A trocar is a sharp, pointed instrument used to puncture through body walls and create a portal for other tools or drainage. It consists of two main parts: a pointed inner rod (called an obturator) and a hollow outer tube (called a cannula). The obturator makes the initial puncture, then gets removed, leaving the cannula in place as a working channel. Trocars are most commonly associated with minimally invasive surgery, but they also appear in veterinary medicine and mortuary science.
How a Trocar Works
The basic concept is straightforward. A surgeon makes a small skin incision, then pushes the trocar through the layers of the abdominal wall. The sharp tip of the obturator does the penetrating work, and the cannula follows right behind it. Once through, the obturator is pulled out, and the cannula stays behind as a port, essentially a hollow tube that keeps the entry point open.
In laparoscopic surgery, this port serves two critical purposes. First, it allows carbon dioxide to be pumped into the abdomen, inflating the space so the surgeon can see and work inside. Second, it acts as a gateway for cameras, scissors, graspers, staplers, and other long, thin instruments that make minimally invasive surgery possible. Most laparoscopic procedures require multiple trocars placed at different points across the abdomen, each serving as a separate entry point. A typical procedure might use three or four, ranging from 5 mm to 12 mm in diameter.
Types of Trocars
Trocars come in several designs, each with a different approach to getting through the abdominal wall.
- Cutting (bladed) trocars: The traditional design. These use a retractable sharp blade at the tip, either pyramidal (three-sided) or single-bladed, to slice through the fascia and muscle layers. They penetrate quickly but create a clean-cut wound.
- Dilating (bladeless) trocars: A newer approach that spreads tissue apart rather than cutting through it. These use a blunt, conical tip to push muscle fibers aside either radially or axially. Animal studies have shown they create a smaller wound in the abdominal wall compared to bladed designs, and they rarely require stitching the deeper tissue layers closed afterward.
- Optical trocars: These have a transparent tip or sheath that allows the surgeon to watch through a camera as the trocar passes through each tissue layer. Some versions use a see-through plastic cannula that eliminates the “blind” entry that makes traditional trocar insertion risky. They can be bladed or bladeless.
Trocars also come in disposable and reusable versions. Disposable trocars are single-use plastic devices with tips that are always factory-sharp, meaning less force is needed to push them through. Reusable trocars are made of stainless steel and can be resharpened, though their tips dull over time. Some newer reusable systems skip the sharp tip entirely, using a threaded cannula that screws into the abdominal wall instead of puncturing it.
How Surgeons Place Trocars
Getting the first trocar into the abdomen is considered one of the riskiest moments in laparoscopic surgery, because the surgeon is entering a closed space without being able to see inside yet. Two main techniques have been used for decades.
The closed technique uses a thin needle (called a Veress needle) to first puncture the abdomen and inflate it with gas. Once the abdomen is expanded, the first trocar is inserted. The open technique, developed by a surgeon named Hasson, involves making a slightly larger incision, cutting down through the tissue layers under direct vision, and placing the trocar into the abdomen without any blind puncture. After the first trocar is in and a camera is inserted through it, all remaining trocars are placed under direct visual guidance, which is much safer.
Each approach has trade-offs. The open technique has been reported in some studies to have a mortality rate of zero, while the closed technique carries a mortality rate of about 0.03%. However, the open method has higher rates of gas leakage around the port site (15% versus 9.5% for the closed technique), which can make it harder to maintain the inflated working space during surgery.
Risks of Trocar Entry
Serious complications from trocar insertion are uncommon but real. A meta-analysis of over 7,500 laparoscopic procedures found that major injuries occurred at a pooled rate of about 0.76 per 1,000 cases. The most feared complications are puncturing a major blood vessel or perforating the bowel. Among the techniques studied, the open entry method had zero vascular injuries in over 2,000 cases, while the closed Veress needle technique had a higher rate of vascular damage.
Trocar site hernias are another concern, particularly after the surgery is over. Hernias are more likely to develop at port sites 10 mm or larger, at the belly button (a naturally weaker spot), and after single-incision procedures where a larger port is used. European and American hernia society guidelines recommend that surgeons stitch the deeper tissue layer closed for any trocar site 10 mm or larger to reduce this risk.
Uses Beyond Laparoscopic Surgery
While minimally invasive surgery is the most common setting for trocars today, the instrument has a much broader history and range of applications.
Veterinary Medicine
In livestock practice, a large trocar can be a life-saving tool. Cattle and other ruminants sometimes develop severe bloat, a condition where gas builds up in the stomach to dangerous levels. When the animal’s life is at risk and other methods have failed, a veterinarian can insert a trocar directly through the flank into the rumen to release the trapped gas. This is an emergency procedure, and it does carry a risk of infection and fluid leakage around the puncture site, but the alternative, a ruptured stomach or suffocation, is worse.
Mortuary Science
Embalmers use a specialized trocar that looks quite different from the surgical version. It is a long, hollow, pointed tube connected to a suction system. During embalming, the trocar is inserted into the chest and abdominal cavities to aspirate fluids and gases that accumulate after death. The instrument is also used to break up soft tissue so fluids can be removed more completely. After aspiration, concentrated preservative fluid is injected back through the same trocar to disinfect and preserve the body cavities.
How Trocar Design Has Evolved
The trocar has been in use since the early days of endoscopic surgery. In the early 1900s, pioneers of laparoscopy inserted trocars directly into the abdomen without inflating it first, a technique that carried significant risk. By the mid-twentieth century, Heinz Kalk, a German gastroenterologist, advanced the field by developing a double-trocar system paired with improved optics. For decades, the instruments used alongside trocars were limited to simple probing tools. It was not until the 1960s that more sophisticated instruments began passing through trocar ports.
Modern trocar design has moved toward reducing the trauma of entry itself. Single-port techniques use one larger trocar site instead of multiple smaller ones, cutting down on the number of abdominal wall punctures. Transparent sheaths allow real-time visualization during insertion. Threaded cannulas grip the abdominal wall to prevent slipping. Each generation of design aims to make the entry point smaller, safer, and less likely to cause complications after the surgery is done.