The more posterior the puncture site, the greater is the risk of EAC perforation. The standard arthroscopic fossa puncture at the peak of the glenoid fossa carries much greater risk than a puncture into the anterior recess.
The angulation of the trocar upon puncture through the capsule of the TMJ should NOT be perpendicular to the skin, but rather angled anteriorly and directed toward the articular eminence, thereby roughly paralleling the EAC. The trocar should then be angled and directed anterosuperiorly during the puncture (Fig. 4.4).
Fig. 4.4 Correct angulation and direction of arthroscopic puncture
Fig. 4.5 Ideal head position
The position of the patient’s head is also critical; the head should be rotated laterally and lay horizontally. Poor head position can result in misdirected punctures due to disorientation of the surgeon (Fig. 4.5).
The depth of puncture should be 20-25 mm and NEVER greater than 25 mm before removing the sharp trocar, inserting the arthroscope, and confirming position in the joint on the monitor screen. Almost all joints can be entered at this depth, and if the EAC is inadvertently punctured at this depth, the tympanic membrane should not be injured, because it lies at a depth of approximately 35 mm from the tip of the tragal cartilage. Therefore, if the puncture does inadvertently enter into the EAC, the complication will be limited to a laceration in the wall with some bleeding, which is relatively simple to manage.
The puncture force must also be controlled and appropriate. The tenacious lateral capsular ligament creates the most resistance to the trocar puncture. The surgeon must be aware of the resistance to trocar advancement and also when the trocar tip is on bone. This will help to avoid puncture through the bony EAC.