Gap Formation Force Research Articles

Biomechanical Analysis of a New Odd-Numbered Strand Suture Technique for Early Active Mobilization After Primary Flexor Tendon Repair

PurposeThe placement of multi-strand sutures during flexor tendon repair is complex and challenging. We developed a new, simpler nine-strand suture, which we term the Tajima nines. The Tajima nines repair method is a new odd-numbered strand tendon technique. MethodsFourteen porcine flexor tendons were transected and repaired using the Tajima nines repair method, without placement of peripheral sutures. This technique is a modification of the Lim and Tsai repair method; it uses a 4-0 monofilament nylon, three-strand line, and two needles. The repaired tendons were tested for linear, noncyclic, load-to-failure tensile strength. The initial gap, 2-mm gap-formation force, and ultimate strength were measured. ResultsThe initial gap-formation force was 27.9 ± 7.5 newtons (N), the 2-mm gap-formation force was 39.2 ± 4.7 N, and the ultimate strength was 76.7 ± 17.2 N. Eight, three, and three of the fourteen tendons repaired using the Tajima nines method demonstrated failure because of thread breakage, knot failure, and suture pull-out, respectively. ConclusionsThis biomechanical study demonstrated that Tajima nines repair was associated with particularly high initial tension at the repair site; there were minor variations in the initial load and 2-mm gap-formation load. Our results suggest that Tajima nines repair with peripheral suturing allows the repaired flexor tendon to tolerate the stresses encountered during early active mobilization. Clinical RelevanceThis simple nine-strand technique will be particularly useful for inexperienced surgeons who perform early active mobilization after primary flexor tendon repair, because the technique is a modification of the Lim and Tsai repair method using a triple strand instead of a double strand.

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.

Abstract: A Comparison of Epitendinous Repair Techniques for Flexor Tenorraphy

INTRODUCTION: The purpose of the epitendinous component of flexor tendon repairs was originally thought to just “tidy-up” the repair site but it is now recognized that it has a structural role and contributes approximately 20% to the strength of the repair. Polypropylene (Prolene™) has been the most popular material for epitendinous repairs yet little research has been carried out on other materials. We hypothesized that a polyester (Ethibond™) epitendinous suture would significantly increase the overall tensile strength of flexor repairs compared to a traditional polypropylene suture in an ex-vivo porcine model. METHODS: Eighty porcine tendons were transected and randomly assigned to one of four repair groups; Group 1: 3-0 polyester core and 5-0 polyester epitendinous; Group 2: 3-0 polyester core and 5-0 polypropylene epitendinous; Group 3: 3-0 polypropylene core and 5-0 polyester epitendinous; and Group 4: 3-0 polypropylene core and 5-0 polypropylene epitendinous. A cross-locked cruciate technique was used for all core sutures. A simple continuous suture was utilized for the epitendinous repair in all groups. Biomechanical testing was carried out with a tensiometer and the ultimate strength, 2mm gap-formation force and method of failure were recorded. RESULTS: Group 1 (96.3 ± 15.77N) with 3-0 polyester core and 5-0 polyester epitendinous repairs had significantly greater tensile strengths and 2mm gap forces than the Groups 2,3 and 4 (70.12 ± 11.4N, 62.9 ± 8.52N and 46.27 ± 9.18N respectively). The addition of a running 5-0 polyester epitendinous repair significantly improved the tensile strengths of both Groups 2 and 3. CONCLUSION: This study has demonstrated that a running polyester epitendinous suture significantly augments the strength of flexor repairs when compared to a traditional epitendinous polypropylene suture. Further study is certainly warranted in animal models looking at different types of epitendinous repair techniques. The authors feel that a 5-0 polyester suture should be considered for the epitendinous component of flexor tenorraphy as we have demonstrated that it produces a stronger repair with less gapping than traditional techniques in a porcine model.

Double-Loop 10-Strand Flexor Tendon Repair

Purpose: To compare mechanical properties of a multistrand suture technique for flexor tendon repair with those of conventional suture methods through biomechanical and clinical studies. Methods: We describe a multistrand suture technique that is readily expandable from 6 to 10 strands of core suture. For biomechanical evaluation, 60 porcine flexor tendons were repaired using one of the following 6 suture techniques: Kessler (2-strand), locking cruciate (4-strand), Lim/Tsai’s 6-strand, and our modified techniques (6-, 8-, or 10-strand). Structural properties of each tenorrhaphy were determined through tensile testing (ultimate failure load and force at 2-mm gap formation). Clinically, we repaired 25 flexor tendons using the described 10-strand technique in zones 1 and 2. Final follow-up results were evaluated according to the criteria of Strickland and Glogovac. Results: In the biomechanical study, tensile properties were strongly affected by repair technique; tendons in the 10-strand group had approximately 106%, 66%, and 39% increased ultimate load to failure (average, 87 N) compared with those in the 4-, 6-, and 8-strand groups, respectively. Tendons in the 10-strand group withstood higher 2-mm gap formation forces (average, 41 N) than those with other suture methods (4-strand, 26 N; 6-strand, 27 N; and 8-strand, 33 N). Clinically, we obtained 21 excellent, 2 good, and 2 fair outcomes after a mean of 16 months (range, 6.53 months) of follow-up. No patients experienced poor results or rupture. Conclusions: The 10-strand suture repair technique not only increased ultimate strength and force at the 2-mm gap formation compared with conventional suture methods, but it also showed good clinical outcomes. This multistrand suture technique can greatly increase the gap resistance of surgical repair, facilitating early mobilization of the affected digit.

Flexor Tenorraphy

INTRODUCTION: Barbed sutures have a growing number of applications in plastic surgery from body contouring to facelifts. Several flexor tendon repair methods have been described using barbed devices yet these have resulted in exposed barbs on the tendon surface that would damage the intricate pulley system in-vivo1-3. We have previously described a barbed technique for flexor tenorraphy without exposed barbs4 (Figure 1). The purpose of this study was to test our novel barbed method using three commercially available barbed devices against a traditional polyester repair technique.Figure 1: The barbed repair technique. The arrows represent the direction of the suture passage.MATERIALS AND METHODS: Eighty porcine tendons were randomly assigned to one of the four repair groups (three barbed repairs, one cross-locked cruciate polyester repair group). The tendons were then transected and repaired. Cross-sectional area at the repair site was measured before and after repair. Biomechanical testing was carried out using a tensiometer and data recorded included ultimate strength, 2mm gap formation force and mode of failure. A running 5-0 epitendinous repair was carried out on all tendons using a 5-0 polypropylene suture. RESULTS: The V-Loc device performed the best out of the barbed devices in relation to ultimate strength and 2mm-gap-formation force (Table 1). In terms of ultimate strength, there was no significant difference between the Ethibond (90.4 ± 11.01 N) and the V-Loc device (88.16 ± 8.3 N). Following repair, the percentage increase in cross-sectional area at the repair site was significantly less in the V-Loc, Quill and Stratafix groups (3.1 ± 0.9%, 3.8 ± 1.1% and 2.9 ± 0.4% respectively) compared to the traditional polyester repair group (8.2 ± 3.7%).Table 1: Data from the biomechanical testing of all four groups. CSA = Cross-sectional area.CONCLUSION: We have demonstrated that the V-Loc barbed device has a comparable tensile strength to a traditional suture for flexor tendon repairs. The V-Loc performed the best out of the barbed sutures due to the larger barbs secondary to the dual angle cut in the barb manufacture. The Stratafix and Quill devices have smaller barbs secondary to a single angle manufactured cut. Furthermore, following repair, all barbed repair groups had a significantly reduced increase in cross-sectional area compared to the polyester repair group. In vivo, this would improve tendon gliding in zone II and lead to less gapping and rupture. Barbed sutures may represent the future of flexor tendon repairs but further study is definitely warranted.

Biomechanical Analysis of the Modified Kessler, Lahey, Adelaide, and Becker Sutures for Flexor Tendon Repair

To compare the biomechanical properties of the modified Kessler, Lahey, Adelaide, and Becker repairs, which are marked by either a locking-loop or a cross-lock configuration. Ninety-six lacerated porcine flexor tendons were repaired using the respective core suture and an epitendinous repair. Biomechanical testing was conducted under static and cyclic loads. Parameters of interest were 2-mm gap formation force, displacement during different loads, stiffness, maximum force, and mode of failure. The meaningful gap formation occurred in all 4 repairs at similar tension loads without any significant differences. Maximum force was highest in the Becker repair with a considerable difference compared with the modified Kessler and Lahey sutures. The Adelaide repair showed the highest stiffness. Overall, the displacement during cyclic loading demonstrated similar results with an exception between the Lahey and the Adelaide repairs at 10 Nload. Failure by suture pull-out occurred in 42% in the modified Kessler, in 38% in the Lahey, and in 4% in the Adelaide repairs. The Becker repair failed only by suture rupture. The results of our study suggest that the difference between the 4-strand repairs with a cross-lock or a locking-loop configuration is minor in regard to gap formation. A strong epitendinous suture and the application of core suture pretension might prevent differences in gapping. However, the modified Kessler and Lahey repairs had an inferior maximum tensile strength and were prone to early failure caused by the narrow locking loops with their limited locking power. We suggest that surgeons should use pre-tension in repaired tendons to improve gap resistance and should avoid narrow locking loop anchoring to the tendon.

A Mechanical Evaluation of Zone II Flexor Tendon Repair Using a Knotless Barbed Suture Versus a Traditional Braided Suture

To determine repair site bulk, gliding resistance, work of flexion, and 1-mm gap formation force in zone II flexor tendon lacerations repaired with knotless barbed or traditional braided suture. Transverse zone II lacerations of the flexor digitorum profundus (FDP) tendon were created in 36 digits from 6 matched human cadaveric pairs. Repair was performed with 2-0 barbed suture (n = 18) or 3-0 polyethylene braided suture (n = 18). Pre- and postrepair cross-sectional area was measured followed by quantification of gliding resistance and work of flexion during cyclic flexion-extension loading at 10 mm/min. Thereafter, the repaired tendons were loaded to failure. The force at 1 mm of gap formation was recorded. Repaired FDP tendon cross-sectional area increased significantly from intact, with no difference noted between suture types. Gliding resistance and work of flexion were significantly higher for both suture repairs; however, we identified no significant differences in either nondestructive biomechanical parameters between repair types. Average 1-mm gap formation force with the knotless barbed suture (52 N) was greater than that of the traditional braided suture (43 N). We identified no significant advantage in using knotless barbed suture for zone II FDP repair in our primary, nondestructive mechanical outcomes in this in vitro study. In vivo studies may be warranted to determine if one suture method has an advantage with respect to the parameters tested at 4, 6, and 12 plus weeks postrepair and the degree of adhesion formation. The combined laboratory and clinical data, in additional to cost considerations, may better define the role of barbed knotless suture for zone II flexor tendon repair.

Comparison of Flexor Tendon Suture Techniques Including 1 Using 10 Strands

To compare mechanical properties of a multistrand suture technique for flexor tendon repair with those of conventional suture methods through biomechanical and clinical studies. We describe a multistrand suture technique that is readily expandable from 6 to 10 strands of core suture. For biomechanical evaluation, 60 porcine flexor tendons were repaired using 1 of the following 6 suture techniques: Kessler (2-strand), locking cruciate (4-strand), Lim/Tsai's 6-strand, and our modified techniques (6-, 8-, or 10-strand). Structural properties of each tenorrhaphy were determined through tensile testing (ultimate failure load and force at 2-mm gap formation). Clinically we repaired 25 flexor tendons using the described 10-strand technique in zones I and II. Final follow-up results were evaluated according to the criteria of Strickland and Glogovac. In the biomechanical study, tensile properties were strongly affected by repair technique; tendons in the 10-strand group had approximately 106%, 66%, and 39% increased ultimate load to failure (average, 87 N) compared with those in the 4-, 6-, and 8-strand groups, respectively. Tendons in the 10-strand group withstood higher 2-mm gap formation forces (average, 41 N) than those with other suture methods (4-strand, 26 N; 6-strand, 27 N; and 8-strand, 33 N). Clinically, we obtained 21 excellent, 2 good, and 2 fair outcomes after a mean of 16 months (range, 6-53 mo) of follow-up. No patients experienced poor results or rupture. The 10-strand suture repair technique not only increased ultimate strength and force at the 2-mm gap formation compared with conventional suture methods, it also showed good clinical outcomes. This multistrand suture technique can greatly increase the gap resistance of surgical repair, facilitating early mobilization of the affected digit. Therapeutic IV.

Biomechanical Analysis of Flexor Tendon Repair Using Knotted Kessler and Bunnell Techniques and the Knotless Bunnell Technique

To evaluate a knotless Bunnell suture in flexor tendon repair. Eighty porcine flexor digitorum tendons were assigned to 4 different suture techniques. Group 1 was repaired using a modified 4-strand knotted Kessler suture and served as a control group. Group 2 was repaired using a 4-strand knotted Bunnell suture. Group 3 used a 4-strand knotless Bunnell suture. Group 4 used a 4-strand knotless Bunnell and knotless peripheral suture. Under static and cyclic testing we studied mode of failure, 2-mm gap formation force, displacement, and maximum load. The 4-strand knotless Bunnell suture did not show a notable difference with regard to 2-mm gap formation force, displacement, or maximum load in comparison to the modified 4-strand knotted Kessler suture. Adding a knotless peripheral suture improved the repair by a significant reduction of gap formation and displacement and an increase in maximum load. The 4-strand knotted Bunnell showed the highest maximum load but also a considerable lower resistance to gap formation and major displacement. Flexor tendon repair using a 4-strand knotless Bunnell suture showed similar tensile strength to a modified 4-strand knotted Kessler suture. Adding a knotless peripheral suture further improved the repair. A complete knotless 4-strand Bunnell suture including a barbed core- and peripheral suture might be an option for flexor tendon reconstruction.

A Barbed Suture Repair For Flexor Tendons

Background:Barbed suture technology has shown promise in flexor tendon repairs, as there is an even distribution of load and the need for a knot is eliminated. We propose that a quick and simple, novel, barbed technique without any exposed barbs on the tendon surface has comparable strength and a smaller cross-sectional area at the repair site than traditional methods of repair.Methods:Forty porcine flexor tendons were randomized to polybutester 4-strand barbed repair or to 4-strand Adelaide monofilament repair. The cross-sectional area was measured before and after repair. Biomechanical testing was carried out and 2-mm gap formation force, ultimate strength of repair, and method of failure were recorded.Results:The mean ultimate strength of the barbed repairs was 54.51 ± 17.9 while that of the Adelaide repairs was 53.17 ± 16.35. The mean 2-mm gap formation force for the barbed group was 44.71 ± 17.86 whereas that of the Adelaide group was 20.25 ± 4.99. The postrepair percentage change in cross-sectional area at the repair site for the Adelaide group and barbed group was 12.0 ± 2.3 and 4.6 ± 2.8, respectively.Conclusions:We demonstrated that a 4-strand knotless, barbed method attained comparable strength to that of the traditional Adelaide repair technique. The barbed method had a significantly reduced cross-sectional area at the repair site compared with the Adelaide group. The 2-mm gap formation force was less in the barbed group than the Adelaide group. Barbed repairs show promise for tendon repairs; this simple method warrants further study in an animal model.

Flexor tendons repair: Effect of core sutures caliber with increased number of suture strands and peripheral sutures. A sheep model

BackgroundSurgeons have aimed to achieve strong repair so as to begin early active rehabilitation programs for flexor tendon injury. Multi-strand suture techniques were developed to gain improved gap resistance and ultimate force compared with the respective two-strand techniques. In vivo studies indicate that multiple strands may cause ischemia during the intrinsic healing process by decreasing the total cross-sectional area of the injured site, unless the total cross-sectional area of the sutures is not decreased. HypothesisThe hypothesis was to design an in vitro study to understand the biomechanical relationship between suture calibers of core sutures with increased number of suture strands and peripheral suture on final repair strength. Materials and methodsSixty fresh sheep forelimb flexor digitorum profundus tendons were randomly placed into three groups (A, B, and C), each containing 20 specimens, for tendon repair. Two-, four-, and eight-strand suture techniques were respectively used in Groups A, B, and C. A simple running peripheral suture technique was used in Subgroups A2, B2, and C2. For each repaired tendon, the 2-mm gap-formation force, 2-mm gap-formation strength, maximum breaking force and maximum breaking strength were determined. ResultsDifferences in 2-mm gap-formation force and 2-mm gap-formation strength were found between Subgroups A1 and A2, B1 and B2, and C1 and C2. Between Groups A and B, A and C, and B and C, there was no difference as well. ConclusionBoth the number of strands and the ratio between the total suture volume and tendon volume at the repair site are important for ideal repair. If the total cross-sectional area of the sutures is equal in 2-strand, 4-strand, and 8-strand procedure, there is no difference in the strength of the repair. A decrease in caliber size suture requires more passes to achieve the same strength. Instead, it is much better to use peripheral suture techniques to improve the strength of the repair with larger diameter 2-strand core sutures.

The Effect of Asymmetric Core Suture Purchase on Gap Resistance of Tendon Repair in Linear Cyclic Loading

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

Effects of Tension Across the Tendon Repair Site on Tendon Gap and Ultimate Strength

Tendons repaired with varying amounts of tension result in different degrees of shortening of the tendon segment within core sutures, which may affect tensile strengths. We aimed to investigate the effects of tension across the repair site on gap formation forces and ultimate strength. Fifty-seven porcine flexor tendons were repaired with a 2-strand modified Kessler repair or a 4-strand cross-lock repair. For each type of repair, the tendons were divided into 3 groups: by 0%, 10%, or 20% shortening of tendon segment encompassed within core sutures. The repaired tendons had a single load-to-failure test in a materials testing machine. The forces required for initial and 2-mm gap formation and ultimate failure were recorded and statistically compared for each group. With either 2-strand or 4-strand repair, the tendons in the 10% tendon-segment shortening group withstood significantly higher initial and 2-mm gap formation forces than those in the group with no shortening, with average increases of 5 to 10 N after 10% shortening. Increasing the tendon-segment shortening to 20% produced a slight increase in the initial and 2-mm gap forces compared with those with 10% shortening, which was statistically significant only in the tendons with the 4-strand repair. The ultimate strengths were not significantly different among the tendons with either 2-strand or 4-strand repair of any degrees of shortening. Tensioning the core suture to shorten its encompassed tendon segment by 10% substantially increases resistance to postoperative gapping. Further tensioning to produce 20% shortening of the tendon segment increased the gapping forces by a much smaller amount. This study suggests that a slightly tensioned surgical repair, shortening the encompassed tendon segment by approximately 10%, is appropriate. Slightly tensioning core sutures across the tendon repair site, such as adding tension to cause 10% tendon-segment shortening, would greatly increase the gap resistance of the surgical repair.

Biomechanical Properties of a New Multilocking Loop Peripheral Suture Technique for the Repair of Flexor Tendons

We aimed to evaluate the biomechanical properties of a new multilocking loop peripheral suture technique. For this aim, 40-deep digital flexor tendons of adult male sheep front limb were divided and then repaired using one of the following methods: simple peripheral suture plus 2- or 4-strand Kessler core suture or a new multilocking loop peripheral suture combined with either 2- or 4-strand Kessler core suture. Intact tendons were used as controls. The following biomechanical parameters were tested: ultimate tensile strength, energy to failure, 2-mm gap formation force, stiffness, and mechanism of failure. Regardless of the number of core suture strands, the new technique resulted in greater ultimate tensile strength, energy to failure, 2-mm gap formation force, and stiffness values, compared with simple running peripheral suture. In conclusion, the new multilocking loop peripheral suture technique represents a biomechanically strong and technically suitable method for flexor tendon repair.

Flexor tendon repair using a new suture technique: a comparative in vitro biomechanical study.

The purpose of this experimental study was to evaluate the biomechanical characteristics of two new four-strand core suture techniques for flexor tendon repair. The two new suture techniques (Marburg 1, Marburg 2) are characterized by four longitudinal stitches which are anchored by a circular or semicircular suture. They were compared with three commonly used core suture techniques (modified Kessler, Tsuge, Bunnell). Fifty porcine flexor tendons were randomly assigned to one of the five core suture techniques. Outcome measures included ultimate tensile strength, maximum of lengthening, mode of failure and 1mm gap formation force. The highest ultimate tensile strength was found for the modified Kessler technique (115N). Both new techniques showed an ultimate load exceeding 50N (57N for Marburg 1, 54N for Marburg 2). The Marburg 1 technique showed the highest gap resistance of all tested suture techniques. The Bunnell and Tsuge core suture techniques produced the poorest mechanical performance. From these experimental results, the new Marburg 1 core suture technique can be considered for flexor tendon repair in a clinical setting with the use of active motion protocols.

Biomechanical study of four modified Kessler flexor tendon suture teclmiques

Objective To compare tensile strength of four different modified Kessler flexor tendon suture techniques. Methods Forty flexor digitorum profundus tendons of white pig hind limbs were transected and repaired using 4 suture techniques, with 10 tendons for each technique. The four suture techniques were Kessler, Double Kessler, Running suture and Kessler plus Running suture. After suturing, 2 mm gap formation force and failure load of the sutures were tested. One-way ANOVA was applied for statistic comparison of each technique. Results Double Kessler suture technique has the greatest tensile strength with its failure load, fonowed by Kessler plus Running suture, Kessler and Running suture. Kessler plus Running suture method had the greatest 2 mm gap formation force, followed by Double Kessler, Running suture and Kessler technique. Conclusion Kessler plus Running suture can better endure early finger active mobilization. Key words: Tendon injuries; Suture techniques; Biomechanics

Biomechanical Evaluation of a Four-Strand Modification of the Tang Method of Tendon Repair

We report a four-strand modification of the Tang technique of tendon repair that uses fewer sutures and fewer knots on the tendon surface. This repair consists of four longitudinal and two horizontal strands that form a "U" configuration within the tendon made with a single looped suture. Thirty-four fresh pig flexor tendons were divided into 3 groups and repaired with the four-strand modified Tang method, a double-looped four-strand method or a double Kessler repair (four-strand). The tendons were subjected to a single cycle of load-to-failure test in a tensile testing machine. The initial force, 2-mm gap formation force and ultimate strength of the four-strand modified Tang repair were statistically identical to those of the double looped suture and were superior to those of the double Kessler repair. Ultimate strength was 43.4+/-4.3N for the four-strand modified Tang method, 45.2+/-4.0N for the double-looped method and 39.1+/-4.0N for the double Kessler repair. The four-strand modification of the Tang method appears to have strength sufficient for protected active finger motion. Given our preliminary clinical experience with this method, we recommend this new and simplified technique for clinical flexor tendon repairs.

Effects of Locking Area on Strength of 2- and 4-Strand Locking Tendon Repairs

The area of the tendon within the locking suture configuration of the modified Pennington repair is an important determinant of eventual tendon strength. This 2-strand repair's loop configurations encompass a large cross-sectional area of the tendon. Many recently proposed repairs, however, consist of locks in a number of narrow sites on the tendon surface and most are multistranded. It is not clear how the area within the locks affects tendon strength and whether the effects of locking areas change according to the number of repair strands. In this study we investigate the effects of locking area on repair strength of 2- and 4-strand tendon repairs. Sixty-five fresh pig flexor tendons were divided equally into 6 groups and were transected completely. They were repaired with 2- or 4-strand techniques. The tendon-suture interface was a circle-locking junction and diameters of the locks were 1, 2, or 3 mm. The tendons were pulled in a tensile testing machine until failure of the repair and the mode of failure, 2-mm gap force, and ultimate strength were measured. In the tendons with either 2- or 4-strand repairs locks with a diameter of 2 or 3 mm had significantly greater gap formation force and ultimate strength than those of 1 mm. The gap formation and ultimate forces were not statistically different between tendons with locks of 2 or 3 mm in diameter. In both the 2- and 4-strand tendon repairs tested in this study repair strength increased as the diameter of locks of the repair increased from 1 mm to 2 or 3 mm. An increase in the diameter from 2 mm to 3 mm, however, did not increase the gap force and ultimate strength. These findings indicate that the cross-sectional area within the locks affects repair strength when the diameter of the locks is within a certain range (2 mm) and that further enlargement of the locking area does not increase strength.

Investigation of Locking Configurations for Tendon Repair

Locking sutures have proven beneficial to the strength of the repaired tendon. In this study we investigated the effects of 3 locks in the tendon-suture junction and their effect on repair strength. Forty-seven fresh pig flexor tendons were transected and repaired using 4-strand repairs with 3 different configurations of locks in each tendon-suture junction: 1 exposed cross-lock, 1 embedded cross-lock, and 1 circle lock. The tendons were subjected to a linear noncyclic load-to-failure test using a tensile testing machine. The initial gap, the 2-mm gap force, and the ultimate strength were measured to compare the biomechanical performance for each repair. Despite noticeable differences in the configurations of locks the gap formation force and ultimate strength were not significantly different among the 3 tested locking configurations. An exposed cross-lock, an embedded cross-lock, and a circle lock at tendon-suture junctions had similar locking power. Circle-lock repairs without cross-locking components produce tensile strength similar to cross-locking repairs. The findings of this study suggest that the creation of cross-configurations in locking repairs used conventionally by many surgeons is not essential to repair strength and that circle locking is as efficient as cross-locking in the repair of lacerated flexor tendons.

Repairs of partial oblique tendon injuries: a biomechanical evaluation

This study evaluated the tensile properties of oblique partial tendon lacerations and the effects of peripheral sutures on their strength. Seventy-four fresh pig flexor digitorum profundus tendons were divided into eight groups and were transected across 90% of their diameter. The lacerations in the tendons of five of the groups were at 0°, 15°, 30°, 45°, and 60° to their transverse cross-section, respectively. In the other three groups the lacerations were 0°, 45°, and 60° to the cross-section and were repaired with running peripheral sutures. The tendons were subjected to load-to-failure tests in a tensile testing machine to determine the initial, 1 and 2 mm gap formation forces, and the ultimate strength. Obliquity of tendon lacerations affected the strength of partially lacerated tendons. The tendons with 45° and 60°oblique lacerations had a significantly lower ultimate strengths than those with transverse (0°), or 15°or 30° oblique lacerations. Running peripheral sutures significantly increased both the gap formation forces and the ultimate strength of the tendons with oblique partial lacerations.