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

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 sutures can enhance the core suture strength and decrease the risk for gaping between repaired tendon ends. We present Q sutures as an alternative to conventional peripheral sutures. Compared to conventional running peripheral sutures, Q sutures are very easy to perform, are time-saving, and demonstrate a superior performance in resisting gapping in tendon repair.

To perform a tendon repair, begin by marking the anterior surface of one of the porcine tendon stumps with two points that are 10 millimeters from the cut tendon, one fourth of the way from the left and right sides of the tendon in the mediolateral direction. Mark each of the left and right lateral surfaces of the tendon with one point that is eight millimeters from each cut tendon end. And locate the point in the middle of the anterior-posterior direction.

Then use a vernier caliper to measure all of the lengths between each set of points. Using four zero sutures, insert a needle into the cut surface of one tendon stump from the middle point in the anterior-posterior direction, and one fourth of the way from the left in the medial-lateral direction. Draw a region of interest around the selected neuron and draw a second larger region of interest around the tail that includes the first region of interest.

Reinsert the needle obliquely from point three and pass the needle transversely toward point four. Pull out the suture to create a small loop at the lateral surface of the tendon, and reinsert the needle obliquely from point two, passing the needle longitudinally toward the cut end. Then pull out the suture.

To form a symmetrical repair, insert the needle into the cut end of the other tendon stump and suture the other stump with the same construct. Tighten the suture with a 10%shortening of the tendon segment within the core suture. And tie the tendon ends together with three to four knots to complete the two-strand core suture.

To complete a four-strand core suture, repeat the suturing process as just demonstrated. To add a Q suture, insert the same needle into the tendon anterior surface, two millimeters away from the joined tendon end. And withdraw the needle on the posterior surface of the tendon.

Reinsert the needle into the posterior surface of the tendon at two millimeters away from the other side of the joined tendon end. Pull out the suture from the anterior surface of the tendon and the tie three knots to complete the first Q suture. Then repeat the procedure to complete the second Q suture.

To add a running suture in the two-strand or four-strand core suture plus running group, use a six zero suture to add a running epitenon suture of nine to 10 stitches to the tendon ends, keeping a similar purchase of 1.5 millimeters and a depth of one millimeter. When all of the sutures have been placed, cover the repaired tendon with wet gauze. Before performing biomechanical testing of the repairs, open the testing software and navigate to the home screen.

Click method to create a test method, and click New to open the create a new test method dialogue box. Select the tension test profile method test type and click create. Click save to name and save the test method file and click control and pretest in the navigation bar to open the control pre-test screen in the method tab.

Click preload and set the control mode to tensile extension, the rate to 25 millimeters per minute, the channel to load, and the value to 5 Newtons. Enable the autobalance and add the available channels of load to the selected channels. Click test to open the setup control test screen, and click edit profile of this cyclic loading to open the test profile or dialog box.

Insert four blocks. In the first block, set the mode to tensile extension, the shape to triangle, the maximum load to eight Newtons in the two-strand repairs and 15 Newtons in the four-strand repairs, the minimum load to zero Newtons, the rate to 25 millimeters per minute, and the cycle to 10. In the second block set the mode to tensile extension, the shape to absolute ramp, the rate to 25 millimeters per minute, and the end point to eight Newtons in the two-strand repairs and 15 Newtons in the four-strand repairs.

In the third block, set the mode to tensile extension, the shape to hold, the criteria to duration, and the duration to eight seconds. In the fourth block, set the mode to tensile extension, the shape to absolute ramp, the rate to 25 millimeters per minute, and the end point as 100 Newtons. Then click save and exit.

Next, open the control end of test screen and set criteria one to rate of load, and the sensitivity to 40%In the calculation setup screen, add available calculations of absolute peak to the selected calculations. Select load in the drop down list of channel and apply the absolute peak to the four absolute ramp. Open the results'one column screen, select a maximum load, and add load to the selected results.

Then click save, and close. To perform a biomechanical test, set the initial distance between the upper and lower clamps of the testing machine to five centimeters. Wrap the tendon with dry gauzes, two to three centimeters away from the cut end, and mount the gauze wrapped then in segments into the upper and lower clamps, keeping the tendon as vertical as possible.

When the tendon has been mounted, click test on the home screen and select the save to test method file. Click next and select a location, and enter a name to save the sample data file. The test tab will be displayed.

Click open load cell set up dialog, calibrate and okay to remove the load from the load cell. Click open live displays set up dialogue and select tensile extension in the drop-down list of channel one. Select cycle count in the dropdown list of channel three, and select three in the live displays.

Click open control panel set up dialog and select balanced load in the dropdown list of key 1, and reset gauge length of key 2. Click balance load, reset gauge length and start to run a test for each specimen in the sample. During the cyclic loading, record the number of tendons with a two millimeter gap between the two ends.

During the eight-second pause at the maximum load after the 10th cycle, measure the gap distance between the tendon ends. After measuring the gap, pull the tendon upward until the repair ruptures, and record the ultimate breaking strain. Then click stop, return, and finish to save the results.

As illustrated in the table, in this representative analysis, the addition of Q suture reduce the number of tendons with two millimeter gapping during cyclic loading in both two-strand and four-strand repairs. All of the tenants repaired with two and four-strand core sutures formed a two-millimeter gap, whereas none of the tendons repaired with two strand plus two Q, and only half of those repaired with four strand plus two Q had a two-millimeter gapping after 10 cycles. Further, more tendons repaired with two-strand plus running or four-strand plus running sutures showed a two millimeter gap, then those augmented with Q sutures.

With two strand repairs, the addition of the Q suture or running sutures both reduce the gap distance between tendon ends after cyclic loading, but only Q suture addition significantly increase the ultimate strength of the repaired tendon. The addition of the Q suture also minimize the gap distance with four-strand repairs, although the ultimate strength of the repaired tendons was not affected. In addition, the average time required for performing two Q sutures was significantly shorter than that for a running suture.

The facts of Q sutures when combined with other types of core sutures warrant for the study to confirm the efficacy of Q sutures.