Immediate postoperative mobilization has been shown to avoid adhesion formation and improve range of motion after flexor tendon repair. A tubular braided construct was designed to allow for these rehabilitation protocols.

In this ex vivo study, 92 ovine flexor tendons were divided randomly into 2 equal groups. After creating a transection, the tendons of the first group were repaired using a tubular braided construct. This construct, consisting of a tubular braid of polypropylene and polyethylene terephthalate fibers, exerts a grasping effect on the tendon ends. The control group received a multistrand modified Kessler repair with a looped polydioxanone suture (PDS) 4-0 suture and a Silfverskiöld epitendinous repair using an Ethilon 6-0 suture. After the repair, a static and an incremental cyclic tensile test was performed until failure.

During the static test, the tubular braid resulted in a significantly higher load at 3 mm gap formation (86.3 N ± 6.0 vs 50.1 N ± 11.6), a higher ultimate load at failure (98.3 N ± 12.7 vs 63 N ± 11.1), higher stress at ultimate load (11.8 MPa ± 1.2 vs 8.1 MPa ± 3.1), and higher stiffness (7.1 N/mm ± 2.9 vs 8.7 N/mm ± 2.2). For the cyclic tests, survival analyses for 1-, 2- and 3-mm gap formation and failure demonstrated significant differences in favor of the tubular braided construct.

The tubular braided construct withstands the required loads for immediate rehabilitation not only in static tests, but also during cyclic tests. This is in contrast with the control group, where sufficient strength is reached during static tests, but failures occur below the required loads during cyclic testing.

The tubular braided construct provides a larger safety margin for immediate intensive rehabilitation protocols.

Forces applied to the repaired flexor tendon should not exceed its yield force during early postoperative rehabilitation to prevent gapping and rupture. We aimed to biomechanically compare the tensile strengths and the 2-mm gapping of 4 different 4-strand core suturing techniques for flexor tendon repair.

Fifty-six goat deep digital flexor tendons were repaired with the 4-strand double-modified Kessler, the 4-strand augmented Becker, the 4-strand Savage, and the 4-strand modified Tang techniques. All tendons were repaired with 4-0 polyester for core suture and 5-0 polyester for continuous epitendinous running suture. The specimens were subjected to static linear tensile testing by applying a single linear load-to-failure pull. After the linear load testing, the yield load, the ultimate strength of the repaired tendons, and the force exerted to yield a 2-mm gap were measured.

All peripheral sutures ruptured near the yield point. All core suture techniques were similar regarding the yield force. The augmented Becker 4-strand technique had the greatest ultimate strength (98.7 [82-125.3] N). The modified double Kessler technique was the weakest in resisting a 2-mm gap formation. The 4-strand modified Tang repair had the shortest (11.3 [7-15] minutes), while the 4-strand augmented Becker had the longest operative time (29 [23-33] minutes).

All 4 techniques demonstrated similar yield force, with differences in operative time, ultimate strength, and resistance to gapping. Future clinical studies can further elucidate their appropriateness for early active motion protocols.

The effect of obliquity of tendon laceration on repair strength is not well studied. The overwhelming majority of biomechanical studies assess repair strength following a laceration that is perpendicular to the long axis of the tendon. The aim of this study was to investigate whether the angle of tendon laceration affects the core suture strength.

In all, 110 fresh human cadaveric flexor tendons were cut at varying angles of 15°, 30°, 45°, and 60° and the control group at 90°. All tendons were repaired with 6-strand modified Tang technique. The repair strength was tested using a custom-made tensioning machine, and the initial static gap force and the ultimate breaking force were measured.

The mean gap force and 95% confidence interval (CI) for the 15°, 30°, 45°, 60°, and 90° groups were 15.2 N (11.4-19.0 N), 15.8 N (13.6-18.1 N), 15.6 N (13.1-18.4 N), 16.6 N (13.7-19.5 N), and 22.3 N (16.6-27.9 N), respectively. In the same respective order, the break force and 95% CI were 25.9 N (21.9-29.8 N), 26.5 N (23.2-29.7 N), 31.1 N (26.1-36.1 N), 35.6 N (28.2-43.1 N), and 51.8 N (62.5-41.0), respectively. The Fisher least significant difference demonstrated significant differences between the control group and all experimental groups for both gap force and break force.

Obliquity of tendon laceration affects the core suture strength when compared with a transverse cut. Flexor tendons cut at 90° demonstrated a higher overall gap force and breaking strength that were statistically significant when compared with all obliquely cut groups. These findings should be considered when repairing and starting postoperative therapy for obliquely cut tendons.

The Pulvertaft weave continues as a staple technique for tendon coaptations. Many have proposed minor alterations to the original technique to improve its strength, though a lack of consensus exists. Our aim was to explore how the number of weaves and suture characteristics contribute to the overall strength of the coaptation.

A comprehensive electronic search was conducted using PubMed, Cochrane Library, and Scopus. Criteria for inclusion consisted of cadaveric human or animal biomechanical studies evaluating ultimate failure load (Newtons, N) as well as number of weaves, suture characteristics, tendon source, and number of coaptations. Weaves with minimum averages of 75 N were deemed successful, and those with >120 N were considered high performing.

A total of 347 tendon transfers from 15 studies met inclusion criteria. Average strength by number of weaves was 36.4 N (n=52) for 1 weave; 54.2 N (n=58) for 2 weaves; 115.9 N (n=174) for 3 weaves; and 81.7 N (n=63) for 4 weaves. Statistical differences were observed between 1 and 2 weaves (p<0.0001); 2 and 3 weaves (p<0.0001); 3 and 4 weaves (p<0.003); and 2 and 4 weaves (p<0.0001). High performing tendon transfers utilized 3 weaves, 3-0 or 4-0 braided sutures, and figure-of-eight or mattress core sutures.

Contrary to the current dogma of 'the more the better', our findings show that Pulvertaft weave strength is optimized when 3 weaves are used to combine donor and recipient tendons. Braided sutures with either figure-of-eight or mattress sutures were associated with highest strength of repair.

Background: The repair of zone 1 flexor tendon injury often relies on re-inserting the flexor digitorum profundus (FDP) tendon to the distal phalanx. The aim of this retrospective study is to compare outcomes at 12 weeks following traditional button-over-nail (BON) versus bone anchor (BA) repair of zone I FDP injury. Methods: Patients undergoing zone 1 FDP repair between April 2007 and September 2018 using a BON or a BA were included in the study. Patient demographics, complications, arc of flexion of distal (distal interphalangeal joint [DIPJ]) and proximal interphalangeal joint (PIPJ) and patient-rated outcomes were analysed. Results: Forty-three patients were included in the study: 21 in the BA group and 22 in the BON group. Good function was achieved by 20 patients in BA versus nine in BON. Complications occurred in five BA patients versus 10 BON patients. Patients achieved a mean active DIPJ flexion of 49° and 31° and PIPJ flexion of 92° and 57° in the BA and BON groups, respectively. Conclusion: Our study demonstrates better arc of motion, patient-rated outcomes and lower complications at 12 weeks after surgery in patients undergoing zone 1 FDP repair using a BA. Level of Evidence: Level III (Therapeutic).

Despite advancements in surgical techniques, suture pull-though and rupture continue to limit the early range of motion and functional rehabilitation after flexor tendon repairs. The aim of this study was to evaluate a suturable mesh compared with a commonly used braided suture in an in vivo rabbit intrasynovial tendon model.

Twenty-four New Zealand female rabbits (3-4 kg) were injected with 2 units/kg botulinum toxin evenly distributed into 4 sites in the left calf. After 1 week, the animals underwent surgical tenotomy of the flexor digitorum tendon and were randomized to repair with either 2-0 Duramesh suturable mesh or to 2-0 Fiberwire using a 2-strand modified Kessler and 6-0 polypropylene running epitendinous suture. Rabbits were killed at 2, 4, and 9 weeks after surgery.

Grouping across time points, 58.3% (7 of 12) of Duramesh repairs were found to be intact for the explant compared with 16.7% (2 of 12) of Fiberwire repairs (P = .09). At 2 weeks, the mean Duramesh repairs were significantly stronger than the Fiberwire repairs with a mean failure load of 50.7 ± 12.7 N compared to 14.8 ± 18.3 N (P = .02). The load supported by the Duramesh repairs at 2 weeks (mean 50.7 ± 12.7 N) was similar to the load supported by both Fiberwire (52.2 ± 13.6 N) and Duramesh (57.6 ± 22.3 N) at 4 weeks. The strength of repair between Fiberwire and Duramesh at 4 weeks and 9 weeks was not significantly different.

The 2-strand tendon repair with suturable mesh achieved significantly greater strength at 2 weeks than the conventional suture material. Future studies should evaluate the strength of repair prior to 2 weeks to determine the strength curve for this novel suture material.

This study evaluates the utility of a novel suturable mesh for flexor tendon repair in an in vivo rabbit model compared with conventional suture material.

Tendon reconstruction is frequently required under conditions of tendon deficiency. The authors sought a technique that could obviate the need for tendon harvest yet meet the minimum load of 45 N required for an early active motion protocol. This study was designed to determine the ideal suture construct utilizing the tendon with Z-lengthening (TWZL) technique.

Sixty fresh-frozen cadaveric flexor digitorum profundus tendons of the index, middle, and ring fingers were randomized into 5 different TWZL construct designs using 3-0 braided polyethylene suture. Constructs were tested on an electromechanical actuator until failure was observed on the load-elongation recording. Data points on maximum yield and load at 8% strain were recorded for each construct.

The maximum yield data revealed the construct with a 4-core suture type configuration (construct #4) had the highest overall mean load to failure at 150 N compared with all other constructs. The construct with the highest mean load at 8% strain was that with a 4-core type repair (construct #4) at 59 N. The constructs with Krackow locking sutures (constructs #2, #3, and #4 were found to withstand a significantly higher mean load at 8% strain than those without Krackow sutures (#0 and #1). Comparison among constructs with Krackow locking sutures #2 (56 N), #3 (48 N), and #4 (59 N) did not show a significant difference in mean load at 8% strain. Construct #3, however, had an SD and 95% confidence interval that fell below the 45 N early active motion threshold, whereas both #2 and #4 had 95% confidence intervals that fell no lower than 50 N.

This study provides evidence that the TWZL technique utilizing either construct #2 or #4 could provide sufficient strength and reproducibility for tendon reconstruction.

The study describes the application of the TWZL technique for utilization in tendon reconstruction and quantifies differences in the yield strengths of the 5 proposed constructs.

Cyclic testing of flexor tendons aims to simulate post-operative rehabilitation and is more rigorous than static testing. However, there are many different protocols, making comparisons difficult. We reviewed these protocols and suggested two protocols that simulate passive and active mobilization.

Literature search was performed to look for cyclic testing protocols used to evaluate flexor tendon repairs. Preload, cyclic load, number of cycles, frequency and displacement rate were categorised.

Thirty-five studies with 42 different protocols were included. Thirty-one protocols were single-staged, while 11 protocols were multiple-staged. Twenty-nine out of 42 protocols used preload, ranging from 0.2 to 5 N. Preload of 2 N was used in most protocols. The cyclic load that was most commonly used was between 11 and 20 N. Cyclic load with increment of 10 N after each stage was used in multiple-staged protocols. The most commonly used number of cycles was between 100 and 1000. Most protocols used a frequency of <1 Hz and displacement rate between 0 and 20 mm/min.

We propose two single-staged protocols as examples. Protocol 1: cyclic load of 15 N to simulate passive mobilization with preload of 2 N and 2000 cycles at frequency of 0.2 Hz.; Protocol 2: cyclic load of 38 N to simulate active mobilization, with the same preload, number of cycles, and frequency as above. This review consolidates the current understanding of cyclic testing and may help clinicians and investigators improve the design of flexor tendon repairs, allow for comparisons of different repairs using the same protocol, and evaluate flexor tendon repairs more rigorously before clinical applications.

Flexor tendon repair consists of circumferential peripheral sutures in combination with core sutures to avoid fraying and reduces the exposure of suture material on tendon surface. The peripheral suture adds up to a tenfold increase of the biomechanical stability compared to the core suture alone. The purpose of our study was to determine the most favourable peripheral repair technique for tendon repair.

Seventy-two porcine flexor tendons underwent standardized tenotomy and repair using one of the following six methods (n = 12): simple-running (SR), simple-locking (SL), Halsted-mattress (HM), lin-locking (LL), Lembert-mattress (LM), and Silfverskiöld cross-stich (SCS) suture technique. The SL- suture was placed 2 mm; the HM, LM, SC, and LL suture were placed 5 mm from the tendon gap. The SR suture was placed 1, 2, and 3 mm from tendon ends; no additional core suture was applied. For cyclic testing (1000 cycles), elongation was calculated; for load to failure construct stiffness, yield load and maximum load were determined.

The mean cyclic elongation for all tested suture techniques was less than 2 mm; there was no significant difference between the groups regarding elongation as well as yield load. The HM, LM, SCS, and LL suture techniques presented significantly higher maximum loads compared to the SR- and SL-sutures. The 3 mm SR showed significantly higher maximum loads compared to the 2 and 1 mm SR.

Beside the distance from tendon gap, the type of linkage of the suture material across and beneath the epitendineum is important for biomechanical stability. Simple-running suture is easy to use, even with a slight increase of the distance from tendon gap significantly increases biomechanical strength. For future repairs of flexor tendon injuries, 3 mm stitch length is highly recommended for simple peripheral suture, while the Halsted-mattress suture unites the most important qualities: biomechanically strong, most part of suture material placed epitendinous, and not too complicated to perform.

Therapy after flexor pollicis longus (FPL) repair typically mimics finger flexor management, but this ignores anatomic and biomechanical features unique to the FPL.

We measured FPL tendon tension in zone T2 to identify biomechanically appropriate exercises for mobilizing the FPL.

Eight human cadaver hands were studied to identify motions that generated enough force to achieve FPL movement without exceeding hypothetical suture strength.

With the carpometacarpal and metacarpophalangeal joints blocked, appropriate forces were produced for both passive interphalangeal (IP) motion with 30° wrist extension and simulated active IP flexion from 0° to 35° with the wrist in the neutral position.

This work provides a biomechanical basis for safely and effectively mobilizing the zone T2 FPL tendon.

Our cadaver study suggests that it is safe and effective to perform early passive and active exercise to an isolated IP joint.

NA.

Tendon lacerations are most commonly managed with surgical repair. Postoperative complications such as adhesions and ruptures often occur with immobilization. Early postoperative mobilization is therefore advised to minimize complications and time required to return to daily life. The aim of this study was to evaluate whether botulinum neurotoxin type-A (BoNT-A) can be used to enhance healing and prevent rupture in mobilized animals with Achilles tenotomy.

Twenty-seven rabbits were divided into 3 groups, namely, I, II, and III, after surgical 1-sided Achilles tenotomy and end-to-end repair. The control group for biomechanical comparisons consisted of randomly selected contralateral (unoperated) healthy Achilles tendons. Group I received BoNT-A (4 U/kg) injection into the calf muscles. One week later, electromyographical confirmation was performed to establish the effects of injection. Surgery was then performed. Animals in the second group (n = 9, group II) were immobilized with a cast postoperatively. The third group (n = 9, group III) was mobilized immediately with no cast or BoNT-A. Tendons were harvested and gap formation or ruptures as well as strength of the repaired tendon were assessed 6 weeks after surgery.

Achilles tendons healed in all animals injected with BoNT-A, whereas all were ruptured in group III. All Achilles tendons of animals in groups I and II healed. However, group I repaired tendons were biomechanically equivalent to healthy tendons, whereas group II repaired tendons demonstrated significantly decreased tensile strength (P = 0.009).

The present study suggests that local injection of BoNT-A can be used for treatment of tendon rupture and may replace the use of cast for immobilization. However, further studies are needed to determine whether BoNT-A injection can have a beneficial effect on the healing of tendon repairs in humans.

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

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

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

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

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

To test the ultimate tensile strength and stiffness of 3 flexor tendon repair techniques using looped suture material.

Seventeen fresh porcine flexor tendons were randomized to a single-throw, 4-strand Kessler technique with a looped structure, a double-throw, 4-strand Tsuge technique with 2 looped structures, or a single-throw, 4-strand Kessler-Tsuge technique with a looped structure. Thirty additional fresh porcine flexor tendons were randomized to the same techniques but with a running epitendinous repair. We measured ultimate tensile strength to failure and stiffness and recorded the cause of failure.

The Tsuge technique had the highest mean ultimate tensile strength at 75 N (SD, 14 N) versus 63 N (SD, 13 N) for the Kessler-Tsuge method and 46 N (SD, 11 N) for the Kessler technique. Differences between the Tsuge and Kessler-Tsuge, the Kessler-Tsuge and Kessler, and the Tsuge and Kessler techniques were significant. Mean suture stiffness was 6.8 N/mm for the Tsuge technique, 5.7 N/mm for the Kessler-Tsuge technique, and 4.6 N/mm for the Kessler technique. The difference between the Tsuge and Kessler techniques was significant. Analyzing the tests with or without an epitendinous suture separately did not affect the significance of the differences.

The modified double-throw, 4-strand Tsuge was the strongest suture technique in this study. It may be a clinically acceptable, albeit slightly weaker alternative to the more complicated Tsuge method.

A combined Kessler-Tsuge approach might be an option for flexor tendon repair.

The effect of core suture geometry on the mechanical interaction with the epitenon suture in terms of gap prevention, failure strength and mode of failure was investigated in a flexor tendon repair model. A total of 48 porcine flexor tendons were repaired using three techniques with distinct core suture geometry: single Kessler; double Kessler; and cruciate repair. Cyclic linear testing was carried out with and without a simple running epitenon suture. At failure load the epitenon suture reduced gapping by 87% in the double Kessler, 42% in the single Kessler and 15% in cruciate repairs. It increased the strengths of the repairs by 58%, 33% and 24%, respectively. Kessler repairs failed mainly by suture rupture, with and without epitenon suture, but cruciate repairs failed mainly by suture pull-out. The epitenon suture did not have a significant mechanical effect on the three repairs. Rather, its effect varied with the core suture geometry. The greatest effect occurred with double Kessler repairs.

The Pulvertaft weave has been the standard tendon junction technique used both in tendon transfers and tendon grafts. A limitation of this repair is the sequential failure of stabilizing sutures, rather than the tendon. A novel loop weave is described and compared with the Pulvertaft weave in biomechanical performance. Ovine deep flexor and extensor tendons were used to simulate Pulvertaft or loop weaves (n = 11) for tensile testing. The Pulvertaft weaves failed at the stabilizing sutures, whereas the loop weaves repairs failed by longitudinal splitting of the motor tendon. The loop weave demonstrated significantly higher mean initial failure and ultimate strengths. Tensile loads required to elongate the loop weave by 4, 6, and 8 mm were significantly higher, while more displacement was associated with the Pulvertaft repair under the application of 50, 75, and 100 N tensile loads. This study demonstrates favourable biomechanical characteristics of the new loop weave technique.

This article summarizes select multinational early motion protocols. Included are flexor and extensor protocols for digital tendon repair in many forms. Custom orthosis design, exercise regimens, and advanced techniques are examples of what to expect. The goal of the article is to expose the reader to new ideas, educate regarding advanced techniques in tendon rehabilitation, and stimulate independent study to further the reader's skill set.

Gap formation is a common and severe complication after flexor tendon repair that can affect the outcome and prolong tendon healing. The purpose of this study was to investigate the effect that a pretensional force applied to the suture during tendon repair has on the repair strength and force that causes gap formation.

We used a total of 48 flexor digitorum profundus tendons from 12 human cadaver hands. We employed a core tendon suture, using the modified Pennington technique, and a running suture for flexor tendon repair. Before tying the knots of the core suture, we preloaded the sutures in each tendon end 0, 5, 10, or 15 N for 10 seconds to compare the effect of loading magnitude on repaired tendon peak force to failure and force causing gap formation.

The force to form a gap of 2 mm in the 15-N preload group was significantly increased compared with the 0-N and 5-N preload groups. At the 3-mm gap formation, the force of all preload groups was significantly higher than the nonpreload group. The peak force with a preload of 10 N and 15 N was significantly higher than 0-N preload.

These findings suggest that pretensioning with 10 to 15 N at the suture-tendon interface before tying the knot has a beneficial effect on both the tendon gap formation and the peak force to failure.

When the surgeons perform tendon repair, pretensioning at the suture-tendon conjunction will increase the repair strength.

FiberWire is a popular suture in flexor tendon repair that allows for early mobilization, but its poor knot-holding properties have raised concerns over the potential effects on tendon healing and strength. We examined how the number of knot throws affects the 2 mm gap force, ultimate tensile strength, and mode of failure in a four-strand cruciate locked tendon repair in porcine flexor tendons in order to elucidate the optimal number of suture throws. There was no effect on the 2 mm gap force with increasing knot throws, but there was a significant increase in ultimate tensile strength. A minimum of six-knot throws prevents unravelling, whereas five out of 10 of repairs unravelled with less than six throws.

This study compared the maximum load, stress, elongation at failure and the mode of failure of three kinds of tendons most frequently used for tendon grafting and tendon transfers, using the Pulvertaft weave suture.

Sixty tendons were used from fresh human cadaver upper and lower extremities. The performed repairs included: 9 specimens of flexor digitorum superficialis or profundus tendon with flexor digitorum superficialis or profundus tendon (thick-thick suture), 10 specimens of flexor digitorum superficialis or profundus tendon with palmaris longus tendon (thick-medium thin suture), and 10 specimens of flexor digitorum superficialis or profundus tendon with plantaris tendon (thick-thin suture). Material testing machine was used to test repairs to failure.

The mean maximum load at failure increased with the thickness of donor tendon. For the thick-thick specimen, the maximum load at failure was 125 newtons (N), for the thick-medium thin specimen it was 86,8N, and for the thick-thin it was 65,2N. These differences were all statistically significant.

The active rehabilitation protocol is possible only with thick-thick connections used, the strength of the thick-medium thin connection is on the border of indications for the active rehabilitation protocol, and the thick-thin connection strength is sufficient only for the passive rehabilitation protocol.

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 1 mm gap formation force.

The highest ultimate tensile strength was found for the modified Kessler technique (115 N). Both new techniques showed an ultimate load exceeding 50 N (57 N for Marburg 1, 54 N 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.

To determine the effects of suture purchase on work of flexion (WOF), 2-mm gap force, and load to failure on the combination cross-locked cruciate-interlocking horizontal mattress (CLC-IHM) flexor tendon repair in zone II.

A total of 33 fresh-frozen cadaveric fingers were mounted in a custom jig, and the flexor digitorum profundus of each finger was fixed to the mobile arm of a tensile strength machine. Initial measurements of WOF were obtained. Each tendon was repaired with the CLC core suture, randomly assigned to placement of 3, 5, 7 or 10 mm from the cut edge of the tendon, and completed with the IHM circumferential suture. After the repair was completed, measurements of WOF were repeated. Each finger was cycled 1000 times. After each 250 cycles, gapping was recorded, and WOF was measured again. Change in WOF (WOF after repair - WOF of intact tendon) was calculated. Tendons were then dissected from the fingers and linearly tested for 2-mm gap force and ultimate load to failure.

The group repaired at 10 mm had the lowest percent increase in WOF (5.2%), the highest 2-mm gap force (89.8 N), and the highest ultimate load to failure (111.5 N). The group repaired at 3 mm had the highest percent increase in WOF (22.1%), the lowest 2-mm gap force (54.6 N), and the lowest ultimate load to failure (84.6 N).

A 10-mm suture purchase is the recommended distance for optimal performance for the CLC-IHM combination repair method. This method with a 10-mm suture purchase has a low increase in WOF, high strength, and high resistance to gapping, and it should be strong enough to tolerate early motion.

To assess in vitro biomechanical properties of a 4-strand flexor tendon suture compared to 3 established suture techniques. This technique, which is made of 2 alternating and staggered sutures, one external to the tendon and the other internal, must be sufficiently resistant to withstand loads applied by modern, early active mobilization protocols.

Forty flexor hallucis longus tendons were harvested from fresh cadavers, cut, and repaired using 4 different suture techniques (Strickland, Wolfe, modified Savage, and a new technique called 4-strand staggered). All repaired tendons were submitted to static loading trials to measure gap formation (2 mm) in relation to tensile force and breaking force of all 4 sutures. Twenty additional tendons were repaired with the new suture technique and submitted to dynamic trials under cyclic loading.

The 4-strand staggered suture technique proved to be statistically superior to Strickland and modified Savage techniques following the static loading trials for gap formation and breaking force. This technique is statistically superior to the Wolfe cruciate suture for breaking force and superior but not statistically significant for gap formation. The dynamic loading trials have shown that the 4-strand staggered suture can tolerate in vitro loads similar to those exerted by modern, early active mobilization protocols.

The suture technique created by the authors proved to hold superior biomechanical properties than the other techniques tested in this study and might be suitable for early active mobilization protocols.

The aims of this study were to examine nonrepaired 90% partial lacerations of human cadaver flexor digitorum profundus (FDP) tendon after simulated active motion, and to assess the residual ultimate tensile strength.

Partial, transverse zone II flexor tendon lacerations were made in the volar 90% of the tendon substance in 10 FDP tendons from 5 fresh-frozen human cadaver hands. The tendons were cycled in the curvilinear fashion described by Greenwald 500 times to a tension 25% greater than the maximum in vivo active FDP flexion force measured by Schuind and colleagues. The tendons were then loaded to failure using the same curvilinear model.

No tendons ruptured during cycling. Triggering occurred in 3 tendons. All 3 began triggering early in the cycling process, and continued to trigger throughout the remainder of the 500 cycles. The observed triggering mechanics in each case involved the interaction of the proximal face of the lacerated tendon with Camper's chiasm and the pulley edges during extension. The load to failure value of the 90% partially lacerated tendons averaged 141.7 +/- 13 N (mean +/- standard deviation). Tendon failure occurred by delamination of the intact collagen fibers from the distal, discontinuous 90% of the tendon.

Cadaveric transverse zone II partial flexor tendon lacerations have residual tensile strength greater than the force required for protected active mobilization.

The fatigue strength of three peripheral suture techniques for flexor tendon repair was compared by cyclic loading of repairs in a cotton dental roll tendon model. Thirty pairs of dental roll were sutured using only peripheral sutures with 6-0 polypropylene. An initial cyclic load of 5 N for 500 cycles was applied and increased by 5 N for an additional 500 cycles at each new load until rupture. The fatigue strength of an interlocking cross-stitch suture was 113% greater than a running suture and 36% greater than a standard cross-stitch suture. Interlocking the cross-stitch prevented shortening of the transverse portions under load and appears to be a useful technique for increasing the strength of the peripheral suture.

To establish the animal flexor tendon that best mimics the biomechanical performance of human flexor tendons. We investigated the biomechanical behavior of core and running sutures in 3 different animal flexor tendons and in human flexor tendons. Additionally, we attempted to help standardize future flexor tendon studies. To that purpose, nearly all variables occurring in the test setup have been highlighted.

The species selected were pig, calf, sheep, and human. Two groups were formed. In the first group we tested 3-0 core sutures (Ticron; Tyco Healthcare, Vienna, Austria), and in the second group we tested 5-0 running sutures (Ethilon; Ethicon, Vienna, Austria). In each group, 10 tendons of each specimen were tested, which yielded a total of 80 tendons. In each group, the repaired tendons were subjected to 3,000 linear load cycles at a load of 15 N. At the end of this procedure, final gap values were recorded. In the next step, ultimate load-to-failure data were obtained from each specimen.

Core sutures behaved similarly in the human, sheep, and pig tendons with respect to ultimate loads. With respect to gap formation, core sutures behaved similarly in the human, sheep, and calf tendons. Deep running sutures behaved similarly in the human, sheep, and pig tendons in terms of ultimate load to failure.

In this study, sheep tendons were found to best mimic the biomechanical behavior of human tendons. Calf tendons seem to be unsuitable. There is a strong need for consistency in biomechanical test setups.

Zone II flexor tendon repairs may create a bulging effect with resistance to tendon gliding. A biomechanical study was performed comparing the 4-strand cross-locked cruciate (CLC) to a 4-strand Strickland repair, both with and without an interlocking horizontal mattress (IHM) suture, in terms of strength characteristics and work of flexion.

Sixteen fresh-frozen human fingers were placed in a custom jig. Flexor digitorum profundus tendons were sectioned at the A3 pulley level. Fingers were separated into 2 repair groups: 4-strand CLC and 4-strand Strickland core suture. Work of flexion was determined for each group, with and without an IHM circumferential suture. Final repair including IHM was tested for 2-mm gap failure and ultimate load to failure.

The CLC-IHM had a significantly smaller increase in work of flexion than the Strickland-IHM. For both suture types, the circumferential suture resulted in a statistically significant increase in work of flexion; however, peak entry force produced upon entry of the repair into the A2 pulley was reduced, although the decrease was not statistically significant for each group. The CLC-IHM had a significantly higher ultimate load to failure.

(1) The CLC-IHM suture method is stronger with less work of flexion than the Strickland-IHM method. (2) This new, combination repair method of CLC core suture with IHM circumferential suture is biomechanically superior to the commonly performed Strickland-IHM technique.

FiberWire, an increasingly popular suture material, allows for strong flexor tendon repair that may allow early mobilization. This study was designed to evaluate the mechanical characteristics of FiberWire for flexor tendon repair and to identify the most effective repair technique using this material.

Forty-nine human cadaver flexor tendons were randomized and tested biomechanically using one of the following techniques of flexor tendon repair performed with 3-0 FiberWire: (1) modified Kessler, (2) modified Pennington, (3) 2-strand multiple grasping, (4) 2-strand multiple locking, (5) 2-strand double cross-locks, (6) Massachusetts General Hospital, and (7) 4-strand locked cruciate. The ultimate tensile strength, 2-mm gap resistance, and failure mode of the repairs were evaluated.

Knot unraveling was the most common failure mode of FiberWire repair in 4 of the 7 techniques. Four-strand repairs and locking repairs provided significantly more strength than 2-strand repairs and grasping repairs. Multiple grasping and multiple locking repairs with 2 knots were significantly weaker than single grasping and locking repairs with a single knot. Four-strand locked cruciate repairs were significantly stronger than the other techniques (mean ultimate tensile strength 107 N, 2-mm gap force 96 N). Two-strand double cross-locks repairs were stronger than the other 2-strand repairs (mean ultimate tensile strength 69 N, 2-mm gap force 53 N).

The strength of the FiberWire repairs increased with locking repair and with increased number of strands but was not influenced by increased number of locking and grasping stitches. Four-strand locked cruciate and 2-strand double cross-locks provided the greatest strength and likely are appropriate for future clinical use in, respectively, 4-strand and 2-strand repairs. However, the poor knot-holding characteristics of FiberWire with the need of a greater number of knot throws may be of concern for surgeons using this product for flexor tendon repairs.

To compare the initial biomechanical properties of zone I flexor tendon to bone repairs performed using pull-out and anchor techniques and to investigate the effect of bone quality and suture materials on the strength of anchor repairs.

Using computed tomography, we measured bone mineral density and cortical thickness of the distal phalanx of 60 cadaver fingers (mean age, 77 years). Flexor digitorum profundus tendons were then transected at their insertion sites and repaired using a 4-strand grasping suture and either pull-out or anchor fixation. For pull-out repair (n = 20), the suture strands (Supramid 3-0; S. Jackson, Inc., Alexandria, VA) were passed through the distal phalanx and tied over a dorsal button. For anchor repair, 2 bone anchors were inserted into the distal phalanx, and tendons were grasped using either Supramid (n = 21), Ethibond (Ethicon, Inc., Somerville, NJ; n = 10), or FiberWire suture (Arthrex Inc., Naples, FL; n = 9) (all 3-0). Mechanical properties of the repaired tendon-bone constructs were determined in linear, load-to-failure loading and correlated with bone characteristics.

The FiberWire-anchor repair group had the best combination of mechanical properties, with ultimate force to failure no different from the pull-out repairs but with greater stiffness and reduced displacement. Pull-out suture repairs had significantly higher ultimate force-to-failure values than did Ethibond-anchor and Supramid-anchor repairs (p < .01). However, pull-out repairs had significantly reduced stiffness and greater displacement at 20 N force than did anchor repairs from all groups (p < .05). Both bone mineral density and cortical thickness correlated significantly with ultimate force (p < .01). Almost all anchors pulled out for bone mineral density below 420 mg/cm(3) or cortical thickness less than 0.31 mm, which occurred only for specimens aged greater than 75 years.

The mechanical properties of the double Mitek bone anchors were sensitive to both suture material and bone quality. FiberWire-anchor repairs provided the best combination of mechanical properties. Pull-out suture repairs had good strength but poor stiffness. Anchor fixation may be contraindicated in patients greater than 75 years because of poor bone quality.

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.

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.

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.

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).

To investigate the effects of 3 different locking configurations on repair strength when used in a cruciate four-strand repair.

Sixty fresh porcine flexor tendons were transected and repaired with cruciate four-strand core suture repairs with 3 different locking configurations: simple locks (a modification of the Pennigton method), circle locks, and cross locks. Half of the repairs in each locking group were reinforced with a peripheral suture. The tendon repairs were subjected to linear load-to-failure testing. Outcome measures were 2-mm gap force and ultimate tensile strength.

The cross lock repair had significantly greater 2-mm gap force and ultimate tensile strength than the simple lock repair, both with and without a peripheral suture. The cross lock repair showed significantly greater 2-mm gap force without a peripheral suture and significantly greater ultimate tensile strength with a peripheral suture than the circle lock repair. With peripheral reinforcement, the cross lock cruciate repair had a mean 2-mm gap force of 92 N and ultimate tensile strength of 119 N. The cross lock cruciate repair consistently produced the strongest biomechanic performance in all outcome measures.

Locking configuration influences the biomechanic performance of cruciate four-strand flexor tendon repairs. Our results suggest that the cruciate repair with cross locks is stronger than repairs with simple locks or circle locks. Whether the results of this ex vivo porcine linear model can be translated to the clinical arena is unknown, because the factors of tendon/sheath friction, tendon healing, and compromised tendon viability from the lock were not addressed.

Although various tendon repair techniques have been reported to achieve stronger repair, suture failures tend to occur near the knot. We experimentally investigated whether the location of a single core suture knot affects the biomechanical properties of the repair.

Transected bovine tendons (male Japanese black cattle, 24 months old) of the medial gastrocnemius (9-11 x 14-16 mm in diameter) were sutured with the side-locking loop technique using a USP2-sized polyethylene and polyester multifilament suture or polyester multifilament suture. The knot was made using 7 simple square ties (a surgeon's knot plus 5 ties) at three locations; on the loop, between the tendon stumps, or between the loops burying the knot in a tendon slit using a scalpel. A cyclical loading protocol from 10N to 100N was used and the loading was repeated 10,000 times.

The gap was most decreased and the ultimate strength was most increased when the knot was located between the loops when using a polyethylene and polyester multifilament suture. Cross-sectional area of the tendon showed the ratio of the buried knot relative to the tendon was only 1.6-2.3%, and the polyethylene and polyester multifilament suture was very durable against frictional abrasion.

We found that the knot between the loops, buried in the bovine tendon provided the optimum results.

The effects of different hand motions and positions used during early protected motion rehabilitation on tendon forces are not well understood. The goal of this study was to determine in vivo forces in human flexor digitorum profundus (FDP) and flexor digitorum superficialis (FDS) tendons of the index finger during active unresisted finger flexion and extension. During open carpal tunnel surgery (n = 12), flexor tendon forces were acquired with buckle force transducers, and finger positions were recorded on video while subjects actively flexed and extended the fingers at two different wrist angles. Mean in vivo FDP tendon forces varied between 1.3N +/- 0.9 N and 4.0 N +/- 2.9 N while mean FDS tendon forces ranged from 1.3N +/- 0.5 N to 8.5 N +/- 10.7 N. FDP force increased with active finger flexion at both wrist angles of 0 degrees or 30 degrees flexion. FDS force increased with finger flexion when the wrist was in 30 degrees flexion, but was unchanged when the wrist was in 0 degrees of flexion. Tendon forces were similar regardless of whether the fingers were moving in the flexion or extension direction. Active finger flexion and extension with the wrist at 0 degrees and 30 degrees flexion may be used during early rehabilitation protocols with limited risk of repair rupture. This risk can be further decreased for a FDS tendon repair by reducing wrist flexion angle.

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.

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.

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.

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.

This study used in vitro cyclic testing protocol to examine the dynamic properties from a survivorship point of view for a modified Kessler core suture with a running epitenon suture, a modified Kessler core suture with a cross-stitched epitenon suture and a 4-strand Savage core suture with a running epitenon suture.

A survivorship analysis using in vitro dynamic mechanical testing was performed using 20 N and 33 N with 500 cycles to simulate early rehabilitation. The gap formation was recorded by direct measurement with an electronic calliper every 100 cycles at the point of lowest force during the cycle at the site of greatest gap formation. Results were analysed using a log rank test for survival analysis and the relative risk of deterioration calculated.

No significant increased risk of gap formation was noted for the Kessler with a cross-stitched epitenon over the standard Kessler repair. A significant decrease in the risk of significant gap formation in the Savage repair over the two Kessler repairs (>10-fold difference in the standard (P < 0.01) and > 7-fold in the cross-stitched (P < 0.05) was found.

The survivorship testing protocol found the Savage repair to be superior to the other methods under dynamic loading. Survival curves and relative risks provide a unique way to assess the properties of different repair techniques.

This article examines basic tendon biomechanics, the anatomy and mechanics of digital flexor tendons, and the digital flexor pulley system. It also explores the various models that have tried to simulate the motion of the flexor tendons and several testing modalities that have been used. Finally, clinical applications are considered, including the biomechanics of flexor tendon repairs and tendon transfers. As we reach limits in the care of flexor tendon injuries, research into molecular, biochemical, and micromechanical methods of tendon repair will become the forefront of future investigation.

Review of the outcomes of clinical flexor tendon repairs reported over the past 15 years showed advances in the outcomes with excellent or good functional return in more than three fourths of primary tendon repairs following a variety of postoperative passive/active mobilization treatments. Strickland and Glogovac criteria are the most commonly adopted methods to assess function. Repair ruptures (4%-10% for zone II finger flexors and 3%-17% for the FPL tendon), adhesion formations, and stiffness of finger joints remain frustrating problems in flexor tendon repairs and rehabilitation. Four approaches are suggested to improve outcomes of the repairs and to solve these difficult problems,which include stronger surgical repairs, appropriate pulleys or sheath management, optimization of rehabilitation regimens, and modern biologic approaches.

Significant advances in the understanding of intrasynovial flexor tendon repair and rehabilitation have been made since the early 1970s. The concept of adhesion-free, or primary tendon healing--that tendons could heal intrinsically without the ingrowth of fibrous adhesions from the surrounding sheath has been validated both experimentally and clinically in studies over the past 25 years. Recent attempts to understand and improve the results of intrasynovial flexor tendon repair have focused upon restoration of the gliding surface, augmentation of early post-operative repair site biomechanical strength and on the elucidation of the molecular biology of early post-operative tendon healing. The goals of the surgical treatment of patients with intrasynovial flexor tendon lacerations remain unchanged: to achieve a primary tendon repair of sufficient tensile strength to allow application of a post-operative mobilization rehabilitation protocol. This program should inhibit the formation of intrasynovial adhesions and restore the gliding surface, while facilitating the healing of the repair site.

To compare the maximum tensile load, change in work of flexion, and gapping at the repair site after zone II flexor digitorum profundus tendon repairs using 2-0, 3-0, and 4-0 braided polyester 4-strand locked cruciate repair technique in fresh-frozen cadaveric hands with standard 6-0 suture epitenon repairs, to determine which suture size is the best for a core repair.

A randomized study was designed using 41 tendons from 15 fresh-frozen cadaveric hands. We included only the flexor digitorum profundus tendons from the index, middle, and ring fingers to minimize variation between digits. Core suture size was randomized for each finger. A sharp laceration through the flexor digitorum profundus in zone II was made and a 4-strand locked cruciate braided polyester core stitch was performed along with a locked epitenon stitch. Cyclic loading was performed for 1,000 cycles. For each tendon the mean work of flexion (before/after zone II repair) and maximum tensile load were measured using a custom-designed tensiometer, as was gapping before maximum tensile loading.

Mean gaps after 1,000 load-unload cycles to 3.9 N of pulp pinch did not approach the clinically significant limit of 3 mm in each group. By using a regression model, we found that the prerepair and postrepair comparisons for mean work of flexion to a 3.9-N pulp pinch showed the greatest change in work of flexion for 2-0 braided polyester. Statistical significance was found between 2-0 braided polyester and 3-0 or 4-0 braided polyester; however, the work of flexion between the 3-0 and 4-0 polyester was not clinically significant. The highest maximum tensile load was obtained with suture size 2-0 braided polyester. The maximal tensile load statistically showed 2-0 braided polyester to be stronger than 4-0 braided polyester but we found no statistically significant difference between 3-0 and 2-0 braided polyester or between 3-0 and 4-0 braided polyester.

In this cadaveric study we found that increasing locking cruciate suture caliber from 4-0 to 2-0 increased maximum tensile strength but also caused increased work of flexion. Gapping was not affected by suture caliber. There was no significant difference in strength or mean change in work of flexion between 3-0 or 4-0 braided polyester sutures.

Independent FDS action has been cited to be problematic with repair of multiple tendons in zone V owing to adhesion formation between the flexor digitorum superficialis (FDS) and the flexor digitorum profundus (FDP) tendons. Of the several described flexor repair techniques the ideal tendon repair should be strong enough to allow for early active motion to minimize adhesion formation and maximize tendon healing. Biomechanical studies have proven the Massachusetts General Hospital (MGH) repair to be strong enough to allow for early active motion. The purpose of this study was to examine the use of the MGH technique for zone V flexor tendon injuries to allow for early protected active motion to achieve independent finger flexion through better differential gliding of the tendons.

We performed a retrospective review 168 zone V finger flexor tendon repairs for 29 patients performed consecutively over 4 years when early active motion was not contraindicated. The same early protected active motion protocol was used for all of these patients. We reviewed total active motion, independent flexion, rupture, and need for tenolysis. These injuries involved 103 FDS and 65 FDP tendons to 103 fingers. The median follow-up period was 24 weeks. Of these 29 patients 19 were men and 10 were women. The average patient age was 28 years.

The total active motion for these zone V repairs was 236 degrees +/- 5 degrees Overall 97 of 103 digits attained good to excellent function and 88 of 103 developed some differential glide. One of these patients required a tenolysis. Three repairs ruptured in 1 patient owing to suture breakage that was associated with noncompliance with the dorsal extension block splint.

Our retrospective review of 168 consecutive flexor tendon repairs showed that the MGH technique allowed for early protected active motion, which provided good to excellent functional outcomes with 88 of 103 developing independent finger flexion at an acceptably low complication risk.

Postoperative rehabilitation for patients who have sustained a laceration to their flexor tendon apparatus is an important factor in maximizing functional outcome. Quality rehabilitation is characterized by the development of a tailored exercise regimen. There is currently no model available to tailor an exercise regimen for a person with an atypical physiologic response pattern. If rehabilitation protocols were classified according to the criteria of forces applied across a tendon juncture and/or excursion, and a clinical method were available to assist in the identification of optimal tendon loading and/or excursion application, then those individuals with atypical response patterns could be treated more efficiently and effectively. The author conducted a literature review and case study. A model for systematic application of progressive loading exercises to the intrasynovial flexor tendon injury and repair is conceptually developed. The model consists of a pyramidal series of eight specific rehabilitation exercises in the following sequence: passive protected extension, place and hold, active composite fist, hook and straight fist, isolated joint motion, resistive composite fist, resistive hook and straight fist, and resistive isolated joint motion. Concepts are developed to implement a three-point clinical adhesion-grading system. Clinical application of the system is highlighted. An excellent outcome was considered 112% total active motion. A model for systematic application of progressive loading exercises has been conceptually developed in concert with a method for determination of optimal tendon loading. Further substantiation is necessary to validate the proposed theory.

The purpose of our study was to determine the most favourable combination of core suture material and peripheral repair technique for Kessler tendon repair. Thirty freshly thawed pig flexor tendons were repaired by a Kessler technique, either with braided polyester or monofilament nylon suture. A peripheral augmentation was done using one of the three techniques-running, cross-stitch and Halsted. All repairs were tested by cyclic loading, followed by load-to-failure. During cyclic loading six of the 15 tendons with a nylon core failed, but none with a braided polyester core. Irrespective of peripheral technique, the monofilament nylon core suture allowed early central cyclic gapping, resulting in failure of the repair. During load-to-failure testing, the running stitch proved weakest and the cross-stitch repair toughest.

We compared the tensile strength of different repair configurations on tendons with oblique and transverse lacerations.

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.

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.

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.

Early active motion limits adhesion formation and thus improves functional performance after tendon grafting. The early strength of distal fixation is critical to successful tendon grafting. We describe a new Y-tunnel technique of distal fixation and compare it with 2 established methods, the Pulvertaft transverse tunnel and the Bunnell button over the fingernail techniques, in a human cadaver model to determine which is the strongest method. Hands with a grafted tendon were rigidly mounted on an anatomic tensiometer testing apparatus and loaded to failure. Mean load to failure (newtons +/- 95% confidence intervals) of the Y-tunnel technique (155.2 +/- 29.4) was greater than those for the Pulvertaft (100.2 +/- 13.2) and Bunnell (57.1 +/- 4.7) techniques. Two-way analysis of variance showed significant differences, and the Bonferroni multiple pairwise comparison test showed that all 3 intergroup comparisons were statistically significant. These results indicate marked improvement in immediate strength with the Y-tunnel technique and lay the groundwork for further studies using a healing tendon model.

Transected flexor tendons are typically treated by suture repair followed by rehabilitation that generates repetitive tendon loading. Recent results in an in vivo canine model indicate that during the first 10 days after injury and repair, there is an increase in the rigidity of the tendon repair site. Our objective was to determine whether or not ex vivo cyclic loading of repaired flexor tendons causes a similar increase in repair-site rigidity. We simulated 10 days of rehabilitation by applying 6000 loading cycles to repaired canine flexor tendons ex vivo at force levels generated during passive motion rehabilitation; we then evaluated their tensile mechanical properties. High-force (peak force, 17 N) cyclic loading increased repair-site rigidity by 100% and decreased repair-site strain by 50%, whereas low-force (5 N) loading did not change the properties of the repair site. This mechanical conditioning effect may explain, in part, the changes in tensile properties observed after only 10 days of healing in vivo. Mechanical conditioning of repaired flexor tendons by repetitive forces applied during rehabilitation may lead to increases in repair-site rigidity and decreases in strain, thereby altering the mechanical loading environment of tissues and cells at the repair site.

To compare the biomechanical performances of six 4-strand flexor tendon repairs at zone II, we used an in situ testing model in 54 cadaver profundus tendons. The techniques studied were the modified Becker, modified double Tsuge, Lee, locked cruciate, Robertson, and Strickland. Prerepair and postrepair comparisons for work of flexion to a 3.9-N pulp pinch (equal to 12.6 N tendon force) showed the greatest interference to gliding in the modified Becker repair and the least in the modified double Tsuge repair. Mean gaps after 1,000 load-unload cycles to a 3.9-N pulp pinch did not approach the clinically important limit of 3 mm in all groups. Ultimate tensile strength was highest in the modified Becker (69.4 +/- 8.2 N) but not significantly higher than the modified double Tsuge (60.3 +/-15.3 N) and locked cruciate (64.1 +/- 16.2 N). In all repair groups the mean pulp pinch forces upon failure were well above values recommended for active mobilization protocols that use external load guides. The locked cruciate, modified double Tsuge, and modified Becker repairs were strong enough for an early active motion protocol after surgery. Locked cruciate and modified double Tsuge were easier to perform and provided less interference to tendon gliding than the modified Becker repair.