An evaluation of suture materials used in tendon surgery

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.

Polymer-Based Constructs for Flexor Tendon Repair: A Review

A flexor tendon injury is acquired fast and is common for athletes, construction workers, and military personnel among others, treated in the emergency department. However, the healing of injured flexor tendons is stretched over a long period of up to 12 weeks, therefore, remaining a significant clinical problem. Postoperative complications, arising after traditional tendon repair strategies, include adhesion and tendon scar tissue formation, insufficient mechanical strength for early active mobilization, and infections. Various researchers have tried to develop innovative strategies for developing a polymer-based construct that minimalizes these postoperative complications, yet none are routinely used in clinical practice. Understanding the role such constructs play in tendon repair should enable a more targeted approach. This review mainly describes the polymer-based constructs that show promising results in solving these complications, in the hope that one day these will be used as a routine practice in flexor tendon repair, increasing the well-being of the patients. In addition, the review also focuses on the incorporation of active compounds in these constructs, to provide an enhanced healing environment for the flexor tendon.

Surgical wounds in reduction mammoplasty: a comparison of Monocryl and Prolene sutures on scars

OBJECTIVE

The type of suture material affects the quality of scars. The aim of this study was to find the superior suture material for reduction mammoplasty between Prolene and Monocryl based on the comparison of scars.

METHOD

A prospective observational study was conducted at a university-based hospital in Mashhad, Iran between October 2015 and September 2017. Monocryl and Prolene suture materials, used for closing the outermost layer in mammoplasty, were compared. Patients' incision scars were assessed objectively according to the Patient and Observer Scar Assessment (POSAS) criteria. The relevant CONSORT guideline was used for reporting this study.

RESULTS

Seventy-eight women with a mean age of 36.8±9.5 years were entered into the study. The frequency of wound healing in both groups was 97.4% 1 month after surgery and by the third visit, 3 months after surgery, only one patient had a stretched scar. Moreover, wound inflammation in the first two visits was less frequent in the Prolene group that healed completely 3 months after surgery (after excluding the one patient with wide scar inflammation). The frequency of itching of the wound in the Monocryl group was 24.4%, 11.5% and 12.8% in the three follow-up visits, respectively, and the values for the Prolene group were 24.4%, 9.0% and 6.4%, respectively. No significant difference was seen between the two groups in terms of wound healing, inflammation and itching (p>0.05). Overall, 94.8% of patients were satisfied with the surgery.

CONCLUSIONS

Our study revealed that there was no significant difference between Monocryl and Prolene. Hence, either of the two suture materials can be used for wound closure in reduction mammoplasty.

Biomechanical evaluation of a novel barbed suture pattern with epitendinous suture augmentation in a canine flexor tendon model

OBJECTIVE

To determine the effect of a novel barbed suture pattern (NBSP) compared to a three-loop-pulley (3LP) with and without epitendinous suture (ES) augmentation on the biomechanical strength and gap formation of repaired canine tendons.

STUDY DESIGN

Ex vivo, cadaveric, randomized, experimental study.

SAMPLE POPULATION

Forty, adult superficial digital flexor tendons (SDFT).

METHODS

SDFT were randomly assigned to one of four groups (n = 10/group). Sharp tenotomy was performed and repaired with 3LP, NBSP, 3LP + ES, and NBSP + ES. Constructs were tested to failure while evaluating yield, peak, and failure loads, loads at 1 and 3 mm gap formation, and failure mode.

RESULTS

Constructs augmented with ES sustained 80% greater yield (p < .001), peak (p < .001), and failure (p < .001) loads, with no difference between 3LP + ES and NBSP + ES constructs regarding peak (p = .614), and failure forces (p = .865). Loads resulting in 1 and 3 mm gap formation were greater when constructs were augmented with an ES (p ≤ .003). Failure mode differed between groups (p < .001), occurring predominantly due to suture pull-through in 3LP and NBSP groups compared to tissue failure distant to the repair site in ES augmented constructs.

CONCLUSION

Tendons repaired with the NBSP used in this study resisted similar forces as those repaired with 3LP. Augmentation with an ES improved the biomechanical properties of repaired constructs, including resistance to gap formation.

CLINICAL RELEVANCE

The NBSP repair tested here may be advantageous over monofilament suture repair as it uses a similar-sized barbed core suture but eliminates the requirement for knot tying.

Biomechanical Comparison of Tendon Coaptation Methods With a Meshed Suture Construct

PURPOSE

Tendon-to-tendon attachment constructs for tendon reconstructions or transfers need to be secure in order to allow early mobilization after surgery. The purpose of this study was to biomechanically compare 2 common constructs secured with a novel mesh suture versus a nonabsorbable braided suture.

METHODS

We used 100 cadaveric tendons to create 5 different tendon coaptation constructs (a to e) (10 coaptations per group): (a) Pulvertaft weave with a braided suture (PTe); (b) mesh suture (PTm); (c) single-pass, side-to-side (SP-STS) coaptation with 30-mm overlap using a mesh suture (SP-STS-30m); (d) SP-STS 50-mm overlap with a mesh suture (SP-STS-50m); and (e) SP-STS with 30-mm tendon overlap using a braided suture (SP-STS-30e). The tensile strength, bulk, gliding resistance, and failure type were compared.

RESULTS

There was no difference between the various tendon constructs and the suture type in terms of coaptation bulk. All SP-STS constructs with mesh suture had higher peak gliding resistance than any of the PT constructs regardless of suture type. Compared with the PT constructs, the SP-STS constructs with mesh or braided suture had a higher peak load, peak load normalized to repair length, and stiffness. Within each tendon coaptation construct group, Pulvertaft or SP-STS, the suture type did not affect any of the investigated parameters.

CONCLUSIONS

The SP-STS constructs are significantly stronger and stiffer than the PT constructs. The SP-STS with mesh suture exhibited greater gliding resistance than the PT constructs and may result in greater gliding resistance through physiological tissue planes. However, the use of a mesh suture did not affect strength, bulk, gliding resistance, or failure type when compared within a construct group.

CLINICAL RELEVANCE

The use of SP-STS constructs for tendon coaptations produces a stronger and stiffer construct than the PT weave; however, the use of a mesh suture may not provide any benefit over a braided suture.

Biomechanical Study Comparing Pulvertaft, Double Side-to-Side, and Locking Side-to-Side Tendon Suture Techniques

PURPOSE

In this study, we present a single-sided locking side-to-side (STS) suture technique as a possible alternative for the Pulvertaft weave in tendon transfers. The aim of the study was to compare the biomechanical characteristics of the single-sided locking STS reconstruction with Pulvertaft and double-sided nonlocking STS reconstructions.

METHODS

Twenty-four human cadaveric extensor digitorum communis tendons and 24 flexor digitorum superficialis tendons were randomly assigned to 1 of 3 groups, resulting in a total of 8 flexor tendons and 8 extensor tendons per group: Pulvertaft, double-sided nonlocking STS, and single-sided locking STS reconstructions. Load to failure was measured with a tensile testing machine. Increase in cross-sectional area was used as a measure of bulkiness at the reconstruction site.

RESULTS

In extensor tendons, single-sided locking STS reconstructions showed a higher load to failure than Pulvertaft reconstructions, whereas no difference was found in load to failure between single-sided locking and double-sided nonlocking STS reconstructions. In flexor tendons, single-sided locking STS reconstructions showed a higher load to failure than Pulvertaft reconstructions. However, load to failure of single-sided locking STS reconstructions was less than double-sided nonlocking STS reconstructions. In both extensor and flexor tendons, the percent increase in cross-sectional area at the reconstruction site was higher in Pulvertaft reconstructions than single-sided locking STS reconstructions, whereas no difference was found between single-sided locking STS and double-sided nonlocking STS reconstructions.

CONCLUSIONS

Single-sided locking and double-sided nonlocking STS reconstructions are suitable alternatives to the Pulvertaft technique for tendon transfers owing to a higher strength and less bulkiness. Because load to failure of both STS reconstructions did not differ in extensor tendon transfers, the single-sided locking STS reconstruction seems especially suitable for extensor tendon transfers.

CLINICAL RELEVANCE

This study provides anatomical evidence that the single-sided locking STS reconstruction yields a higher strength and is less bulky than the Pulvertaft reconstruction in tendon transfers.

The V-shaped subscapularis tenotomy for anatomic total shoulder arthroplasty

PURPOSE

Management of the subscapularis tendon during anatomic total shoulder arthroplasty (TSA) remains controversial. In our unit, subscapularis tenotomy is the preferred technique; however, the potential for tendon gapping and failure is recognised. The purpose of this study is to describe and provide early clinical results of a novel, laterally based V-shaped tenotomy (VT) technique hypothesised to provide greater initial repair strength and resistance to gapping than a transverse tenotomy (TT), with both clinically and radiologically satisfactory post-operative tendon healing and function.

METHODS

A retrospective study of patients who underwent primary TSA with VT over a three year period was performed using shoulder and subscapularis-specific outcome scores, radiographs, and ultrasound. A separate cohort of patients who underwent TSA using a subscapularis sparing approach was also reviewed to provide comparative clinical outcomes of a group with TSA and an un-violated subscapularis.

RESULTS

Eighteen patients were reviewed at mean 30.4 months (± 11.7). Constant (78.2 ± 12.3), UCLA (8.4 ± 1.5), pain VAS (2.3 ± 2.8), and strength in internal rotation were no different from the comparison group. Likewise, neither were the clinical outcomes of range-of-motion, belly-press, lift-off, and shirt-tuck tests. One patient (5.5%) was found to have a failed subscapularis repair on ultrasound.

CONCLUSION

VT during TSA appears to provide healing rates at least equal to those reported for TT, and not dissimilar from those of lesser tuberosity osteotomy. Clinical outcomes are comparable to reported results in the literature for alternative techniques, and not different from those observed here in a comparison cohort with TSA performed without violating the subscapularis tendon. VT therefore potentially offers a more effective and secure tendon repair than a traditional TT, with at least comparable clinical outcomes.

Biomechanical analysis of a new 8-strand technique for flexor tendon repair

We sought to compare the strength and rupture sites of a new 8-strand suture technique with those of an established 6-strand flexor tendon repair through biomechanical analysis. This new 8-strand suture pattern places minimal suture material in the remodeling zone and focuses on protecting the knot, a well-known weak point of the suture construct. The knot was buried within the tendon so as to not interfere with tendon gliding. In a biomechanical simulation, strength and rupture sites were compared with those of the 6-strand repair. We repaired a total of 54 porcine flexor tendons using one of the two techniques (n=27 each). Tensile strength at 2-mm gap formation and ultimate failure load were determined. Afterwards, we dissected the tendons to identify the rupture site of the suture material. The new 8-strand suture had a significant higher ultimate load to failure (87.7N) and 2-mm gap load (71.6N) compared to the 6-strand technique (57.7N and 45.9N) (P<0.001). Whereas the rupture site of the core suture in the 6-strand technique was mainly located next to the knot (81.5%), the suture seemed to fail independently from this weak spot in the 8-strand technique (11.1%). This new 8-strand technique achieves a strong flexor tendon repair in a biomechanical model. Additional cross-locking on either side of the knot seems to contribute to the repair's strength. The resulting higher ultimate failure load and 2-mm gap load may allow more aggressive active motion-based postoperative rehabilitation.

The evidence-base for the management of flexor tendon injuries of the hand: Review

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There is no consensus on the optimal flexor tendon repair technique at each anatomical flexor zone.

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There is paucity of high quality evidence.

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Heterogenous study designs limit inter-study comparisons.

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Patient reported outcome measures are crucial but there is a perennial need for robust disease-specific tools to be utilised.

Asymmetric 6-Strand Flexor Tendon Repair - Biomechanical Analysis Using Barbed Suture

Background: This study investigates the biomechanical performance of the Asymmetric flexor tendon repair technique using barbed suture. The Asymmetric repair technique using monofilament nylon suture was previously reported to have a higher tensile strength than the modified Lim-Tsai repair technique, but its repair stiffness and load to gap force were significantly lower. There is hence an unmet need to improve this technique and the substitution of nylon suture with barbed sutures may be the solution. Methods: Two groups consisting of 10 porcine tendons each were repaired with the six-strand Asymmetric repair technique using V-Loc^® 3-0 and Supramid^® 4-0 respectively. The repairs were subjected to a mechanical tester for static testing. The ultimate tensile strength, load to 2 mm gap force, repair stiffness, time taken to complete a repair and failure mechanism of the repairs were recorded and analyzed. Results: All the repairs using V-Loc^® 3-0 sutures had significantly higher median values of ultimate tensile strength (64.1 N; 56.9 N), load to 2 mm gap force (39.2 N; 19.7 N), repair stiffness (6.4 N/mm; 4.7 N/mm) and time taken to complete a repair (9.4 mins; 7.7 mins). All the repairs using V-Loc^® sutures failed by suture breakage while 80% of repairs using Supramid^® sutures failed by suture pullout. Conclusions: The use of the barbed sutures in the Asymmetric repair technique, whilst more time consuming, has shown promising improvement to its biomechanical performance (i.e. better ultimate tensile strength, stiffness and resistance to gap formation).

The Effect of Suture Materials on the Biomechanical Performance of Different Flexor Tendon Repairs and the Concept of Construct Efficiency

BACKGROUND

To propose a new term ('construct efficiency') for the evaluation of multi strands flexor tendon repairs using different suture materials.

METHODS

A total of twenty specimens from 4-0 braided polyblend sutures (FiberLoop/FiberWire; Arthrex, Naples, FL) and 4-0 nylon sutures (Supramid Extra II; S. Jackson, Inc., Alexandria, VA) were subjected to tensile testing using Pneumatic Cord-and-Yarn Grips (Instron Corp., Canton MA, USA). The ultimate tensile strengths of the suture materials were measured. The expected repair strengths and construct efficiencies were computed based on the experimental results and from available literature on actual repair strengths of the 4-strand Becker, Cruciate repairs and 6-strand Tang, modified Lim-Tsai repairs.

RESULTS

The ultimate tensile strength of nylon suture was 15.4 ± 0.6N, lower than that of braided polyblend suture (45.3 ± 2.3N) with a difference of 194%. The construct efficiency of multi strand repairs varied with respect to different repair techniques and suture materials. It was found that the Becker repairs using FiberWire had the highest construct efficiency (55.7%) followed by the modified Lim-Tsai using Supramid (50.9%), Tang repair using Supramid (49.8%), Cruciate repair using Fiberwire (49.1%), and modified Lim-Tsai repair using FiberLoop (33.5%).

CONCLUSIONS

The construct efficiency is more accurate in showing that, in terms of biomechanical strength, the use of FiberWire for the 4-strand Becker and Cruciate repair is more efficient than that of using FiberLoop for 6-strand modified Lim-Tsai repair.

Positioning of the cross-stitch on the modified Kessler core tendon suture

Cryopreserved human tendons were sutured with different variations of a modified Kessler-type grasping suture in a series of different designs in order to assess the influence of the distance between the cross-stitch on the core suture (5 and 10 mm from the cut tendon edge) on the peripheral suture. An original mathematical model was employed to explain the mechanical behavior (strength, deformation, and distribution of load) of the different suture designs. The effect of the peripheral epitendinous suture, combined with the distance of the core suture, was evaluated. The variation of core suture distance had no relevant consequences on the overall resilience of the design. However, increasing the distance between the cross-stitches of the core suture reduces the deformation that is absorbed not only by the core suture itself but also by the peripheral suture. Adding a peripheral epitendinous suture to a 10-mm design almost doubles the breaking load in absolute values. The mathematical model predicts that the peripheral suture will support a greater load when the distance of the core suture cross-stitches is increased. The evidence level is II.

A Comparative Analysis of the Biomechanical Behaviour of Five Flexor Tendon Core Sutures

Five core suture techniques were compared by static tensile testing in vitro. Fifty porcine tendons were used. The core sutures were performed with 3-0 or 4-0 braided polyester suture (Ticron®) and the over-and-over running peripheral sutures with 6-0 monofilament polypropylene (Prolene®). The core sutures were: (1) Pennington modified Kessler (3-0), (2) Double Pennington modified Kessler (3-0), (3) 4-strand Savage (3-0), (4) 4-strand Savage (4-0), and (5) 6-strand Savage (4-0). Repairs were compared as paired in regard to one variable: the number of core suture strands, the suture calibre, or the suture configuration. Biomechanical differences between the repair groups started during the linear region, with the yield force and stiffness increasing along with the number of core suture strands. All three variables influenced the strain at the yield point. Thus, the strength of the intact repair can be improved by modifying the core suture. In all repairs gap formation started near the yield point after failure of the peripheral suture. The yield force represents the strength of the intact repair composite and should be considered the strength of the tendon repair.

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.

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.

Recent advances in biodegradable metals for medical sutures: a critical review

Sutures that biodegrade and dissolve over a period of several weeks are in great demand to stitch wounds and surgical incisions. These new materials are receiving increased acceptance across surgical procedures whenever permanent sutures and long-term care are not needed. Unfortunately, both inflammatory responses and adverse local tissue reactions in the close-to-stitching environment are often reported for biodegradable polymeric sutures currently used by the medical community. While bioabsorbable metals are predominantly investigated and tested for vascular stent or osteosynthesis applications, they also appear to possess adequate bio-compatibility, mechanical properties, and corrosion stability to replace biodegradable polymeric sutures. In this Review, biodegradable alloys made of iron, magnesium, and zinc are critically evaluated as potential materials for the manufacturing of soft and hard tissue sutures. In the case of soft tissue closing and stitching, these metals have to compete against currently available degradable polymers. In the case of hard tissue closing and stitching, biodegradable sternal wires could replace the permanent sutures made of stainless steel or titanium alloys. This Review discusses the specific materials and degradation properties required by all suture materials, summarizes current suture testing protocols and provides a well-grounded direction for the potential future development of biodegradable metal based sutures.

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.

The Effect of the Epitendinous Suture on Gliding in a Cadaveric Model of Zone II Flexor Tendon Repair

PURPOSE

We hypothesized that increasing core sutures (4-6) may be preferable in terms of gliding coefficient (GC) measurements when compared with adding an epitendinous suture to zone II flexor tendon repairs. We hypothesized that the inclusion of epitendinous suture in 2 standard repairs would contribute negatively to the GC of the repaired tendon.

METHODS

Nineteen fresh-frozen cadaveric fingers were used for testing. We compared a control group (dissected digits without repair) and 4-strand or 6-strand core tendon repairs with and without epitendinous suture. Arc of motion was driven by direct loading, and digital images were acquired and analyzed. Outcomes were defined as the difference in GC between the native uninjured and the repaired state at each load. A linear mixed-model analysis was performed with comparisons between repairs to evaluate the statistically relevant differences between groups.

RESULTS

The test of fixed effects in the linear model revealed that repair type and the use of epitendinous suture significantly affected the change in GC. The addition of an epitendinous suture produced a significant decrement in gliding regardless of repair type.

CONCLUSIONS

There was significant improvement in GC with the omission of the epitendinous suture in both repair types (4- or 6-strand).

CLINICAL RELEVANCE

The epitendinous suture used in this model resulted in poorer gliding of the repair, which may correspond with an expected increase in catching or triggering.

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

PURPOSE

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

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.

Influence of different length of core suture purchase among suture row on the strength of 6-strand tendon repairs

In multi-strand suture methods consisting of several suture rows, the different length of core suture purchase between each suture row may affect the strength of repairs. We evaluated the influence of the different length of core suture purchase between each suture row on the strength of 6-strand tendon repairs. Rabbit flexor tendons were repaired by using a triple-looped suture technique in which the suture purchase length in each suture row was modified. Group 1, all lengths are 8-mm. Group 2, all lengths are 10-mm. Group 3, two are 10-mm and one is 8-mm. Group 4, one is 10-mm and two are 8-mm. The repaired tendons were subjected to load-to-failure test. The gap strength was significantly greater in Group 1 and Group 2 than in Group 3 and Group 4. This study demonstrates that maintaining equal core suture purchase lengths of each suture row increases the gap resistance.

Improving results of flexor tendon repair and rehabilitation

BACKGROUND

The global time and effort attributed to improving outcomes in the management of flexor tendon injury are large, but the degree of advancement made over the past 50 years is relatively small. This review examines the current perceived wisdom in this field and aims to explore the limitations to the authors' understanding of the tendon healing process, examining how this may be a factor that has contributed to the authors' modest progress in the field.

METHODS

The authors critically evaluate the sum of laboratory and clinical literature on the topic of zone II flexor tendon management that has guided their practice and provide evidence to support their methods.

RESULTS

The review highlights some of the key developments over the years and assesses their influence on changing current practice. It also highlights recent innovations, which have the potential to influence flexor tendon outcomes by altering the surgical approach, techniques, and rehabilitation regimens. Future innovations in the field will also be discussed to examine their potential in expanding the development in the management of flexor tendon injury.

CONCLUSIONS

A better understanding of flexor tendon biology will allow progress in developing new therapies for flexor tendon injuries; however, there are as yet few real breakthroughs that will dramatically change current practice.

A barbed suture repair for flexor tendons: a novel technique with no exposed barbs

Background:

Barbed suture technology has shown promise in flexor tendon repairs, as there is an even distribution of load and the need for a knot is eliminated. We propose that a quick and simple, novel, barbed technique without any exposed barbs on the tendon surface has comparable strength and a smaller cross-sectional area at the repair site than traditional methods of repair.

Methods:

Forty porcine flexor tendons were randomized to polybutester 4-strand barbed repair or to 4-strand Adelaide monofilament repair. The cross-sectional area was measured before and after repair. Biomechanical testing was carried out and 2-mm gap formation force, ultimate strength of repair, and method of failure were recorded.

Results:

The mean ultimate strength of the barbed repairs was 54.51 ± 17.9 while that of the Adelaide repairs was 53.17 ± 16.35. The mean 2-mm gap formation force for the barbed group was 44.71 ± 17.86 whereas that of the Adelaide group was 20.25 ± 4.99. The postrepair percentage change in cross-sectional area at the repair site for the Adelaide group and barbed group was 12.0 ± 2.3 and 4.6 ± 2.8, respectively.

Conclusions:

We demonstrated that a 4-strand knotless, barbed method attained comparable strength to that of the traditional Adelaide repair technique. The barbed method had a significantly reduced cross-sectional area at the repair site compared with the Adelaide group. The 2-mm gap formation force was less in the barbed group than the Adelaide group. Barbed repairs show promise for tendon repairs; this simple method warrants further study in an animal model.

Tendon-holding capacities of two newly designed implants for tendon repair: an experimental study on the flexor digitorum profundus tendon of sheep

Background:

Two main factors determine the strength of tendon repair; the tensile strength of material and the gripping capacity of a suture configuration. Different repair techniques and suture materials were developed to increase the strength of repairs but none of techniques and suture materials seem to provide enough tensile strength with safety margins for early active mobilization. In order to overcome this problem tendon suturing implants are being developed. We designed two different suturing implants. The aim of this study was to measure tendon-holding capacities of these implants biomechanically and to compare them with frequently used suture techniques

Materials and Methods:

In this study we used 64 sheep flexor digitorum profundus tendons. Four study groups were formed and each group had 16 tendons. We applied model 1 and model 2 implant to the first 2 groups and Bunnell and locking-loop techniques to the 3rd and 4th groups respectively by using 5 Ticron sutures.

Results:

In 13 tendons in group 1 and 15 tendons in group 2 and in all tendons in group 3 and 4, implants and sutures pulled out of the tendon in longitudinal axis at the point of maximum load. The mean tensile strengths were the largest in group 1 and smallest in group 3.

Conclusion:

In conclusion, the new stainless steel tendon suturing implants applied from outside the tendons using steel wires enable a biomechanically stronger repair with less tendon trauma when compared to previously developed tendon repair implants and the traditional suturing techniques.

Sutured tendon repair; a multi-scale finite element model

Following rupture, tendons are sutured to reapproximate the severed ends and permit healing. Several repair techniques are employed clinically, with recent focus towards high-strength sutures, permitting early active mobilisation thus improving resultant joint mobility. However, the arrangement of suture repairs locally alters the loading environment experienced by the tendon. The extent of the augmented stress distribution and its effect on the tissue is unknown. Stress distribution cannot be established using traditional tensile testing, in vivo, or ex vivo study of suture repairs. We have developed a 3D finite element model of a Kessler suture repair employing multiscale modelling to represent tendon microstructure and incorporate its highly orthotropic behaviour into the tissue description. This was informed by ex vivo tensile testing of porcine flexor digitorum profundus tendon. The transverse modulus of the tendon was 0.2551 \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\pm $$\end{document}± 0.0818 MPa and 0.1035 \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\pm $$\end{document}± 0.0454 MPa in proximal and distal tendon samples, respectively, and the interfibrillar tissue modulus ranged from 0.1021 to 0.0416 MPa. We observed an elliptically shaped region of high stress around the suture anchor, consistent with a known region of acellularity which develop 72 h post-operatively and remain for at least a year. We also observed a stress shielded region close to the severed tendon ends, which may impair collagen fibre realignment during the remodelling stage of repair due to the lack of tensile stress.

Flexor tendon healing within the tendon sheath using bioabsorbable poly-L/D-lactide 96/4 suture. A histological in vivo study with rabbits

The bioabsorbable poly-L/D-lactide (PLDLA) 96/4 suture has good biomechanical and knot properties, and sufficient tensile strength half-life for flexor tendon repair. In the present study, the biocompatibility of PLDLA suture was compared with that of coated braided polyester suture in the rabbit flexor digitorum profundus tendon repaired within the tendon sheath. Postoperative unrestricted active mobilization was allowed. The tendons were studied histologically after 1-, 3-, 6-, 12-, 26-, and 52-week follow-ups. No differences were found in the biocompatibility between the suture materials, with only scattered multinuclear giant cells near the sutures in both groups from 6 weeks onwards. At 52 weeks, most of the PLDLA material was absorbed and the histological structure of the tendon appeared normal, whereas in the polyester repairs the suture knots filled the repair site, causing bulking of the tendon surface, and the collagen alignment appeared disoriented. The results suggest that the PLDLA 96/4 is a suitable suture material for flexor tendon repair.

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.

Two-stage desorption-controlled release of fluorescent dye and vitamin from solution-blown and electrospun nanofiber mats containing porogens

In the present work, a systematic study of the release kinetics of two embedded model drugs (one completely water soluble and one partially water soluble) from hydrophilic and hydrophobic nanofiber mats was conducted. Fluorescent dye Rhodamine B was used as a model hydrophilic drug in controlled release experiments after it was encapsulated in solution-blown soy-protein-containing hydrophilic nanofibers as well as in electrospun hydrophobic poly(ethylene terephthalate) (PET)-containing nanofibers. Vitamin B2 (riboflavin), a partially water-soluble model drug, was also encapsulated in hydrophobic PET-containing nanofiber mats, and its release kinetics was studied. The nanofiber mats were submerged in water, and the amount of drug released was tracked by fluorescence intensity. It was found that the release process saturates well below 100% release of the embedded compound. This is attributed to the fact that desorption is the limiting process in the release from biopolymer-containing nanofibers similar to the previously reported release from petroleum-derived polymer nanofibers. Release from monolithic as well as core-shell nanofibers was studied in the present work. Moreover, to facilitate the release and ultimately to approach 100% release, we also incorporated porogens, for example, poly(ethylene glycol), PEG. It was also found that the release rate can be controlled by the porogen choice in nanofibers. The effect of nanocracks created by leaching porogens on drug release was studied experimentally and evaluated theoretically, and the physical parameters characterizing the release process were established. The objective of the present work is a detailed experimental and theoretical investigation of controlled drug release from nanofibers facilitated by the presence of porogens. The novelty of this work is in forming nanofibers containing biodegradable and biocompatible soy proteins to facilitate controlled drug release as well as in measuring detailed quantitative characteristics of the desorption processes responsible for release of the model substance (fluorescent dye) and the vitamin (riboflavin) in the presence of porogens.

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

PURPOSE

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

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.

Flexor tenorrhaphy using absorbable suture materials

BACKGROUND

Nonabsorbable sutures are favorable for repairing flexor tendons. However, absorbable sutures have performed favorably in an animal model.

METHODS

Two-strand sutures using the interlocking modified Kessler method with polydioxanone absorbable sutures 4-0 were used to repair completely ruptured flexor tendons in 55 fingers from 41 consecutive patients. The medical records of average 42 follow up weeks were analyzed retrospectively. The data analyzed using the chi-squared test, and Fisher's exact test was used for postoperative complications. The results were compared with those of other studies.

RESULTS

Among the index, middle, ring, and little fingers were injured in 9, 17, 16, and 13 fingers, respectively. The injury levels varied from zone 1 to 5. Of the 55 digits in our study, there were 26 (47%) isolated flexor digitorum profundus (FDP) injuries and 29 (53%) combined FDP and with flexor digitorum superficialis injuries. Pulley repair was also conducted. Concomitant injuries of blood vessels and nerves were found in 17 patients (23 fingers); nerve injuries occurred in 5 patients (10 fingers). Two patients had ruptures (3.6%), and one patient had two adhesions (3.6%). Using the original Strickland criteria, all the patients were assessed to be excellent or good. Also, fibrosis and long-term foreign body tissue reactions such as stitch granuloma were less likely occurred in our study. Compared to the Cullen's report that used nonabsorbable sutures, there was no significant difference in the rupture or adhesion rates.

CONCLUSIONS

Therefore, this study suggests that appropriate absorbable core sutures can be used safely for flexor tendon repairs.

Biomechanical trial of modified flexor tendon sutures: an in vitro study

Proven benefits of early active mobilisation for intra-synovial flexor tendon repairs have inducted new criteria for a 'perfect suture'. This study has examined different variations of modified Kessler's suture, which could fulfil the new criteria. A total of 93 swine extensor tendons were transected, repaired and tested using a dynamometer with constant rate of extension. The first part of study tested clinically the most used modified Kessler suture, a variation of double modified Kessler suture and intact tendons as a control group. Further variations in the second part of study were due to type of suture, location and number of the knots and type of peripheral suture. According to the results, the tested version of double modified Kessler suture with crossed peripheral suture was the strongest one among all tested variations. The ultimate force for the authors preferred modification of the double modified Kessler (DMK) is significantly higher than modified Kessler suture. The version of DMK with crossed peripheral suture is the strongest one among all tested variations. The lowest strength manifests variation with two knots between tendon ends. The variations with interlocked and outsided knot or monofilament tread are not statistically significant regarding ultimate force. The frequency of suture failure events (suture pull out or tendon and/or suture rupture) is equal respecting braided or monofilament suture. The preferred modification of the double modified Kessler (DMK) suture with crossed peripheral suture is the strongest one among all tested variations and could achieve, concerning range of force, early active mobilisation. Further variations due to the type of thread and location, type and number of the knots did not show statistical significance.

Comparison of elastic versus rigid suture material for peripheral sutures in tendon repair

BACKGROUND

For secure tendon repair, while core suture materials have been previously investigated, the optimum material for peripheral sutures remains unclear.

METHODS

Transected bovine gastrocnemius tendons were repaired by 2-strand side-locking loop technique using no.2 braided polyblend polyethylene thread for the core suture. Then, 8-strand peripheral cross-stitches were added using either 2-0 rigid sutures (braided polyblend polyethylene) or USP 2-0-sized elastic sutures (nylon). The holding area of each peripheral suture was set at either 3 × 1 mm (shallow holding) or 6 × 2 mm (deep holding). Therefore, 4 groups were compared (the shallow-rigid, deep-rigid, shallow-elastic, and deep-elastic groups). The gap formation, ultimate tensile strength, and suture migration state were measured after 500 cyclic loadings (from 10 to 200 N).

METHODS

The shallow-rigid group had inferior outcomes compared to the other groups. Although the deep-rigid group had the smallest gap and highest ultimate strength, all peripheral sutures had failure prior to core suture rupture. The two elastic groups showed no significant differences, irrespective of the size of the holding area. Suture migration did not occur in the two elastic groups until the ultimate strength was reached and the core suture ruptured.

INTERPRETATION

Depending on the suturing method, rigid suture material may not be appropriate for peripheral sutures, when accompanying rigid core suture material. If peripheral sutures can be made with accurate deep holding, rigid suture material will provide favorable outcome. However, in other cases, elastic suture material is considered best for supporting a rigid core suture, as elasticity is another important factor for peripheral sutures.

[Flexor tendon surgery: advances in the field of hand surgery]

Reconstruction of the flexor tendon injuries is one of the most difficult problems in hand surgery, because the postoperative end-results are often unfavorable. The author discusses the history of the flexor tendon surgery, and then he describes the development of the knowledge regarding the anatomy, the blood supply and the tendon healing of the flexor tendons from the beginning until now. After that he describes the development in suture materials, suture techniques, primary and secondary tendon reconstruction operations, postoperative treatment and rehabilitation programmes. The author describes what kind of progress to be expected in this field in the near future, and then he expresses his viewpoint about the development in the international and national hand surgical societies. He encloses a detailed list of literature for those who are interested in the field.

[Mechanical behaviour of three types of surgical knots using 4/0 monofilament]

OBJECTIVE

To experimentally study the behaviour of 4 types of monofilament with 3 knotting techniques, very often used in surgery, employing mechanical tests.

MATERIAL AND METHODS

Four 4/0 monofilaments were chosen, two of nylon, and the other two of polypropylene. Three types of knot designs were made with each thread. The first design (D-S-S) consisted of a double half-knot (D) followed by one single (S) in the opposite direction, a third S in turn in the opposite direction. The configuration of the second design was D-S-D, and the third, S-S-D. A mechanical fracture test was performed by stretching the thread at a rate of 4N/s, the force and deformation being recorded at intervals of 100 ms.

RESULTS

There was a decrease in the force and deformation in the tests on threads with knots compared to threads without knots. In all cases the rupture of the thread occurred in the knot area, presumably due to damage caused to the thread during the knotting process. The D-S-D knot had the greatest resistance with polypropylene threads, and S-S-D provided the greatest resistance with nylon threads

CONCLUSIONS

Polypropylene threads, with D-S-D knots, should be more indicated to suture tissues that have to support great forces and with little deformation of the suture (e.g., tendons). Nylon threads, with S-S-D knots, would be better indicated for tissues that have to support smaller forces and that require greater elasticity (e.g., skin).

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.

Knot security: how many throws does it really take?

The purpose of this study was to determine the minimum number of throws needed for knot security for square knots using 5 common suture materials and 3 common sizes by in vitro single load to failure biomechanical testing. The hypothesis was that each suture combination studied would share a common minimum of at least 5 throws to guarantee security. Five suture materials (FiberWire [Arthrex, Inc, Naples, Florida], Monosof, Surgipro, Maxon, and Polysorb [Covidien, Mansfield, Massachusetts]) with varying suture sizes (#5, #2, 0, 2-0, and 4-0) were tied in vitro, varying the number of square knot throws (3, 4, 5, and 6). Twenty knots for each combination were statically loaded to failure in tension; whether the knot failed by fracture or slippage and the tensile strength at knot failure was determined. For the tested materials, at least 5 flat square throws should be used to confer knot security based on a binomial proportion score 95% confidence interval (CI) 0.84 to 1.0 or at least 4 throws for a 95% CI of 0.76 to 0.99. FiberWire requires 6 flat square throws per knot for security at either 95% CI level. Unless a surgeon has specific knowledge of experimental evidence that fewer throws are necessary for a specific application, the default should be a minimum of 4 throws, with 5 conferring additional security in most situations, and FiberWire requiring 6 throws.

An overview of the management of flexor tendon injuries

Flexor tendon injuries still remain a challenging condition to manage to ensure optimal outcome for the patient. Since the first flexor tendon repair was described by Kirchmayr in 1917, several approaches to flexor tendon injury have enabled successful repairs rates of 70-90%. Primary surgical repair results in better functional outcome compared to secondary repair or tendon graft surgery. Flexor tendon injury repair has been extensively researched and the literature demonstrates successful repair requires minimal gapping at the repair site or interference with tendon vascularity, secure suture knots, smooth junction of tendon end and having sufficient strength for healing. However, the exact surgical approach to achieve success being currently used among surgeons is still controversial. Therefore, this review aims to discuss the results of studies demonstrating the current knowledge regarding the optimal approach for flexor tendon repair. Post-operative rehabilitation for flexor tendon surgery is another area, which has caused extensive debate in hand surgery. The trend to more active mobilisation protocols seems to be favoured but further study in this area is needed to find the protocol, which achieves function and gliding but avoids rupture of the tendons. Lastly despite success following surgery complications commonly still occur post surgery, including adhesion formation, tendon rupture and stiffness of the joints. Therefore, this review aims to discuss the appropriate management of these difficulties post surgery. New techniques in management of flexor tendon will also be discussed including external laser devices, addition of growth factors and cytokines.

An analysis of the pull-out strength of 6 suture loop configurations in flexor tendons

PURPOSE

New, stronger suture materials have been introduced for flexor tendon surgery. The advantage of these materials can be lost if the suture loop pulls out from the tendon. The aim of this study was to compare the ability of various locking loops to grip the tendon.

METHODS

We inserted 4 different standard and 2 experimental locking loops with 200-μm nitinol wire into human cadaveric flexor digitorum profundus tendons. The standard loops were: group 1, cruciate; group 2, Pennington modified Kessler; group 3, cross-stitch; and group 4, Lim-Tsai. The experimental loops were: group 5, a composition of Pennington modified Kessler with a cross-stitch loop; and group 6, a locking Kessler type of loop with a superficial transverse component. We loaded the loops until failure. We recorded the pull-out strength and stiffness and documented failure mechanisms during the pull-out test.

RESULTS

The cruciate loop had the weakest holding capacity, 20 N, which was significantly less than in groups 2 to 6. The cross-stitch loop, Lim-Tsai loop, and modified Kessler loop performed similarly (36 N, 37 N, and 39 N, respectively). The experimental loops had the highest pull-out strength (group 5, 59 N; and group 6, 60 N, both significantly greater than groups 1 to 4). The mode of failure was pull-out for all of the standard loops and 7 of the experimental loops. Of 20 experimental loops, 13 failed by suture rupture.

CONCLUSIONS

The 2 experimental loop configurations demonstrated higher pull-out strength and may have advantages when used with newer and stronger suture materials. The number of the locking components in the loops and the way the tension is transmitted to the tendon fibrils explain the results.

CLINICAL RELEVANCE

The loops presented in this study and that grip the tendon better may be useful with new materials that have high tensile strength.

Flexor tendon repair with a knotless barbed suture: a comparative biomechanical study

PURPOSE

To test the hypothesis that a flexor tendon repair with only a knotless barbed suture technique provides a repair with a greater maximal load to failure and 2-mm gapping resistance than a traditional technique using a 4-strand core plus a running-locking epitendinous suture.

METHODS

We assigned 41 fresh-frozen cadaveric flexor digitorum profundus tendons for repair by either a traditional technique using a 4-strand core (Tajima and horizontal mattress) plus a running-locking epitendinous suture (n = 20) or a bidirectional barbed suture technique using a knotless, 4-strand core secured with 3 transverse passes (n = 21). A biomechanical study was performed on each tendon-suture construct and the tendons were linearly distracted to failure at 100 mm/min. The maximal tensile load to failure, 2-mm gapping tensile load, and mode of failure were determined and statistically compared.

RESULTS

The average maximal load to failure was not significantly different between the traditional repair (48 ± 12 N) and the barbed suture repair (50 ± 14 N). The average 2-mm gapping load was also insignificantly different between the traditional repair (42 ± 12 N) and the barbed suture repair (32 ± 9 N). The traditional repair failed by knot unraveling and suture rupture 35% and 65% of the time, respectively. The barbed suture repair failed by suture pull-out and rupture 67% and 33% of the time, respectively. The average load to failure by suture rupture was insignificantly different between the traditional repair (51 ± 13 N) and the barbed suture repair (63 ± 16 N). The average load to failure by knot unraveling using the traditional repair was 43 ± 11 N, whereas the average load to failure by suture pull-out using the barbed suture repair was 43 ± 8 N.

CONCLUSIONS

The barbed suture repair did not demonstrate a significant difference in maximal load to failure and 2-mm gapping resistance compared with the traditional method of repair.

CLINICAL RELEVANCE

This study examines the biomechanical differences between 2 types of flexor-tendon repair, which can help guide the surgical management for these injuries.

Comparison of a new multifilament stainless steel suture with frequently used sutures for flexor tendon repair

PURPOSE

To investigate the mechanical properties of some common suture materials currently in use and compare them with a new multifilament stainless steel suture.

METHODS

We investigated the mechanical properties of 3-0 and 4-0 Fiberwire, 3-0 Supramid, 3-0 Ethibond, and a new 3-0 and 4-0 multifilament stainless steel suture. All suture material was tested in a knotted configuration and all but the Supramid was tested in an unknotted configuration. We measured the load, elongation at failure, and stiffness during both tests.

RESULTS

The 4-0 multifilament stainless steel showed the least elongation, whereas the 3-0 multifilament stainless steel withstood the highest load of any material in both the knotted and unknotted tests. There was no difference in stiffness between the 3-0 and 4-0 multifilament stainless steel when untied; however, the 3-0 multifilament stainless steel was stiffer when tied. Soaking in a saline solution had no significant effect on the ultimate load, elongation at failure, or stiffness of any of the sutures. The 3-0 Fiberwire and 3-0 Ethibond required at least 5 throws to resist untying.

CONCLUSIONS

Multifilament stainless steel exhibited promising mechanical advantages over the other sutures tested. More research is needed to determine how this material will affect the clinical outcomes of primary flexor tendon repair.

CLINICAL RELEVANCE

With a secure attachment to the tendon, the multifilament stainless steel's lower elongation and better knot-holding ability may result in a higher force to produce a 2-mm gap and a higher ultimate tensile strength in a tendon repair.

Biomechanical evaluation of flexor tendon repair using barbed suture material: a comparative ex vivo study

PURPOSE

Barbed suture material for tendon repair opens up the possibility of a knotless reconstruction due to an increased suture-tendon interaction. The aim of this study was to compare the tensile strength of a knotted technique with a monofilament polydioxane suture to that of a knotless technique with a barbed suture material, by using a multistrand, modified Kirchmayr-Kessler tenorrhaphy.

METHODS

Sixty human flexor digitorum tendons were randomized into 4 groups. A modified, knotted, multistrand Kirchmayr-Kessler technique with an absorbable, monofilament polydioxane suture was compared with a modified, knotless, multistrand Kirchmayr-Kessler technique with an absorbable, unidirectional barbed glycolic-carbonate suture. Tendons were distracted to failure. Mode of failure and load to failure were recorded.

RESULTS

The knotless 2-strand Kirchmayr-Kessler barbed suture shows a significantly lower tensile strength than the knotted 2-strand polydioxane suture (p < .001). The comparison of the maximum tensile strength of the knotless (glycolic-carbonate) technique with that of the knotted (polydioxane) 4-strand technique resulted in no significant difference in either technique utilized (p = .737). The tensile strength of the 4-strand technique was greater than that of the corresponding 2-strand technique (p < .001).

CONCLUSIONS

The 2-strand Kirchmayr-Kessler barbed suture proved to be insufficient and significantly weaker than the 2-strand polydioxane suture, and therefore it cannot be recommended. With the knotless 4-strand Kirchmayr-Kessler technique, the barbed suture material has the potential to be used in flexor tendon surgery, but it has no advantage over the 4-strand polydioxane suture.

Influence of locking stitch size in a four-strand cross-locked cruciate flexor tendon repair

PURPOSE

The 4-strand cross-locked cruciate technique (Adelaide technique) for repairing flexor tendons in zone II is a favorable method in terms of strength and simplicity. The purpose of this study was to investigate the effects of varying the cross-lock stitch size in this repair technique. Outcomes measured were load to failure and gap formation.

METHODS

We harvested 22 deep flexor tendons from adult pig forelimbs and randomly allocated them into 2 groups. After cutting the tendons at a standard point, we performed a 4-strand cross-locked cruciate repair using 3-0 braided polyester with either 2-mm cross-locks (n = 11) or 4-mm cross-locks (n = 11). All repairs were completed with a simple running peripheral suture using 6-0 polypropylene. Repaired tendons were loaded to failure and the mechanism of failure, load to failure, stiffness, and load to 2-mm gap formation were determined.

RESULTS

All repairs failed by suture breakage; we noted no suture pullout. There was no difference in load to failure (71.7-71.1 N; p = .89) or stiffness (4.1-4.6 N/mm; p = .23) between the 2-mm cross-lock and the 4-mm cross-lock groups. There was a trend toward higher resistance to 2-mm gap formation with the 4-mm cross-locks (55-62.2 N; p = .07).

CONCLUSIONS

Four-strand cross-locked cruciate repairs with cross-lock sizes of 2 and 4 mm provide high tensile strength and are resistant to pullout. Repairs with 4-mm cross-locks tend to provide a more central load distribution and better gapping resistance than repairs with 2-mm cross-locks.

Nickel-titanium wire in circumferential suture of a flexor tendon repair: a comparison to polypropylene

PURPOSE

Nickel-titanium (NiTi) has been proposed as an alternative material for flexor tendon core suture. To our knowledge, its suitability as a circumferential suture of flexor tendon repair has not been investigated before. The purpose of this ex vivo study was to investigate the biomechanical properties of NiTi circumferential repairs and to compare them with commonly used polypropylene.

METHODS

Forty porcine flexor tendons were cut and repaired by simple running or interlocking mattress technique using 100 microm NiTi wire or 6-0 polypropylene.

RESULTS

The NiTi circumferential repairs showed superior stiffness, gap resistance, and load to failure when compared to polypropylene repairs with both techniques.

CONCLUSIONS

Nickel-titanium wire seems to be a potential material for circumferential repair of flexor tendons.

Cross-sectional area and strength differences of fiberwire, prolene, and ticron sutures

PURPOSE

Flexor tendons should be repaired with suture material strong enough to permit early motion and small enough for the resulting knot to allow unimpeded tendon glide and healing. This study sought to define differences in cross-sectional area and knotted tensile strength among Fiberwire, Prolene, and Ticron sutures.

METHODS

Five strands, each of 3-0 and 4-0 Prolene, Ticron, and Fiberwire sutures, were embedded in polymethylmethacrylate and sectioned in a linear precision saw to obtain 10 cross-sections of each material and size. These were examined by scanning electron microscopy and digitally analyzed for cross-sectional areas. Ten strands of each suture material and size had a single throw knot placed, and they were loaded to failure in a micromechanical tester.

RESULTS

Prolene and Ticron cross-sections were circular. Fiberwire was noncircular. The 3-0 Fiberwire sutures had greater cross-sectional area than the 3-0 Ticron sutures (p < .001), which in turn were larger than 3-0 Prolene (p < .05). The 4-0 Fiberwire cross-sectional area was also greater than that of 3-0 Ticron and Prolene (p < .05). After relating knotted tensile strength to cross-sectional area, Fiberwire was 10% stronger than Prolene, and 25% stronger than Ticron.

CONCLUSIONS

Fiberwire is not only stronger, but also larger than other sutures in the same or even higher suture size category. Failure to meet the United States Pharmacopeia standards for suture diameter is declared in the product information sheet, although surgeons may not be aware of these size variations. Suture size definitions are currently based on diameter, a consistent measure for circular monofilament sutures, but not for braided or noncircular sutures.

A new technique for small and secure knots using slippery polyethylene sutures

BACKGROUND

Suture knots used in tendon surgery must be strong but small enough so that they do not hinder gliding. For this purpose, we devised a unique "antislip" knot.

METHODS

Three suture materials were used: Ethibond, Fiberwire, and Nespron. They were tied with either the antislip knot using a pair of United States Pharmacopeia (USP) 2 sutures or with a conventional reef knot using USP2 single sutures. The volume and tensile strength of the knots were measured (n = 25 for each combination of suture and method).

FINDINGS

The maximum tensile strength was observed with Fiberwire antislip knots with five throws (mean 587 N) and six throws (mean 590 N), and Nespron antislip knots with five throws (mean 554 N) and six throws (mean 552 N); no significant differences were found among the four knots. Tensile strength per volume showed maximum values with Fiberwire antislip knots with four throws (mean 17.4 N/microl) and five throws (mean 16.8 N/microl), and Nespron antislip knots with four throws (mean 17.6 N/microl) and five throws (mean 16.8N/microl), which were not significantly different and were over 1.25-fold greater than the value for a reef knot. Ethibond had less tensile strength than Fiberwire and Nespron.

INTERPRETATION

The antislip knot is smaller for the same or greater strength than a conventional reef knot. The 4- or 5-throw antislip knot was most effective for slippery polyethylene sutures such as Fiberwire and Nespron. The antislip knot should improve biological healing of repaired tendons through accelerated rehabilitation.