In-Depth Analysis Of The Basic Principles, Structural Composition, And Working Mechanism Of Disposable Trocars

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The disposable trocar, medically known as the Disposable Laparoscopic Trocar, is the core entry instrument in Minimally Invasive Surgery (MIS) for establishing abdominal wall access, maintaining pneumoperitoneum, and allowing the passage of endoscopes and surgical instruments. Essentially, it is a precision assembly consisting of an obturator, a cannula sleeve, a sealing system, and an insufflation tap. In procedures such as laparoscopic cholecystectomy, appendectomy, hernia repair, gynecological hysterectomy, and thoracic VATS, the surgeon first makes a tiny incision in the abdominal wall, inserts the assembled trocar vertically or obliquely into the abdominal cavity, removes the obturator while retaining the cannula as the working channel, and simultaneously injects CO₂ through the side port to establish and maintain a pneumoperitoneum pressure of 12–15 mmHg. This expands the surgical field for the alternating use of the camera and operating instruments.

Structurally, the obturator of modern disposable trocars is typically made of medical-grade stainless steel 304/316L or high-strength transparent polycarbonate (PC, such as Makrolon 2458 or Lexan HP1). The tip is categorized into bladed (pyramidal blade), bladeless (blunt/conical/radial dilating), and optical viewing types. Among these, bladeless tips reduce postoperative port-site hernias by separating rather than cutting fascial fibers. The cannula sleeve is usually a transparent PC or nylon tube body with external threads; lengths typically range from 75–150 mm, with diameters of 5, 8, 10, 11, 12, and 15 mm. The threaded design screws into the abdominal wall fascia to increase anchoring force and prevent intraoperative slippage. The sealing system is the most critical functional component, comprising a zero-closure valve (duckbill valve, which automatically closes and maintains pressure when no instrument is inserted) and an instrument sealing valve (silicone or thermoplastic elastomer annular seal, maintaining airtightness even when instruments of different diameters are inserted and withdrawn). High-end products also include reducers to accommodate smaller-caliber instruments.

The insufflation tap is generally located on the proximal side wall of the cannula, connecting to the insufflator tubing to continuously supply gas to the abdominal cavity or to open for exhaust at the end of the procedure. Some models integrate a check valve to prevent gas backflow. The entire device is sterilized using Ethylene Oxide (EO), double-packaged in Tyvek-PE bags, and leaves the factory with a Sterility Assurance Level (SAL) of 10⁻⁶. Compared to reusable metal trocars, the stainless steel inserts of disposable trocars are electropolished to Ra ≤ 0.2 μm with no burrs, plastic components are precision-injected without shrinkage or bubbles, and the entire assembly is pre-assembled and subjected to random airtightness inspections. Surgeons can use them immediately upon opening the package without additional checks. It is this seemingly simple "tube + valve + obturator" trinity system that bears the dual mission of the most critical initial access safety and continuous pneumoperitoneum stability in minimally invasive surgery.