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

Inflammatory reaction to suture materials after flexor tendon repair. A retrospective study of 594 patients

We report granuloma formation after using FiberWire^® for flexor tendon repairs. Four subcutaneous granulomas were identified in 115 patients with FiberWire^® core sutures, none in 426 with braided polyester. Foreign body reactions were found in the granuloma cases. We suggest early suture removal if this specific complication is encountered.

A Biomechanical Comparison of Gliding Resistance between Modified Lim Tsai and Asymmetric Tendon Repair Techniques in Zone II Flexor Tendon Repairs

Background: Early active motion protocols have shown better functional outcomes in zone II flexor tendon lacerations. Different techniques of tendon repair have different effects on gliding resistance, which can impact tendon excursion and adhesion formation. For successful initiation of early active mobilisation, the repair technique should have high breaking strength and low gliding resistance. Previous studies have shown the Modified Lim-Tsai technique demonstrates these characteristics. The Asymmetric repair has also shown superior ultimate tensile strength. This study aims to compare the gliding resistance between the two techniques. Methods: FDP tendons from ten fresh frozen cadaveric fingers were randomly divided into two groups, transected completely distal to the sheath of the A2 pulley and repaired using either the Modified Lim-Tsai or Asymmetric technique. The core repair was performed with Supramid 4-0 looped sutures and circumferential epitendinous sutures were done with nylon monofilament Prolene 6-0 sutures. The gliding resistance and ultimate tensile strength were then tested. Results: The gliding resistance of the Asymmetric and Modified Lim-Tsai repair techniques were 0.2 and 0.95 N respectively. This difference was significant (p = 0.008). The Modified Lim-Tsai technique had a higher ultimate tensile strength and load to 2 mm gap formation, though this was not significant. Conclusions: Gliding resistance of the Asymmetric repair is significantly less than that of Modified Lim-Tsai. Ultimate tensile strength and load to 2 mm gap formation are comparable.

The consistency and reliability of six-strand and four-strand flexor tendon repairs: a comparative porcine cadaveric study

The aim of this study was to compare the consistency and reliability of the six-strand Gan modification of the Lim-Tsai flexor tendon repair with the four-strand Adelaide repair, both with 3-0 sutures and with eight to ten runs of simple 5-0 running peripheral suture as well as the influence of the surgeons' level of experience on the strength of the repair in a cadaveric animal setup. Thirty-nine surgeons repaired 78 porcine flexor digitorum profundus tendons with either the Adelaide technique (39 tendons) or the modified Lim-Tsai technique (39 tendons). Each repaired tendon was tested in a material testing machine under a single cycle load-to-failure test. The forces were recorded when the gap between the two tendon stumps reached 1 and 2 mm and when irreversible elongation or total rupture occurred. We found no significant differences in gap formation force and yielding strength of the tendons between the two methods. The surgeon's previous experience in tendon repairs did not improve the consistency, reliability or tensile strength of the repairs. We conclude that if a strong peripheral suture is added, the modified Lim-Tsai repair has the same technical reliability and consistency as the Adelaide repair in term of ultimate loading strength in this test setup.

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.

A Modified Flexor Tendon Suture Technique Combining Kessler and Loop Lock Flexor Tendon Sutures

OBJECTIVES

In the present study, a novel single knot tenorrhaphy was developed by combining the modified Kessler flexor tendon suture (MK) with the loop lock technique.

METHODS

A total of 48 porcine flexor digitorum profundus tendons were collected and randomly divided into six groups. The tendons were transversely cut and then repaired using six different techniques, the MK method, double knot Kessler-loop lock flexor tendon suture (DK), and single knot Kessler-loop lock flexor tendon suture (SK), each in combination with the epitendinous suture (P), and the same three techniques without P. Furthermore, by performing the load-to-failure tests, the biomechanical properties and the time taken to complete a repair, for each tenorrhaphy, were assessed.

RESULTS

Compared to the MK+P method, DK+P was more improved, thereby enhancing the ultimate tensile strength. The SK+P method, which required fewer knots than DK+P, was easier to perform. Moreover, the SK+P repair increased the force at a 2-mm gap formation, while requiring lesser knots than DK+P.

CONCLUSION

As opposed to the traditional MK+P method, the SK+P method was improved and exhibited better biomechanical properties, which may facilitate early mobilization after the 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.

An Exploratory Study Using Semi-Tabular Plate in Zone II Flexor Tendon Repair

Background: This study evaluated the feasibility of using a low-profile titanium (Ti) plate implant, also known as the Ti-button, for Zone II flexor tendon repair. We hypothesize that the use of the Ti-button can distribute the tensile force on the digital flexor tendons to achieve better biomechanical performance.

Methods: Twenty lacerated porcine flexor tendons were randomly divided into two groups and repaired using Ti-button or 6-strand modified Lim-Tsai technique. Ultimate tensile strength, load to 2 mm gap force, and mode of failure were recorded during a single cycle loading test. We also harvested twelve fingers with lacerated flexor digitorum profundus tendons from six fresh-frozen cadaver hands and repaired the tendons using either Ti-button method or modified Lim-Tsai technique. A custom-made bio-friction measurement jig was used to measure the gliding resistance and coefficient of friction of the tendon sheath interface at the A2 pulley.

Results: The ultimate tensile strength, load to 2 mm gap force, stiffness, and gliding resistance of the Ti-button repairs were 101.5 N, 25.7 N, 7.8 N/mm, and 2.2 N respectively. Ti-button repairs had significantly higher ultimate tensile strength and stiffness than the modified Lim-Tsai repair. However, Ti-button also increased the gliding resistance and coefficient of friction but there was no significant difference between the two repair techniques.

Conclusions: Ti-button repair displayed comparable mechanical properties to the traditional repair in terms of 2-mm gap formation and gliding resistance, but with a stronger repair construct. Thus, this deepened our interest to further investigate the potential of using Ti-button implant in Zone II flexor tendon repair by studying both the mechanical and biochemical (tendon healing) properties in more in-depth.

Flexor Tendon Injuries and Repairs: A Single Centre Experience

Background: Although flexor tendon injuries cause significant morbidities and socio-economic implications, there have been limited data on patient demographics, injury characteristics and surgical details. The aim of this study is to describe our experience in flexor tendon injuries and repairs.

Methods: We performed a retrospective study of all digital flexor tendon injuries that were repaired from January 2011 to December 2014. The collected data included patient demographics, injury characteristics and surgical details.

Results: A total of 214 patients, 308 digits with 446 flexor tendon repairs were identified. We found that males, non-residents, and 20–29 age group were most prone to flexor tendon injuries. Cleaners, labourers and related occupations were the most vulnerable. The mechanism of injury was usually work-related and mostly caused by glass. Most injuries involve both flexor digitorum profundus and flexor digitorum superficialis tendons. Concomitant digital nerve and vessel injuries were common. Most patients suffered zone 2 laceration of a single digit of the non-dominant hand. Most patients underwent procedures that lasted 1 to 2 hours, including multiple flexor tendon repairs, microsurgical repairs and other interventions.

Conclusions: This study is the largest study on patient demographics, injury characteristics and surgical details on flexor tendon injuries and repairs. It could be used to plan resources and policies for the management and prevention of flexor tendon injuries.

Biomechanical comparison of modified Lim/Tsai tendon repairs with intra- and extra-tendinous knots

We compared the Lim/Tsai tendon repair technique using an extra-tendinous knot with modification using an intra-tendinous knot. The ultimate tensile strength, load to 2 mm gap force, stiffness, mode of failure, location of failure, and time taken to repair each tendon were recorded during a single cycle loading test in 20 tendons with each repair method. We found that the ultimate tensile strength and 2 mm gap force of the modified Lim/Tsai repair with an extra-tendinous knot (56 SD 5 N and 14 SD 2 N, respectively) were statistically significantly higher than that of the modified Lim/Tsai repair with intra-tendinous knot (51 SD 7 N and 11 SD 2 N, respectively). We conclude that the modified Lim/Tsai repair with extra-tendinous knot is stronger, despite having the same number of core strands.

The effect of modified locking methods and suture materials on Zone II flexor tendon repair-An ex vivo study

The failure rate of intrasynovial tendon repair is high due to substantial elongation at the repair site and to the development of adhesions between the tendon’s surface and the surrounding digital sheath. To minimize these complications, we sought to reduce the incidence of gapping and to facilitate the initiation of early motion by improving the time zero structural properties of repair. The Winters-Gelberman 8-strand repair technique was modified by adding surface lock loops and by using Fiberwire suture material. Forty-eight canine flexor digitorum profundus tendons were transected and repaired with one of three 8-strand techniques (Pennington modified Kessler, half hitch loops, or surface locking Kessler) using either 3–0 Supramid or 4–0 Fiberwire suture. Biomechanical testing was performed to determine the physiologic and failure mode properties of the repairs. The surface locking Kessler technique improved repair maximum load, load necessary to create a 2 mm repair site gap, and yield force compared to the modified Kessler and half hitch loop techniques. Fiberwire suture improved maximum load, the load necessary to create a 2 mm repair site gap, stiffness, and yield force compared to Supramid suture. Failure occurred by both suture pull out and by suture breakage in the modified Kessler, Supramid suture repair group. Failure occurred consistently by suture breakage in the surface locking Kessler, Supramid suture repair group. These results reveal that a novel locking Kessler repair is significantly stronger than the current state-of-the art flexor tendon suture repair technique. The use of a surface locking Kessler technique with Fiberwire suture markedly improves the mechanical properties of intrasynovial tendon repair by reducing the risk of post-operative gapping and rupture.

Primary flexor tendons repair in zone 2: Current trends with GEMMSOR survey results

The repair of flexor tendon lesions in zone 2 remains a highly controversial subject in hand surgery. Currently, there is no consensus about the management of these lesions intra- and postoperatively, but the literature suggests that a solid suture will allow early active motion. We hypothesized that the management of flexor tendon injury in zone 2 varies widely. Two online surveys were conducted with surgeons and hand therapists. The questions captured the demographics of the surveyed population, surgical technique, common complications, postoperative management (duration of immobilization, type of splint, rehabilitation techniques and principles of self-rehabilitation). The responses were compared to current literature data. We collected 366 responses to the "surgery" survey and 206 responses to "rehabilitation" survey. Most surgeons performed suture repair with at least 4 strands (75.9%). Active rehabilitation protocols were used in 48.9% of cases. The "rehabilitation" survey underlined the lack of information provided to therapists by surgeons. Therapists used active protocols in 79.7% of cases. This study found a large variation in the management of flexor tendon injuries, which is not always consistent with current published recommendations. Ideally, the suture repair should be a 4-strand pattern with an epitendinous circumferential suture and a release of the pulley in the suture area. Mobilization and rehabilitation should be started on the 3rd day using an active protocol.

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.

Cyclic Testing of the 6-Strand Tang and Modified Lim-Tsai Flexor Tendon Repair Techniques

PURPOSE

In this study, we compared the Tang repair technique with the 6-strand modified Lim-Tsai repair technique under cyclic testing conditions.

METHODS

Twenty fresh-frozen porcine flexor tendons were randomized into 2 groups for repair with either the modified Lim-Tsai or the Tang technique using Supramid 4-0 core sutures and Ethilon 6-0 epitendinous running suture. The repaired tendons were subjected to 2 stage cyclic loading. The survival rate and gap formation at the repair site were recorded.

RESULTS

Tendons repaired by the Tang technique achieved an 80% survival rate. None of the modified Lim-Tsai repairs survived. The mean gap formed at the end of 1000 cycles was 1.09 mm in the Tang repairs compared with 4.15 mm in the modified Lim-Tsai repairs.

CONCLUSIONS

The Tang repair is biomechanically stronger than the modified Lim-Tsai repair under cyclic loading.

CLINICAL RELEVANCE

The Tang repair technique may exhibit a higher tolerance for active mobilization after surgery with less propensity for gap formation.

A Biomechanical Comparison Between Asymmetric Pennington Technique and Conventional Core Suture Techniques: 6-Strand Flexor Tendon Repair

PURPOSE

To evaluate the fatigue strength and gap sizes of the asymmetric Pennington technique compared with 2 conventional 6-strand core suture techniques: the triple-looped suture and the Yoshizu #1.

METHODS

We recorded the fatigue strength (forces × cycles) and gap sizes of a 6-strand flexor tendon repair with different core suture techniques under cyclic loading in 30 porcine tendons. The asymmetric Pennington technique was performed with a Pennington repair of equal suture purchase in the 2 tendon stumps, with the 2 other Pennington repairs shifted by 3 mm, respectively, along the longitudinal axis of the tendon in relation to the first Pennington repair. The triple-looped suture technique was made with triple Tsuge sutures. The Yoshizu #1 technique was performed with a combined Pennington repair (using a double strand) and Tsuge suture.

RESULTS

The asymmetric Pennington technique showed significantly greater fatigue strength and significantly smaller gaps in comparison to the triple-looped suture and Yoshizu #1 techniques.

CONCLUSIONS

This study demonstrated that the asymmetric Pennington technique generated increased fatigue strength and reduced gap sizes compared with 2 conventional 6-strand core suture techniques, the triple-looped suture and Yoshizu #1.

CLINICAL RELEVANCE

The asymmetric Pennington technique may permit an early active motion rehabilitation protocol similar to the triple-looped suture and Yoshizu #1 techniques.

A Biomechanical Study of a Novel Asymmetric 6-Strand Flexor Tendon Repair Using Porcine Tendons

BACKGROUND

This study evaluated the biomechanical performance of a novel asymmetric 6-strand flexor tendon repair technique without locking loops.

METHODS

Twenty porcine flexor tendons were equally repaired by using the asymmetric technique and compared with the modified Lim-Tsai repair technique. The ultimate tensile strength, load to 1-mm gap force, stiffness, and mechanism of failure were measured.

RESULTS

The asymmetric repair technique had significantly higher tensile strength (63.3 ± 3.7 N) than the modified Lim-Tsai repairs (46.7 ± 8.3 N).

CONCLUSIONS

A novel flexor tendon repair technique with improved biomechanical performance may be available for use in flexor tendon repairs.

Biomechanical comparison of the Lim/Tsai tendon repair with a modified method using a single looped suture

The Lim/Tsai tendon repair technique has been modified clinically to achieve a 6-strand repair using a single looped suture with one extratendinous knot. We compared biomechanical performance of the original and modified methods using 20 porcine flexor digitorum profundus tendons. The ultimate tensile strength, load to 2 mm gap force, mode of failure, and time taken to repair each tendon were recorded during a single cycle loading test in 10 tendons with each repair method. We found that despite having the same number of core strands, the single looped suture modified Lim/Tsai technique possessed significantly greater ultimate tensile strength and load to 2 mm gap force. Also, less repair time was required. We conclude that the modified 6-strand repair using a single looped suture has better mechanical performance than the original method. The difference likely was due to the changes in locations of the knots and subsequent load distribution during tendon loading.

A Biomechanical Analysis of the Interlock Suture and a Modified Kessler-Loop Lock Flexor Tendon Suture

OBJECTIVE

In this work, we attempted to develop a modified single-knot Kessler-loop lock suture technique and compare the biomechanical properties associated with this single-knot suture technique with those associated with the conventional modified Kessler and interlock suture techniques.

METHODS

In this experiment, a total of 18 porcine flexor digitorum profundus tendons were harvested and randomly divided into three groups. The tendons were transected and then repaired using three different techniques, including modified Kessler suture with peritendinous suture, interlock suture with peritendinous suture, and modified Kessler-loop lock suture with peritendinous suture. Times required for suturing were recorded and compared among groups. The groups were also compared with respect to 2-mm gap load, ultimate failure load, and gap at failure.

RESULTS

For tendon repair, compared with the conventional modified Kessler suture technique, the interlock and modified Kessler-loop lock suture techniques resulted in significantly improved biomechanical properties. However, there were no significant differences between the interlock and modified Kessler-loop lock techniques with respect to biomechanical properties, gap at failure, and time required.

CONCLUSIONS

The interlock and modified Kessler-loop lock techniques for flexor tendon sutures produce similar mechanical characteristics in vitro.

Outcomes After Flexor Tendon Repair Combined With the Application of Human Amniotic Membrane Allograft

PURPOSE

Clinically proven methods to prevent adhesion formation after flexor tendon repair have not yet been established. The aim of this pilot study was to assess the feasibility of amniotic membrane allograft as a mechanical barrier to decrease adhesion formation.

METHODS

Ten patients having flexor tendon injuries were planned to be recruited to the pilot study. The operative treatment consisted of tendon repair and fixation of amniotic membrane allograft around the repaired tendon. The primary outcome variable was the range of motion of the operated finger 6 months after the operation. Patients were monitored for infections and repair failures.

RESULTS

The study was terminated owing to unfavorable results after treatment of 5 patients. One patient had extensive stiffness and was subjected to tenolysis and joint release. Histopathological analysis of the tendon sheath revealed focal fibrosis. Another patient had a repair failure. The other 3 patients had fair to good results.

CONCLUSIONS

It seems improbable that the use of amniotic membrane allograft would yield clinically relevant improvement compared with the existing techniques. However, it remains unclear whether the unfavorable results are associated with technical factors, amniotic membrane allograft itself, or an irregular distribution of complications.

TYPE OF STUDY/LEVEL OF EVIDENCE

Therapeutic V.

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.

Effect of the Optimal Asymmetry on the Strength of Six-Strand Tendon Repair: An Ex Vivo Biomechanical Study

PURPOSE

To evaluate the mechanical properties of a 6-strand core suture repair with asymmetric purchase in the 2 tendon ends, in comparison with a repair with symmetric suture purchases.

METHODS

Under cyclic loading of the tendons, we recorded the fatigue strength (Forces × Cycles) of a 6-strand flexor tendon repair with different symmetry in the lengths of suture purchase in 60 porcine tendons. The symmetric repair was made with 3 groups of parallel Kessler repairs of equal suture purchase (10 mm from the cut end) in the 2 tendon stumps. The asymmetric core suture repairs were then made with a Kessler repair of equal suture purchase (10 mm from the cut end) in the 2 tendon stumps, and shifting 2 other Kessler repairs by 1, 2, 3, 4, or 5 mm, respectively, along the longitudinal axis of the tendon in relation to the first (symmetric) Kessler repair.

RESULTS

The core repairs with 2 mm or more asymmetry in suture purchases in 2 tendon ends showed significantly greater fatigue strength compared with those with symmetric suture placement. The core repairs with 3 mm or more asymmetry in suture purchases in 2 tendon ends showed significantly smaller gaps compared with those with symmetric suture placement.

CONCLUSIONS

The core repairs with 3 mm or more asymmetry in suture purchases in 2 tendon ends generated increased fatigue strength and reduced gap sizes compared with those with symmetric suture placement in an ex vivo porcine model.

CLINICAL RELEVANCE

An asymmetric core suture repair with 3 mm or more difference in purchase length may allow for earlier rehabilitation and reduce the risk of postoperative complications.

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.

Suture configurations and biomechanical properties of flexor tendon repairs by 16 hand surgeons in Finland

The aim of this study was to find out how common it is to modify standard core suture configurations in flexor tendon repair and whether the use of standard core suture configurations gives a stronger repair. A total of 16 hand surgeons or residents participated in a workshop, in which they were asked to draw the suture configurations they used and to repair a porcine tendon. The properties of the repaired tendons were measured. Seven participants used a standard core suture configuration, and nine used a modified core suture. The biomechanical properties of the repairs were not affected by modifications to the core suture. However, they were affected by the number and lengths of peripheral suture bites, type of peripheral suture and the location of the core suture knot.

Asymmetric six-strand core sutures enhance tendon fatigue strength and the optimal asymmetry

Under cyclic loading, we recorded the fatigue strength of a six-strand tendon repair with different symmetry in the lengths of suture purchase in two stumps of 120 dental rolls and in 30 porcine tendons. First, the strengths of the repairs with 1, 2, 3, 4 and 5 mm asymmetry were screened using the dental rolls. The asymmetric core suture repairs were then made with a Kessler repair of equal suture purchase (10 mm) in two tendon stumps, and shifting two other Kessler repairs by 1, 3 or 5 mm, respectively, along the longitudinal axis of the tendon in relation to the first (symmetric) Kessler repair. The core repairs with 3 mm or more asymmetry in suture purchases in two tendon ends showed significantly greater fatigue strength and significantly smaller gaps compared with 1 mm asymmetry in core suture repair. Our results support that asymmetric placement of core sutures in two tendon ends favour resisting gapping at the repair site and 3 mm or more asymmetry is needed to produce such beneficial effects.

Direct Radiological Visualization of Loading on Four Flexor Tendon Repair Suture Configurations

PURPOSE

To study the deformation of 4 suture configurations used in flexor tendon repair using fluoroscopy.

METHODS

All flexor tendon repair techniques have a longitudinal component, a link component, and/or a transverse component. We had previously described 4 types of link components, namely an arc (grasping loop), a simple loop (locking loop), a complex loop, and a knot. The effect of loading on suture configurations using each of these link components was tested in flexor tendon from the first ray of porcine feet. Forty flexor tendons were divided into 4 groups of 10 each, and one-half of a tendon repair was simulated on each group using 0.5 mm stainless steel wire. The tendons were mounted on a materials testing machine, and tensile force was applied until failure. The deformation of the suture within the tendon substance was observed using an image intensifier, and the maximal load to failure was measured.

RESULTS

The loading of the suture led to unraveling of the suture in an arc, constriction and unraveling in a simple loop, and initial constriction with no further change of the construct in the complex loop with no change in the knot design. The mean pullout strength of the complex loop was statistically greater than all the other 3 designs.

CONCLUSIONS

Each of the link component designs demonstrated unique deformation characteristics. The complex loop design had the strongest grasping ability.

CLINICAL RELEVANCE

This study identified the differences in the deformation characteristics of the 4 types of link components used in flexor tendon repair. This knowledge may allow for the development of better flexor tendon repair techniques and the adoption of a more precise classification of flexor tendon repair techniques.

Biomechanical Study of the Digital Flexor Tendon Sliding Lengthening Technique

PURPOSE

To compare the mechanical properties of sliding lengthening (SL) and Z-lengthening (ZL) for flexor tendon elongation used for conditions such as Volkmann contracture, cerebral palsy, and poststroke spasticity.

METHODS

We harvested 56 flexor tendons, including flexor pollicis longus tendons, flexor digitorum superficialis tendons (zones II to IV), and flexor digitorum profundus tendons (zones II to V) from 24 upper limbs of 12 fresh cadavers. Each tendon was harvested together with its homonymous tendon from the opposite side of the cadaver and paired. We used 28 pairs of tendons and divided them randomly into 4 groups depending on the lengthening distance (20 or 30 mm) and type of stitching (single or double mattress sutures). Then we divided each pair into either the SL or ZL group. Each group was composed of 7 specimens. The same surgeon lengthened all tendons and stitched them with 2-0 polyester sutures. We tested biomechanical tensile strength immediately after completing lengthening and suturing in each group.

RESULTS

Ultimate tensile strengths were: 23 N for the SL 20-mm lengthening and single mattress suture and 7 N for the ZL; 25 N for the SL 20-mm lengthening and double mattress suture and 10 N for the ZL; 15 N for the SL 30-mm lengthening and single mattress suture and 8 N for the ZL; and 18 N for the SL 30-mm lengthening and double mattress suture and 10 N for the ZL.

CONCLUSIONS

The SL technique may be a good alternative to the ZL technique because it provides higher ultimate tensile strength.

CLINICAL RELEVANCE

Because of its higher ultimate tensile strength, the SL technique may allow for earlier rehabilitation and reduced risk of postoperative complications.

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.

[Ligament bracing--augmented cruciate ligament sutures: biomechanical studies of a new treatment concept]

BACKGROUND

In the context of acute knee dislocations, suture repair of ruptured cruciate ligaments leads to good clinical results in 80% of cases. Disadvantages are low primary stability and subsequently secondary elongation of the sutured ligaments. In the present study, we compared primary stability of suture repair, reinforced by different suture augments, to cruciate ligament reconstruction.

OBJECTIVE

The concept of ligament bracing with transosseous suture repair of the cruciate ligaments and additional suture augmentation is biomechanically superior to cruciate ligament reconstruction.

MATERIAL AND METHODS

A total of 42 porcine knee joints divided into seven groups were examined. The stability of four different suture/augmentation combinations were compared to cruciate ligament reconstruction with human hamstring tendons. The investigational setup consisted of testing 1000 cycles with 20 N to 154 N load in a.-p. translation and 60° flexion. Elongation and load to failure were measured.

RESULTS

Neither reconstruction (3.13 ± 1.65 mm; 362 ± 51 N) nor augmented suture repair (1.89-2.5 mm; 464-624 N) achieved the primary stability of the intact cruciate ligament (0.63 ± 0.34 mm, 1012 ± 91 N). In comparison to ligament reconstruction, all four augmented suture repairs showed minor elongation in the cyclic test and a higher load to failure. The isolated suture repair showed poor results (6.79 ± 4.86 mm, 177 ± 73 N).

CONCLUSION

Augmented suture repair provides significantly higher stability compared with isolated suture repair and reconstruction with hamstring tendons. The concept of ligament bracing could be a promising future treatment option in acute knee dislocations. Clinical results remain to be seen.

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.

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.

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.

Evidence-based medicine: Flexor tendon repair

LEARNING OBJECTIVES

After studying this article, the participant should be able to: (1) Describe and apply the current evidence-based treatment of acute flexor tendon injuries. (2) Compare and contrast the current postoperative therapy regimens following repair of flexor tendons. (3) Apply an evidence-based decision-making process for suture techniques of flexor tendon injuries.

SUMMARY

Flexor tendon repair remains a challenge for hand surgeons to reliably obtain excellent results. Surgical decisions should rely on the surgeon's experience, outcome studies, and direct evidence. This review is a compilation of the evidence from the literature on optimizing outcomes for flexor tendon repair.

The effect of asymmetric core suture purchase on gap resistance of tendon repair in linear cyclic loading

PURPOSE

To evaluate the biomechanical properties of an asymmetric core suture for tendon repair.

METHODS

Sixty porcine flexor tendons were repaired with 3 different 4-strand sutures using different core suture purchases: 2 sets of identical purchases of 10 mm, 2 sets of asymmetric purchases (8 mm proximal/distal stump and 12 mm distal/proximal stump), and 2 sets of identical purchases of 12 mm. The tendons were subjected to the cyclic loading for 20 cycles. The number of tendons with gaps at each cycle, elongation of gap area between tendon ends and tendon segment, gap formation forces, and ultimate strengths were recorded.

RESULTS

Tendons repaired with the asymmetric core suture purchases had the smallest gaps during cyclic loading. The elongation of gaps and tendon segments were significantly smaller than those with symmetric suture purchase of 10 or 12 mm. The asymmetric core suture repair had significant higher gap resistance forces than the symmetric suture repair at the final loading cycle.

CONCLUSIONS

A 4-strand core suture repair with asymmetric purchases on the tendon stumps generated greater gapping resistance than that with an equal length of suture purchase.

CLINICAL RELEVANCE

The asymmetric core suture purchase may be a practical measure to improve gapping resistance and fatigue strength when the suture purchase meets essential length requirements.

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.

2D motion analysis of rabbits after Achilles tendon rupture repair and histological analysis of extracted tendons: can the number of animals be reduced by operating both hind legs simultaneously?

BACKGROUND

Considering the 3Rs principle in animal experiments, there is a demand to perform research experiments with the fewest number of animals possible while warranting the welfare of the animals. Orthopaedic experimental studies involving operations on the hind legs of rabbits are either performed on one hind leg with the second hind leg serving as control or on both hind legs simultaneously (control: rabbits with no operations at all).

METHODS

The Achilles tendon of rabbits was transected and sutured, and the two-dimensional motion pattern of animals having only one leg operated was compared to rabbits having both hind legs operated (control: non-treated animals). Step length, maximum ankle angle, minimum ankle angle and the resulting range of motion of both hind legs were determined weekly over a time span from 3 weeks to 12 weeks post-operation. The results were fitted by a linear mixed effects model including time dependency. Moreover, all tendon specimen were analysed histologically. Tenocyte and tenoblast density, tenocyte and tenoblast nuclei width, inflammation level and collagen fibre alignment were determined.

RESULTS

Statistically significant differences in the motion pattern were found when one-leg treated and two-leg treated animals were compared. However, the absolute differences were on average less than 20%. Histologically, 1-leg treated animals had tendon tissue with higher cell density, but lower inflammation and less ondulated collagen fibres compared to 2-leg treated animals; the nuclei width was the same for both groups. With regard to welfare, all animals were fine during the experiments.

CONCLUSIONS

While comparative studies should be performed with one-leg treated animals due to interaction effects, for proof-of-principle studies, operating two legs per animal may be justified as the welfare of the animals is warranted. This is a great benefit in the sense of the 3Rs because up to 50% of animals can be spared.

Outcomes and evaluation of flexor tendon repair

This article reviews recent reports of outcomes of flexor tendon repair and discusses the problems associated with such surgeries. Reports of no repair rupture in individual case series have emerged recently. Their results move toward the clinical goal of primary repair without repair rupture. The Strickland method remains the most common to record the outcomes. Outcomes should be provided by subzones of the tendon injuries, and the level of expertise of the surgeons expertise should be reported to allow comparisons of the results.