What is the purpose of a trocar?

Trocars are used during laparoscopic procedures and other minimally invasive surgery (MIS) to make small, puncturelike incisions in outer tissue layers. These incisions allow surgeons to insert cannulas through which surgical instruments can be introduced. MIS procedures allow faster recovery times than traditional open procedures as well as minimal patient discomfort--but at the same time, they entail a certain amount of risk. Trocar-related injuries and complications range from minor bleeding to, on rare occasions, death. In this Guidance Article, we describe what trocars are, how they are used, and how these complications can be avoided. Our discussion includes the use of trocar tip shields, which are designed to reduce th risks of trocar use--but whose value is the subject of considerable debate among surgeons. It also covers the relative merits of reusable and disposable models. In addition, the article includes an overview of the trocar-cannula market, listing current suppliers and the types of trocars they offer.

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A trocar is a versatile, specialized surgical device that proves useful in a variety of procedures. They are best known for their application in laparoscopic (also known as keyhole) surgery. By using a trocar, a surgeon is able to access the abdomen or peritoneal cavity. Physicians also employ trocars in treating ascites and hydrothorax, and for the implantation of slow-release hormone pellets beneath the skin. Embalmers use trocars to remove fluids and gas from the bodies of the descendants they prepare.

What Is a Trocar?

Every trocar consists of three parts.

There is a cannula, the shaft pushed through the skin and subdermal tissue to reach a body cavity.

There is also a seal at the top of the cannula. The seal ensures that gasses do not escape from the body cavity the cannula reaches. Maintaining air pressure inside the body is essential to the surgeon's ability to visualize the tissues being operated on. The seal also allows the surgeon to pass instruments and excised tissue through the cannula.

At the opposite end of the trocar, there is an obturator. This is the mechanism that allows the trocar to make the initial penetration into the cavity the surgeon wishes to reach.

History of Trocars

Nineteenth-century English physician Reginald S. Southey (1835-99) studied medicine at The London School of Medicine and Dentistry while he was also a student at Christ Church, Oxford. He pursued further studies at St. Bartholomew’s Hospital, as well as in Continental Europe, before an appointment to the Hospital for Diseases of the Chest in London, where he developed a special interest in treating diseases of the kidneys.

When Southey began practicing medicine, all the major cities had metalsmiths available to make surgical tools for individual surgeons on request. Doctors would experiment with modifications of their surgical tools to achieve better outcomes for their patients. After several successes, the doctor would then get an instrument maker to build a prototype. If the new instrument proved successful, or the doctor was influential, then instrument makers across the city would make copies of the prototype.

Dr. Southey spent the major part of his time as a working member of the "Lunacy Commission," a forerunner of a modern psychiatric department, but he had a large number of patients who suffered from anasarca, an accumulation of fluid in the interstitial space.

Anasarca results from capillary filtration in excess of lymphatic drainage. The condition frequently caused accumulation of fluid in the lower limbs in both sexes, scrotal swelling in males, and deep, weeping venous ulcers if it were left untreated. Before Southey, the most common treatment for the condition was to wrap the skin in tight cloth bandages, so tight that they made movement difficult or impossible.

Southey observed that skin blisters caused by anasarca leaked fluid. He reasoned that draining fluid from the tissues beneath skin ulcerations might relieve the disease. Southey inserted a rigid tube under the skin, attaching it to a rubber hose that drained fluid into a bowl. The procedure was successful, so he refined his design, adding a trocar and a very thin cannula. He replaced the rubber tubing with a silver pipette so it could be reused.

Subsequent modifications to the design made trocars even easier to use. They were miniaturized so doctors could carry them in their pockets. They became the standard of care for treating ascites.

Dr. Southey even used his invention on himself. The son of England's foremost authority on treating tuberculosis, Southey contracted the disease early in life. In 1879, Southey reported to the Clinical Society of London that he had used his trocar on himself, inserting drainage tubes into this chest that allowed him to continue working.

Types of Trocars

Twenty-first century trocars can be divided into two main groups:

Cutting trocars have a sharp plastic or metal blade that cuts through layers of tissue as pressure is applied. They are designed for easy entry into subcutaneous (usually abdominal) cavities.

Dilating trocars have a blunt tip for dilating and separating tissues when pressure is applied. These non-cutting trocars are intended to minimize the risk of injury to internal organs in surgical procedures.

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There is a tremendous variety of instruments within these two categories to provide the features specialists require. There are trocars with camera ports, working ports, retraction ports, and static ports. For straightforward surgical procedures, such as diagnostic laparoscopy, an optic trocar with a 5 mm port is more than adequate for lighting and control. When removal of large masses requires a morcellator, a trocar with a 12 mm port is likely to be adequate.

Disposable cutting trocars are growing in popularity. They offer a guaranteed-sharp tip and are also guaranteed sterile with no risk of cross contamination.

Procedures That Use a Trocar

Abdominal laparoscopic surgery has become the iconic application of the trocar. Laparoscopy is indicated as a tool of diagnosis when less-invasive procedures, such as computed tomography and ultrasound, fail to yield a definitive diagnosis. Surgeons use trocars to perform laparoscopic procedures to examine:

• The appendix,

• The bowel (both small intestine and large intestine),

• The gallbladder,

• The liver,

• The pancreas,

• The pelvic cavity, and

• Female reproductive organs.

Surgeons can use laparoscopy to assess the progress of treatment and the staging of diseases. Laparoscopy also allows for a minimal incision when removing gallstones, fibromas, and benign and cancerous tumors of most kinds. The ability to operate on the abdomen with a small incision minimizes time under anesthesia, accelerates recovery, and usually eliminates scarring. Patients recover much faster from laparoscopic procedures than from conventional open-incision surgical procedures.

Another popular application of the trocar is the insertion of slow-release hormone pellets for treatment of male and female endocrine disorders. Use of a modern trocar allows insertion of the hormone through the smallest possible incision. Small incisions reduce trauma to the skin, since the cannula cannot move around during the procedure.

When the pellet is inserted through an incision no wider than 5 mm, there is no need to stitch the fascia binding tissue beneath the skin, and the already-small risk of hernia is reduced even further.

Trocar Supplies is a specialist supplier of trocar for the placement of extended-release hormones. We feature products that minimize skin damage, reducing infection risk, and leaving patients with a minimum of discomfort.

Trocar Supplies offersdisposable trocars just 3.2 mm wide, for deep or shallow insertion. Also, available is a reusable 3.5 mm stainless steel bevel tip, to be autoclaved between uses. Trocar Supplies also sells disposable medical tray kits and trocar wrap kits.

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