Porcine Flexor Digitorum Profundus Tendons Research Articles

Influence of the direction of suture strands on the tensile strength after flexor tendon repairs.

We assessed the influence of different directions of suture strands using the double Tsuge repair on the resistance to gap formation and mode of failure. In total, 25 porcine flexor digitorum profundus tendons were split into two groups. One group was repaired using a conventional double Tsuge suture created by two bands of looped suture placed longitudinally parallel (parallel method), and the other group was repaired using a new technique comprising two bands of looped suture placed in a crossed fashion in the anterior and posterior half of the tendon (cruciate method). The repaired tendons were subjected to linear, non-cyclic load-to-failure tensile testing. The cruciate method had a significantly higher mean load at a 2-mm gap tensile load (29.7 N [SD, 8.3]) than the parallel method (21.6 N [SD, 4.9]) and failed significantly more often due to suture pull-out. The direction of a core suture and its location within the tendon affect both gap resistance and the mode of failure of repair when using the double Tsuge suture technique, with a cruciate configuration achieving a greater gap resistance than a parallel one.

A pilot study on lengthening potentials and biomechanical effects of double and triple hemisection on tendon with slide lengthening

The current study explored the slide-lengthening potentials of double and triple hemisections and the biomechanical effects of different inter-hemisection distances. Forty-eight porcine flexor digitorum profundus tendons were divided into double- and triple-hemisection groups (Groups A and B) and a control group (Group C). Group A was divided into Group A1 (distance between hemisections were the same as Group B) and Group A2 (distance between hemisections corresponded to the greatest distance between hemisections in Group B). Biomechanical evaluation, motion analysis, and finite element analysis (FEA) were performed. Failure load of intact tendon was significantly highest among groups. When the distance was 4 cm, the failure load of Group A increased significantly. When the distance between the hemisections was 0.5 or 1 cm, the failure load of Group B was significantly lower than Group A. Tendon elongation and failure load of Group B were significantly lower than those in Group A when the greatest distance between hemisections was the same. Consequently, Double hemisections had a similar lengthening ability to that of triple hemisections with the same distance, but better when the distances between extreme hemisections matched. However, the driving force for the initiation of lengthening may be greater.

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 study of a newly developed continuous double knots technique compared with the 4-strand double-modified Kessler technique for flexor tendon repair

PurposeIn this study we compare the biomechanical properties of a novel suture technique that we developed called the continuous double knots technique for repairing flexor tendon injuries with the standard 4-strand double-modified Kessler technique.MethodsThis was an experimental study. Eighty porcine flexor digitorum profundus tendons were harvested and divided randomly into two groups of 40. The first group (N = 40) was repaired using the 4-strand double modified Kessler technique and the second group (N = 40) was repaired using our new continuous double knots technique. The two groups were randomly divided and the ultimate failure load (n = 20) and cyclic testing to failure (n = 20) were compared.ResultsThe mean ultimate failure load was 25.90 ± 7.11 (N) and cyclic testing to failure 88 ± 47.87 (cycles) for the 4-strand double modified Kessler technique and 34.56 ± 6.60 (N) and 189 ± 66.36 (cycles) for our new continuous double knots technique. The T-test revealed a significant difference between the 2 techniques (p < 0.05). In terms of biomechanical properties in tendon repair, the continuous double knots technique group had a higher tensile strength than the 4-strand double-modified Kessler technique group. There were also significant differences between the ultimate failure load and cyclic testing to failure for the flexor tendon sutures.ConclusionsThe continuous double knots technique suture technique had significantly higher maximum tensile strength and cyclic testing than the 4-strand double modified Kessler technique in an in vitro study, and in thus an optional technique for flexor tendon repair.

Transosseous Sutures in Tendon-to-Bone Repairs: the Role of the Epitendinous Suture

Background: Numerous transosseous fixation techniques for flexor tendon injuries in Zone 1 of the hand have been described in the literature. While relatively high maximal loads to failure are documented in different biomechanical experiments, several tests revealed a low 2 mm gapping resistance of the tendon-to-bone repairs. We therefore aimed to investigate the effect on gap formation adding a peripheral suture to an established transosseous fixation technique. In addition, we analyzed the influence of different suture materials (braided vs. non-braided) on the stability of the core suture. Method: A total of 30 porcine flexor digitorum profundus tendons were divided into 3 groups (n = 10 each) and repaired using the transverse intraosseous loop technique (TILT). In group 1 and group 2 the repairs were performed using PDS 3-0 or Ethibond 3-0, respectively. In group 3, a peripheral suture was added to the core suture (PDS 3-0) consisting of two figure-of-eight stitches with PDS 5-0. The biomechanical performance of the repaired tendons was analyzed using a standardized protocol. Results: The suture material and peripheral suture showed no effect on the ultimate failure load in our testing. However, the addition of a peripheral suture led to a statistically significantly higher 2 mm gap force when compared with the repair with a core suture only. Conclusion: In conclusion, addition of a palmar epitendinous suture to the transosseous core suture significantly increases the load to 2 mm gap formation in Zone 1 flexor tendon repairs and thus allows an immediate controlled mobilization.

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.

The Management of Partial Zone II Intrasynovial Flexor Tendon Lacerations: A Literature Review of Biomechanics, Clinical Outcomes, and Complications

Sir: We read with great interest the recent article entitled “The Management of Partial Zone II Intrasynovial Flexor Tendon Lacerations: A Literature Review of Biomechanics, Clinical Outcomes, and Complications,” by Lineberry et al.,1 published in Plastic and Reconstructive Surgery. We credit the authors for their extensive work in evaluating a large number of studies of variable methodologies, in an attempt to provide clarity on management of partial flexor tendon injuries. We agree with the authors’ conclusions that all suspected partial tendon lacerations should be explored surgically with direct visualization of the flexor tendon. However, we believe the authors are drawing conclusions from outdated research. Only four of 24 studies (16.6 percent) in this review were published after 2008. Over the past decade, there has been a dramatic evolution in flexor tendon management regarding suture material, tenorrhaphy techniques, and greater excursion on the repaired tendon postoperatively. Subsequently, we question the authors’ ability to make recommendations based on these studies, in particular, the grade (percent) of partial tendon laceration necessitating surgical repair and the type of tenorrhaphy when surgical intervention is required. Early active motion following flexor tendon repair encourages intrinsic healing and decreases adhesion formation.2 This postoperative therapy requires a strong, gap-free tenorrhaphy resisting forces up to 30 to 50 N.3,4 Gap formation within the repair is detrimental, as this correlates clinically to adhesion formation and rupture,5 especially for intrasynovial tendon injuries. Our department struggles to comprehend how a simple epitendinous-only repair in a partial flexor tendon laceration greater than 80 percent of the total tendon surface area can resist 2-mm gap formation during forces exerted during early active motion. Consequently, we conducted our own biomechanical assessment of 90 fresh porcine flexor digitorum profundus tendons. Partial lacerations of 70, 80, and 90 percent of the total tendon surface area were created with digital calipers. Thirty tendons in each partial laceration group were divided randomly into (1) no repair, (2) running epitendinous repair with 6-0 Prolene (Ethicon, Inc., Edinburgh, United Kingdom), and (3) four-strand Adelaide technique core repair with 3-0 Ethibond (Ethicon) with an epitendinous suture. Our findings support the authors’ conclusions that nonrepaired partial tendon lacerations of 90 percent have enough residual strength to resist rupture during early active motion. However, the forces creating 2-mm gap formation in partial lacerations of 80 percent (4.9 N) and 90 percent (3.8 N) are well below the requirements for early active motion. Tenorrhaphy with epitendinous sutures only increased resistance to the gapping to 25.1 N in the 80 percent and 15.9 N in the 90 percent partial laceration group. The addition of core suture significantly increased the resistance to 2-mm gap formation in both groups (p < 0.05). Results are displayed in Figure 1.Fig. 1.: A comparison of resistance to 2-mm gap formation between 70, 80, and 90 percent partial flexor digitorum profundus laceration.Up-to-date research on partial flexor tendon lacerations, as evident in this review, is rare. We have demonstrated that an epitendinous-only repair of partial tendon laceration greater than 80 percent does not provide adequate strength to prevent 2-mm gap formation during early active motion. We disagree with the authors’ conclusions and believe that partial tendon laceration greater than 80 percent should be managed similarly to a complete tendon laceration with both a core suture and an epitendinous suture. DISCLOSURE The authors have no financial interest to declare in relation to the content of this communication. Conor M. Sugrue, M.R.C.S., B.C.H., B.A.O.George Rahmani, M.R.C.S., B.C.H., B.A.O.Department of Plastic and Reconstructive SurgeryGalway University HospitalGalway, IrelandGSD CriúGalway, Ireland Jack L. Kelly, F.R.C.S.(Plast.)Department of Plastic and Reconstructive SurgeryGalway University HospitalGalway, Ireland

Biomechanical and microbiological effects of local vancomycin in anterior cruciate ligament (ACL) reconstruction: a porcine tendon model.

Although there is increasing evidence for the successful use of local vancomycin applied by soaked compresses during ACL reconstruction, there are still little data on its microbiological and biomechanical effects. Furthermore, exact dosage of vancomycin with respect to tendon stability and microbiological effectivity is still unknown. 63 porcine flexor digitorum profundus tendons were harvested under sterile conditions from fresh cadaver legs. After contamination with Staphylococcus epidermidis (S. epidermidis), tendons were wrapped into sterile compresses moistened with different concentrations of vancomycin for 10 or 20min. Sterile sodium chloride was used for control. After treatment, tendons were rolled onto blood-agar plates to test for residual bacterial contamination and tested for maximum load and stiffness using a uniaxial testing device with cryo-clamps for tendon fixation. Agar plates were checked after 1week of culture at 36°C for signs of bacterial growth. When applying vancomycin for only 10min, bacterial contamination was found in all dosage groups ranging from 28.6% contamination (n = 2 of 7 tendons) when using 10mg/ml up to 85.7% (n = 6 of 7 tendons) when using 1mg/ml. Applying vancomycin-soaked compresses for 20min, bacterial contamination was still found in the groups using 1mg/ml and 2.5mg/ml (contamination rate 85.7 and 42.9% respectively). When using 5mg/ml and 10mg/ml, no bacterial contamination could be perceived after 7days of culture. With regard to biomechanical properties, no differences were found regarding maximum load or Young's modulus between groups. This study showed no signs of biomechanical impairment of porcine flexor tendons after the use of vancomycin wraps with concentration ranging from 1 to 10mg/ml for 10 or 20min at a time zero testing. Contamination with S. epidermidis was cleansed in 100% of tendons when using at least 5mg/ml of vancomycin for 20min.

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.

Biomechanical investigation of uneven load bearing in six-strand Lim-Tsai flexor tendon repair using FiberLoop®

We hypothesized that, in providing biomechanical strength, at least one of the two middle strands in a modified six-strand Lim-Tsai flexor tendon repair could be divided without obvious reduction in repair strength owing to uneven load bearing. A total of 40 porcine flexor digitorum profundus tendons were repaired using the six-strand Lim-Tsai technique with a 4-0 FiberLoop® suture and then divided into four equal groups. (no cut, one middle strand cut, both middle strand cut, one side strand cut). The biomechanical performance of repaired tendons was tested and found to vary according to the location of the cuts.

Are porcine flexor digitorum profundus tendons suitable graft substitutes for human hamstring tendons in biomechanical in vitro-studies?

Although a plenty of studies exist assessing the strength of ligamentous fixation techniques using porcine flexor digitorum profundus tendons as graft substitutes for human hamstring tendons, there is no biomechanical study comparing these two tendons. To interpret the results obtained with porcine flexor digitorum profundus tendons, knowledge of their biomechanical properties is essential. The purpose of this study was to compare the biomechanical properties of human hamstring tendons and porcine flexor digitorum profundus tendons. A total of six human hamstring tendons and six porcine flexor digitorum profundus tendons were analysed in this study. Quadruple-bundle human hamstring tendons and double-bundle porcine flexor digitorum profundus tendons with a diameter of 9mm were used. Specimens were placed into a tensile loading fixation of a servohydraulic testing machine. Biomechanical analysis included pretensioning of the constructs at 50N for 10min following cyclic loading of 1500 cycles between 50 and 200N at 0.5Hz for measurement of elongation. Subsequently, ultimate failure load and failure mode analysis were performed with a ramp speed of 20mm/min. Human hamstring tendons showed significantly higher maximum load to failure values compared to porcine flexor digitorum profundus tendons (1597±179.6N vs. 1109±101.9N; p=0.035). Human hamstring tendons yielded significantly lower initial elongation during preload, but not during cyclical loading. When porcine flexor digitorum profundus tendons are used as graft substitutes for human hamstring tendons in biomechanical studies, maximum load to failure is underestimated while elongation is comparable to that of human hamstring tendons. Transferring results of biomechanical studies into clinical practice, the lower maximum load to failure of porcine flexor digitorum profundus tendons needs to be taken into consideration.

Close-looped graft suturing improves mechanical properties of interference screw fixation in ACL reconstruction

In anterior cruciate ligament reconstruction with looped soft-tissue grafts, an interference screw is frequently used for tibial fixation. This study compared three alternatives thought to improve the initial mechanical properties of direct bioabsorbable interference screw fixation: suturing the graft to close the loop, adding a supplementary staple, or increasing the oversize of the screw diameter relative to the bone tunnel from 1 to 2mm. Twenty-eight porcine tibiae and porcine flexor digitorum profundus tendons were randomized into four testing groups: a base fixation using 10-mm-diameter screw with open-looped graft, base fixation supplemented by an extracortical staple, base fixation but closing the looped graft by suturing its ends, and base fixation but using an 11-mm screw. Graft and bone tunnel diameters were 9mm in all specimens. Constructs were subjected to cyclic tensile load and finally pulled to failure to determine their structural properties. The main mode of failure in all groups was pull-out of tendon strands after slippage past the screw. The sutured graft group displayed significantly lower residual displacement (mean value reduction: 47-67%) and higher yield load (mean value increase: 38-54%) than any alternative tested. No other statistical differences were found. Suturing a soft-tissue graft to form a closed loop enhanced the initial mechanical properties of tibial fixation with a bioabsorbable interference screw in anterior cruciate ligament reconstructions using a porcine model, and thus, this may be an efficient means to help in reducing post-operative laxity and early clinical failure. No mechanical improvement was observed for an open-looped tendon graft by adding an extracortical staple to supplement the screw fixation or by increasing the oversize of the screw to tunnel diameter from 1 to 2mm.

A Knotless Flexor Tendon Repair Technique Using a Bidirectional Barbed Suture

Flexor tendon repairs using conventional suture require knots that enlarge the cross-sectional area at the repair site. This enlargement increases the force of finger flexion and jeopardizes the integrity of a nascent tendon repair during rehabilitation. The authors hypothesized that a knotless flexor tendon repair using bidirectional barbed suture has similar strength and with reduced cross-sectional area compared with traditional techniques. Sixty-six fresh porcine flexor digitorum profundus tendons were divided randomly into three groups. Tendons were transected and repaired with one of the following techniques: two-strand Kessler technique, four-strand Savage technique, or four-strand knotless technique. The cross-sectional area of each tendon was calculated at the repair site before and after repair. All tendons underwent mechanical testing to assess the 2-mm-gap formation force and ultimate strength. The 2-mm-gap formation force and ultimate strength of the Savage and knotless technique groups were not significantly different; however, both were significantly greater than those of the Kessler repair group (p<0.05). The repair-site cross-sectional area of tendons repaired with the knotless technique was significantly smaller than that of tendons repaired with the Kessler or Savage technique (p<0.01). Tendons repaired with the knotless technique also had a significantly smaller change in repair-site cross-sectional area (p<0.01). The authors demonstrate that knotless flexor tendon repair with barbed suture has equivalent strength and reduced repair-site cross-sectional area compared with traditional techniques. The smaller tendon profile may decrease gliding resistance, thus reducing the risk for postsurgical tendon rupture during rehabilitation.

Biomechanical Evaluation of a Novel Application of a Fixation Device for Bone-Tendon-Bone Graft (EndoButton CL BTB) to Soft-Tissue Grafts in Anatomic Double-Bundle Anterior Cruciate Ligament Reconstruction

The purpose of this biomechanical study was to compare the structural properties of the flexor tendon graft connected to the EndoButton CL BTB (ECL-BTB) (Smith & Nephew Endoscopy, Andover, MA), which is newly developed to fix the bone-tendon-bone graft, with those of the same graft connected to the EndoButton CL (ECL) (Smith & Nephew Endoscopy), which is commonly used as a standard fixation device. We randomly divided 40 porcine flexor digitorum profundus tendons into 4 groups. An ECL and an ECL-BTB were attached to the doubled tendon measuring 6 mm in diameter in groups I and II, respectively. An ECL and an ECL-BTB were attached to the doubled tendon measuring 7 mm in diameter in the same manner in groups III and IV, respectively. Tensile testing was performed with a tensile tester. The linear stiffness of the tendon-device composite (mean +/- SD) was 131.8 +/- 18.3 N/mm, 109.7 +/- 14.9 N/mm, 132.4 +/- 20.5 N/mm, and 123.8 +/- 10.7 N/mm in groups I, II, III, and IV, respectively. The 2-way analysis of variance (ANOVA) showed a significant difference (P = .0058) between the ECL and the ECL-BTB. Concerning the maximum load and the elongation at failure of the tendon-device composite, the 2-way ANOVA showed no significant difference between the 2 fixation devices. Regarding the cross-sectional area, the 2-way ANOVA indicated no significant difference between the 2 fixation devices. This study has shown that the maximum load of the flexor tendon graft connected to the ECL-BTB is similar to that of the ECL whereas the stiffness of the ECL-BTB is inferior to that of the ECL. This study has suggested that patients should not be permitted to perform vigorous activities in the early period after anterior cruciate ligament reconstruction by use of the ECL-BTB fixation technique, because of its low stiffness compared with the ECL device.

Comparison of Different Sizes of Bioabsorbable Interference Screws for Anterior Cruciate Ligament Reconstruction Using Bioabsorbable Bead Augmentation in a Porcine Model

The aim of this study was to compare the initial fixation strength of tendon grafts between different sizes of bioabsorbable interference screws (BioScrew; Linvatec, Largo, FL) with bioabsorbable bead (EndoPearl; Linvatec) augmentation through biomechanical analysis of a porcine femoral bone model. Forty pairs of porcine femurs and porcine flexor digitorum profundus tendons were divided into control and study groups. In the control group 8 x 30-mm BioScrews alone (n = 10) were inserted, whereas different sizes of BioScrews, measuring 7 x 30 mm (n = 10), 8 x 30 mm (n = 10), and 9 x 30 mm (n = 10), with 8-mm EndoPearl augmentation were inserted individually for fixation of tendon grafts in the study groups. All specimens were cyclically loaded with axial forces between 50 and 250 N at 1 Hz for 3,000 cycles and then incrementally loaded to failure at a rate of 150 mm/min. BioScrews with EndoPearl augmentation had a significantly higher failure load than BioScrews alone (8-mm BioScrew alone v 8-mm BioScrew and EndoPearl, P < .05). There were no significant differences in the ultimate failure load (8 mm v 7 mm and 9 mm, P = .201 and P = .871, respectively), stiffness (8 mm v 7 mm and 9 mm, P = .789 and P = .823, respectively), displacement (8 mm v 7 mm and 9 mm, P = .695 and P = .781, respectively), and bone mineral density (P = .728 for all comparisons) except insertion torque (8 mm v 7 mm and 9 mm, P = .045 and P = .518, respectively) between study groups. Less tendon laceration by the screw thread was noted in the group in which smaller-sized BioScrews were used. When EndoPearl augmentation was used, smaller-sized BioScrews (BioScrew size 1 mm smaller than bone tunnel) offered equivalent graft fixation strength to BioScrews of similar or larger sizes. Smaller-sized BioScrews can be chosen if EndoPearl augmentation has been used, and EndoPearl augmentation may reduce the risk of tendon rupture while BioScrews are inserted.