2-strand Repair Research Articles

The Effects of the TSOL Knot on the Repair Strength and Gliding Resistance Following Flexor Tendon Repair.

The stability of a suture knot construct has been realized as an important parameter that affects the strength of flexor tendon repairs. A novel 2-strand-overhand-locking (TSOL) knot, which is not commonly used in the clinical setting, recently was reported to increase repair strength and to decrease tendon gliding resistance in a 2-strand repair technique. The purpose of the present study was to investigate the effect of the TSOL knot on tendon repair strength and gliding resistance compared with a typical surgical knot in both 2-strand and 4-strand repair techniques using an in vitro turkey flexor tendon model. Sixty flexor digitorum profundus tendons from the long digit of the turkey foot were divided evenly into 4 groups and repaired with the following techniques: (1) a 2-strand modified Pennington repair with a square knot, (2) a 2-strand modified Pennington repair with a TSOL knot, (3) a 4-strand grasping cruciate repair with a square knot, and (4) a 4-strand grasping cruciate repair with a TSOL knot. Repaired tendons were tested for failure mode, gliding resistance, and repair strength at failure. The repair strength and stiffness of the 4-strand repairs were significantly higher than those of the 2-strand repairs, regardless of knot type (p < 0.05). The repair strength at failure of the TSOL knot was significantly greater than that of the square knot in 2-strand repairs (p < 0.05) but not in 4-strand repairs. The gliding resistance of the TSOL knot was significantly decreased compared with that of the square knot in both 2-strand and 4-stand repairs (p < 0.05). With regard to failure mode, the TSOL knot was less likely to fail due to knot unravelling. In this in vitro biomechanical study involving the use of turkey flexor tendons to compare gliding resistance and repair strength characteristics for knot-inside 2 and 4-strand repairs, the TSOL knot was associated with decreased repaired tendon gliding resistance, regardless of the number of strands used. Although the TSOL knot also increased the repair strength, the difference was only significant when 2-strand repairs were used. The results of our study support the use of the TSOL knot in the clinical setting of flexor tendon repair using 2 or 4-strand, knot-inside methods. In surgical repair of flexor tendons, there is substantial interest in maximizing strength while minimizing friction. This study shows the potential utility of the TSOL knot to increase repair strength while decreasing gliding resistance, particularly in 2-strand repairs.

Zone II Flexor Tendon Repairs in the United States: Trends in Current Management

The repair of zone II flexor tendon injuries is an evolving topic in hand surgery with current literature suggesting the use of a 4-strand repair; 3-0 or 4-0 braided, nonabsorbable sutures; and an epitendinous repair. It was hypothesized that variability would exist within the hand surgeon community in treatment of zone II flexor tendon repairs in surgical material used, surgical technique, and postoperative rehabilitation protocol. An online single-answer multiple-choice survey was distributed to the American Society for Surgery of the Hand members' database. Surgeons were asked questions about demographics, surgical technique, suture type, common complications, postoperative management,and the factor that plays the largest role in guiding their surgical preferences. Responses were compared with current medical evidence. A total of 410 individuals responded to the survey. In regards to technique, the majority of surgeons reported using a 4-strand repair; with 3-0 or 4-0 core braided, nonabsorbable sutures; and performing an epitendinous repair. Only 20% of surgeons surveyed reported ever using wide-awake local anesthesia, no tourniquet and postoperative protocols were split between early active and early passive rehabilitation. Senior surgeons (≥ 15 years in practice) were more likely than their colleagues to use a 2-strand repair and a passive rehabilitation protocol. This study demonstrates that the majority of respondents are performing zone II flexor tendon repairs in accordance with the best currently available evidence, although there is variability with respect to suture material, surgical technique, and rehabilitation protocols. There is still a need for high-quality studies on surgical technique and rehabilitation protocols.

Multistrand Tendon Repairs With Early Active Motion Versus 2-Strand Repairs With Passive Motion

Objective: To report the results of an audit of repair of zone 2 flexor tendons in 68 digits using two different repair methods and rehabilitation protocols. Materials and Methods: From January 2014 to January 2015, we treated 35 digits in 21 consecutive patients who had complete divisions of flexor tendons in zone 2. All tendon repairs followed an established surgical and rehabilitation protocols. The flexor digitorum profundus (FDP) tendons in 31 fingers and flexor pollicis longus tendons in 4 thumbs were repaired using either 6-strand M-Tang or 4-strand U-Tang methods. In 13 fingers, we vented part of the A2 pulley, and the entire A4 pulley was vented in 5 fingers. Active digital motion started from 4 days post-surgery. In 2013, the same surgical team repaired zone 2 flexor tendons in 25 consecutive patients (33 digits) with a conventional 2-strand modified Kessler repair with a passive motion protocol. Their outcomes were collected as the historical controls. Results: In evaluations of 35 digits with multistrand repair with early active motion 10 to 16 months postsurgery, the outcomes were excellent in 27 (80%), good in 3 (8.5%), fair in 3 (8.5%), and poor in 1 (2.2%) digits according to Strickland and Glogovac criteria. There were no repair ruptures. Four thumbs were all rated as excellent. No bowstringing was found in the 18 fingers, where either a part of the A2 pulley or entire A4 pulley was vented. The outcomes of 33 digits with a modified Kessler repair with passive motion were excellent in 13 (39.3%), good in 9 (27.2%), fair in 4 (12.1%), and poor in 7 (21.1%) digits. Repair ruptures were noted in 6 (18.2%) digits. Conclusions: Multi-strand core repairs with early active motion significantly improve outcomes over a conventional 2-strand repair with early passive motion in zone 2 flexor tendon repair.

The Impact of Fiberwire, Fiberloop, and Locking Suture Configuration on Flexor Tendon Repairs

Suture technique, suture material, and the number of strands all play critical roles in achieving optimal strength of flexor tendon repairs. We evaluated the contribution to the tensile strength of flexor tendon repair using the strongest suture material, Fiberwire, and the best surgical technique (locking configuration) using 2- and 4-strand core repair to see what factor played the most important role in tendon repair. Human cadaver flexor tendons were harvested and repaired in a randomized fashion using locking configuration as derived from Pennington's report. Ten tendons per group were repaired using either 4-0 Fiberloop, 4-0 Fiberwire, or 2-0 Fiberwire. During load-to-failure testing, visible gap force and maximum tensile strength were statistically analyzed. All flexor tendon repairs failed by suture pullout. The 4-strand 4-0 Fiberwire double-Pennington repair was found to be significantly stronger than the 4-strand 4-0 Fiberloop single-Pennington repair. When the 2-strand repair (2-0 Fiberwire) was compared to the 4-strand single-Pennington repair (4-0 Fiberloop), there was no significant difference found. The suture strand configuration rather than the strict number of strands or the strength of the suture material yielded the maximum tensile strength with reduced gapping at the repair site.

The relationship between gap formation and grip-to-grip displacement during cyclic testing of repaired flexor tendons

The assessment of repair site gap formation during cyclic loading of reconstructed flexor tendons provides important data on the performance of repair techniques in the early postoperative period. This study describes our cyclic testing protocol and evaluates the relationship between changes in optical gap and grip-to-grip displacement. Sixteen sheep hind limb deep flexor tendons were randomized into four repair groups (n=4 per group): a 2-strand repair (modified Kessler) and 4-strand repair (Adelaide), both with and without a simple running peripheral suture. Repaired tendons were cycled for 1000 cycles at appropriate rehabilitation loads for the reconstruction. Tendons were paused at 18 pre-determined cycle points to measure gap and displacement. A strong positively linear relationship between gap and displacement was demonstrated for all repair groups (R2>0.90). An initial non-linear region during the first 10 cycles was noted with some combined core and peripheral repairs. Although trends in displacement after 10 cycles can be used to reflect gapping behaviour, direct optical measurement of gap remains preferable. We hypothesized that the adjustment of suture strands and equilibration of forces within the reconstruction occurs mostly during the initial 10 cycles. Gap–cycle curves provide a good illustration of dynamic changes at the repair site, and should be added more frequently to cyclic testing studies.

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

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

Two-, four-, and six-strand zone II flexor tendon repairs: An in situ biomechanical comparison using a cadaver model

A dynamic in vitro model of zone II flexor tendon repair was used to compare gliding resistance, gap formation, and ultimate strength of the 2-, 4-, and 6-strand repair techniques. Each of 12 hands was mounted to a loading frame with 3 flexor tendons attached to individual pneumatic cylinders. A spring attached to a pin through the distal end of each digit provided a 1.25-kg resistance force. The force required to flex each proximal interphalangeal joint to 90 degrees was determined. Following this, the tendons were sectioned and each was repaired using a different technique so that each specimen acted as its own control. The 2- and 4-strand core sutures were placed using a suture interlock technique with radial and ulnar grasping purchase of the tendon on each side of the transverse part of the repair. Each repair was accomplished using a single core stitch with the knot buried between the tendon ends. The 4-strand repair involved an additional horizontal mattress suture with the knot buried. Repair of the dorsal side of the tendon was performed followed by core suture placement. The palmar portion of the peripheral locking suture was completed after core suture placement. Following repair, each hand was remounted on the frame and cycled 1,000 times. After cyclic loading, the resulting gap between the repaired ends of each tendon was measured, the tendons were removed from the hand, and each was loaded to failure in tension. All tendon repairs showed a small, but not statistically significant, increase in gliding resistance after reconstruction. The 2-strand repair had significantly greater gap formation after cyclic loading (mean gap, 2.75 mm) than either the 4-strand (0.30 mm) or 6-strand (0.31 mm) repair. The tensile strength of the 6-strand repair (mean, 78.7 N) was significantly greater than either the 4-strand (means, 43.0 N) or 2-strand (mean, 33.9 N) repair.