The authors acknowledge support from Graduate Research Innovation Project of Jiangsu Province (YKC16061).

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
<ol>
	<li>Purchase fresh adult pig hind-leg trotters from a slaughtering house. Remove the skin and subcutaneous tissues to expose the pulley and tendon sheath (Figure 1A). 
	NOTE: The pulley and tendon sheath are dense in texture, which form an obvious fibro-osseous tunnel for the gliding tendons. The subcutaneous tissues are relatively loose in texture and very easy to be removed.</li>
	<li>Incise the pulley and tendon sheath longitudinally along the central line to expose the flexor tendons (Figure 1B).</li>
	<li>Dissect the flexor digitorum superficialis (FDS) tendon to expose the branches of the flexor digitorum profundus&#160;(FDP) tendons (Figure 1C).</li>
	<li>Harvest the FDP tendons by cutting proximally at about 5 cm to the bifurcation of the FDP tendon and distally at the tendon insertion to the distal phalanx. (Figure 1D).</li>
	<li>Wash the tendon samples with clean water and remove the paratenon using surgical scissors.</li>
	<li>Cut the tendon along the midline from the end that was proximal to the bifurcation (Figure 1E).</li>
	<li>Cut the FDP tendon transversely into 2 stumps at the level that structurally corresponds to the middle part of human zone 2 flexor tendons. The resulting 2 tendon stumps are ready to be repaired (Figure 1F).</li>
</ol>
2. Tendon repair
<ol>
	<li>Mark the anterior surface of one of the tendon stumps with 2 points that are 10 mm from the cut tendon end, with each point locating one-fourth of the way from the left (point 1) and the right (point 2), respectively, in the medial-lateral direction (Figure 2A).</li>
	<li>Mark each of the left (point 3) and right (point 4) lateral surfaces of the tendon with one point that is 8 mm from the cut tendon end and locate in the middle in the anterior-posterior direction&#160;(Figure 2A). Determine all lengths with a Vernier caliper (rated accuracy of 0.02 mm).</li>
	<li>Repair the tendon with 4-0&#160;suture. Insert the needle into the cut surface of one tendon stump from the point that is in the middle in the anterior-posterior direction and one-fourth of the way from the left in the medial-lateral direction (Figure 2B). Pass the needle longitudinally through the tendon and withdraw the needle on the anterior surface of the tendon, exiting from point 1 (Figure 2B).</li>
	<li>Re-insert the needle obliquely from point 3 and pass it transversely toward point 4, creating a small loop at the lateral surface of the tendon (Figure 2C). Pull out the suture and re-insert the needle obliquely from point 2 and pass it longitudinally toward the cut end (Figure 2D,E).</li>
	<li>Insert the needle into the cut end of the other tendon stump and repair it with the same construct, forming a symmetrical repair (Figure 2F).</li>
	<li>Tighten the suture with 10% shortening of the tendon segment within the core suture. Tie the tendon ends together with 3 to 4 knots and complete the 2-strand core suture (Figure 2G).</li>
	<li>Repeat the operation once to complete the 4-strand core suture. Do not cut off the first core suture when performing the second core suture.</li>
	<li>Insert the same needle into the tendon anterior surface 2 mm away from the joined tendon end and pass through the full thickness of the tendon stump (Figure 3A).</li>
	<li>Withdraw the needle on the posterior surface of the tendon and re-insert the needle into the posterior surface of the tendon 2 mm away from the other side of the joined tendon end (Figure 3B).</li>
	<li>Pull out the suture from the anterior surface of the tendon and tie 3 knots to complete 1 Q suture (Figure 3C). Repeat the procedure to complete the second Q suture (Figure 3D).</li>
	<li>In the 2-strand and 4-strand core suture plus running group, add a running epitendinous suture of 9 to 10 stitches to the tendon ends using 6-0 suture. Keep a similar purchase of 1.5 mm and depth of 1 mm (Figure 3E,F,G).</li>
	<li>Keep the repaired tendon moist by wet gauzes before biomechanical testing.</li>
</ol>
3. Software setting
<ol>
	<li>Open the testing software and go to the Home screen. Click Method to create a test method. Click New to open the Create a New Test Method dialog box. Select the test type Tension-TestProfile Method and click Create. Click Save As to name and save the test method file.</li>
	<li>Open the Control-Pre-Test screen in the Method tab by clicking Control | Pre-Test in the navigation bar. Click Preload. Set the control mode as Tensile Extension, the rate as 25 mm/min, the channel as load, and the value as 0.5 N. Enable Auto balance. Add the Available Channels of Tensile strain and Load to the Selected Channels.</li>
	<li>Open the Control-Test screen in the Method tab and click Edit Profile of the cyclic loading. Insert 4 blocks.
	<ol>
		<li>In the first block, set the Mode as Tensile extension, Shape as Triangle, Maximum load as 8 N in the 2-strand repairs and 15 N in the 4-strand repairs, Minimum load as 0 N, Rate as 25 mm/min, and Cycle as 10.</li>
		<li>In the second block, set the Mode as Tensile extension, Shape as Absolute Ramp, Rate as 25 mm/min, and Endpoint as 8N in the 2-strand repairs and 15 N in the 4-strand repairs.</li>
		<li>In the third block, set the Mode as Tensile extension, Shape as Hold, Criteria as Duration, and Duration as 8 s.</li>
		<li>In the fourth block, set the Mode as Tensile extension, Shape as Absolute Ramp, Rate as 25 mm/min, and Endpoint as 100 N. Click Save and Close.</li>
	</ol>
	</li>
	<li>Open the Control-End of Test screen in the Method tab. Set Criteria 1 as Rate of Load, and Sensitivity as 40%.</li>
	<li>Open the Calculation-Setup screen in the Method tab. Select Absolute peak and add to the Selected calculations. Select Load in the drop-down list of Channel. Apply to the 4. Absolute Ramp.</li>
	<li>Open the Results 1-Columns screen in the Method tab. Select Maximum Load and add Load to the selected results. Click Save and Close.</li>
</ol>
4. Biomechanical test
<ol>
	<li>Turn on the testing machine and the computer that runs the software (Figure 4A). Open the testing software and go to the Home screen (Figure 4A). Set the initial distance between the upper and lower clamps of the testing machine to 5 cm (Figure 4B).</li>
	<li>Wrap the tendon with dry gauzes 2&#8211;3 cm away from the cut end. Mount the tendon segments wrapped with gauzes into the upper and lower clamps and keep the tendon vertical as much as possible (Figure 4C).</li>
	<li>Click Test on the Home screen. Choose the test method file saved in step 3.6&#160;above. Click Next.</li>
	<li>Enter a name and choose a location for the sample data file. Click Next. The Test tab displays. Open Load Cell Setup dialog and click Calibrate to remove load from load cell.</li>
	<li>Open Control Panel Setup Dialog and select Balance Load in the drop-down list of Key 1 and Reset Gauge Length of Key 2. Click Balance Load and Reset Gauge Length. Click Start to run a test for each specimen in the sample. Record the number of tendon when a 2-mm gap is formed between the 2 ends during the cyclic loading.</li>
	<li>Measure the gap distance between tendon ends during a pause of 8 s at the maximum load of the 10th cycle (Figure 4D).</li>
	<li>Pull the tendon upwards until the repair ruptures and record the ultimate breaking strength (Figure 4E).</li>
	<li>Click Stop, Return, and Finish to save the results.</li>
</ol>
5. Statistical Analysis
<ol>
	<li>Present data as mean and standard deviation (SD).</li>
	<li>Analyze data on gap distance and ultimate strength of tendons repaired by different methods using a one-way analysis of variance (ANOVA).</li>
	<li>Perform multiple comparisons using LSD tests. Set the level of significance at P &#60; 0.05.</li>
</ol>

<ol>
	<li>Linnanmaki, L., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Gap+Formation+During+Cyclic+Testing+of+Flexor+Tendon+Repair.">Gap Formation During Cyclic Testing of Flexor Tendon Repair.</a> Journal of Hand Surgery - American volume. 43 (6), 570 (2018).</li><li>Zhao, C., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Effect+of+gap+size+on+gliding+resistance+after+flexor+tendon+repair.">Effect of gap size on gliding resistance after flexor tendon repair.</a> Journal of Bone and Joint Surgery - American volume. 86 (11), 2482-2488 (2004).</li><li>Gelberman, R. H., Boyer, M. I., Brodt, M. D., Winters, S. C., Silva, M. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+effect+of+gap+formation+at+the+repair+site+on+the+strength+and+excursion+of+intrasynovial+flexor+tendons.+An+experimental+study+on+the+early+stages+of+tendon-healing+in+dogs.">The effect of gap formation at the repair site on the strength and excursion of intrasynovial flexor tendons. An experimental study on the early stages of tendon-healing in dogs.</a> Journal of Bone and Joint Surgery - American volume. 81 (7), 975-982 (1999).</li><li>Sull, A., Inceoglu, S., Wongworawat, M. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Does+Barbed+Suture+Repair+Negate+the+Benefit+of+Peripheral+Repair+in+Porcine+Flexor+Tendon.">Does Barbed Suture Repair Negate the Benefit of Peripheral Repair in Porcine Flexor Tendon.</a> Hand. 11 (4), 479-483 (2016).</li><li>Merrell, G. A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+effect+of+increased+peripheral+suture+purchase+on+the+strength+of+flexor+tendon+repairs.">The effect of increased peripheral suture purchase on the strength of flexor tendon repairs.</a> Journal of Hand Surgery - American volume. 28 (3), 464-468 (2003).</li><li>Rawson, S., Cartmell, S., Wong, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Suture+techniques+for+tendon+repair;+a+comparative+review.">Suture techniques for tendon repair; a comparative review.</a> Muscles, Ligaments, and Tendons Journal. 3 (3), 220-228 (2013).</li><li>Dona, E., Turner, A. W., Gianoutsos, M. P., Walsh, W. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Biomechanical+properties+of+four+circumferential+flexor+tendon+suture+techniques.">Biomechanical properties of four circumferential flexor tendon suture techniques.</a> Journal of Hand Surgery - American volume. 28 (5), 824-831 (2003).</li><li>Mishra, V., Kuiper, J. H., Kelly, C. P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Influence+of+core+suture+material+and+peripheral+repair+technique+on+the+strength+of+Kessler+flexor+tendon+repair.">Influence of core suture material and peripheral repair technique on the strength of Kessler flexor tendon repair.</a> Journal of Hand Surgery - British and European Volume. 28 (4), 357-362 (2003).</li><li>Moriya, T., Zhao, C., An, K. N., Amadio, P. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+effect+of+epitendinous+suture+technique+on+gliding+resistance+during+cyclic+motion+after+flexor+tendon+repair:+a+cadaveric+study.">The effect of epitendinous suture technique on gliding resistance during cyclic motion after flexor tendon repair: a cadaveric study.</a> Journal of Hand Surgery - American volume. 35 (4), 552-558 (2010).</li><li>Takeuchi, N., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Strength+enhancement+of+the+interlocking+mechanism+in+cross-stitch+peripheral+sutures+for+flexor+tendon+repair:+biomechanical+comparisons+by+cyclic+loading.">Strength enhancement of the interlocking mechanism in cross-stitch peripheral sutures for flexor tendon repair: biomechanical comparisons by cyclic loading.</a> Journal of Hand Surgery - European volume. 35 (1), 46-50 (2010).</li><li>Mao, W. F., Wu, Y. F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Effects+of+a+Q+Suture+Technique+on+Resistance+to+Gap+Formation+and+Tensile+Strength+of+Repaired+Tendons:+An+Ex+Vivo+Mechanical+Study.">Effects of a Q Suture Technique on Resistance to Gap Formation and Tensile Strength of Repaired Tendons: An Ex Vivo Mechanical Study.</a> Journal of Hand Surgery - American volume. 45 (3), 258 (2020).</li><li>Hirpara, K. M., Sullivan, P. J., O'Sullivan, M. E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+effects+of+freezing+on+the+tensile+properties+of+repaired+porcine+flexor+tendon.">The effects of freezing on the tensile properties of repaired porcine flexor tendon.</a> Journal of Hand Surgery - American volume. 33 (3), 353-358 (2008).</li><li>Tang, J. B., Zhang, Y., Cao, Y., Xie, R. G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Core+suture+purchase+affects+strength+of+tendon+repairs.">Core suture purchase affects strength of tendon repairs.</a> Journal of Hand Surgery - American volume. 30 (6), 1262-1266 (2005).</li><li>Cao, Y., Zhu, B., Xie, R. G., Tang, J. B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Influence+of+core+suture+purchase+length+on+strength+of+four-strand+tendon+repairs.">Influence of core suture purchase length on strength of four-strand tendon repairs.</a> Journal of Hand Surgery - American volume. 31 (1), 107-112 (2006).</li><li>Kim, J. B., de Wit, T., Hovius, S. E., McGrouther, D. A., Walbeehm, E. T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=What+is+the+significance+of+tendon+suture+purchase.">What is the significance of tendon suture purchase.</a> Journal of Hand Surgery - European volume. 34 (4), 497-502 (2009).</li><li>Lee, S. K., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+effects+of+core+suture+purchase+on+the+biomechanical+characteristics+of+a+multistrand+locking+flexor+tendon+repair:+a+cadaveric+study.">The effects of core suture purchase on the biomechanical characteristics of a multistrand locking flexor tendon repair: a cadaveric study.</a> Journal of Hand Surgery - American volume. 35 (7), 1165-1171 (2010).</li><li>Vanhees, M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+effect+of+suture+preloading+on+the+force+to+failure+and+gap+formation+after+flexor+tendon+repair.">The effect of suture preloading on the force to failure and gap formation after flexor tendon repair.</a> Journal of Hand Surgery - American volume. 38 (1), 56-61 (2013).</li><li>Smith, G. H., Huntley, J. S., Anakwe, R. E., Wallace, R. J., McEachan, J. E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Tensioning+of+Prolene+reduces+creep+under+cyclical+load:+relevance+to+a+simple+pre-operative+manoeuvre.">Tensioning of Prolene reduces creep under cyclical load: relevance to a simple pre-operative manoeuvre.</a> Journal of Hand Surgery - European volume. 37 (9), 823-825 (2012).</li><li>Wu, Y. F., Tang, J. B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Effects+of+tension+across+the+tendon+repair+site+on+tendon+gap+and+ultimate+strength.">Effects of tension across the tendon repair site on tendon gap and ultimate strength.</a> Journal of Hand Surgery - American volume. 37 (5), 906-912 (2012).</li><li>Wu, Y. F., Tang, J. B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=How+much+does+a+Pennington+lock+add+to+strength+of+a+tendon+repair.">How much does a Pennington lock add to strength of a tendon repair.</a> Journal of Hand Surgery - European volume. 36 (6), 476-484 (2011).</li></ol>

The authors have nothing to disclose.

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 &#730;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&#8211;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&#8211;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.

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 Silfverski&#246;ld 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 &#8220;Q&#8221;, 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.

<table><tbody><tr><td>4-0 suture</td><td>Ethicon, Somerville, NJ</td><td>Ethilon 1667</td><td></td></tr><tr><td>6-0 suture</td><td>Ethicon, Somerville, NJ</td><td>Ethilon 689</td><td></td></tr><tr><td>biomechanical testing machine</td><td>Instron Corp, Norwood, MA</td><td>Instron 3365</td><td></td></tr><tr><td>biomechanical testing software</td><td>Instron Corp, Norwood, MA</td><td>Bluehill 2</td><td></td></tr></tbody></table>

using q suture to enhance resistance to gap formation and tensile strength of repaired flexor tendons

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.

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.
<img alt="Figure 1" class="xfigimg" src="/files/ftp_upload/61445/61445fig01.jpg" /> 
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. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/61445/61445fig01large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 2" class="xfigimg" src="/files/ftp_upload/61445/61445fig02.jpg" /> 
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. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/61445/61445fig02large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 3" class="xfigimg" src="/files/ftp_upload/61445/61445fig03.jpg" /> 
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. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/61445/61445fig03large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 4" class="xfigimg" src="/files/ftp_upload/61445/61445fig04.jpg" /> 
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. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/61445/61445fig04large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td></td>
			<td>Number of Tendons with 2-mm Gap</td>
			<td>Gap Size (mm)</td>
			<td>Ultimate Strength (N)</td>
			<td>Surgical Time (min)</td>
		</tr>
		<tr>
			<td>2-strand core suture</td>
			<td>10</td>
			<td>8.7 + 1.1</td>
			<td>21.7 + 1.4</td>
			<td></td>
		</tr>
		<tr>
			<td>2-strand core suture plus 2Q</td>
			<td>0</td>
			<td>1.1 + 0.4*</td>
			<td>25.7 + 4.1*</td>
			<td>1.8 + 0.2*</td>
		</tr>
		<tr>
			<td>2-strand core suture plus running</td>
			<td>2</td>
			<td>0.8 + 0.2*</td>
			<td>22.9 + 1.5</td>
			<td>3.2 + 0.2</td>
		</tr>
		<tr>
			<td colspan="5"></td>
		</tr>
		<tr>
			<td>4-strand core suture</td>
			<td>10</td>
			<td>8.2 + 1.1</td>
			<td>32.8 + 4.3</td>
			<td></td>
		</tr>
		<tr>
			<td>4-strand core suture plus 2Q</td>
			<td>5</td>
			<td>1.8 + 0.8*</td>
			<td>32.4 + 3.3</td>
			<td></td>
		</tr>
		<tr>
			<td>4-strand core suture plus running</td>
			<td>9</td>
			<td>6.5 + 2.8*#</td>
			<td>33.8 + 5.5</td>
			<td></td>
		</tr>
		<tr>
			<td colspan="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.</td>
		</tr>
	</tbody>
</table>
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.

Watch this Scientific Journal Video about Using Q Suture to Enhance Resistance to Gap Formation and Tensile Strength of Repaired Flexor Tendons at JoVE.com

Using Q Suture to Enhance Resistance to Gap Formation and Tensile Strength of Repaired Flexor Tendons

Here, we present a &#8220;Q&#8221; 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 ...

using-q-suture-to-enhance-resistance-to-gap-formation-tensile

Nanyang Technological University

Research

JoVE Journal

Medicine

5.6K Views.  Nantong University. Randhechtingen kunnen de hechtsterkte van de kern versterken en het risico op gapen tussen gerepareerde peeseinden verminderen. We presenteren Q hechtingen als een alternatief voor conventionele perifere hechtingen. In vergelijking met conventionele lopende randhechtingen, Q hechtingen zijn zeer eenvoudig uit te voeren, zijn tijdbesparend, en tonen een superieure prestaties in het weerstaan van gapping in pees reparatie.Om een peesreparatie uit te voeren, begin met het markeren van het...

Video: Using Q Suture to Enhance Resistance to Gap Formation and Tensile Strength of Repaired Flexor Tendons

Tri-layered Electrospinning to Mimic Native Arterial Architecture using Polycaprolactone, Elastin, and Collagen: A Preliminary Study

Throughout native artery, collagen and elastin play an important role, providing a mechanical backbone, preventing vessel rupture, and promoting recovery under pulsatile deformations. The goal of this study was to mimic the structure of native artery by fabricating a multi-layered electrospun conduit composed of poly(caprolactone) (PCL) with the addition of elastin and collagen with blends of 45-45-10, 55-35-10, and 65-25-10 PCL-ELAS-COL to demonstrate mechanical properties indicative of native arterial tissue, while remaining conducive to tissue regeneration. Whole grafts and individual layers were analyzed using uniaxial tensile testing, dynamic compliance, suture retention, and burst strength. Compliance results revealed that changes to the middle/medial layer changed overall graft behavior with whole graft compliance values ranging from 0.8 - 2.8 % / 100 mmHg, while uniaxial results demonstrated an average modulus range of 2.0 - 11.8 MPa. Both modulus and compliance data displayed values within the range of native artery. Mathematical modeling was implemented to show how changes in layer stiffness affect the overall circumferential wall stress, and as a design aid to achieve the best mechanical combination of materials. Overall, the results indicated that a graft can be designed to mimic a tri-layered structure by altering layer properties.

The aim of this study was to mimic the native three layered architecture of the arterial wall. To accomplish this, electrospinning was employed with the use of a 3-1 (input-output) nozzle and blends of polycaprolactone, elastin, and collagen.

Throughout native artery, collagen and elastin play an important role, providing a mechanical backbone, preventing vessel rupture, and promoting recovery ...

Bioengineering

The Measurement and Treatment of Suppression in Amblyopia

Amblyopia, a developmental disorder of the visual cortex, is one of the leading causes of visual dysfunction in the working age population. Current estimates put the prevalence of amblyopia at approximately 1-3%1-3, the majority of cases being monocular2. Amblyopia is most frequently caused by ocular misalignment (strabismus), blur induced by unequal refractive error (anisometropia), and in some cases by form deprivation.
Although amblyopia is initially caused by abnormal visual input in infancy, once established, the visual deficit often remains when normal visual input has been restored using surgery and/or refractive correction. This is because amblyopia is the result of abnormal visual cortex development rather than a problem with the amblyopic eye itself4,5 . Amblyopia is characterized by both monocular and binocular deficits6,7 which include impaired visual acuity and poor or absent stereopsis respectively. The visual dysfunction in amblyopia is often associated with a strong suppression of the inputs from the amblyopic eye under binocular viewing conditions8. Recent work has indicated that suppression may play a central role in both the monocular and binocular deficits associated with amblyopia9,10 .
Current clinical tests for suppression tend to verify the presence or absence of suppression rather than giving a quantitative measurement of the degree of suppression. Here we describe a technique for measuring amblyopic suppression with a compact, portable device11,12 . The device consists of a laptop computer connected to a pair of virtual reality goggles. The novelty of the technique lies in the way we present visual stimuli to measure suppression. Stimuli are shown to the amblyopic eye at high contrast while the contrast of the stimuli shown to the non-amblyopic eye are varied. Patients perform a simple signal/noise task that allows for a precise measurement of the strength of excitatory binocular interactions. The contrast offset at which neither eye has a performance advantage is a measure of the "balance point" and is a direct measure of suppression. This technique has been validated psychophysically both in control13,14 and patient6,9,11 populations.
In addition to measuring suppression this technique also forms the basis of a novel form of treatment to decrease suppression over time and improve binocular and often monocular function in adult patients with amblyopia12,15,16 . This new treatment approach can be deployed either on the goggle system described above or on a specially modified iPod touch device15.

Amblyopia is a developmental disorder of the visual cortex that is often accompanied by strong suppression of one eye. We present a new technique for measuring and treating interocular suppression in patients with amblyopia that can be deployed using virtual reality goggles or a portable iPod Touch device.

Amblyopia, a developmental disorder of the visual cortex, is one of the leading causes of visual dysfunction in the working age population. Current ...

A Novel Tenorrhaphy Suture Technique with Tissue Engineered Collagen Graft to Repair Large Tendon Defects

Surgical management of large tendon defects with tendon grafts is challenging, as there are a finite number of sites where donors can be readily identified and used. Currently, this gap is filled with tendon auto-, allo-, xeno-, or artificial grafts, but clinical methods to secure them are not necessarily translatable to animals because of the scale. In order to evaluate new biomaterials or study a tendon graft made up of collagen type 1, we have developed a modified suture technique to help maintain the engineered tendon in alignment with the tendon ends. Mechanical properties of these grafts are inferior to the native tendon. To incorporate engineered tendon into clinically relevant models of loaded repair, a strategy was adopted to offload the tissue engineered tendon graft and allow for the maturation and integration of the engineered tendon in vivo until a mechanically sound neo-tendon was formed. We describe this technique using incorporation of the collagen type 1 tissue engineered tendon construct.

In this paper, we present an in vitro and in situ protocol to repair a tendon gap of up to 1.5 cm by filling it with engineered collagen graft. This was performed by developing a modified suture technique to take the mechanical load until the graft matures into the host tissue.

Surgical management of large tendon defects with tendon grafts is challenging, as there are a finite number of sites where donors can be readily ...

Adapted Resistance Training Improves Strength in Eight Weeks in Individuals with Multiple Sclerosis

Hip weakness is a common symptom affecting walking ability in people with multiple sclerosis (MS). It is known that resistance strength training (RST) can improve strength in individuals with MS, however; it remains unclear the duration of RST that is needed to make strength gains and how to adapt hip strengthening exercises for individuals of varying strength using only resistance bands. This paper describes the methodology to set up and implement an adapted resistance strength training program, using resistance bands, for individuals with MS. Directions for pre- and post-strength tests to evaluate efficacy of the strength-training program are included. Safety features and detailed instructions outline the weekly program content and progression. Current evidence is presented showing that significant strength gains can be made within 8 weeks of starting a RST program. Evidence is also presented showing that resistance strength training can be successfully adapted for individuals with MS of varying strength with little equipment.

Hip weakness is a common symptom affecting walking ability in people with multiple sclerosis. Isolated muscle strengthening is a useful method to target specific weaknesses. This protocol describes a progressive resistance-training program using exercise bands to increase hip muscle strength.

Hip weakness is a common symptom affecting walking ability in people with multiple sclerosis (MS). It is known that resistance strength training (RST) can ...

Murine Flexor Tendon Injury and Repair Surgery

Tendon connects skeletal muscle and bone, facilitating movement of nearly the entire body. In the hand, flexor tendons (FTs) enable flexion of the fingers and general hand function. Injuries to the FTs are common, and satisfactory healing is often impaired due to excess scar tissue and adhesions between the tendon and surrounding tissue. However, little is known about the molecular and cellular components of FT repair. To that end, a murine model of FT repair that recapitulates many aspects of healing in humans, including impaired range of motion and decreased mechanical properties, has been developed and previously described. Here an in-depth demonstration of this surgical procedure is provided, involving transection and subsequent repair of the flexor digitorum longus (FDL) tendon in the murine hind paw.&#160;This technique can be used to conduct lineage analysis of different cell types, assess the effects of gene gain or loss-of-function, and to test the efficacy of pharmacological interventions in the healing process. However, there are two primary limitations to this model: i) the FDL tendon in the mid-portion of the murine hind paw, where the transection and repair occur, is not surrounded by a synovial sheath. Therefore this model does not account for the potential contribution of the sheath to the scar formation process. ii) To protect the integrity of the repair site, the FT is released at the myotendinous junction, decreasing the mechanical forces of the tendon, likely contributing to increased scar formation. Isolation of sufficient cells from the granulation tissue of the FT during the healing process for flow cytometric analysis has proved challenging; cytology centrifugation to concentrate these cells is an alternate method used, and allows for generation of cell preparations on which immunofluorescent labeling can be performed. With this method, quantification of cells or proteins of interest during FT healing becomes possible.

Flexor tendons in the hand are commonly injured, leading to impaired hand function. However, the scar-tissue healing response is not well characterized. A murine model of flexor tendon healing is demonstrated here. This model can enhance overall understanding of the healing process and assess therapeutic approaches to improve healing.

Tendon connects skeletal muscle and bone, facilitating movement of nearly the entire body. In the hand, flexor tendons (FTs) enable flexion of the fingers ...

A Training and Testing System for Performing Vascular Reconstruction In Vitro

Manual vascular reconstruction training is essential for a beginner surgeon. However, an optimal training system for vascular reconstruction in vitro has yet to be developed. In this study, we introduce an in vitro training and testing system using a magnetic anchoring technique with which a trainee can practice manual vascular reconstruction individually. Additionally, this system can also be used to test the quality of the reconstruction. The described system includes a vascular reconstruction training machine, magnetic tractors, and a magnetic suture puller. In this manuscript, we detail an end-to-end vein anastomosis using porcine right and left iliac veins. To identify the potential damage caused by a magnetic suture puller on the suture, we created three groups with six segments of 4-0 polypropylene sutures each: a control group with no intervention on the polypropylene suture, a group in which the polypropylene suture is manually pulled with sterile gloves 20x, and a magnetic puller group in which the magnetic puller pulled the polypropylene suture 20x. These groups were tested by light microscopy and breaking strength tests, and the effect of reconstruction was assessed. In the light microscopy test, the control group was less likely to be damaged (p &#60; 0.05) and the number of damaged points of the manual group and magnetic puller group were similar (p &#62; 0.05). The results of the breaking strength test were compared across groups and no significant difference was observed (p &#62; 0.05). The end-to-end anastomosis of the porcine iliac veins was successfully performed using this training system, and the reconstructed veins could undergo 2.0 kPa perfusion pressure. Using this training and testing system the trainee can practice manual vascular reconstruction in vitro individually with the aid of magnetic tractors and a magnetic suture puller, and the quality of the reconstruction can be tested.

Here we present a training and testing system where a trainee can complete manual vascular reconstruction in vitro individually using a magnetic anchoring technique. The system can also be used to test the quality of reconstruction.

Manual vascular reconstruction training is essential for a beginner surgeon. However, an optimal training system for vascular reconstruction in vitro has ...

Polytetrafluoroethylene (PTFE) as a Suture Material in Tendon Surgery

With the evolution of suture materials, there has been a change in paradigms in primary and secondary tendon repair. Improved mechanical properties allow more aggressive rehabilitation and earlier recovery. However, for the repair to hold against higher mechanical demands, more advanced suturing and knotting techniques must be assessed in combination with those materials. In this protocol, the use of polytetrafluoroethylene (PTFE) as a suture material in combination with different repair techniques was investigated. In the first part of the protocol, both linear tension strength and elongation of knotted against not-knotted strands of three different materials used in flexor tendon repair were evaluated. The three different materials are polypropylene (PPL), ultra-high molecular weight polyethylene with a braided jacket of polyester (UHMWPE), and polytetrafluoroethylene (PTFE). In the next part (ex vivo experiments with cadaveric flexor tendons), the behavior of PTFE using different suture techniques was assessed and compared with PPL and UHMWPE.
This experiment is comprised of four steps: harvesting of the flexor tendons from fresh cadaveric hands, transection of the tendons in a standardized manner, tendon repair by four different techniques, mounting, and measurement of the tendon repairs on a standard linear dynamometer. The UHMWPE and PTFE showed comparable mechanical properties and were significantly superior to PPL in terms of linear traction strength. Repairs with four- and six-strand techniques proved stronger than two-strand techniques. Handling and knotting of PTFE are a challenge due to very low surface friction but fastening of the four- or six-strand repair is comparatively easy to achieve. Surgeons routinely use PTFE suture material in cardiovascular surgery and breast surgery. The PTFE strands are suitable for use in tendon surgery, providing a robust tendon repair so that early active motion regimens for rehabilitation can be applied.

Polytetrafluoroethylene PTFE as a Suture Material in Tendon Surgery

The present protocol illustrates a method for assessing the biophysical properties of tendon repairs ex vivo. A polytetrafluoroethylene (PTFE) suture material was evaluated by this method and compared to other materials under different conditions.

With the evolution of suture materials, there has been a change in paradigms in primary and secondary tendon repair. Improved mechanical properties allow ...

Tensile Strength of Resorbable Biomaterials

Source: <a href="https://www-jove-com.remotexs.ntu.edu.sg/author/Peiman_Shahbeigi-Roodposhti">Peiman Shahbeigi-Roodposhti</a> and Sina Shahbazmohamadi, Biomedical Engineering Department, University of Connecticut, Storrs, Connecticut
For over 4000 years, sutures have been used as a medical intervention. The earliest records indicate linen was the biomaterial of choice. Catgut, which is still in use today, was reportedly used to treat gladiators around 150 AD. Today, there are numerous materials being used for sutures. Sutures are classified by their composition (natural or synthetic) and their absorption (non-resorbable or resorbable).
Resorbable (or absorbable) sutures degrade in the body through either enzymatic degradation or programmed degradation caused by the interaction of water with specific groups in the polymer chain. These sutures are often created from synthetic materials, such as polyglycolic acid, polydioxanone, and polycaprolactone, or natural biomaterials, such as silk. They are usually used for certain internal procedures, like general surgery. Resorbable sutures will hold the wound together for a time frame long enough for healing, but then they eventually disintegrate by the body. On the other hand, non-resorbable sutures do not degrade and must be extracted. They are usually derived from polypropylene, nylon, and stainless-steel. These sutures are usually implemented for orthopedic and cardiac surgery and require a medical professional to remove them at a later date.
Here, the tensile strength of two types of resorbable sutures will be tested after exposing them to neutral, acidic, and alkaline solutions, which correspond to the different pH environments found within the human body. The test will consist of two parts. First, control samples will be prepared and analyzed via tensile testing. Then, samples will be tested after the continuous exposure to solutions of varying pH over the course of several weeks.

Tensile Strength and Loss Profile of Resorbable Biomaterials

Source: Peiman Shahbeigi-Roodposhti and Sina Shahbazmohamadi, Biomedical Engineering Department, University of Connecticut, Storrs, Connecticut
For over ...

Education

JoVE Science Education

Engineering

Biomedical Engineering

Q Suture Technique: A Suturing Technique to Reduce Gap Formation and Increase Tensile Strength in Tendon Repair

Source: Mao, W. F., et al., <a href="https://www-jove-com.remotexs.ntu.edu.sg/v/61445">Using Q Suture to Enhance Resistance to Gap Formation and Tensile Strength of Repaired Flexor Tendons.</a> J. Vis. Exp. (2020).
In this video, we demonstrate suturing techniques &#8212; core suture and Q suture &#8212; to repair the foot flexor tendon in an ex vivo porcine model. Q sutures enhance the strength of the core suture in tendon repair and decrease gapping at the tendon repair site.

Source: Mao, W. F., et al., Using Q Suture to Enhance Resistance to Gap Formation and Tensile Strength of Repaired Flexor Tendons. J. Vis. Exp. (2020).
In ...

Using Q Suture to Enhance Resistance to Gap Formation and Tensile Strength of Repaired Flexor Tendons

Samenvatting

Meer video's verkennen

Hoofdstukken in deze video