A Novel V-Shaped Intraluminal Knife for Minimally Invasive Removal of Inadvertently Sutured Drainage Tubes After Lumbar Spine Surgery: A Rabbit Model Study with Clinical Application

After major back surgery, surgeons often place a thin, flexible tube under the skin to drain away fluid and blood that naturally accumulate as the body heals. This simple step prevents dangerous pressure from building up and helps the wound close safely. However, a rare and frustrating accident can occur while the surgeon is stitching the skin back together: the needle used to close the wound can accidentally pierce the drainage tube itself. When this happens, the tube becomes tied down, anchored firmly to the surrounding tissue. Normally, removing such a tube is a quick, painless tug. But when it is caught by a suture, pulling on it becomes impossible without causing damage.

For decades, the only solution to this problem has been to cut the skin open again. A patient must return to a procedure room, often under anesthesia, so a surgeon can carefully find the knot, cut the thread, and free the tube. This unplanned second procedure adds stress, cost, and risk of infection to the patient's recovery. It turns a minor snag into a significant medical event. The question facing medical teams has been whether there is a way to free the tube from the inside, avoiding the need to cut the skin a second time.

A team of researchers from Ningxia Medical University in China has developed a new tool designed to solve this specific problem without reopening the wound. They created a tiny, specialized knife that fits inside the hollow center of the drainage tube. The device is made from a standard medical wire, sharpened at one end into a specific shape. The researchers tested this new tool in a controlled experiment using rabbits and then applied it successfully to a human patient who had suffered the same complication. Their work suggests that a simple change in the shape of the blade can turn a difficult, often failed task into a quick, reliable procedure.

The researchers built two versions of this internal knife to see which design worked best. One version had a simple, wedge-shaped tip, similar to a standard arrowhead. The other version, which became the focus of their study, featured a "V" shape with small, blunt bumps on either side of the cutting edge. The idea behind the bumps was to act like a funnel. As the tool is pushed up inside the tube, these bumps would catch the stray thread holding the tube down and guide it into the sharp "V" notch, where the blade could slice through it cleanly. The simple wedge design lacked these guides, relying only on the sharp edge to hit the thread directly.

To test these tools, the team performed a series of operations on ten healthy rabbits. They surgically placed two drainage tubes in each animal and intentionally tied a thread through the wall of each tube to simulate the accidental suture. This created a perfect, safe model of the problem. On the fourth day after the surgery, when the tubes were ready to be removed, the researchers attempted to free them using the internal knives. For each rabbit, one tube was treated with the V-shaped knife and the other with the simple wedge knife. The person performing the extraction did not know which tool was being used on which side until the moment of use, ensuring the results were unbiased.

The difference in performance between the two tools was immediate and striking. The V-shaped knife succeeded in freeing the tube in every single attempt, all ten out of ten. On average, it took the researchers just over two minutes to locate the thread, cut it, and pull the tube out. In contrast, the simple wedge knife only worked half the time, succeeding in five out of ten attempts. When it did work, it took nearly seven minutes on average. In the five cases where the wedge knife failed, the thread simply slipped off the sharp edge or could not be caught, leaving the tube still stuck. The researchers noted that the V-shaped design's ability to funnel the thread into the cut was the key factor, whereas the wedge shape often let the thread slide away.

Following the successful animal trials, the team applied the V-shaped tool to a real-world case. A 56-year-old man who had undergone back surgery found his drainage tube stuck on the fourth day after his operation. Instead of reopening his incision, the medical team used the new V-shaped knife. They cut the tube just outside the skin, inserted the tool, and guided it up to the hidden knot. The blunt bumps on the tool caught the thread, guided it into the sharp notch, and sliced it cleanly. The tube was then pulled out intact, and the patient felt only mild pressure. The wound healed normally, and the patient recovered without needing a second surgery or facing any complications.

The study highlights that this solution is not only effective but also practical and accessible. The tool is made from a common medical wire that is inexpensive and available in almost any hospital. It does not require complex machinery or special imaging to use. The procedure can be performed at the patient's bedside with standard cleaning supplies, eliminating the need for an operating room and the risks associated with returning to surgery. While the researchers acknowledge that their study involved a small number of animals and only one human patient, the results were clear: the V-shaped design with its guiding bumps is significantly more reliable than a simple sharp edge for this specific task.

This work offers a straightforward path forward for a complication that has long been treated with invasive measures. By turning a difficult mechanical problem into a simple matter of geometry, the researchers have provided a method that could spare patients from unnecessary pain and hospitals from extra costs. The success of the V-shaped knife in both the rabbit model and the human case suggests that this low-tech innovation could become a standard part of surgical care, turning a potential crisis into a routine, five-minute fix.