Relationship between the canthal-tragus distance and the puncture point in temporomandibular joint arthroscopy

This study investigated whether a relationship exists between the length of the canthal-tragus line and the distance from the tragus at which the puncture point for arthroscope insertion should be made. On one side of 11 cadaver heads, a puncture point was marked 7 mm from the midtragus and 2 mm below the canthal-tragus line. On the other side, the distances were 10 mm and 2 mm, respectively. The arthroscope trocar and cannula were inserted at the marked points. The anatomical location of the arthroscope after insertion was confirmed by open dissection with the arthroscope in place. Following dissection, the canthal-tragus line was measured on each side of the cadaver's head. For measurements > 70 mm, puncture points 10 mm from the midtragus led to insertion of the arthroscope inside the upper joint compartment. For measurements < or = 70 mm, puncture points 7 mm from the midtragus led to insertion of the arthroscope inside the upper joint compartment. This suggests that for canthal-tragus distances of > 70 mm, the arthroscope should be inserted 10mm from the midtragus and for distances < or = 70 mm it should be inserted at 7 mm for the greatest likelihood of entering the upper joint compartment of the TMJ.