Investigation of locking configurations for tendon repair

PURPOSE: 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. METHODS: 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. RESULTS: 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. CONCLUSIONS: 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.     

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.     

Effects of locking area on strength of 2- and 4-strand locking tendon repairs

PURPOSE: 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. METHODS: 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. RESULTS: 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. CONCLUSIONS: 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.     

How much does a Pennington lock add to strength of a tendon repair?

Pennington advocated adding locking components to the Kessler-type repair to increase the repair strength, but did not actually test the repairs with this lock. Subsequent investigators have extensively cited that a Pennington lock is beneficial to the gain of repair strength. Thirty-three tendons were used to determine the exact strength differences between two grasping Kessler repairs and a Kessler repair with Pennington locks complemented with running peripheral suture. Two types of grasping repairs only had slightly lower resistance to gap formation compared with the repair with Pennington locks, and their ultimate strengths were not significantly different. We also compared the strength of four-strand Kessler repair with and without Pennington locks using 20 tendons, and found no difference in either gapping or ultimate strength. We conclude that a Pennington lock adds only a little to the capacity to gap resistance of a repair, but does not increase the ultimate strength.     

Flexor tendon repairs: the impact of fiberwire on grasping and locking core sutures

PURPOSE: Immediate surgical repair and early mobilization are essential in preventing adhesion formation and finger stiffness. A new polyethylene-based, braided suture material, Fiberwire (Arthrex, Naples, FL), touting increased strength, presents the potential for stronger repairs and, therefore, earlier active motion after surgery with a greater safety margin. The purpose of this biomechanic study was to investigate the differences in gap formation, tensile strength, and mode of failure for 2 distinct repair techniques using nylon, Ethibond (Ethicon, Somerville, NJ), and Fiberwire. METHODS: Human cadaver flexor tendons were harvested and repaired in a randomized fashion with either the Strickland or Massachusetts General Hospital (MGH) repairs using either nylon, Ethibond, or Fiberwire. Twelve tendons per group were repaired for each combination of material and method. During load-to-failure testing, 2-mm gap force and maximum tensile strength were statistically analyzed. RESULTS: Strickland repairs failed by suture pull-out in 74% of repairs, whereas 99% of the MGH repairs failed by suture breakage. For MGH repairs, Fiberwire suture provided significantly more tensile strength than Ethibond and nylon. For Strickland repairs, where the mode of failure was more often by suture pull-out rather than breakage, differences between type of suture were not significant. When comparing repair techniques using Fiberwire, the MGH repair was significantly stronger than the Strickland repair. CONCLUSIONS: Biomechanic testing shows that Fiberwire outperforms both Ethibond and nylon suture when using a locked flexor tendon repair suture (MGH repair) but not when using a grasping-type, nonlocking repair (Strickland repair).     

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.     

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

PURPOSE: To investigate the biomechanic influence of triple-stranded sutures and the spatial arrangement of the strands on the strength of the 6-strand Pennington modified Kessler repair. METHODS: In the present ex vivo study of pig extensor tendons 2 techniques were used: (1) triple-stranded suture (3 suture strands in the same needle) and (2) triple-stranded bound suture (3 suture strands in the same needle that were bound together, parallel to each other, side by side). The repairs were subjected to static tensile testing. RESULTS: The 6-strand modified Kessler repair performed with triple-stranded bound suture reached significantly higher yield force, ultimate force, and both partial and total 1-, 2-, and 3-mm gap forces compared with the repairs performed with triple-stranded suture. The stiffness and strain values at the yield point and at the ultimate point did not differ significantly. CONCLUSIONS: This experimental study introduces a way to improve the strength of the tendon repair. The triple-stranded bound suture significantly increased both the gap resistance and ultimate force of the 6-strand modified Kessler repair. We assume the improvements are due to increased holding capacity of the locking loops. The triple-stranded bound suture is easy to use and avoids several problems associated with traditional multistrand repairs. Further studies are needed before clinical use can be considered.     

Effects of direction of tendon lacerations on strength of tendon repairs

PURPOSE: We compared the tensile strength of different repair configurations on tendons with oblique and transverse lacerations. METHOD: Seventy-two fresh pig flexor tendons were divided randomly and repaired using the modified Kessler, the cruciate, or the 4-strand Massachusetts General Hospital (MGH) repair methods. The tendons were lacerated either transversely or obliquely. They were repaired with conventional and oblique suture repairs. The 2-mm gap formation force and ultimate strength were determined as biomechanical performance for each repair. RESULTS: The gap formation and ultimate strength of the tendons vary with orientations of tendon lacerations and suture methods. In the tendons repaired with the modified Kessler or the cruciate methods, the 2-mm gap formation and ultimate strength of obliquely cut tendons were significantly lower than those of transversely cut tendons. The obliquely placed modified Kessler or cruciate sutures significantly improved the repair strength in the tendons with an oblique laceration. In the tendons repaired with the MGH method, no statistical differences were found in the repair strength of obliquely and transversely lacerated tendons. CONCLUSIONS: The direction of tendon lacerations affects strength of certain repair configurations. The nonlocking modified Kessler or the cruciate tendon repairs are weakened considerably when the tendon laceration is oblique but their mechanical performance is strengthened by re-orienting the repair strands to lie parallel to the laceration. The cross-locked configuration of the MGH repair is not affected by the obliquity of the tendon laceration.     

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

Purpose

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

Methods

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

Results

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

Conclusions

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

Influence of core suture purchase length on strength of four-strand tendon repairs

PURPOSE: Recently the length of core suture purchase has been identified as a variable affecting the strength of tendon repairs. The influence of the length of the core suture purchase on the strength of multistrand locking and grasping suture repairs, however, has not been studied extensively in transversely lacerated tendons. We assessed the effects of the length of the core suture purchase on the strength of three 4-strand grasping or locking repair techniques. METHODS: Seventy-four fresh adult pig flexor tendons were cut transversely and repaired with 1 of 3 methods: double-modified Kessler, locking cruciate, and modified Savage. Each method was assessed using 2 different lengths of core suture purchase (1.0 and 0.4 cm). The tendons were subjected to a linear noncyclic load-to-failure test in a tensile testing machine. We recorded the forces required for gap formation, ultimate strength, stiffness of the tendon, and the mode of repair failure. RESULTS: The resistance to gap formation, the ultimate strength of all 3 repairs, and the stiffness of the tendons with the double-modified Kessler and modified Savage repairs decreased significantly as the length of core sutures decreased from 1.0 to 0.4 cm. Locking and grasping repairs had a similar decrease in strength when the purchase was decreased from 1.0 to 0.4 cm. All tendons with modified Savage repairs with 1.0-cm purchase failed by suture breakage and tendons with 0.4-cm purchase failed predominantly by pullout. CONCLUSIONS: The length of core suture purchase significantly affects the strength of these 4-strand tendon repairs. The forces required for gap formation and the ultimate failure of repairs with 0.4-cm purchase were 20% to 45% lower than those of the repairs with 1.0-cm purchase. Locking repairs did not show a greater capacity to offset the decrease in strength than grasping repairs when the length of core suture purchase was decreased from 1.0 to 0.4 cm. Our study indicates that the length of suture purchase directly influences the strength of both locking and grasping core tendon repair methods.     

Locking repairs for obliquely cut tendons: Effects of suture purchase and directions of locking circles

PURPOSE: Oblique cuts in tendons weaken conventional repairs but locking sutures improve the repair strength of the tendon. In this study we assessed how suture purchase and direction (or type) of locking sutures affect the repair strength. METHODS: Ninety-three fresh pig flexor tendons were transected obliquely (45 degrees to the long axis of the tendon) and repaired with either a locking Kessler repair (with perpendicular or horizontal locking circles) or a locking cruciate method (with oblique locking or perpendicular locking circles). The suture purchase in the short side of the tendon stump with a perpendicular locking Kessler repair ranged from 0.3 to 1.2 cm. The gap formation and ultimate strength were measured to compare the biomechanical performance for each repair. RESULTS: The repair strength increased significantly as the suture purchase increased from 0.3 to 1.0 cm in oblique tendon lacerations, with a suture span of 1.0 cm being the strongest. The strength decreased significantly when the span was 1.2 cm. The repairs with horizontal locking sutures were significantly weaker than those with perpendicular locking sutures. The locking cruciate repair with the perpendicular locking circles had strength identical to that of the cruciate with oblique locking circles. CONCLUSIONS: Both suture purchase and the direction of locking circles affect the repair strength remarkably. For locking repairs the suture purchase of 1.0 cm in an obliquely cut tendon produced the highest strength; the repairs with a purchase less than 0.4 cm had significantly reduced strength. The strength of the repairs with locking circles perpendicular to the long axis of the tendon was significantly greater than that of the repairs with locking circles parallel to the long axis of the tendon.     

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.     

Biomechanic comparison of the Teno Fix tendon repair device with the cruciate and modified Kessler techniques

PURPOSE: To compare the mechanical behavior of a novel internal tendon repair device with commonly used 2-strand and 4-strand repair techniques for zone II flexor tendon lacerations. METHODS: Thirty cadaveric flexor digitorum profundus tendons were randomized to 1 of 3 core sutures: (1) cruciate locked 4-strand technique, (2) modified Kessler 2-strand core suture technique, or (3) Teno Fix multifilament wire tendon repair device. Each repair was tested in the load control setting on a Instron controller coupled to an MTS materials testing machine load frame by using an incremental cyclic linear loading protocol. A differential variable reluctance transducer was used to record displacement across the repair site. Cyclic force (n-cycles) to 1-mm gap and repair failure was recorded using serial digital photography. RESULTS: There was no significant difference in differential variable reluctance transducer displacement between the cruciate, modified Kessler, and Teno Fix repairs. The cruciate repair had greater resistance to visual 1-mm repair-site gap formation and repair-site failure when compared with the Kessler and Teno Fix repairs. No significant difference was found between the modified Kessler repair and the Teno Fix repair. In all specimens, the epitenon suture failed before the core suture. Repair failure occurred by suture rupture in the 7 cruciate specimens that failed, with evidence of gap formation before failure. Seven of 10 modified Kessler repairs failed by suture rupture. All of the Teno Fix repairs failed by pullout of the metal anchor. CONCLUSIONS: The Teno Fix repair system did not confer a mechanical advantage over the locked cruciate or modified Kessler suture techniques for zone II lacerations in cadaveric flexor tendons during cyclic loading in a linear testing model. This information may help to define safe boundaries for postoperative rehabilitation when using this internal tendon repair device.     

A biomechanical analysis of suture materials and their influence on a four-strand flexor tendon repair

PURPOSE: Flexor tendon repair strength depends on the suture technique and the suture material used. Configurations that incorporate locking loops prevent sutures from pulling through the tendon but typically fail because of suture breakage. The choice of suture material therefore influences repair strength. This study investigated the mechanical properties of 5 nonabsorbable 4-0 suture materials (monofilament nylon, monofilament polypropylene, braided polyester, braided stainless steel wire, and braided polyethylene) and evaluated their performance when used in a locking 4-strand flexor tendon repair configuration. METHODS: Five samples of 2 strands of each suture type were tested mechanically to determine the material stiffness and ultimate load. In addition, 50 fresh porcine flexor tendons were divided and repaired with each of the 5 suture materials using a 4-strand single-cross technique. Gap force, ultimate strength, and stiffness were measured to compare biomechanical performance. RESULTS: All repairs failed by suture rupture at the locking loop. Fibrewire and stainless-steel sutures and repairs were significantly stronger and stiffer than the other suture types. The results for Prolene and Ethibond were similar in the tendon repair groups with respect to gap and ultimate forces although Ethibond provided significantly increased repair stiffness. Nylon sutures and repairs consistently produced the poorest mechanical performance in all outcome measures. CONCLUSIONS: Suture material strongly influences the biomechanical performance of multistrand tendon repairs and is an important consideration for the surgeon. Fibrewire and stainless steel are the most biomechanically suitable suture materials for flexor tendon repair whereas nylon is the least suitable. Further developments in suture materials are important for advancements in flexor tendon repair strength.     

Cross stitch peripheral tendon repair: a mechanical comparison with core stitch techniques

The purpose of this experimental study was to compare certain mechanical properties of a true epitendineal cross stitch suture with simple and double locking core tendon repairs. Using tensile strength and tendon lengthening until gap formation as measurement parameters, these three types of repair were tested in human flexor and extensor tendons from fresh cadavers. The peripheral cross stitch and the locked core repairs were found to have a greater lengthening capacity than the simple core suture, whereas the latter significantly better withstood axial load. Our findings established that, at least when used as a true epitendinous suture, the cross stitch technique alone was not suited for the repair of severed tendons. However, its design is particularly useful in preventing the suture site from potentially restrictive bulking.     

An assessment of the tensile properties and technical difficulties of two- and four-strand flexor tendon repairs

This study compares the mechanical properties of locking Kessler and four-strand flexor tendon repairs and examines for difficulties related to technical ability. Two trainee surgeons each carried out 10 locking Kessler and 10 four-strand single-cross flexor tendon repairs on an in vitro porcine model. Outcome measures included gap formation and ultimate forces, operative time and repair bulk. Ultimate force was 81% greater for the four-strand repair compared to the Kessler (52 N, SD 5, versus 29 N, SD 6). Operating times were similar between the two techniques (Kessler 10.0 minutes, four strand 10.1 minutes). Rupture force and operating times improved slightly during the study for the Kessler repairs, but in the four strand repairs results remained stable throughout the study. We conclude that the single-cross four-strand repair tolerates superior loads yet is no more technically demanding than the modified Kessler, and can be reliably performed without additional operating time.     

Zone I flexor digitorum profundus repair: an ex vivo biomechanical analysis of tendon to bone repair in cadavera

PURPOSE: Biomechanical studies of standard flexor digitorum profundus (FDP) tendon to bone repairs show ultimate strengths greater than the applied loads of early motion rehabilitation protocols. Strain data, however, indicate the potential for significant repair site gapping under these physiologic loads. Gaps in excess of 3 mm have been shown to prevent the time accrual of strength in midsubstance tendon repairs and may prevent the restoration of the normal architecture of the tendon-bone interface. Improving the time-zero tensile properties of FDP insertion site repairs may help obviate these issues and improve clinical outcomes. The purpose of this study was to evaluate the ex vivo biomechanical properties of 2 new repair techniques in comparison with the standard FDP tendon to distal phalanx cortical surface repair. METHODS: Thirty human cadaver FDP tendons were released from their insertion sites by sharp dissection and repaired to bone using 1 of 3 repair techniques. Load to failure testing was performed with a servohydraulic materials-testing system (model 8500R; Instron, Canton, MA) analyzing ultimate force, strain at 20 N, rigidity, force to 2-mm gap formation, and displacement at failure. RESULTS: The results of the failure tests indicate that repairs performed with the addition of a peripheral suture had a greater ultimate force, had increased resistance to gap formation, and had increased rigidity and decreased strain at 20 N compared with the tunnel-only and volar cortical surface to the distal phalanx repairs. Although there were no statistically significant differences in ultimate force or rigidity between the tunnel-only and volar cortical surface repairs, the tunnel-only repairs showed lower strain values and increased values for resistance to 2-mm gap formation when compared with the volar cortical surface repairs. There were no differences among any of the repair groups with regard to the magnitude of tendon displacement from the repair site at failure. CONCLUSIONS: The addition of a peripheral suture to the FDP tendon to bone tunnel repair construct improves the time-zero tensile properties as evidenced by statistically significant increases in ultimate force, rigidity, and resistance to gap formations of 2 mm. In comparison with a volar cortical surface repair, the bone tunnel-only repairs were effective at decreasing the amount of repair site strain during applied loads of 20 N. If these improved time-zero tensile properties persist during the early stages of healing, they may help decrease the incidence of repair-site gap formation associated with the forces of early motion rehabilitation protocols.     

Gliding characteristics and gap formation for locking and grasping tendon repairs: a biomechanical study in a human cadaver model

PURPOSE: The purpose of this study was to compare the frictional characteristics and mechanical properties of various locking and grasping suture techniques in a human in vitro model of flexor tendon repair. METHODS: Forty-five cadaveric human flexor digitorum profundus tendons were transected in zone II and repaired using 1 of 5 core suture methods (n = 9 per group): either grasping (modified grasping Kessler, modified Lee) or locking (Pennington, modified Pennington, locking Lee) loop suture techniques. All repairs used 4-0 Supramid looped core suture and an epitenon running suture of 6-0 nylon. Gliding resistance at the tendon-pulley interface was measured along with failure strength and gap formation. The force to produce 0.5-, 1.0-, 1.5-, and 2.0-mm gaps were measured. RESULTS: One of the locking repairs, the locking Lee, had a gliding resistance significantly higher than that of one of the grasping repairs (modified grasping Kessler) and the other 2 locking repairs (Pennington, modified Pennington) (p <.05). There was no significant difference between the other grasping (modified Kessler, modified Lee) and locking (Pennington, modified Pennington) suture configurations (p =.21). The maximum force of one of the locking repairs, the modified Pennington repair (48.0 N; standard deviation, 3.9) was significantly higher than the other locking and grasping repairs (p <.05). The force required to produce more than 1.5 mm of gap for the modified Pennington repair was also significantly higher than that for some of the other grasping (modified Kessler, modified Lee) and locking (Pennington) repairs (p <.05). CONCLUSIONS: The lack of significant difference in gliding resistance among the similarly designed modified grasping Kessler, Pennington, and modified Pennington repairs (overall mean, 0.87 N; standard deviation, 0.16) suggests that the locking loop configuration itself does not adversely affect tendon gliding resistance. The modified Pennington repair increased not only ultimate strength but also resistance to gap formation more than 1.5 mm.     

The mechanical properties of locking and grasping suture loop configurations in four-strand core suture techniques

We have compared the effect of locking and grasping suture loop configurations in four-strand core suture techniques for tendon repair. Forty canine flexor digitorum profundus tendons were repaired with one of four suture techniques (the grasping cruciate, the double-modified grasping Kessler, the locking cruciate and the double-modified locking Kessler) and tested to failure in a tensile testing machine. The mode of failure in all the locking suture specimens was breakage of the sutures in the locking loops or at suture knots. The sutures did not pull out of the tendon, as was seen in the grasping suture specimens. The greatest tensile strength was found with the double-modified locking Kessler technique which incorporated eight rectangular locking loop configurations.     

The biomechanical analysis of a tendon fixation device for flexor tendon repair

PURPOSE: Stainless steel suture is high in tensile strength but is not widely used in flexor tendon repair because of difficulty with handling and knot tying. The purpose of this study was to examine the biomechanical characteristics of the single-strand multifilament stainless steel Teno Fix device (Ortheon Medical, Winter Park, FL) designed for zone II flexor digitorum profundus (FDP) tendon repair. METHODS: Sixty cadaveric flexor tendons were transected and randomized to receive a Teno Fix or 4-stranded (3-0 or 4-0 braided polyester) suture repair; all repairs were tested with and without a 5-0 monofilament polypropylene circumferential epitendinous suture. By using a material testing system all tendons were tested to failure in tension using a linear model with a loading rate of 1 mm/s. Stiffness, force, and energy at both 2-mm gap and peak force were calculated from the resulting force-displacement curves. RESULTS: The 2-mm gapping force was significantly greater for the Teno Fix and the 3-0 repairs than for the 4-0 repairs. The energy absorbed up to 2-mm gap was significantly greater for the Teno Fix, however, than for all suture repairs both with and without a circumferential suture. There was no statistically significant difference in peak force or energy absorbed at peak force between the Teno Fix and suture repairs; the average gap at peak force for all repairs was 5.2 mm. The addition of a circumferential suture increased the 2-mm gapping and peak forces of the Teno Fix repair to 54.5 N and 66.7 N, respectively. CONCLUSIONS: Increased strength and energy absorbed at 2-mm gap and ease of installation makes the Teno Fix a promising repair method.