Trocars are generally used as access devices for introduction of other surgical instruments into a patient. A conventional thoracic trocar is disclosed in U.S. Pat. No. 5,279,575 to Sugarbaker. In U.S. Pat. No. 5,279,575 the trocar has a pair of flukes which are pivotally coupled to the body with pins. The trocar also includes a rigid clamp which is slidably on the outer tube for securing the trocar to a body wall. The inner tube slides longitudinally relative to the outer tube for moving the flukes to the open position. A distal end of the inner tube engages a camming surface on each of the flukes for camming the flukes outward.
The trocar disclosed in U.S. Pat. No. 5,279,575 suffers from a number of drawbacks. First, the clamp is relatively stiff and does not conform to the shape of the patient. As such, the trocar may be difficult to tilt at a desired angle when passing between adjacent ribs. Another drawback of the trocar is that the hinges create a relatively large profile since the hinges extend beyond the outer, cylindrical surface of the tube. The relatively large profile increases trauma to the patient which is particularly problematic when the trocar is rotated or otherwise displaced after initial placement. Yet another drawback of U.S. Pat. No. 5,279,575 is that the clamp is mounted to a third tube which slides over the outer tube. The three tube configuration also increases the profile of the device and trauma to the patient.