Positional relationship between medial canthal tendon and common canalicular orifice: A cadaveric study.
To examine the positional relationship between the medial canthal tendon (MCT) and the common canalicular orifice (CCO) in cadavers. This experimental anatomical study was conducted using 75 orbits from 48 embalmed Japanese cadavers fixed in 10% buffered formalin (24 orbits from 17 males and 51 orbits from 31 females; 38 right and 37 left; mean age at time of death, 84.1±9.2 years). The vertical width of the MCT on the level of the medial orbital rim and the angle between the MCT and axial plane were measured. In addition, the vertical distance from the CCO to the lower edge of the MCT was measured. Positive values of the distance were indicated when the CCO was located below the lower edge of the MCT. The vertical distance from the CCO to the lower edge of the MCT was -1.43±1.31mm. Only 13 orbits (17.3%) showed the CCO located on the same level (2 orbits, 2.7%) or below the lower edge of the MCT (11 orbits, 14.7%), while the CCO was located above the lower edge of the MCT in 62 orbits (82.7%). In multiple regression analyses, both the MCT width and angle between the MCT and axial plane were not correlated with the distance (P>0.050). As the CCO was mostly found to be located above the inferior margin of the MCT, the creation of the bony window up to the MCT's inferior margin is not sufficient in external dacryocystorhinostomy to completely expose the CCO.