The strength of the 6-strand modified Kessler repair performed with triple-stranded or triple-stranded bound suture in a porcine extensor tendon model: an ex vivo study

Flexor digitorum profundus tendon injuries in Zone 2 repaired with a modified Mantero technique

From January 2010 to January 2017, 81 complete flexor digitorum profundus tendon disruptions in Zones 2B and 2C were treated using the modified Mantero technique. The patients were re-examined at a mean of 62 months (range 30-96) after operation. We analysed outcomes against ages, gender, pulley integrity, associated injuries and follow-up times. The median total range of motion of both interphalangeal joints, distal interphalangeal joint alone and Quick DASH scores were significantly better for the group with pulley vented versus no pulley vented. According to the Strickland and Glogovac criteria, 76 (91%) had excellent or good, five fair and none had poor results. There were no complications except for one deep and one superficial infection at the site of the injury. There were no tendon ruptures and only three patients (3.7%) required secondary tenolysis. The modified Mantero repair is recommended as an alternative in the repair of tendon disruptions in Zone 2B and 2C. The good results and absence of ruptures suggest that the tendon healing and strength of repair are adequate for immediate postoperative motion.Level of evidence: IV.

Risk of tendon failure with repeated passage of Kirschner wires or hypodermic needles: an experimental study

During hand surgery, tendons may be at risk of damage. This biomechanical study aims to assess the risk of tendon rupture due to passage of Kirschner wires or hypodermic needles. Porcine extensor tendons were divided into four groups. Group 1: a control group was tested to ensure that repeated stress alone did not cause failure. Group 2a: 1.1-mm Kirschner wires were hand pushed through tendons 50 times and then stressed to 40 N, repeated until tendon failure. In Group 2b, K-wires were passed while rotating using a drill. Group 3: the experiment was repeated using a 20 G hypodermic needle. Group 2a tendons required a median of 2450 passes (1150-3500) to propagate failure, Group 2b a median of 2250 (1200-3850) and Group 3a median of 200 passes (150-450). The risk of tendon rupture from wires or hypodermic needles in procedures appears very low.

Fine tuning of the side-to-side tenorrhaphy: A biomechanical study assessing different side-to-side suture techniques in a porcine tendon model

Recent studies conclude that a new technique for tendon transfers, the side-to-side tenorrhaphy by Fridén (FR) provides higher biomechanical stability than the established standard first described by Pulvertaft (PT). The aim of this study was to optimize side-to-side tenorrhaphies. We compared PT and FR tenorrhaphies as well as a potential improvement, termed Woven-Fridén tenorrhaphy (WF), with regard to biomechanical stability. Our results demonstrate superior biomechanical stability and lower bulk of FR and, in particular, WF over PT tenorrhaphies. The WF and FR technnique therefore seem to be a notable alternative to the established standard tenorrhaphy as they display lower bulk and higher stability, permitting successful immediate active mobilization after surgery.

Investigating mechanisms of tendon damage by measuring multi-scale recovery following tensile loading

Tendon pathology is associated with damage. While tendon damage is likely initiated by mechanical loading, little is known about the specific etiology. Damage is defined as an irreversible change in the microstructure that alters the macroscopic mechanical parameters. In tendon, the link between mechanical loading and microstructural damage, resulting in macroscopic changes, is not fully elucidated. In addition, tendon damage at the macroscale has been proposed to initiate when tendon is loaded beyond a strain threshold, yet the metrics to define the damage threshold are not determined. We conducted multi-scale mechanical testing to investigate the mechanism of tendon damage by simultaneously quantifying macroscale mechanical and microstructural changes. At the microscale, we observe full recovery of the fibril strain and only partial recovery of the interfibrillar sliding, indicating that the damage initiates at the interfibrillar structures. We show that non-recoverable sliding is a mechanism for tendon damage and is responsible for the macroscale decreased linear modulus and elongated toe-region observed at the fascicle-level, and these macroscale properties are appropriate metrics that reflect tendon damage. We concluded that the inflection point of the stress-strain curve represents the damage threshold and, therefore, may be a useful parameter for future studies. Establishing the mechanism of damage at multiple length scales can improve prevention and rehabilitation strategies for tendon pathology.

STATEMENT OF SIGNIFICANCE

Tendon pathology is associated with mechanically induced damage. Damage, as defined in engineering, is an irreversible change in microstructure that alters the macroscopic mechanical properties. Although microstructural damage and changes to macroscale mechanics are likely, this link to microstructural change was not yet established. We conducted multiscale mechanical testing to investigate the mechanism of tendon damage by simultaneously quantifying macroscale mechanical and microstructural changes. We showed that non-recoverable sliding between collagen fibrils is a mechanism for tendon damage. Establishing the mechanism of damage at multiple length scales can improve prevention and rehabilitation strategies for tendon pathology.

Advances in Quantification of Meniscus Tensile Mechanics Including Nonlinearity, Yield, and Failure

The meniscus provides crucial knee function and damage to it leads to osteoarthritis of the articular cartilage. Accurate measurement of its mechanical properties is therefore important, but there is uncertainty about how the test procedure affects the results, and some key mechanical properties are reported using ad hoc criteria (modulus) or not reported at all (yield). This study quantifies the meniscus' stress-strain curve in circumferential and radial uniaxial tension. A fiber recruitment model was used to represent the toe region of the stress-strain curve, and new reproducible and objective procedures were implemented for identifying the yield point and measuring the elastic modulus. Patterns of strain heterogeneity were identified using strain field measurements. To resolve uncertainty regarding whether rupture location (i.e., midsubstance rupture versus at-grip rupture) influences the measured mechanical properties, types of rupture were classified in detail and compared. Dogbone (DB)-shaped specimens are often used to promote midsubstance rupture; to determine if this is effective, we compared DB and rectangle (R) specimens in both the radial and circumferential directions. In circumferential testing, we also compared expanded tab (ET) specimens under the hypothesis that this shape would more effectively secure the meniscus' curved fibers and thus produce a stiffer response. The fiber recruitment model produced excellent fits to the data. Full fiber recruitment occurred approximately at the yield point, strongly supporting the model's physical interpretation. The strain fields, especially shear and transverse strain, were extremely heterogeneous. The shear strain field was arranged in pronounced bands of alternating positive and negative strain in a pattern similar to the fascicle structure. The site and extent of failure showed great variation, but did not affect the measured mechanical properties. In circumferential tension, ET specimens underwent earlier and more rapid fiber recruitment, had less stretch at yield, and had greater elastic modulus and peak stress. No significant differences were observed between R and DB specimens in either circumferential or radial tension. Based on these results, ET specimens are recommended for circumferential tests and R specimens for radial tests. In addition to the data obtained, the procedural and modeling advances made in this study are a significant step forward for meniscus research and are applicable to other fibrous soft tissues.

Clinical Results of Flexor Tendon Repair in Zone II Using a six Strand Double Loop Technique

The purpose of this study is to report the clinical results after repair of flexor tendon zone II injuries utilizing a 6-strand double-loop technique and early post-operative active rehabilitation. We retrospectively reviewed 22 patients involving 51 cases with zone II flexor tendon repair using a six strand double loop technique from September 1996 to December 2012. Most common mechanism of injuries was sharp lacerations (86.5 %). Tendon injuries occurred equally in manual and non-manual workers and were work-related in 33 % of the cases. The Strickland score for active range of motion (ROM) postoperatively was excellent and good in the majority of the cases (81 %). The rupture rate was 1.9 %. The six strand double loop technique for Zone II flexor tendon repair leads to good and excellent motion in the majority of patients and low re- rupture rate. It is clinically effective and allows for early postoperative active rehabilitation.

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.

Looped suture properties: implications for multistranded flexor tendon repair

Multiple-strand repair techniques are commonly used to repair cut flexor tendons to achieve initial biomechanical strength. Looped sutures achieve multiple strands with fewer passes and less technical complexity. Their biomechanical performance in comparison with an equivalent repair using a single-stranded suture is uncertain. This study examined the mechanical properties of double-stranded loops of 3-0 and 4-0 braided polyester (Ticron) and polypropylene monofilament (Prolene). Double loops were generally less than twice the strength of a single loop. Ticron and Prolene had the same strengths, but Ticron was stiffer. The 4-0 double loops had significantly higher stiffness than 3-0 single loops. Increasing the size of sutures had a larger relative effect on strength than using a double-stranded suture. However, a double-strand loop had a larger effect on increasing stiffness than using a single suture of a larger equivalent size. Looped suture repairs should be compared with standard techniques using a thicker single suture.

A new modified Tsuge suture for flexor tendon repairs: the biomechanical analysis and clinical application

Purpose

This study is to develop a new suturing technique for flexor tendon repair by modifying the extant Tsuge repair techniques and to use biomechanical analysis to compare the new method with four established repair techniques and evaluate its clinical efficacy in the repair of 47 flexor tendons in 22 patients.

Methods

The biomechanical analysis relied on 50 flexor digitorum profundus tendons harvested from fresh cadavers. The tendons were randomly divided into five groups, transected, and repaired by use of a 1. double-loop suture, 2. double modified locking Kessler, 3. four-strand Savage, 4. modified six-strand Savage, and 5. the new technique. The tensile force and breaking force of all repaired tendons were measured by static loading trials. For clinical application, 22 patients with acute flexor tendon injuries were treated with the new modified Tsuge suture and follow-up for more than 12 months.

Results

While differences in the tensile force and breaking force in the modified Tsuge sutures and modified six-strand Savage sutures were not statistically significant, static loading trials showed the tensile force, in the form of a 2-mm gap formation, and the breaking force of the new modified Tsuge sutures were, statistically, both higher than the ones characteristic of double-loop sutures, double modified locking Kessler, and four-strand Savage sutures. After 12 months, restored functions were observed in all the patients during the postoperative 12 months. Total active motion (TAM) score demonstrated that more than 90% fingers were estimated as excellent or good.

Conclusion

The new modified Tsuge sutures described here have evident higher tensile and breaking forces compared to other four-strand core suture techniques, suggesting, in turn, that this new technique is a good alternative for flexor tendon repairs in clinical applications.

Modified Brunelli pull-out suture technique in zone II flexor tendon rupture: a fresh human cadaver study

PURPOSE

The aim of our study is to develop a suture technique that has sufficient strength of active mobilization.

METHODS

Thirty two fingers of six fresh human cadavers were divided into two groups. Flexor digitorum profundus (FDP) tendons in the study group were repaired by modified Brunelli suture technique and modified Kessler suture technique, while those in the control group were repaired by Modified Kessler suture technique. Flexion and extension movements were performed with 10 N of load, increasing 1 N at a time to the tendons in both groups. Rupture and significant gap formation was evaluated up to 20 N of load. In the study, to evaluate the resistance to active motion, 1000 times flexion and extension motion cycle was performed with a load of 20 N. The succeeding repaired tendons was also tested with flexion and extension movements increasing the load 1 N at a time.

RESULTS

In the study group, failure and significant gap formation on the repair zone were not observed after 20 N of load and 1000 times cyclic flexion and extension movements for resisting to active motion. The rupture and significant gap formation was observed on a average load of 98.43 ± 0.47 N. In the Modified Kessler suture technique, on the eight tendons before reaching the 20 N of load for resisting to active motion, and the remaining eight tendons, during the 20 N loaded motion cycle essential for active motion, rupture and significant gap formation was observed. The failure and significant gap formation was observed on a average load of 18.37 ± 1.89 N. It is measured that by accompanying Modified Brunelli suture to the Modified Kessler suture technique, the resistance was increased up to 5-6 times.

DISCUSSION

By the Modified Brunelli suture technique, active motion can be started to the finger without a dorsal block sling immediately after the surgery. Clinical Relavans: By the modified technique, the rehabilitation difficulty and joint stiffness will be minimized.

Tissue engineering in flexor tendon surgery: current state and future advances

Tissue engineering of flexor tendons addresses a challenge often faced by hand surgeons: the restoration of function and improvement of healing with a limited supply of donor tendons. Creating an engineered tendon construct is dependent upon understanding the normal healing mechanisms of the tendon and tendon sheath. The production of a tendon construct includes: creating a three-dimensional scaffold; seeding cells within the scaffold; encouraging cellular growth within the scaffold while maintaining a gliding surface; and finally ensuring mechanical strength. An effective construct incorporates these factors in its design, with the ultimate goal of creating tendon substitutes that are readily available to the reconstructive hand surgeon.

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

OBJECTIVE

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Comparison of the holding capacity of round monofilament, round multifilament, and flat multifilament nitinol suture loops in human cadaveric flexor tendon

Tendon repairs done with strong suture materials fail by suture pull out. To avoid pull out, suture loop needs to have a strong grip on the tendon. The aim of this study was to determine whether a single suture loop has a better grip of the tendon when multifilament or flat sutures are used compared with a conventional monofilament round suture. A cross-locking or simple grasping suture loop was placed into the distal end of a human cadaveric tendon using nitinol wire sutures in the following configurations: round monofilament (200 µm), round multifilament (4 × 100 µm), and flat multifilament (4 × 30 µm × 445 µm). The mean pull-out strength of the round multifilament (49.4 N) and flat multifilament sutures (50.7 N) were significantly higher than that of the round monofilament nitinol suture (36.5 N) when a locking loop was used. Suture grip can be improved by using a multifilament suture and a locking type of suture configuration.

Simplifying four-strand flexor tendon repair using double-stranded suture: a comparative ex vivo study on tensile strength and bulking

We have compared a simple four-strand flexor tendon repair, the single cross-stitch locked repair using a double-stranded suture (dsSCL) against two other four-strand repairs: the Pennington modified Kessler with double-stranded suture (dsPMK); and the cruciate cross-stitch locked repair with single-stranded suture (Modified Sandow). Thirty fresh frozen cadaveric flexor digitorum profundus tendons were transected and repaired with one of the core repair techniques using identical suture material and reinforced with identical peripheral sutures. Bulking at the repair site and tendon-suture junctions was measured. The tendons were subjected to linear load-to-failure testing. Results showed no significant difference in ultimate tensile strength between the Modified Sandow (36.8 N) and dsSCL (32.6 N) whereas the dsPMK was significantly weaker (26.8 N). There were no significant differences in 2 mm gap force, stiffness or bulk between the three repairs. We concluded that the simpler dsSCL repair is comparable to the modified Sandow repair in tensile strength, stiffness and bulking.

A study of the anatomy and repair strengths of porcine flexor and extensor tendons: are they appropriate experimental models?

Although both porcine flexor and extensor tendons have been used in tendon repair research, no studies have specifically studied the anatomical differences and repair strengths in both types of tendons. We used 12 pig trotters to observe the anatomy of these tendons and compared the 2 mm gap and ultimate strengths of flexor and extensor tendons. There were four annular (A1, A2, A3, and A4) pulleys and one oblique pulley, which form a fibro-osseous tunnel for the flexor tendons, but the anatomy of the porcine extensor tendons was markedly different from the human flexor or extensor tendons. The diameter of flexor tendons was significantly greater than that of the extensors. The 2 mm gap and ultimate strengths of the flexor tendon with either two-strand or four-strand repairs were significantly greater than those of the extensor tendon. We conclude that the porcine flexor tendon systems are similar to those in the human, but the extensor tendons are not similar to either the flexor or extensor tendons in humans. Flexor and extensor tendons have different repair strengths which should be taken into account when interpreting findings from investigations using these tendons.

Bioabsorbable poly-L/D-lactide (PLDLA) 96/4 triple-stranded bound suture in the modified Kessler repair: an ex vivo static and cyclic tensile testing study in a porcine extensor tendon model

Previously the biomechanical properties of the bioabsorbable poly-L: /D: -lactide (PLDLA) 96/4 suture were found suitable for flexor tendon repair. In this study, three PLDLA suture strands were bound together parallel to each other side-by-side to form a triple-stranded bound suture and the modified Kessler tendon repair was performed. The biomechanical properties of the PLDLA repair in porcine extensor tendons ex vivo were investigated with static and cyclic tensile testing. In both biomechanical tests, the strength of the PLDLA repair achieved the estimated forces needed to withstand active mobilization.