Comparative biomechanic study of flexor tendon repair using FiberWire

The effect of the number of strands and knot throws of core suture techniques on the mechanical properties of the repaired flexor tendon

Flexor tendon injury is a common hand trauma that requires surgical repair. The objective was to compare the repaired strength and gliding resistance with a varied number of repair strands and of square knots using a two-strand-overhand locking (TSOL) knot. First, isolated suture loops with different number of suture strands and number of closing knots were compared in mechanical strength and failure mode. Then, 90 flexor digitorum profundus (FDP) tendons from turkey digits were used for the tendon repair experiment. Both phases followed a similar 3 × 3 matrix comparing the knot type including TSOL+1SK (square knot), TSOL+2SK, and TSOL+3 SK and repair techniques including two-, four-, and six-strand repairs techniques respectively. The repaired tendons were tested for tendon resistance against pulley (friction), maximum force, force at 2 mm displacement, stiffness, and failure mode. Increasing the number of strands and closing square knots increases the tensile strength and stiffness of flexor tendon repairs and isolated suture loops without a significant effect on tendon friction. An increase in the number of square knots have shown increased strength only in Pennington repair, which correlated with the increased number of knot unraveling, a weak knot failure model. Our data demonstrated that increasing the number of strands is effective for improving the overall strength of tendon repair. When a two-strand repair is chosen, increasing knot number can improve repair strength. However, the number of knots appears not affecting repair strength in six-strand repair technique.

Biomechanical Evaluation of a Tubular Braided Construct for Primary Deep Flexor Tendon Surgery

PURPOSE

Immediate postoperative mobilization has been shown to avoid adhesion formation and improve range of motion after flexor tendon repair. A tubular braided construct was designed to allow for these rehabilitation protocols.

METHODS

In this ex vivo study, 92 ovine flexor tendons were divided randomly into 2 equal groups. After creating a transection, the tendons of the first group were repaired using a tubular braided construct. This construct, consisting of a tubular braid of polypropylene and polyethylene terephthalate fibers, exerts a grasping effect on the tendon ends. The control group received a multistrand modified Kessler repair with a looped polydioxanone suture (PDS) 4-0 suture and a Silfverskiöld epitendinous repair using an Ethilon 6-0 suture. After the repair, a static and an incremental cyclic tensile test was performed until failure.

RESULTS

During the static test, the tubular braid resulted in a significantly higher load at 3 mm gap formation (86.3 N ± 6.0 vs 50.1 N ± 11.6), a higher ultimate load at failure (98.3 N ± 12.7 vs 63 N ± 11.1), higher stress at ultimate load (11.8 MPa ± 1.2 vs 8.1 MPa ± 3.1), and higher stiffness (7.1 N/mm ± 2.9 vs 8.7 N/mm ± 2.2). For the cyclic tests, survival analyses for 1-, 2- and 3-mm gap formation and failure demonstrated significant differences in favor of the tubular braided construct.

CONCLUSION

The tubular braided construct withstands the required loads for immediate rehabilitation not only in static tests, but also during cyclic tests. This is in contrast with the control group, where sufficient strength is reached during static tests, but failures occur below the required loads during cyclic testing.

CLINICAL RELEVANCE

The tubular braided construct provides a larger safety margin for immediate intensive rehabilitation protocols.

Knotless Tendon Repair with a Resorbable Barbed Suture: An In-vivo Comparison in the Turkey Foot

Background: Un-knotted barbed suture constructs are postulated to decrease repair bulk and improve tension loading along the entire repair site resulting in beneficial biomechanical repair properties. Applying this repair technique to tendons has shown good results in ex-vivo experiments previously but thus far no in-vivo study could confirm these. Therefore, this current study was conducted to assess the value of un-knotted barbed suture repairs in the primary repair of flexor tendons in an in-vivo setting. Methods: Two groups of 10 turkeys (Meleagris gallapovos) were used. All turkeys underwent surgical zone II flexor tendon laceration repairs. In group one, tendons were repaired using a traditional four-strand cross-locked cruciate (Adelaide) repair, while in group two, a four-strand knotless barbed suture 3D repair was used. Postoperatively repaired digits were casted in functional position, and animals were left free to mobilise and full weight bear, resembling a high-tension post-op rehabilitation protocol. Surgeries and rehabilitations went uneventful and no major complications were noted. The turkeys were monitored for 6 weeks before the repairs were re-examined and assessed against several outcomes, such as failure rate, repair bulk, range of motion, adhesion formation and biomechanical stability. Results: In this high-tension in-vivo tendon repair experiment, traditionally repaired tendons performed significantly better when comparing absolute failure rates and repair stability after 6 weeks. Nevertheless, the knotless barbed suture repairs that remained intact demonstrated benefits in all other outcome measures, including repair bulk, range of motion, adhesion formation and operating time. Conclusions: Previously demonstrated ex-vivo benefits of flexor tendon repairs with resorbable barbed sutures may not be applicable in an in-vivo setting due to significant difference in repair stability and failure rates. Level of Evidence: Level IV (Therapeutic).

A 3-Dimensional Suture Technique for Flexor Tendon Repair: A Biomechanical Study

PURPOSE

Flexor tendon injury continues to pose a number of challenges for hand surgeons. Improving mechanical properties of repairs should allow for earlier and unprotected rehabilitation. A 3-dimensional (3D) 4-strand suture technique has been proposed to combine high tensile strength and low gliding resistance without causing suture pullout due to tendon delamination. Our hypothesis is that the 3D technique can result in better mechanical properties than the Adelaide technique.

METHODS

Four groups of 10 porcine flexor tendons were sutured using the 3D or Adelaide technique with a 3-0 polypropylene or ultrahigh molecular weight polyethylene (UHMWPE) suture. The axial traction test to failure was performed on each tendon to measure 2-mm gap force and ultimate tensile strength.

RESULTS

The mean 2-mm gap force was 49 N for group A (3D + polypropylene), 145 N for group B (3D + UHMWPE), 47 N for group C (Adelaide + polypropylene), and 80 N for group D (Adelaide + UHMWPE). Failure mode was caused by suture breakage for group A (10/10) and mainly by suture pullout for the other groups (8/10 up to 10/10). With the UHMWPE suture, the mean ultimate tensile strength was 145 N for the 3D technique and 80 N for the Adelaide technique.

CONCLUSIONS

Porcine flexor tendons repaired using the 3D technique and UHMWPE suture exceeded a 2-mm gap force and tensile strength of 140 N. The ultimate tensile strength was superior to that of the Adelaide technique, regardless of the suture material.

CLINICAL RELEVANCE

This in vitro study on porcine flexor tendon suture highlights that the mechanical properties of 3D repair are better than those of 3D repair using the Adelaide technique when a UHMWPE suture is used.

The Effects of the TSOL Knot on the Repair Strength and Gliding Resistance Following Flexor Tendon Repair

BACKGROUND

The stability of a suture knot construct has been realized as an important parameter that affects the strength of flexor tendon repairs. A novel 2-strand-overhand-locking (TSOL) knot, which is not commonly used in the clinical setting, recently was reported to increase repair strength and to decrease tendon gliding resistance in a 2-strand repair technique. The purpose of the present study was to investigate the effect of the TSOL knot on tendon repair strength and gliding resistance compared with a typical surgical knot in both 2-strand and 4-strand repair techniques using an in vitro turkey flexor tendon model.

METHODS

Sixty flexor digitorum profundus tendons from the long digit of the turkey foot were divided evenly into 4 groups and repaired with the following techniques: (1) a 2-strand modified Pennington repair with a square knot, (2) a 2-strand modified Pennington repair with a TSOL knot, (3) a 4-strand grasping cruciate repair with a square knot, and (4) a 4-strand grasping cruciate repair with a TSOL knot. Repaired tendons were tested for failure mode, gliding resistance, and repair strength at failure.

RESULTS

The repair strength and stiffness of the 4-strand repairs were significantly higher than those of the 2-strand repairs, regardless of knot type (p < 0.05). The repair strength at failure of the TSOL knot was significantly greater than that of the square knot in 2-strand repairs (p < 0.05) but not in 4-strand repairs. The gliding resistance of the TSOL knot was significantly decreased compared with that of the square knot in both 2-strand and 4-stand repairs (p < 0.05). With regard to failure mode, the TSOL knot was less likely to fail due to knot unravelling.

CONCLUSIONS

In this in vitro biomechanical study involving the use of turkey flexor tendons to compare gliding resistance and repair strength characteristics for knot-inside 2 and 4-strand repairs, the TSOL knot was associated with decreased repaired tendon gliding resistance, regardless of the number of strands used. Although the TSOL knot also increased the repair strength, the difference was only significant when 2-strand repairs were used. The results of our study support the use of the TSOL knot in the clinical setting of flexor tendon repair using 2 or 4-strand, knot-inside methods.

CLINICAL RELEVANCE

In surgical repair of flexor tendons, there is substantial interest in maximizing strength while minimizing friction. This study shows the potential utility of the TSOL knot to increase repair strength while decreasing gliding resistance, particularly in 2-strand repairs.

Biomechanical Study of Modified Massachusetts General Hospital Flexor Tendon Repair Using Looped Sutures

Background: Massachusetts General Hospital (MGH) repair is one of the widely used 4-strand flexor tendon repair techniques. However, it uses two single strand sutures that are each passed twice across the repair site. This is time consuming and may cause imbalance of the load across the repair. We modified the MGH repair by using a looped suture and call it the looped MGH repair. The aim of this study is to compare the strength of the looped MGH repair performed with three different looped sutures against the strength of original MGH repair.

Methods: Forty porcine flexors were used for the study. The original MGH repair was performed with Prolene® 4-0. Looped MGH repair was performed with three different loop sutures, Supramid® 4-0, Tendo-Loop® 4-0 and FiberLoop® 4-0. Mechanism of failure, ultimate tensile strength, stiffness, load to 2-mm gap formation and repair time were recorded for comparison.

Results: There was no significant difference between the original MGH repair and the looped repair using Supramid® regarding their biomechanical performance. Looped MGH repair using Tendo-Loop® and FiberLoop® showed significantly higher ultimate tensile strength and FiberLoop® had highest 2-mm gap force. All looped MGH repairs required significant less time compared to original MGH repair.

Conclusions: Our modification of the MGH repair using a looped Supramid® 4-0 suture took significantly lesser time to perform while providing the same strength as the original MGH repair using Prolene® 4-0. The use of the FiberLoop® 4-0 provided significantly greater strength while taking lesser time.

Dynamic Tendon Grip (DTG™) novel knot array compared to traditional sutures for zone two flexor tendon injury - a biomechanical feasibility study

BACKGROUND

Flexor tendon injuries pose many challenges for the treating surgeon, the principal of which is creating a strong enough repair to allow early active motion, preserving a low-profile of the repair to prevent buckling and subsequent pulley venting. A main concern is that a low-profile repair is prone to gap formation and repair failure. The Dynamic Tendon Grip (DTG™) all suture staple device claims to allow a strong and low-profile repair of the flexor tendon. The purpose of this study is to test the effects of the DTG™ device in early active motion simulation on range of motion, load to failure and gap formation and to compare it to traditional suturing technique.

METHODS

Twelve fresh-frozen cadaveric fingers were assigned to two groups: DTG™ device (n = 9) and traditional suturing (double Kessler 4-core suture and a peripheral suture, n = 3). The deep flexor was incised and repaired in zone 2, and active motion simulation was carried out with a cyclic flexion-extension machine. Finger range of motion and gap formation were measured, as well as load to failure and method of repair failure.

RESULTS

Following motion simulation, ROM decreased from 244.0 ± 9.9° to 234.5 ± 5.8° for the DTG™ device compared to 234.67 ± 6.51° to 211.67 ± 10.50° for traditional suturing. The DTG™ repair demonstrated gap formation of 0.93 ± 0.18 mm in 3 of 8 specimens after applying 1 kg load, which negated after load removal. Load to failure averaged 76.51 ± 23.15 N for DTG™ and 66.31 ± 40.22 N for the traditional repair. Repair failure occurred as the suture material broke for the DTG™ array and at the knot level for the traditional repair.

CONCLUSIONS

The DTG™ all-suture stapling concept achieved a strong low-profile repair in zone 2 flexor tendon injury after active motion simulation. Further clinical studies will be needed to determine the effectiveness of this device compared to traditional techniques.

Gene electrotransfer of FGF2 enhances collagen scaffold biocompatibility

Tendon injuries are a common athletic injury that have been increasing in prevalence. While there are current clinical treatments for tendon injuries, they have relatively long recovery times and often do not restore native function of the tendon. In the current study, gene electrotransfer (GET) parameters for delivery to the skin were optimized with monophasic and biphasic pulses with reporter and effector genes towards optimizing underlying tendon healing. Tissue twitching and damage, as well as gene expression and distribution were evaluated. Bioprinted collagen scaffolds, mimicking healthy tendon structure were then implanted subcutaneously for biocompatibility and angiogenesis analyses when combined with GET to accelerate healing. GET of human fibroblast FGF2 significantly increased angiogenesis and biocompatibility of the bioprinted implants when compared to implant only sites. The combination of bioprinted collagen fibers and angiogenic GET therapy may lead to better graft biocompatibility in tendon repair.

Polytetrafluoroethylene (PTFE) suture vs fiberwire and polypropylene in flexor tendon repair

BACKGROUND

In this study, we evaluate the value of novel suture material based on monofilamentous-extruded polyfluoroethylene (PTFE) compared to polypropylene (PPL) and Fiberwire (FW).

MATERIALS AND METHODS

60 flexor tendons were harvested from fresh cadaveric upper extremities. 4-0 sutures strands were used in the PPL, FW and PTFE group. Knotting properties and mechanical characteristics of the suture materials were evaluated. A 4-strand locked cruciate (Adelaide) or a 6-strand (M-Tang) suture technique was applied as core sutures for a tendon repair. Two-way ANOVA tests were performed with the Bonferroni correction.

RESULTS

Stable knotting was achieved with 5 throws with the PPL material, 7 throws for FW and 9 throws for PTFE. In the PPL group, linear tensile strength was 45.92 ± 12.53 N, in the FW group 80.11 ± 18.34 N and in the PTFE group 76.16 ± 29.10 N. FW and PTFE are significantly stronger than PPL but show no significant difference among each other. Similar results were obtained in the subgroup comparisons for different repair techniques. The Adelaide and the M-Tang knotting technique showed no significant difference.

CONCLUSION

Fiberwire showed superior handling and knotting properties in comparison to PTFE. However, PTFE allows easier approximation of the stumps. In both, M-Tang and Adelaide repairs, PTFE was equal to FW in terms of repair strength. Both PTFE and FW provide for a robust tendon repair so that early active motion regimens for rehabilitation can be applied.

Evaluation of biomechanical properties on partial and complete epitendinous suture in human cadaver flexor tendon repair

Objective

This study was designed to compare the ultimate tensile strength and force to 2 mm gap formation among 50% partial, 75% partial, and complete circumferential epitendinous suture with a combination of 4-strand core suture in human cadaver flexor tendon.

Materials and methods

Forty-five flexor tendons from four soft human cadavers were used to evaluate the biomechanical property among 50% partial, 75% partial, and complete circumferential epitendinous suture with a combination of 4-strand core suture.

Results

The force to 2 mm gap of complete epitendinous was significantly greater than partial epitendinous suture (P < 0.05); however, there was no difference between 50% partial and 75% partial epitendinous suture (P > 0.05). For the ultimate strength, there was no significant difference between partial and complete epitendinous suture (P > 0.05). The partial epitendinous was approximately 60% of the complete epitendinous suture in force to 2 mm gap and also 70% of complete epitendinous suture in ultimate tensile strength with a combination of core sutures.

Conclusions

The complete epitendinous suture showed better ultimate tensile strength and force to 2 mm gap compared with a partial 50% and 75% epitendinous suture. However, in some clinical scenario which the complete epitendinous suture is not possible to perform, the authors suggested only partial epitendinous suture with 50% circumference is recommended as the additional epitendinous repair up 75% circumference cannot provide any mechanical benefit to the repaired site.

Biomechanical Comparison of Tape Versus Suture in Simulated Achilles Tendon Midsubstance Rupture

As sutures have progressed in strength, increasing evidence supports the suture tendon interface as the site where most tendon repairs fail. We hypothesized that suture tape would have a higher load to failure versus polyblend suture due to its larger surface area. Eleven matched pairs of cadaveric Achilles tendons were sutured with 2 mm wide braided ultrahigh molecular weight polyethylene tape (Tape) or 2 mm wide braided ultrahigh molecular weight polyethylene suture (Suture) using a Krackow repair method. All Achilles repair constructs were cyclically loaded, after which they were loaded to failure. Change in suture footprint height, clinical and ultimate load to failure, and location of failure was recorded. Clinical loads to failure for Tape and Suture were 290.4 ± 74.8 and 231.7 ± 70.4 Newtons, respectively (p= .01). Ultimate loads to failure for Tape and Suture were 352.9 ± 108.1 and 289.8 ± 53.7 Newtons, respectively (p = .11). Cyclic testing resulted in significant changes in footprint height for both Tape and Suture, but the 2 sutures did not differ in terms of the magnitude of change in footprint height (p = .52). The suture tendon interface was the most common site of failure for both Tape and Suture. Our results suggest that Tape may provide added repair strength in vivo for Achilles midsubstance rupture.

Beyond the Core Suture: A New Approach to Tendon Repair

Despite significant improvements in zone II flexor tendon repair over the last 2 decades, function-limiting complications persist. This article describes 2 novel repair techniques utilizing flexor digitorum superficialis (FDS) autografts to buttress the flexor digitorum profundus (FDP) repair site without the use of core sutures. The hypothesis being that the reclaimed FDS tendon autograft will redistribute tensile forces away from the FDP repair site, increasing overall strength and resistance to gapping in Zone II flexor tendon injuries compared with the current clinical techniques.

Methods

Two novel FDP repair methods utilizing portions of FDS have been described: (1) asymmetric repair (AR), and (2) circumferential repair. Ultimate tensile strength and cyclical testing were used to compare novel techniques to current clinical standard repairs: 2-strand (2-St), 4-strand (4-St), and 6-strand (6-St) methods. All repairs were performed in cadaveric sheep tendons (n = 10/group), by a single surgeon.

Results

AR and circumferential repair techniques demonstrated comparable ultimate tensile strength to 6-St repairs, with all 3 of these techniques able to tolerate significantly stronger loads than the 2-St and 4-St repairs (P < 0.0001). Cyclical testing demonstrated that AR and circumferential repair were able to withstand a significantly higher total cumulative force (P < 0.001 and P = 0.0064, respectively) than the 6-St, while only AR tolerated a significantly greater force to 2-mm gap formation (P = 0.042) than the 6-St repair.

Conclusion

Incorporating FDS as an autologous graft for FDP repair provides at least a comparable ultimate tensile strength and a significantly greater cumulative force to failure and 2-mm gap formation than a traditional 6-St repair.

The use of barbed sutures in the Pulvertaft weave: a biomechanical study

The use of barbed sutures in tendon repair and reconstruction is advantageous because it allows for a knotless suturing technique. In this biomechanical study, we compared barbed sutures with conventional sutures in tendon transfers using the Pulvertaft weave technique in a human cadaveric model. Thirty human cadaveric finger flexor tendons were transected and divided into three groups of ten tendons, which were then reconstructed by the Pulvertaft weave technique using 3-0 Prolene (Ethicon, Inc., Somerville, NJ, USA), 3-0 Ethilon (Ethicon, Inc., Somerville, NJ, USA) or 3-0 V-Loc (Covidien Deutschland GmbH, Neustadt, Germany) sutures. Biomechanical testing showed that repairs in the V-Loc group had significantly greater ultimate tensile strength and stiffness than conventional sutures. The time taken to complete the weave and the length of sutures used were also the least in the V-Loc group. Our study has shown that the barbed suture has a better biomechanical performance than conventional suture types when used in the Pulvertaft weave technique.

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

PURPOSE

To compare flexor tendon repair strength and speed between a tendon coupler and a standard-core suture in a cadaver model.

METHODS

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.

RESULTS

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.

CONCLUSIONS

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.

CLINICAL RELEVANCE

This tendon coupler may eventually be an option for strong, reproducible, rapid flexor tendon repair.

Biomechanics Study of the Holding Power between Tendon and Suture Using Different Techniques

Background: The holding power of a repaired flexor tendon injury is related to surface sutures, suture material and different techniques. Nowadays, a barbed suture material offers the possibility of knotless flexor tendon repair but many hospitals use non-barbed suture materials. The purpose of this study was to compare a barbed suture material and a non-barbed suture material for primary stability under static loading and increased knots in the non-barbed suture material (knot technique) for increased holding power of tendons in animal testing. Methods: Forty-five fresh porcine tendons were randomized into three groups: Group 1 (grasping technique group) used a four-strand core suture grasping a four-strand modified Kessler suture by non-barbed suture material [Non-absorbable monofilament polybutester 3-0] was used to repair the tendon with a surgical knot; in Group 2 (knot technique group) a four-strand core suture used the knot technique by non-barbed suture material [Non-absorbable monofilament polybutester 3-0] to repair the tendon with a continuous suture adding surgical knots in the same place as the surgical knot at the repair sites; and Group 3 (knotless technique group) used a four-strand core suture with the knotless technique in modified Kessler suture with barbed suture material [Non-absorbable monofilament polybutester 3-0] to repair the tendon without a knot. Our objective was to compare the ultimate tensile strength between the groups. Results: The mean tensile strength was 30.38 ± 5.04 N for group 1, 41.71 ± 2.62 for group 2 and 47.53 ± 4.89 for the group 3. The ANOVA test revealed a significant difference among the various techniques (p < 0.05). The highest tensile strength was found in the knotless technique using barbed suture material group. Conclusions: The knotless technique using barbed suture material demonstrated the highest tensile strength in suture repairs. The maximum tensile strength was significantly higher in this group.

Tendon With Z-Lengthening Technique and Construct Assessment: A Biomechanical Study for Use in Tendon Reconstructions

PURPOSE

Tendon reconstruction is frequently required under conditions of tendon deficiency. The authors sought a technique that could obviate the need for tendon harvest yet meet the minimum load of 45 N required for an early active motion protocol. This study was designed to determine the ideal suture construct utilizing the tendon with Z-lengthening (TWZL) technique.

METHODS

Sixty fresh-frozen cadaveric flexor digitorum profundus tendons of the index, middle, and ring fingers were randomized into 5 different TWZL construct designs using 3-0 braided polyethylene suture. Constructs were tested on an electromechanical actuator until failure was observed on the load-elongation recording. Data points on maximum yield and load at 8% strain were recorded for each construct.

RESULTS

The maximum yield data revealed the construct with a 4-core suture type configuration (construct #4) had the highest overall mean load to failure at 150 N compared with all other constructs. The construct with the highest mean load at 8% strain was that with a 4-core type repair (construct #4) at 59 N. The constructs with Krackow locking sutures (constructs #2, #3, and #4 were found to withstand a significantly higher mean load at 8% strain than those without Krackow sutures (#0 and #1). Comparison among constructs with Krackow locking sutures #2 (56 N), #3 (48 N), and #4 (59 N) did not show a significant difference in mean load at 8% strain. Construct #3, however, had an SD and 95% confidence interval that fell below the 45 N early active motion threshold, whereas both #2 and #4 had 95% confidence intervals that fell no lower than 50 N.

CONCLUSIONS

This study provides evidence that the TWZL technique utilizing either construct #2 or #4 could provide sufficient strength and reproducibility for tendon reconstruction.

CLINICAL RELEVANCE

The study describes the application of the TWZL technique for utilization in tendon reconstruction and quantifies differences in the yield strengths of the 5 proposed constructs.

The use of bidirectional barbed suture in the treatment of a complete common calcanean tendon rupture in a dog: Long-term clinical and ultrasonographic evaluation

The canine common calcanean tendon can be repaired successfully using a modified Kessler knotless barbed technique. A long-term ultrasound follow-up showed improved and increased normal tendon fibrillar echotexture and homogeneity.

Biomechanical Properties of a Novel Mesh Suture in a Cadaveric Flexor Tendon Repair Model

PURPOSE

Conventional suture repairs, when stressed, fail by suture rupture, knot slippage, or suture pull-through, when the suture cuts through the intervening tissue. The purpose of this study was to compare the biomechanical properties of flexor tendon repairs using a novel mesh suture with traditional suture repairs.

METHODS

Sixty human cadaveric flexor digitorum profundus tendons were harvested and assigned to 1 of 3 suture repair groups: 3-0 and 4-0 braided poly-blend suture or 1-mm diameter mesh suture. All tendons were repaired using a 4-strand core cruciate suture configuration. Each tendon repair underwent linear loading or cyclic loading until failure. Outcome measures included yield strength, ultimate strength, the number of cycles and load required to achieve 1-mm and 2-mm gap formation, and failure.

RESULTS

Mesh suture repairs had significantly higher yield and ultimate force values when compared with 3-0 and 4-0 braided poly-blend suture repairs under linear testing. The average force required to produce repair gaps was significantly higher in mesh suture repairs than in conventional suture. Mesh suture repairs endured a significantly greater number of cycles and force applied before failure compared with both 3-0 and 4-0 conventional suture.

CONCLUSIONS

This ex vivo biomechanical study of flexor tendon repairs using a novel mesh suture reveals significant increases in average yield strength, ultimate strength, and average force required for gap formation and repair failure with mesh suture repairs compared with conventional sutures.

CLINICAL RELEVANCE

Mesh suture-based flexor tendon repairs could lead to improved healing at earlier time points. The findings could allow for earlier mobilization, decreased adhesion formation, and lower rupture rates after flexor tendon repairs.

Flexor tendon repair with a polytetrafluoroethylene (PTFE) suture material

BACKGROUND

There is a consensus that after a flexor tendon repair an aggressive rehabilitation protocol with early active motion can improve functional outcome, provided that the combination of material and suturing technique can meet the higher biomechanic demands. Bearing this in mind we evaluated a polytetrafluoroethylene (PTFE) suture (SERAMON^®, Serag-Wiessner) as a possible material for flexor tendon repair.

MATERIALS AND METHODS

40 flexor tendons were harvested from fresh cadaveric upper extremities. 3-0 and 5-0 strands were used both in the polypropylene (PPL) as well as in the PTFE group. In the first phase of the study, we evaluated knotting properties and mechanical characteristics of the suture materials themselves. In the second phase, a 2-strand Kirchmayr-Kessler suture technique was applied for a core suture of a flexor tendon (n = 16). In the third phase, we performed a tendon repair including an epitendinous running suture with 5-0 PPL or 5-0 PTFE material (n = 22). One way ANOVA tests were performed.

RESULTS

The linear loading strength of single strand knotted PPL 3-0 was 19.87 ± 0.59 N. The linear loading strength of knotted PTFE 3-0 was 32.47 ± 1.67 N. For PPL 3-0 maximum linear strength was achieved with five knots, for PTFE 3-0 with eight knots. When a Kirchmayr-Kessler core-only repair was performed, then in the PPL group the loading strength of the repaired tendon was 30.74 ± 9.77 N. In the PTFE group the loading strength was 23.74 ± 5.6 N (p = 0.10). However, all repairs in the PTFE group failed due to cheese wiring. When a Kirchmayr-Kessler core and epitendinous repair technique was used, then in the PPL group the loading strength of the repaired tendon was 49.90 ± 16.05 N. In the PTFE group the loading strength was 73.41 ± 19.81 N (p = 0.006).

CONCLUSION

PTFE demonstrates superior strength properties in comparison to PPL for flexor tendon repairs. However, standard 2 strand techniques have proved inadequate to bear the higher biomechanic demands.

Rotator cuff repair with a novel mesh suture: An ex vivo assessment of mechanical properties

Surgical repair is a common treatment for rotator cuff tear; however, the retear rate is high. A high degree of suture repair strength is important to ensure rotator cuff integrity for healing. The purpose of this study was to compare the mechanical performance of rotator cuffs repaired with a mesh suture versus traditional polydioxanone suture II and FiberWire sutures in a canine in vitro model. Seventy-two canine shoulders were harvested. An infraspinatus tendon tear was created in each shoulder. Two suture techniques-simple interrupted sutures and two-row suture bridge-were used to reconnect the infraspinatus tendon to the greater tuberosity, using three different suture types: Mesh suture, polydioxanone suture II, or FiberWire. Shoulders were loaded to failure under displacement control at a rate of 20 mm/min. Failure load was compared between suture types and techniques. Ultimate failure load was significantly higher in the specimens repaired with mesh suture than with polydioxanone suture II or FiberWire, regardless of suture technique. There was no significant difference in stiffness among the six groups, with the exception that FiberWire repairs were stiffer than polydioxanone suture II repairs with the simple interrupted technique. All specimens failed by suture pull-out from the tendon. Based on our biomechanical findings, rotator cuff repair with the mesh suture might provide superior initial strength against failure compared with the traditional polydioxanone suture II or FiberWire sutures. Use of the mesh suture may provide increased initial fixation strength and decrease gap formation, which could result in improved healing and lower re-tear rates following rotator cuff repair. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:987-992, 2018.

Biomechanical Analysis of Barbed Suture in Flexor Tendon Repair versus Conventional Method: Systematic Review and Meta-Analysis

BACKGROUND

The barbed suture technique uses newly developed materials for flexor tendon repair. In this study, the authors examine the effectiveness of using barbed sutures in flexor tendon repair compared with conventional methods.

METHODS

A systematic literature review and meta-analysis was performed using MEDLINE, Embase, and Cochrane databases. Barbed suture and conventional suture methods were extracted as predictor variables, and maximum force, gap formation force, and cross-sectional area were extracted as outcome variables. Subgroup analyses were performed according to the source of suture materials and the number of strands. The Newcastle-Ottawa Scale was used to assess the quality of studies. Publication bias was evaluated using funnel plots.

RESULTS

The search strategy identified 86 publications. After screening, 12 articles were selected for review. Barbed sutures are comparable in effectiveness to conventional methods in terms of maximum force, gap formation force, and cross-sectional area. In the subgroup analysis, barbed sutures also have comparable effects to conventional methods in terms of maximum force and gap formation force.

CONCLUSIONS

The authors' meta-analysis found that the use of barbed sutures in flexor tendon repair was competitive compared to conventional methods in terms of maximum force and gap formation force. Long-term in vivo studies are needed to confirm these findings.

CLINICAL QUESTION/LEVEL OF EVIDENCE

Therapeutic, V.

A Biomechanical Comparison of Different Knots Tied on Fibrewire Suture

BACKGROUND

Synthetic sutures such as Fiberwire used in flexor tendon repairs have high tensile strength. Proper application allows early mobilisation, decreasing morbidity from repair rupture and adhesions while preserving range of motion. Suture stiffness can cause poorer knot holding, contributing to gapping, peritendinous adhesions or rupture. Previous studies recommended more throws in knots tied on Fiberwire to prevent knot slippage. These larger knots are voluminous and prominent. In tendon repairs they can cause "catching", increase friction and work of flexion. Other studies advocated certain complicated knots as being more secure. We evaluated several knots and their biomechanical properties with the aim of finding a compact knot with less potential for slippage to maximise strength potential of flexor tendon repairs using Fiberwire.

METHODS

A series of different knots tied on Fiberwire 4-0 sutures were pulled to failure on a mechanical tester. Mean tensile strengths, knot volumes and tensile strength to knot volume ratios were compared.

RESULTS

Tensile strengths and knot volume increased with more throws and loops. Four variations of the square knot (the 4=4=1, 2=2=2=2, 1=1=1=1=1, 2=1=1=1=1 knots) had tensile strengths greater than 35N. The specialised anti-slip knot had highest tensile strength and suture volume but lower strength-to-volume ratio.

CONCLUSIONS

The anti-slip knot had highest tensile strength but it also had the highest volume. The greater strength of repair may not translate into improved clinical outcome. The 1=1=1=1=1 knot has superior knot strength-to-volume ratio with good knot strength adequate for early active mobilisation in flexor tendon repairs.

Comparison of Barbed Sutures in Porcine Flexor Tenorrhaphy

Background: Barbed suture use has become more popular as technology and materials have advanced. Minimal data exist regarding performance of the 2 commercially available products, V-LocTM and StratafixTM in tendon repairs. The purpose of this study was to compare gap resistance and ultimate tensile strength of both suture materials and nonbarbed suture in a porcine ex vivo model. Methods: Porcine flexor tendons were harvested and divided into 3 groups of 10 of varying suture material (3-0 PDS™, 3-0 V- V-Loc 180™, or 3-0 Stratafix™). A modified 4-strand cruciate technique was used to repair each tendon. Knotless repair was performed using barbed suture, whereas a buried 6-throw square knot was done using conventional suture. A servohydrolic tester was used for biomechanical testing of linear 2-mm gap resistance and maximum tensile strength. Results: No difference was found in 2-mm gap resistance among the 3 groups. No difference was found in ultimate tensile strength between V-Loc™ (76.0 ± 9.4 N) and Stratafix™ (68.1 ± 8.4 N) repairs, but the ultimate strength of the PDS™ control group (83.4 ± 10.0 N) was significantly higher than that of Stratafix™. Conclusions: Barbed (knotless) and nonbarbed suture repairs demonstrate equivalent 2-mm gap resistance. Stratafix™ repairs show slightly inferior performance to nonbarbed repairs in ultimate tensile strength, although this occurred at gap distances far beyond the 2-mm threshold for normal tendon gliding. Both barbed and nonbarbed 4-strand cruciate flexor tendon repairs may require peripheral repair to withstand physiologic loads.

Biomechanical investigation of 'figure of 8' flexor tendon repair techniques

This biomechanical study compared the original Al-Qattan repair with other modifications postulated to reduce bulk and friction, thereby potentially improving outcome. A total of 32 cadaveric digits with intact flexor apparatus were used. In each digit, the flexor digitorum profundus and flexor digitorum superficialis tendons were cut cleanly in Zone 2. We tested Al-Qattan's technique along with three modifications using stronger suture material and varying the number of strands across the repair site. Of the four repair techniques, the modified Al-Qattan's technique using two 'figure of 8' 4-0 Fiberwire core sutures (Group 4) had the best balance of ultimate tensile strength (50.9 N), 2 mm gapping force (38 N) and friction. The modified technique provided a stronger repair for early active mobilization and has less friction than the originally described repair.

Causes of Flexor Tendon Repair Failures in Two Common Repair Techniques: A Cadaver Study

BACKGROUND

Flexor tendon repair failures have primarily been attributed to either core suture rupture or core suture pull out. Recent studies have suggested that knot unravelling may also cause failure of a tendon repair. The aim of this study was to investigate the causes of core suture failure in two types of common flexor tendon repairs.

METHODS

Twenty four cadaver tendons were divided into three groups of eight. Each group tested a specific flexor tendon repair. The repairs tested included an Adelaide repair using 4/0 Ethibond (Ethicon), an Adelaide repair using 4/0 Fiberwire (Arthrex) and the Tsai repair with 4/0 Fiberloop (Arthrex). The repaired tendons were pull-tested to failure. The mechanism of failure, maximum tensile strength and 2 mm gap force were recorded.

RESULTS

The predominant mode of failure was by the knot unravelling. This occurred in 50-88% of the tendon repairs. The sequence of failure was initiated with gapping at the repair site followed by failure of the epitendinous suture. Next the core suture knot unravels. Once the knot unravels, the suture thread slips out of the tendon resulting in the repair failure. Failures due to knot slippage occurred at a lower maximum tensile strength in Ethibond and Fiberloop sutures than failure due to core rupture or pull out. However, given the small number of tendons tested, this result was not significant.

CONCLUSIONS

This study has clearly demonstrated one of the main causes of flexor tendon repair failure in two common repair techniques is knot unravelling.

Structural Failure Mechanisms of Common Flexor Tendon Repairs

BACKGROUND

This study investigated the exact failure mechanisms of the most commonly used conventional tendon repair techniques. A new method, radiographing repair constructs in antero-posterior and lateral projections before and after tensioning was used. This allowed to precisely analyse failure mechanisms in regards to geometrical changes in all three dimensions. Additionally the biomechanical stability focusing on gapping was tested.

METHODS

Sheep fore limb deep flexor tendons were harvested and divided in eight groups of ten tendons. Three common variants of the Kessler repair method and four common 4-strand repair techniques were tested. Additionally a new modification of the Adelaide repair was tested.

RESULTS

Biomechanical testing showed no significant differences in gapping for the three tested 2-strand Kessler repair groups. Once a double Kessler or 4-strand Kessler repair was performed the stability of the repair improved significantly. Further significant improvements in biomechanical stability could be achieved by using cross locks in the repair like in the Adelaide repair method. Qualitative analysis using radiographs showed that all Kessler repair variants unfolded via rotations around the transverse suturing component, no matter which variant was used.

CONCLUSIONS

Additional to the commonly described constriction of the repair construct, the rotating deformation is the main reason for repair site gapping in Kessler tendon repair methods. The term "locking" in a Kessler repair is misleading. The cruciate repairs tended to loose grip and drag (cheese-wire) through the tendon and therefore lead to gapping. The most stable repair constructs in all three dimensions were the Adelaide repair and its interlocking modification. This is due to the superior anchoring qualities of its cross locks and three dimensional stability.

The effect of a collagen-elastin matrix on adhesion formation after flexor tendon repair in a rabbit model

PURPOSE

The outcome of flexor tendon surgery is negatively affected by the formation of adhesions which can occur during the healing of the tendon repair. In this experimental study, we sought to prevent adhesion formation by wrapping a collagen-elastin scaffold around the repaired tendon segment.

METHODS

In 28 rabbit hind legs, the flexor tendons of the third and fourth digits were cut and then repaired using a two-strand suture technique on the fourth digit and a four-strand technique on the third digit. Rabbits were randomly assigned to study and control groups. In the control group, the operation ended by closing the tendon sheath and the skin. In the study group, a collagen-elastin scaffold was wrapped around the repaired tendon segment in both digits. After 3 and 8 weeks, the tendons were harvested and processed histologically. The range of motion of the digits and the gap formation between the repaired tendon ends were measured. The formation of adhesions, infiltration of leucocytes and extracellular inflammatory response were quantified.

RESULTS

At the time of tendon harvesting, all joints of the operated toes showed free range of motion. Four-strand core sutures lead to significantly less diastasis between the repaired tendon ends than two-strand core suture repairs. The collagen-elastin scaffold leads to greater gapping after 3 weeks compared to the controls treated without the matrix. Within the tendons treated with the collagen-elastin matrix, a significant boost of cellular and extracellular inflammation could be stated after 3 weeks which was reflected by a higher level of CAE positive cells and more formation of myofibroblasts in the αSMA stain in the study group. The inflammatory response subsided gradually and significantly until the late stage of the study. Both the cellular and extracellular inflammatory response was emphasized with the amount of material used for the repair.

CONCLUSION

The use of a collagen-elastin matrix cannot be advised for the prevention of adhesion formation in flexor tendon surgery, because it enhances both cellular and extracellular inflammation. Four-strand core sutures lead to less gapping than two-strand core sutures, but at the same time, the cellular and extracellular inflammatory response is more pronounced.

Four-Strand Core Suture Improves Flexor Tendon Repair Compared to Two-Strand Technique in a Rabbit Model

Introduction. This study was designed to investigate the influence of the amount of suture material on the formation of peritendinous adhesions of intrasynovial flexor tendon repairs. Materials and Methods. In 14 rabbits, the flexor tendons of the third and the fourth digit of the right hind leg were cut and repaired using a 2- or 4-strand core suture technique. The repaired tendons were harvested after three and eight weeks. The range of motion of the affected toes was measured and the tendons were processed histologically. The distance between the transected tendon ends, the changes in the peritendinous space, and cellular and extracellular inflammatory reaction were quantified by different staining. Results. A 4-strand core suture resulted in significantly less gap formation. The 2-strand core suture showed a tendency to less adhesion formation. Doubling of the intratendinous suture material was accompanied by an initial increase in leukocyte infiltration and showed a greater amount of formation of myofibroblasts. From the third to the eighth week after flexor tendon repair, both the cellular and the extracellular inflammation decreased significantly. Conclusion. A 4-strand core suture repair leads to a significantly better tendon healing process with less diastasis between the sutured tendon ends despite initially pronounced inflammatory response.

Does plastic suture deformation induce gapping after tendon repair? A biomechanical comparison of different suture materials

Plastic deformation of sutures creates an irreversible extension during load. To test our hypothesis that such plastic deformation causes gap formation after tendon repair, we determined the plasticity of five different suture materials commonly used in tendon surgery. Prolene, Polydioxanone (PDS), Ethibond, Vicryl, and FiberWire sutures were biomechanically tested to determine their offset yield strength, initial extension, creep, relaxed elongation, peak-to-peak displacement, stiffness, and maximum tensile strength under static, constant, and cyclic loading. In addition, 35 porcine hindlimb tendons were used to evaluate gap formation and the biomechanical behavior of the suture materials after tendon repair. Prolene had a low offset yield strength and high initial extensions at 30, 60, and 90N combined with relatively large creep, relaxed elongation, and peak-to-peak displacement. Aside from the low maximum tensile strength and stiffness, these parameters indicate an early plastic deformation during loading. The material properties of PDS were generally better for suturing than those of Prolene, but no difference was found in offset yield strength or initial extension. In contrast to the monofilament materials Prolene and PDS, the braided Ethibond, Vicryl, and FiberWire materials showed significantly less plastic deformation. The lowest amount of plastic deformation was found in the FiberWire and the results for Ethibond and Vicryl were equal. Gap formation occurred at the lowest tension force in the Prolene group, but only FiberWire required a significantly larger tension force to produce gapping at the repair site, indicating a higher resistance to gap formation. The results of this study show that plastic deformation occurs at a lower tension force in the monofilament sutures Prolene and PDS than in the braided materials Ethibond, Vicryl, and FiberWire. After tendon repair, FiberWire likely prevents gap formation, whereas Prolene induces gapping through low-tension plastic deformation. Therefore, plastic deformation should be considered when selecting suture materials for tendon repair surgery.

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

PURPOSE

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.

METHODS

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.

RESULTS

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.

CONCLUSIONS

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.

CLINICAL RELEVANCE

Hand surgeons are urged to be aware of the biomechanic characteristics of different flexor tendon repair techniques used in the clinical setting.

Comparison of Flexor Tendon Suture Techniques Including 1 Using 10 Strands

PURPOSE

To compare mechanical properties of a multistrand suture technique for flexor tendon repair with those of conventional suture methods through biomechanical and clinical studies.

METHODS

We describe a multistrand suture technique that is readily expandable from 6 to 10 strands of core suture. For biomechanical evaluation, 60 porcine flexor tendons were repaired using 1 of the following 6 suture techniques: Kessler (2-strand), locking cruciate (4-strand), Lim/Tsai's 6-strand, and our modified techniques (6-, 8-, or 10-strand). Structural properties of each tenorrhaphy were determined through tensile testing (ultimate failure load and force at 2-mm gap formation). Clinically we repaired 25 flexor tendons using the described 10-strand technique in zones I and II. Final follow-up results were evaluated according to the criteria of Strickland and Glogovac.

RESULTS

In the biomechanical study, tensile properties were strongly affected by repair technique; tendons in the 10-strand group had approximately 106%, 66%, and 39% increased ultimate load to failure (average, 87 N) compared with those in the 4-, 6-, and 8-strand groups, respectively. Tendons in the 10-strand group withstood higher 2-mm gap formation forces (average, 41 N) than those with other suture methods (4-strand, 26 N; 6-strand, 27 N; and 8-strand, 33 N). Clinically, we obtained 21 excellent, 2 good, and 2 fair outcomes after a mean of 16 months (range, 6-53 mo) of follow-up. No patients experienced poor results or rupture.

CONCLUSIONS

The 10-strand suture repair technique not only increased ultimate strength and force at the 2-mm gap formation compared with conventional suture methods, it also showed good clinical outcomes. This multistrand suture technique can greatly increase the gap resistance of surgical repair, facilitating early mobilization of the affected digit.

TYPE OF STUDY/LEVEL OF EVIDENCE

Therapeutic IV.

Barbed Sutures and Tendon Repair-a Review

INTRODUCTION

Traumatic tendon lacerations are a common problem encountered by hand surgeons worldwide. Although the use of barbed suture to repair tendon lacerations has gained theoretical popularity in recent years, there is little information available regarding the safety, efficacy, longevity, or complications encountered when used in tenorraphy. In this study, we review the available literature on the use of barbed suture in tendon repair.

METHODS

Studies conducted between 1980 and 2014 were identified using several databases, including EMBASE, SCOPUS, MEDLINE, and Web of Science. Keywords used to search for appropriate studies included the following: barbed, v loc, quill, tendon, tendon injuries, suture, tenorraphy, injury, and laceration, in various combinations.

RESULTS

Our initial literature search identified 47 articles, and 8 were deemed appropriate for review after applying our exclusion criteria. The data from each of the articles is reviewed for the following major categories:Maximum load to failureMode of failureLoad to 2-mm gapChange in cross-sectional areaType of repair.

CONCLUSIONS

Barbed suture tenorraphy has a myriad of theoretical advantages, supported by varying ex vivo studies, as compared to traditional techniques. However, due to the non-uniformity in current studies and the lack of available data in a live model, we are unable to argue for or against barbed suture tenorraphy. We believe our review provides the most in-depth analysis of barbed suture tenorraphy to date, illuminates the potential advantages of using barbed sutures, and highlights the need for further investigation into this technique.

Biomechanical evaluation of 4-strand flexor tendon repair techniques, including a combined Kessler-Tsuge approach

PURPOSE

To test the ultimate tensile strength and stiffness of 3 flexor tendon repair techniques using looped suture material.

METHODS

Seventeen fresh porcine flexor tendons were randomized to a single-throw, 4-strand Kessler technique with a looped structure, a double-throw, 4-strand Tsuge technique with 2 looped structures, or a single-throw, 4-strand Kessler-Tsuge technique with a looped structure. Thirty additional fresh porcine flexor tendons were randomized to the same techniques but with a running epitendinous repair. We measured ultimate tensile strength to failure and stiffness and recorded the cause of failure.

RESULTS

The Tsuge technique had the highest mean ultimate tensile strength at 75 N (SD, 14 N) versus 63 N (SD, 13 N) for the Kessler-Tsuge method and 46 N (SD, 11 N) for the Kessler technique. Differences between the Tsuge and Kessler-Tsuge, the Kessler-Tsuge and Kessler, and the Tsuge and Kessler techniques were significant. Mean suture stiffness was 6.8 N/mm for the Tsuge technique, 5.7 N/mm for the Kessler-Tsuge technique, and 4.6 N/mm for the Kessler technique. The difference between the Tsuge and Kessler techniques was significant. Analyzing the tests with or without an epitendinous suture separately did not affect the significance of the differences.

CONCLUSIONS

The modified double-throw, 4-strand Tsuge was the strongest suture technique in this study. It may be a clinically acceptable, albeit slightly weaker alternative to the more complicated Tsuge method.

CLINICAL RELEVANCE

A combined Kessler-Tsuge approach might be an option for flexor tendon repair.

Biomechanical analysis of flexor tendon repair using knotted Kessler and Bunnell techniques and the knotless Bunnell technique

PURPOSE

To evaluate a knotless Bunnell suture in flexor tendon repair.

METHODS

Eighty porcine flexor digitorum tendons were assigned to 4 different suture techniques. Group 1 was repaired using a modified 4-strand knotted Kessler suture and served as a control group. Group 2 was repaired using a 4-strand knotted Bunnell suture. Group 3 used a 4-strand knotless Bunnell suture. Group 4 used a 4-strand knotless Bunnell and knotless peripheral suture. Under static and cyclic testing we studied mode of failure, 2-mm gap formation force, displacement, and maximum load.

RESULTS

The 4-strand knotless Bunnell suture did not show a notable difference with regard to 2-mm gap formation force, displacement, or maximum load in comparison to the modified 4-strand knotted Kessler suture. Adding a knotless peripheral suture improved the repair by a significant reduction of gap formation and displacement and an increase in maximum load. The 4-strand knotted Bunnell showed the highest maximum load but also a considerable lower resistance to gap formation and major displacement.

CONCLUSIONS

Flexor tendon repair using a 4-strand knotless Bunnell suture showed similar tensile strength to a modified 4-strand knotted Kessler suture. Adding a knotless peripheral suture further improved the repair.

CLINICAL RELEVANCE

A complete knotless 4-strand Bunnell suture including a barbed core- and peripheral suture might be an option for flexor tendon reconstruction.

Update on Zone II Flexor Tendon Injuries

Flexor tendon repair in zone II is particularly challenging because tendon gliding must be restored within a tight fibro-osseous sheath while minimizing the formation of adhesions in surrounding tissues. Meticulous surgical technique using a multistrand core suture and a peripheral suture is needed to produce a tendon that is strong enough to withstand early mobilization. Mechanical strength increases with the number of strands crossing the repair, regardless of the core suture configuration. Early mobilization after flexor tendon repair enhances the strength of the repair and decreases the risk of adhesions and joint stiffness. Satisfactory results have been achieved with either early passive or early active motion rehabilitation protocols; therefore, the choice of postoperative rehabilitation program is at the discretion of the surgeon. Factors such as repair integrity, concurrent injuries, and anticipated patient compliance should be considered in the decision-making process.

Biomechanical comparison of Krackow locking stitch versus nonlocking loop stitch with varying number of throws

BACKGROUND

Common suture configuration techniques used for ligament and tendon grafts and repair are the Krackow locking stitch and a nonlocking loop stitch, such as a whipstitch. Clinically, the preferences of orthopaedic surgeons vary.

HYPOTHESIS

The Krackow locking stitch and the nonlocking whipstitch, with varying suture loops, produce different biomechanical and physical effects on the tendon end.

STUDY DESIGN

Controlled laboratory study.

METHODS

A total of 52 fresh-frozen porcine flexor digitorum tendons were used and assigned into 10 groups. Two stitch configurations (Krackow stitch [K] and whipstitch [W]) with varying number of loops (2 throws, n = 6; 4 throws, n = 5; 6 throws, n = 5; 8 throws, n = 5; 10 throws, n = 5) were tested. No. 2 FiberWire was used. Each sample was preloaded to 5 N and then cyclically loaded for 200 cycles to 200 N at 1 Hz, and then the tendon-suture construct was analyzed for gap formation, tendon elongation, and tendon end width. Next, each tendon was loaded to failure, and ultimate strength and mode of failure were recorded. Data were evaluated with 2-way analysis of variance.

RESULTS

For gap formation, the Krackow stitch produced less gap compared with the whipstitch (15.2 ± 4.0 mm [K] vs 18.9 ± 6.8 mm [W]; P = .012). Gap formation was larger when the number of loops increased from 2 to ≥6 (P = .015). For elongation, the Krackow technique increased the tendon length after cyclic loading. In contrast, the whipstitch was noted to shorten the length of the tendon (1.17 ± 0.97 mm [K] vs -0.14 ± 1.13 mm [W]; P < .001). For tendon end width, the Krackow better preserved the transverse width (-0.64 ± 0.81 mm [K] vs -1.39 ± 0.64 mm [W]; P = .001). Both stitch types had similar ultimate strength (322.1 ± 20.3 N [K] vs 319.7 ± 20.4 N [W]; P = .676) and modes of failure (all by suture breakage; therefore, no statistical calculation was performed). There was no statistical difference in tendon elongation, width, failure load, or mode regardless of the number of throws.

CONCLUSION/CLINICAL RELEVANCE

Given the finding that the Krackow suture had less gap formation and better preservation of tendon architecture (length and width) compared with the whipstitch, coupled with the finding that ultimate strength is similar with both types of sutures, the Krackow stitch is recommended for tendon reconstruction when these parameters are important.

Flexor tendon repairs: techniques, eponyms, and evidence

The evolution in surgical technique and suture technology has provided an abundance of options for flexor tendon repairs. Multiple biomechanical studies have attempted to identify the best surgical technique based on suture properties, technical modifications, and repair configurations. However, the burgeoning amount of research on flexor tendon repairs has made it difficult to follow, and no gold standard has been determined for the optimal repair algorithm. Therefore, it seems that repairs are usually chosen based on a combination of familiarity from training, popularity, and technical difficulty. We will discuss the advantages, disadvantages, and technical aspects of some of the most common core flexor tendon repairs in the literature. We will also highlight the nomenclature carried through the years, drawings of the repairs referred to by that nomenclature, and the data that support those repairs.

Flexor Tendon Injuries in the Hand: A UK Survey of Repair Techniques and Suture Materials—Are We Following the Evidence?

Introduction. Injuries to the hand are common, and poor functional outcomes can have significant long-term consequences affecting both work and social activities. Good outcomes following flexor tendon lacerations in the hand are dependent on a sound surgical repair allowing early active mobilisation. Materials and Methods. We reviewed the literature regarding the choice of suture material and repair technique. We then carried out a nationwide postal survey of plastic surgery hand units to assess the level of compliance with the evidence. Results. Fifty-four units were surveyed. The response rate was 72%, with the most popular core suture being Prolene (64%) and the most popular technique being the Kessler repair (36%). Discussion. Current evidence advocates a multistrand repair using Ethibond. We found that the majority of units are not following the evidence. We suggest the use of evidence-based departmental guidelines to improve the practice and outcomes following these common injuries.

Flexor tendon repair, rehabilitation, and reconstruction

BACKGROUND

Flexor tendon injury is a common problem that plastic surgeons are called on to treat. Despite their common nature, they present a challenge, not necessarily in the surgical treatment per se but in the ability to achieve a "normal" finger as the end result. Because of the difficulty in attaining good outcomes, much continues to be studied and written about flexor tendon injury.

METHODS

The current literature on flexor tendon repair, rehabilitation, and reconstruction is reviewed.

RESULTS

Aspects reviewed include type of anesthesia, suture material and configuration, repairs in the different flexor tendon zones, types of tendon rehabilitation, complications of flexor tendon surgery, and flexor tendon reconstruction.

CONCLUSION

This review provides an update on the current standards in the treatment of flexor tendon injury.

Recent developments in flexor tendon repair techniques and factors influencing strength of the tendon repair

Over the last decade, both basic researchers and surgeons have sought to identify the most appropriate techniques to be applied in flexor tendon repairs. Recent developments in experimental tendon repairs and clinical outcomes of newer repair techniques have been reviewed in an attempt to comprehensively summarize the most critical mechanical factors affecting the performance of tendon repairs and the surgical factors influencing clinical outcomes. Among them, attention to annular pulleys, the purchase and tension of the core suture, and the direction and curvature of the path of tendon motion have been found to be determining factors in the results of tendon repair.

Biomechanical comparison of the four-strand cruciate and Strickland techniques in animal tendons

OBJECTIVE

The objective of this study was to compare two four-strand techniques: the traditional Strickland and cruciate techniques.

METHODS

Thirty-eight Achilles tendons were removed from 19 rabbits and were assigned to two groups based on suture technique (Group 1, Strickland suture; Group 2, cruciate repair). The sutured tendons were subjected to constant progressive distraction using a universal testing machine (Kratos®). Based on data from the instrument, which were synchronized with the visualized gap at the suture site and at the time of suture rupture, the following data were obtained: maximum load to rupture, maximum deformation or gap, time elapsed until failure, and stiffness.

RESULTS

In the statistical analysis, the data were parametric and unpaired, and by Kolmogorov-Smirnov test, the sample distribution was normal. By Student's t-test, there was no significant difference in any of the data: the cruciate repair sutures had slightly better mean stiffness, and the Strickland sutures had longer time-elapsed suture ruptures and higher average maximum deformation.

CONCLUSIONS

The cruciate and Strickland techniques for flexor tendon sutures have similar mechanical characteristics in vitro.

A nitinol based flexor tendon fixation device: gapping and tensile strength measurements in cadaver flexor tendon

In this study, a new nitinol based fixation device was investigated for use in repairing severed digital flexor tendons. The device, composed of superelastic nitinol, is tubular in shape with inward facing tines for gripping tissue. Its cellular structure was designed such that it has a large effective Poisson's ratio, which facilitates a “finger trap” effect. This allows for reduced tendon compression during a resting state (to permit vascular perfusion) and increased compression during loading (to drive the tines into the tissue for gripping). To test the feasibility of using this device for flexor tendon repair, it was tested on cadaver flexor digitorum profundus tendons. The tendons were excised, cut in the region corresponding to a zone II laceration, and repaired using the device. The device was easy to install and did not prevent the tendon from bending. Constant strain rate tensile testing revealed a mean tensile strength of 57.6 ± 7.7 N, with a force of 53.2 ± 7.8 N at a 2 mm gap. This exceeds the suggested primary repair strength of 45 N, which has been proposed as the necessary strength for enabling early mobilization. Although considerable future studies will be needed to determine the suitability of the new repair device for clinical use, this study demonstrates the feasibility of utilizing a tubular, nitinol repair device for flexor tendon fixation.

Beyond the square knot: a novel knotting technique for surgical use

BACKGROUND

Knot holding strength is essential to maintain wound closure and ensure tissue contact for healing. Knot unraveling can lead to severe complications, especially for high-tension closures such as tendon repairs, which have recently been reported to have knot unraveling rates as high as 86%. In the current study, a novel surgical knot, the two-strand-overhand locking (TSOL) knot, was designed and mechanically evaluated with use of different suture materials and knot configurations and in actual tendon repairs.

METHODS

The knot holding strength of the TSOL knot was compared with that of a 4-throw square knot with use of three different suture materials that are in common clinical use. With use of braided polyblend suture, the TSOL knot was also compared with five other surgical knot configurations. Finally, the strength of tendon repairs performed with use of the TSOL knot and a 4-throw square knot was studied.

RESULTS

Compared with the 4-throw square knot, the holding strength of the TSOL knot was 143% greater for braided polyblend, 216% greater for polydioxanone, and 118% greater for polyester suture, with a significantly lower knot unraveling rate compared with that of the 4-throw square knot regardless of suture material. The TSOL knot holding strength was also greater than that of the other surgical knot configurations. The strength and stiffness of tendon repairs with a TSOL knot were significantly increased over those of repairs with a 4-throw square knot.

CONCLUSIONS

The TSOL knot provided superior knot holding strength compared with some commonly used surgical knots.

CLINICAL RELEVANCE

The TSOL knot has potential clinical applications, especially when knot security is important and high loads are expected, as in tendon or ligament repairs.

Tendon healing, edema, and resistance to flexor tendon gliding: clinical implications

Early flexor tendon healing is characterized by peak cellular apoptosis of both inflammatory and tendon cells in the first week, followed by progressively greater tenocyte proliferation in the second and third weeks. Tenocyte apoptosis is a predominant event, but proliferation of tenocytes is minimal in the middle and late healing periods. Edematous subcutaneous tissues, edema of the tendon, the intact annular pulleys, and extensor tendons all greatly contribute to the resistance. Careful consideration of the contributing factors and dynamics offers insight into strategies to reduce repair rupture and maximize tendon gliding through surgery and postoperative motion protocols.

Comparison of a multifilament stainless steel suture with FiberWire for flexor tendon repairs--an in vitro biomechanical study

Our goal was to investigate and compare the mechanical properties of multifilament stainless steel suture (MFSS) and polyethylene multi-filament core FiberWire in flexor tendon repairs. Flexor digitorum profundus tendons were repaired in human cadaver hands with either a 4-strand cruciate cross-lock repair or 6-strand modified Savage repair using 4-0 and 3-0 multifilament stainless steel or FiberWire. The multifilament stainless steel repairs were as strong as those performed with FiberWire in terms of ultimate load and load at 2 mm gap. This study suggests that MFSS provides as strong a repair as FiberWire. The mode of failure of the MFSS occurred by the suture pulling through the tendon, which suggests an advantage in terms of suture strength.

Analysis of a knotless flexor tendon repair using a multifilament stainless steel cable-crimp system

PURPOSE

To compare the biomechanical and technical properties of flexor tendon repairs using a 4-strand cruciate FiberWire (FW) repair and a 2-strand multifilament stainless steel (MFSS) single cross-lock cable-crimp system.

METHODS

Eight tests were conducted for each type of repair using cadaver hand flexor digitorum profundus tendons. We measured the required surgical exposure, repair time, and force of flexion (friction) with a custom motor system with an inline load cell and measured ultimate tensile strength (UTS) and 2-mm gap force on a servo-hydraulic testing machine.

RESULTS

Repair time averaged less than 7 minutes for the 2-strand MFSS cable crimp repairs and 12 minutes for the FW repairs. The FW repair was performed with 2 cm of exposure and removal of the C-1 and A-3 pulleys. The C-1 and A-3 pulleys were retained in each of the MFSS cable crimp repairs with less than 1 cm of exposure. Following the FW repair, the average increase in friction was 89% compared with an average of 53% for the MFSS repairs. Six of the 8 MFSS specimens achieved the UTS before any gap had occurred, whereas all of the FW repairs had more than 2 mm of gap before the UTS, indicating that the MFSS was a stiffer repair. The average UTS appeared similar for both groups.

CONCLUSIONS

We describe a 2-strand multifilament stainless steel single cross-lock cable crimp flexor repair system. In our studies of this cable crimp system, we found that surgical exposure, average repair times, and friction were reduced compared to the traditional 4-strand cruciate FW repair. While demonstrating these benefits, the crimp repair also produced a stiff construct and high UTS and 2-mm gap force.

CLINICAL RELEVANCE

A cable crimp flexor tendon repair may offer an attractive alternative to current repair methods. The benefits may be important especially for flexor tendon repair in zone 2 or for the repair of multiple tendons.

The effect of suture preloading on the force to failure and gap formation after flexor tendon repair

PURPOSE

Gap formation is a common and severe complication after flexor tendon repair that can affect the outcome and prolong tendon healing. The purpose of this study was to investigate the effect that a pretensional force applied to the suture during tendon repair has on the repair strength and force that causes gap formation.

METHODS

We used a total of 48 flexor digitorum profundus tendons from 12 human cadaver hands. We employed a core tendon suture, using the modified Pennington technique, and a running suture for flexor tendon repair. Before tying the knots of the core suture, we preloaded the sutures in each tendon end 0, 5, 10, or 15 N for 10 seconds to compare the effect of loading magnitude on repaired tendon peak force to failure and force causing gap formation.

RESULTS

The force to form a gap of 2 mm in the 15-N preload group was significantly increased compared with the 0-N and 5-N preload groups. At the 3-mm gap formation, the force of all preload groups was significantly higher than the nonpreload group. The peak force with a preload of 10 N and 15 N was significantly higher than 0-N preload.

CONCLUSIONS

These findings suggest that pretensioning with 10 to 15 N at the suture-tendon interface before tying the knot has a beneficial effect on both the tendon gap formation and the peak force to failure.

CLINICAL RELEVANCE

When the surgeons perform tendon repair, pretensioning at the suture-tendon conjunction will increase the repair strength.

Number of suture throws and its impact on the biomechanical properties of the four-strand cruciate locked flexor tendon repair with FiberWire

FiberWire is a popular suture in flexor tendon repair that allows for early mobilization, but its poor knot-holding properties have raised concerns over the potential effects on tendon healing and strength. We examined how the number of knot throws affects the 2 mm gap force, ultimate tensile strength, and mode of failure in a four-strand cruciate locked tendon repair in porcine flexor tendons in order to elucidate the optimal number of suture throws. There was no effect on the 2 mm gap force with increasing knot throws, but there was a significant increase in ultimate tensile strength. A minimum of six-knot throws prevents unravelling, whereas five out of 10 of repairs unravelled with less than six throws.

Intrasynovial flexor tendon repair: a biomechanical study of variations in suture application in human cadavera

To improve the functional outcomes of intrasynovial tendon suture, prior experiments evaluated individual technical modifications used in the repair process. Few studies, however, have assessed the combinatorial effects of those suture modifications in an integrated biomechanical manner, including a sample size sufficient to make definitive observations on repair technique. Two hundred fifty-six flexor tendon repairs were performed in human cadavera, and biomechanical properties were determined. The effects of five factors for flexor tendon repair were tested: core suture caliber (4-0 or 3-0), number of sutures crossing the repair site (four- or eight-strand), core suture purchase (0.75 or 1.2 cm), peripheral suture caliber (6-0 or 5-0), and peripheral suture purchase (superficial or 2 mm). Significant factors affecting the properties of the repair were the number of core suture strands and the peripheral suture purchase. The least significant factors were core suture purchase and peripheral suture caliber. The choice of core suture caliber affected the properties of repair marginally. Based on these results, we recommend that surgeons continue to focus on multi-strand repair methods, as the properties of eight-strand repairs were far better than those of four-strand repairs. To resist gap formation and enhance repair strength, a peripheral suture with 2 mm purchase is also recommended. Finally, since core suture caliber affected some biomechanical properties, including the failure mode, a 3-0 suture could be considered, provided that future in vivo studies can confirm that gliding properties are not adversely influenced.

A biomechanical comparison of 3 loop suture materials in a 6-strand flexor tendon repair technique

PURPOSE

The braided polyblend (FiberWire) suture is recognized for its superiority in tensile strength in flexor tendon repair. The purpose of this study was to compare the biomechanical performance of 3 loop-suture materials used in a locking 6-strand flexor tendon repair configuration: braided polyblend (FiberLoop 4-0), cable nylon (Supramid Extra II 4-0), and braided polyester (Tendo-Loop 4-0). We hypothesized that, using this technique, the braided polyblend suture would give superior tensile strength compared with the other 2 suture materials.

METHODS

We divided 30 fresh porcine flexor tendons transversely and repaired each with 1 of the 3 suture materials using a modified Lim-Tsai 6-strand suture technique. We loaded the repaired tendons to failure using a materials testing machine and collected data on the mechanism of failure, ultimate tensile strength, gap strength, and stiffness.

RESULTS

Failure mechanisms for the repaired specimens were as follows: the braided polyblend had 50% suture breakage and 50% suture pullout; the cable nylon had 100% suture breakage; and the braided polyester had 80% suture breakage and 20% suture pullout. Specimens repaired with the braided polyblend suture had the highest mean ultimate tensile strength (97 N; standard deviation, 22) and the highest mean gap force (35 N; standard deviation, 7).

CONCLUSIONS

This study supports the findings of previous studies showing superior strength of the braided polyblend suture.

CLINICAL RELEVANCE

We were able to achieve up to 124 N in ultimate tensile strength and 48 N of gap force with this suture in porcine tendons. This gives greater confidence in starting immediate controlled passive or active rehabilitation after repair of flexor tendon injuries.