Stitching for Strength

Stitching for Strength - Overview Video

Problem: Which type of surgical suturing technique holds the most amount of weight?

Hypothesis: I think that the stitch that will hold the most weight before ripping is the Pulley Suture, because instead of being a continuous stitch, it is an interrupted stitch, so if one loop breaks it will also have backup loops to support the strength.

Background Information: The first stitch is the Simple Running Locking Suture. The simple running locking suture is a continuous, self-locking technique. Next, A Subcuticular Running Suture is used for the cosmetic and specialized closure of clean, straight, surgical incisions and is also my second suture I will be testing. The third stitch is the Simple Running Suture, and it is used for closing clean, low-tension skin incisions and linear lacerations. The next suturing technique, is the Simple Suture which is used for lacerations and tension-free wounds, and it is also not a continuous suture technique and stops after you make the loop. My next one is the Vertical Mattress Suture which is actually an interrupted Stitch that is usually used mostly for high-tension wounds. My last and final stitch is the Pulley Stitch. The Pulley Stitch is a special, high tension suture technique that is used to close the stubborn, high-tension surgical wounds by acting a lot like a mechanical lever to draw the skin edges together. It is used for high-tension wounds, tissue approximation, and also reducing tension.

Materials: Some of the materials that I used for this project include:

3mm Tattoo Synthetic Skin

Non-Absorbable Nylon Monofilament 2/0 USP

Mayo Hegar Needle Holder

Iris Scissors Straight

Adson Tweezers

Weights

Surgical Gloves

Bucket

Clamps

Pennies

Scale

Jute Twine

Controlled Variables:

Non-Absorbable Nylon Monofilament 2/0 USP

3mm Tattoo Synthetic Skin

Weight

Bucket

Securing Clamps

Independent Variables:

The amount of weight used for each suture to fail

Procedure:

Step One: Cut the four synthetic skin sheets in half.

Step Two: Tie a knot on the beginning of the second sheet of the cut fake skin and perform a Simple Running Locking Suture.

Step Three: Tie a knot to the inside of the skin and then making insertions on the inside of the cut and tying a knot when you get to the end to perform a Subcuticular Running Suture

Step Four: Tie a knot, then perform a Simple Running Suture until you get to the end of the cut.

Step Five: Tie alLoop knot and make a Simple Suture at the beginning of the cut, then repeat this process until you get to the end of the wound.

Step Six: Tie a Vertical Mattress Suture at the beginning of the cut and then tie more throughout the cut at an even distance from each other.

Step Seven: Tie the first pulley suture at the beginning of the cut, then continue placing additional pulley sutures at even distances.

Step Eight: Clamp one side of a sutured skin sample to a stable surface and clamp the other end to a bucket.

Step Nine: Add weight to the bucket until each suture technique rips.

Step Ten: Measure the bucket and everything inside of it to find the proper weight at which the suture failed and record.

Results:

First place was the Simple Running Locking Suture holding 36.0 pounds.

Second place was the Pulley Suture holding 27.6 pounds.

Third place was the Simple Running Suture holding 19.9 pounds.

Fourth place was the Simple Suture holding 13.8 pounds.

Fifth place was the Vertical Mattress Suture holding 9.8 pounds.

Sixth place was the Subcuticular Running Suture holding 5.7 pounds.

Observations:

The Simple Running Locking Suture was easily the strongest stitch. It was so strong that we had to add even heavier weights than originally planned. However, the knot ripped, and not the actual stitch pattern. Before it tore, the skin and even the thread were stretching so wide because of the weight that it had a gap between the two pieces of skin that was probably about two inches stretched in some parts.

The Pulley Suture was actually strong and was clearly a solid stitch. For this one, I actually assumed that it was going to be strong from the beginning because background research said it is used for high-tension skin lacerations. It looked really tight and also sturdy and overall really strong.

The Simple Running Suture is one of the stronger techniques. It was similar to the Simple Running Locking Suture, but not as strong. It took a little more than just coins to have enough weight to fail. Overall, it was a strong suture and was also one of the easier techniques to stitch as well.

The Simple Suture was unique because it didn’t rip any of the skin like the others, and instead the knots of all the stitches ripped. It ripped fairly easily compared to the Simple Running Suture and the Simple Running Locking Suture. I also noticed that the green thread (same type and weight of thread according to the package but green) stayed and didn't rip, but the blue thread ripped easier.

The Vertical Mattress Suture was the second last one, and it was quite weak. It was easy to tell that it wasn't that strong just by looking at it with the bucket attached. It had already begun to rip soon adter adding weight.

The Subcuticular Running Suture was also weak and tore easily. I went to lower the bucket with the five pounds and some pennies and before I even completely lowered the bucket, the knot snapped and the stitch came completely out of the skin.

In the end, my hypothesis was incorrect. I thought that since the Pulley Suture was an interrupted suture, it would be stronger because each individual stitch would need to break for the closure to fail. In the end though, the Simple Running Locking Suture was the strongest stitch pattern. The experiment was eye-opening, because I did not believe the stitches could be as strong as they were, forcing me to abandon coins as weight and use heavier weights. I also learned that having a continuous or running stitch pattern creates more strength than interrupted stitches. And of course, I learned a lot about various suture types and was able to practice the techniques.

Some potential problems with my work are that I am not a trained surgeon and my techniques are not as well practiced as a skilled surgeon and the rubbery material may not have reacted the same. In addition, these stitches are used for different wounds (muscle, epidermis, dermis), so they aren't meant for the same type of closure in real surgery.

Looking ahead, there are other suture types I would like to investigate. Through learning further techniques, I might consider creating new techniques and test those for a future project. This project was a great first step towards future investigations.

I would like to say thanks to my science teacher, Mr. Morrison, who gave my class lots of work blocks to work on science fair, which teaches us many important skills. I would also like to say thanks to Michael Edwards from Science East, who came to me school and provided guidance and suggestions to prepare for the Canada Wide Science Fair. Finally, I would also like to say thanks to my father who helped me with the testing for my project.

Mastering the Simple Running Suture: a Step-by-step Guide for Beginners

surgicalsuture.org. (2026). Surgicalsuture.org. http://surgicalsuture.org

Simple Interrupted Suture

The evolution of Neurosurgery Learning. (2020). UpSurgeOn. https://upsurgeon.com

Running Percutaneous

(2026). Suture.app. https://suture.app

Suture Like A Surgeon

Mastenbiork, & Meloni. (2024). Suture like a Surgeon [Review of Suture like a Surgeon].