The Posterior Limb in the Medial Canthal Tendon in Asians: Does It Exist?

Abstract

To analyze the medial canthal tendon and to clarify the true anatomic nature of the posterior limb of this tendon. Observational anatomic study. Eleven postmortem eyelids of 9 Asian cadavers (6 right and 5 left eyes; age average, 77.2 years) were analyzed. Axial sections in parallel to the eyelid margin starting at 1 mm above the upper eyelid margin were made. The sliced specimens were dehydrated and embedded in paraffin, cut into 7-μm thickness sections, and stained with Masson trichrome. To demonstrate the hardness felt when the Horner muscle is pulled, 3 additional postmortem eyelids of 2 Asians (2 right and 1 left eyes; age, 70 and 75 years at death) were analyzed. The pulling process was documented with a video camera. The posterior limb of the medial canthal tendon was not detected in any of the specimens. The Horner muscle originated via its tendon from the posterior lacrimal crest and the anterior area of the medial orbital wall. The lacrimal diaphragm around the posterior lacrimal crest ran almost parallel to the Horner muscle and usually was difficult to distinguish from the tendon of the Horner muscle. The medial check ligament supported the posterior aspect of the Horner muscle and was inserted into the medial orbital wall. The hard sensation that was felt when the Horner muscle was pulled was demonstrated in the video. The posterior limb of the medial canthal tendon was not detected in any of the specimens. This anatomic structure seems to be a part of the Horner muscle.