repaired with either a 1- or a 2-knot construct. The repaired flexor tendons were fixed in a servohydraulic material testing system and were loaded to failure either with uniaxial tension or cyclically. The average force at failure was 43 N for the 1-knot repair and 28 N for the 2-knot repair. The mode of failure of 15 of the flexor tendon repairs that were cyclically loaded to failure was suture pull-out. The average number of cycles and force in cyclic testing that caused failure of flexor tendon repairs was 134 cycles and 31 N for tendons repaired with looped 3-0 suture tied with 1 knot and 94 cycles and 33 N for tendons repaired with looped 3-0 suture tied with 2 knots. Our hypothesis was disproved by the results of this study. This study suggests that, when using looped suture, tying 2 independent knots instead of tying a single knot does not increase the strength of the flexor tendon repair.

Comparison of Flexor Tendon Repair Between 6-Strand Lim-Tsai With 4-Strand Cruciate and Becker Technique

To compare the strength of 6-strand Lim-Tsai repair with 4-strand cruciate and Becker repair, which were done using braided polyblend. We hypothesized that the biomechanical strength of 4-strand repair could be as strong as 6-strand repair because of different flexor tendon repair configurations and uneven load bearing. We harvested 60 porcine flexor tendons. A transverse cut at the middle of the tendons was made to perform tendon repair. Six-strand Lim-Tsai repair (consisting of 2 Lim-Tsai locking loops), 4-strand cruciate repair (with 3 cross-stitch loops), and 4-strand Becker repair (with 2 double cross-stitch locking loops) were used for the repairs. The repaired tendons were pulled until failure using a mechanical tester. We recorded ultimate tensile strength, load to 2-mm gap force, stiffness, and mechanism of failure. The Becker repairs had significantly greater tensile strength than the cruciate and Lim-Tsai repairs. The load to 2-mm gap force and stiffness were significantly greater for cruciate repairs and Becker repairs than Lim-Tsai repairs. The biomechanical strength of 4-strand and Becker repairs could be as strong as 6-strand Lim-Tsai repairs. This study implies that the number of strands crossing the repair site of tendons may not be proportional to the biomechanical strength of flexor tendon repair. Hand surgeons are urged to be aware of the biomechanic characteristics of different flexor tendon repair techniques used in the clinical setting.

Surgical adhesive BioGlue™ does not benefit tendon repair strength: an ex vivo study.

Surgical adhesives are useful supplements in surgery, but their benefit in tendon repair is uncertain. The purpose of this study was to evaluate the effect of BioGlue™ on strength of flexor tendon repair. A total of 60 porcine flexor tendons were divided into three groups. In group one, a conventional core and peripheral suture repair was used. In group two, a core suture and BioGlue™ were used. In group three, a conventional core and peripheral suture repair and BioGlue™ were used. We performed static and cyclic axial load testing and measured diameter of the repair site. We found that BioGlue™ did not improve the tensile strength when added to a core and peripheral suture and that there was an increase in bulk at the repair site. We conclude that BioGlue™ application cannot replace a peripheral suture as tensile strength significantly decreases without a peripheral suture, and it does not benefit a tendon already repaired with a core and peripheral suture. n/a.

A2 pulley integrity and the strength of flexor tendon repair: a biomechanical study in a chicken model.

This study assesses the influence of A2 pulley integrity on the strength of the repair. Part 1- The flexor digitorum profundus (FDP) tendons of 72 Cobb chicken feet were severed and repaired in the region of the A2 pulley using a modified Kessler core suture and an epitendinous suture. The A2 pulley was either left intact, divided for 50% of its length, or divided in its entirety. The distal interphalangeal joint was fixed at a position of 20°, 40° or 60° of joint flexion. The load to failure, integrity of the A2 pulley and the site of tendon failure were analysed. Part 2- A further 32 chicken feet were used to exclude the effects of freezing and thawing on results and to analyse differences when using a core suture only. No difference in failure load between any of the test groups or subgroups was identified. The integrity of the A2 pulley was preserved in all specimens. The most common cause of failure was distal suture pull-out. This study does not demonstrate that release of the A2 pulley provides an advantage in increasing tendon repair strength. Division of 50% of the A2 pulley does not predispose to pulley rupture. Flexor tendon repair strength did not alter with distal interphalangeal joint flexion between 20° and 60°. The findings of this study do not support division of the A2 pulley to prevent flexor tendon repair failure if repair methods of appropriate strength are utilised.

The Impact of Fiberwire, Fiberloop, and Locking Suture Configuration on Flexor Tendon Repairs

Suture technique, suture material, and the number of strands all play critical roles in achieving optimal strength of flexor tendon repairs. We evaluated the contribution to the tensile strength of flexor tendon repair using the strongest suture material, Fiberwire, and the best surgical technique (locking configuration) using 2- and 4-strand core repair to see what factor played the most important role in tendon repair. Human cadaver flexor tendons were harvested and repaired in a randomized fashion using locking configuration as derived from Pennington's report. Ten tendons per group were repaired using either 4-0 Fiberloop, 4-0 Fiberwire, or 2-0 Fiberwire. During load-to-failure testing, visible gap force and maximum tensile strength were statistically analyzed. All flexor tendon repairs failed by suture pullout. The 4-strand 4-0 Fiberwire double-Pennington repair was found to be significantly stronger than the 4-strand 4-0 Fiberloop single-Pennington repair. When the 2-strand repair (2-0 Fiberwire) was compared to the 4-strand single-Pennington repair (4-0 Fiberloop), there was no significant difference found. The suture strand configuration rather than the strict number of strands or the strength of the suture material yielded the maximum tensile strength with reduced gapping at the repair site.

The Effects of Exogenous Basic Fibroblast Growth Factor on Intrasynovial Flexor Tendon Healing in a Canine Model

Studies have demonstrated that flexor tendon repair strength fails to increase in the first three weeks following suturing of the tendon, a finding that correlates closely with the timing of many clinical failures. The application of growth factors holds promise for improving the tendon-repair response and obviating failure in the initial three weeks. The effects of basic fibroblast growth factor on flexor tendon healing were evaluated with use of a canine model. Operative repair followed by the sustained delivery of basic fibroblast growth factor, at two different doses, was compared with operative repair alone. Histological, biochemical, and biomechanical methods were used to evaluate the tendons twenty-one days after repair. Vascularity, cellularity, and adhesion formation were increased in the tendons that received basic fibroblast growth factor as compared with the tendons that received operative repair alone. DNA concentration was increased in the tendons that received 1000 ng of basic fibroblast growth factor (mean and standard deviation, 5.7 ± 0.7 μg/mg) as compared with the tendons that received 500 ng of basic fibroblast growth factor (3.8 ± 0.7 μg/mg) and the matched control tendons that received operative repair alone (4.5 ± 0.9 μg/mg). Tendons that were treated with basic fibroblast growth factor had a lower ratio of type-I collagen to type-III collagen, indicating increased scar formation compared with that seen in tendons that received operative repair alone (3.0 ± 1.6 in the group that received 500-ng basic fibroblast growth factor compared with 4.3 ± 1.0 in the paired control group that received operative repair alone, and 3.4 ± 0.6 in the group that received 1000-ng basic fibroblast growth factor compared with 4.5 ± 1.9 in the paired control group that received operative repair alone). Consistent with the increases in adhesion formation that were seen in tendons treated with basic fibroblast growth factor, the range of motion was reduced in the group that received the higher dose of basic fibroblast growth factor than it was in the paired control group that received operative repair alone (16.6° ± 9.4° in the group that received 500 ng basic fibroblast growth factor, 13.4° ± 6.1° in the paired control group that received operative repair alone, and 29.2° ± 5.8° in the normal group [i.e., the group of corresponding, uninjured tendons from the contralateral forelimb]; and 15.0° ± 3.8° in the group that received 1000 ng basic fibroblast growth factor, 19.3° ± 5.5° in the paired control group that received operative repair alone, and 29.0° ± 8.8° in the normal group). There were no significant differences in tendon excursion or tensile mechanical properties between the groups that were treated with basic fibroblast growth factor and the groups that received operative repair alone. Although basic fibroblast growth factor accelerated the cell-proliferation phase of tendon healing, it also promoted neovascularization and inflammation in the earliest stages following the suturing of the tendon. Despite a substantial biologic response, the administration of basic fibroblast growth factor failed to produce improvements in either the mechanical or functional properties of the repair. Rather, increased cellular activity resulted in peritendinous scar formation and diminished range of motion.

Evaluation of Simple and Looped Suture and New Material for Flexor Tendon Repair

Flexor tendon repair strength is proportional to the number of suture strands crossing the repair site but it is not clear if each strand needs to result from a separate pass through the tendon. We examined whether one throw of looped suture across a repair site equals two separate throws of suture and whether fewer passes with stronger material such as Fiberwire is equivalent to more passes with a comparatively weaker material such as Supramid. When evaluating the repairs for force required to generate a 2 mm gap and for gap formed at the instant prior to failure, looped suture cannot substitute for two separate passes of suture (Supramid Kessler looped vs. separate passes, 14 N vs. 35 N and 8.8 mm vs. 4.1 mm, respectively; Fiberwire Kessler looped vs. separate passes, 25 N vs. 43 N and 7.6 mm vs. 4.6 mm, respectively; all p<0.05). Two-stranded Fiberwire Kessler repair equalled four-stranded cruciate repair with Supramid for all tested parameters (force at 2 mm gap: 17 N vs. 22 N, respectively; force at failure: 42 N vs. 46 N; and gap formed prior to instant of failure: 6.9 mm vs. 5.6 mm; all p>0.05).

A Biomechanical Analysis of Suture Materials and Their Influence on a Four-Strand Flexor Tendon Repair

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. 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. 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. 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.

Aggressive active mobilization following zone II flexor tendon repair using a two-strand heavy-gauge locking loop technique

AbstractIn vitro and in vivo experimental studies have shown that a new two-strand technique increases the tensile strength of flexor tendon repair and eliminates gap formation at the healing repair site. The purpose of the current study was to clinically evaluate the new technique, followed by an aggressive active mobilization program. Seven digits with zone II flexor tendon lacerations were treated using the technique, employing a heavy (2-0) braided polyester suture. The patients were encouraged to perform active mobilization of the injured digits by themselves with almost a full range of flexion and extension after they were instructed by the surgeon for few days from the first postoperative day. All patients were followed up for at least 6 months, except for one, with whom contact was lost in 14 weeks postoperatively. Six of the seven digits were evaluated as excellent in 6 months by the original Strickland criteria, thus showing that the combination of the new repair technique and aggressive active mobilization is effective for zone II flexor tendon repair.

Factors affecting the strength of flexor tendon repair

The effects of different thicknesses and configurations of core sutures were studied in human cadaveric flexor tendon repairs. Both straight and cyclic load tests were employed. To exploit the full strength of 4/0 suture material, the Kessler repair using four locked single knots would seem to be appropriate.

The effect of immediate constrained digital motion on the strength of flexor tendon repairs in chickens

Profundus tendon lacerations were repaired in the central toes of 216 chickens, and the digits were either immobilized in a cast or allowed immediate constrained motion in a tethering splint. The effect of digital motion on the early phases of tendon healing was investigated by comparing the rupture strengths of the two groups during the first 40 days after repair. The repairs in immobilized digits showed marked decreases in strength during the first 20 days, while the tendons in mobilized digits showed immediate and progressive gains in strength through the time intervals studied. By 5 days, the difference in strength between the two groups was significant (p less than 0.05), and the magnitude of this difference increased with time. The model developed in this study demonstrates that an initial loss of flexor tendon repair strength is not inevitable. Immediate constrained digital mobilization allows progressive tendon healing without an intervening phase of tendon softening.