Here, we present a “Q” suture technique that can be performed in tendon repair and its effects on the gap formation and tensile strength of the repaired tendons. Q suture is shown to be efficient in enhancing the tensile resistance and tendon repair strength.
Peripheral epitendinous sutures are believed to enhance core suture strength in tendon repair and decrease the risk of gapping between tendon ends. Here Q suture, an alternative to peripheral sutures, is presented for the use in tendon repair. Its effects on gap formation and tensile strength of the repaired tendons were compared with conventional running peripheral sutures. Three 2-strand sutures and three 4-strand sutures were used in repairing porcine tendons. The time required for performing 2Q and running sutures were recorded. The repaired tendons were subjected to a cyclic loading test, and the cycle number, during which a 2-mm gap was formed, was determined. After the cyclic loading, the gap size at the tendon ends and the ultimate strength of the repaired tendons were measured. Augmentation with the Q sutures reduced the number of tendons showing 2-mm gaps at tendon ends during cyclic loading. With addition of Q sutures 2-strand sutures significantly increased the ultimate strength of the repaired tendons and 4-strand sutures decreased the gap distance at the repair site of tendons. The time required for performing 2Q sutures was significantly less than that for running sutures. Therefore, we conclude that the Q suture is efficient in enhancing the tensile resistance and tendon repair strength and can be an alternative to conventional peripheral sutures.
Gap formation at tendon repair site affects tendon repair strength and gliding resistance substantially. The consequences of gapping between tendon ends may ultimately impede tendon healing in vivo1. It has been reported that the presence of a gap larger than 2 mm at the repair site lead to a significant increase in the gliding resistance of repaired intrasynovial tendon in cadaveric hands2. A study in a canine model has shown that a gap size larger than 3 mm would impair the tendon healing strength and stiffness3. Therefore, improving resistance and decreasing the risk of gapping between tendon ends are critical for tendon repair.
Addition of peripheral sutures has been shown to reduce the gapping at the tendon repair site thereby improving gliding function of the repaired tendons4,5,6. During the last few decades, a number of peripheral sutures have been developed, including the interlocking cross stitch (IXS), interlocking horizontal mattress (IHM), and cross-linked Silfverskiöld and Lembert, et al7,8,9,10. These peripheral sutures have proven to be superior to running peripheral sutures with respect to gapping resistance in tendon repair. However, many of these sutures are complex in structure and difficult to perform, thereby limiting their widespread applications. An ideal suture for tendon repair should aim to prevent gap formation while avoiding the addition of bulk to the repair site after tendon repair. Currently, running peripheral suture remains a popular technique due to its simplicity.
In a recent study, a technique, alternative to peripheral suture, named Q suture, because its shape is similar to the letter “Q”, is presented11. Here, we compared this suturing technique with running peripheral suture to check for the differences in gapping resistance and the tensile strength of repaired tendons. The results showed that Q suture was more efficient in enhancing the gapping resistance and ultimate strength of the repaired tendons in the cyclic loading test. Therefore, this article aims to provide a detailed description of how to perform Q suture technique and the biomechanical settings for testing the effects of Q suture on the properties of the repaired tendons.
All experimental procedures described were approved by the Administration Committee of Experimental Animals of the Nantong University. Thirty porcine tendons were repaired with three 2-strand repairs: 2-strand core suture, 2-strand core suture plus 2Q, and 2-strand core suture plus running peripheral sutures. The other 30 porcine tendons were repaired with three 4 strand repairs: 4-strand core suture, 4-strand core suture plus 2Q, and 4-strand core suture plus running peripheral sutures.
1. Preparation of porcine tendons
2. Tendon repair
3. Software setting
4. Biomechanical test
5. Statistical Analysis
Table 1 shows that addition of Q suture reduced the number of tendons with 2-mm gapping during cyclic loading in both 2-strand and 4-strand repairs. All tendons repaired with 2-strand and 4-strand core sutures formed a 2-mm gap, whereas none of the tendons repaired with 2-strand plus 2Q and only half of those repaired with 4-strand plus 2Q had a 2-mm gapping after 10 cycles. More tendons repaired with 2-strand plus running or 4-strand plus running sutures showed a 2-mm gap than those augmented with Q sutures.
Table 1 also shows that with 2-strand repairs, addition of the Q suture and running sutures both reduced the gap distance between tendon ends after cyclic loading, but only Q suture addition significantly increased the ultimate strength of the repaired tendons. The addition of the Q suture also minimized the gap distance with 4-strand repairs, albeit the ultimate strength of the repaired tendons was not affected. The average time required for performing 2Q sutures was significantly shorter than that for a running suture.
Figure 1: Preparation of porcine tendons for tendon repair.
(A) Skin and subcutaneous tissues were removed. (B) Pulley and tendon sheath were incised. (C) Flexor digitorum superficialis (FDS) tendon was dissected. (D) Flexor digitorum profundus (FDP) tendons were harvested. (E) Tendon was cut along the midline. (F) FDP tendon was cut transversely into 2 stumps. Please click here to view a larger version of this figure.
Figure 2: 2-strand core suture in tendon repair.
(A) Surface of tendon stump was marked with point 1, 2, 3, and 4. (B-E) Core suture in one tendon stump was completed. (F) The entire core suture was completed. (G) Suture was tightened, and knots were tied. Please click here to view a larger version of this figure.
Figure 3: Q and running peripheral sutures in tendon repair.
(A-D) 2Q sutures were added. (E-G) Running peripheral sutures were added. (H) Tendons repaired with 4-strand core suture plus 2Q and 4-strand core suture plus running sutures. Please click here to view a larger version of this figure.
Figure 4: Biomechanical test of repaired tendons.
(A) Testing machine and computer that runs the software. (B) Distance between the upper and lower clamps was set to 5 cm. (C) Tendon segments were mounted into the clamps. (D) Gap distance between tendon ends was measured after cyclic loading. (E) Tendon was pulled upwards until the repair ruptures. Please click here to view a larger version of this figure.
Number of Tendons with 2-mm Gap | Gap Size (mm) | Ultimate Strength (N) | Surgical Time (min) | |
2-strand core suture | 10 | 8.7 + 1.1 | 21.7 + 1.4 | |
2-strand core suture plus 2Q | 0 | 1.1 + 0.4* | 25.7 + 4.1* | 1.8 + 0.2* |
2-strand core suture plus running | 2 | 0.8 + 0.2* | 22.9 + 1.5 | 3.2 + 0.2 |
4-strand core suture | 10 | 8.2 + 1.1 | 32.8 + 4.3 | |
4-strand core suture plus 2Q | 5 | 1.8 + 0.8* | 32.4 + 3.3 | |
4-strand core suture plus running | 9 | 6.5 + 2.8*# | 33.8 + 5.5 | |
The data of 2-strand core suture and 4-strand core suture are analyzed separately. *Significant different from those data without an asterisk in the same column. #Significantly different from 4-strand core suture plus 2Q data in the same column. |
Table 1: Number of tendons with 2-mm gap formation during cyclic loading, gap size at the repair site after cyclic loading, ultimate strength of the repaired tendons, and surgical time for 2Q and running sutures.
The results of the current study showed that Q suture not only reduced the gapping and improves tensile strength of the repaired tendons but was also timesaving and labor-saving. Nonetheless, some key points regarding tendon repair in the current study should be noted.
First, we tried to select tendon samples that were similar in shape and size because we were not sure whether tendon size would have a notable impact on tensile strength after repair. In addition, tendon samples can be preserved at -20 ˚C if they cannot be repaired and tested in time. It has been shown that freezing tendons does not significantly alter the repair strength of tendons and is considered an acceptable method for preserving tendons12. However, repeated freeze–thaw cycles should be avoided. Once thawed, tendon specimens should be kept moist; otherwise, the properties of tendon tissue will change drastically.
Second, the core suture purchase of tendon repair in the current study was set as 10 mm. Core suture purchase is defined as the exit and entry distance of the core suture from the cut ends of the tendon. Previous studies reported that lengthening of the suture purchase effectively increased the repair strength of tendon. The optimal length is considered to be between 0.7 and 1.0 cm13,14. A purchase length of less than 0.7 cm results in a significantly weaker repair, while further increasing the length of purchase to more than 1.0 cm does not improve the strength of tendon repair. The underlying mechanisms involved may include a greater tendon–suture interaction, a more secure grip power of sutures on the tendon surface, and increased stiffness to counteract tensile forces by the increased length of the suture purchase15,16.
Third, the core sutures should be tightened to a certain degree before tying knots because addition of a slight tension to the core suture has been shown to be beneficial in reducing the risk of gapping in tendon repair17,18. Wu and Tang reported that 10% of tendon shortening by tensioning of core suture markedly increased the gap formation forces without obvious increase in tendon bulkiness19. Slight tensioning of the core suture might help equalize the load on the core suture strands, which prevented gap formation in the repaired tendons. Further shortening of the tendon segment by 20% through tensioning increased the gapping resistance by a small amount. However, the further increase led to a bulge in the repair site of the tendon, which might increase sliding friction in vivo thereby increasing the gliding impairment.
Fourth, previous studies have demonstrated that the tensile strength of repaired tendon was significantly affected by the depth and purchase of peripheral sutures. Peripheral suture with a depth of 1 mm and purchase of 1.5 mm were considered optimal for strengthening the core suture without adding too much bulk at the tendon ends20. The Q suture differs from conventional peripheral sutures in that it passes through the full thickness of the tendon substance. We set the purchase of Q suture to 2 mm and found it could hold the tendon stumps tightly without obvious bulk.
Lastly, the maximum loads were set at 8 N for the 2-strand repairs and 15 N for the 4 strand repairs in the cyclic loading test. These forces were predetermined in a preliminary experiment, which showed that these forces could lead to differences in gap formation at the repair site in different groups during cyclic loading. Gapping at the repair site would not occur if the loading force decreased, while all tendons would show immediate gapping if loading force increased. Therefore, the maximum loading forces had been carefully determined based on the preliminary experiment to avoid immediate gapping or absence of gapping at the repair site when the tendons were subjected to a cyclic loading test.
A limitation of the current study is that only 1 type of core suture was used. Future studies should employ additional core suture techniques to evaluate the effects of Q suture. In addition, we did not study the gliding resistance of the repaired tendon ex vivo and the effects of Q suture on tendon healing in vivo, which also warrants further investigations.
Base on the present study, the Q suture shows superior performance in resisting gapping in tendon repair when compared with running peripheral sutures. This suture is also very easy to perform, as well as timesaving and could be an alternative to conventional peripheral sutures.
The authors have nothing to disclose.
The authors acknowledge support from Graduate Research Innovation Project of Jiangsu Province (YKC16061).
4-0 suture | Ethicon, Somerville, NJ | Ethilon 1667 | |
6-0 suture | Ethicon, Somerville, NJ | Ethilon 689 | |
biomechanical testing machine | Instron Corp, Norwood, MA | Instron 3365 | |
biomechanical testing software | Instron Corp, Norwood, MA | Bluehill 2 |