Medial canthal tendon (MCT) avulsion is an eyelid injury in which all or part of the eyelid, including the medial canthus (inner corner of the eye), is torn away from its normal anatomical position.
The medial canthal tendon is a structure that closely surrounds the lacrimal drainage system and plays an important role in supporting the medial canthus, maintaining the position of the eyelids and eyeball, and preserving lacrimal drainage function. The medial canthal tendon is formed by muscle fibers from the anterior portion of the orbital septum and the anterior tarsal plate extending medially, with the upper and lower limbs joining to form a common medial canthal tendon. It then divides into anterior and posterior limbs.
Anterior limb: passes in front of the lacrimal sac and attaches to the frontal process of the maxilla and the anterior lacrimal crest. It helps keep the punctum in the proper position. It is the stronger of the two limbs.
Posterior limb: passes behind the lacrimal sac and attaches to the posterior lacrimal crest of the lacrimal bone. It is important for maintaining the medial eyelid position and keeping it closely apposed to the eyeball. Because it is relatively weak against outward traction, it is more likely to avulse.
The anterior surface of the lacrimal sac body is covered by the medial canthal tendon. The lateral surface of the upper half of the lacrimal sac is covered by Horner-Duverney’s muscle through connective tissue. The canaliculi run behind the medial canthal tendon and connect to the lacrimal sac at the common internal punctum. From the punctum to the lacrimal sac, the canaliculi travel about 2 mm vertically and then run horizontally 8 to 10 mm within the orbicularis muscle; in more than 80% of cases, the upper and lower canaliculi join to form a common canaliculus (3 to 5 mm) that drains into the posterolateral wall of the lacrimal sac. The canaliculi are 1 to 2 mm in diameter.
The lacrimal sac performs a pumping function (lacrimal pump function) in coordination with contraction and relaxation of the orbicularis muscle and Horner’s muscle during blinking and eyelid opening and closing. If the medial canthal tendon or Horner’s muscle is torn, this pumping function is impaired and can cause epiphora.
QWhy is the medial canthal tendon closely related to the lacrimal drainage system?
A
The canaliculi run behind the medial canthal tendon and are anatomically linked to it. For this reason, when medial canthal tendon avulsion occurs, canalicular laceration is frequently associated. Lateral displacement of the punctum is a sign of this linked injury.
Rounding of the inner eye corner (rounding): The sharp shape of the inner eye corner is lost.
Increased distance between the inner corners of the eyes (telecanthus): The distance between the inner corners of both eyes increases after injury.
Horizontal shortening of the eyelid opening: The eyelid opening becomes shorter because the medial canthal ligament detaches.
Lateral displacement of the tear duct opening: Sign of injury to the attachment of the anterior limb of the medial canthal ligament. Suggests an associated canalicular laceration.
Examination findings
Ligament attachment assessment: Apply traction with hook forceps and assess the integrity of the superior and inferior limbs by palpation.
Confirmation of the posterior lacrimal crest attachment: Evaluate the posterior ligament attachment and determine the extent of the avulsion.
Canalicular stump: The stump appears as a shiny, ring-like structure that is off-white or gray-white.
QWhat appearance changes occur in medial canthal tendon avulsion?
A
The main findings are rounding of the medial canthal angle, acquired telecanthus, horizontal shortening of the palpebral fissure, and lateral displacement of the punctum. When these occur together, they produce a characteristic change in appearance.
Medial canthal tendon avulsion is caused by external forces such as the following.
Blunt trauma: Such as blows or being struck by a ball. It often causes a laceration on the medial side of the eyelid accompanied by canalicular rupture.
Animal bites: Such as dog bites. Appropriate antibiotic treatment may be needed.
Traffic accidents, falls, and assault: External forces that apply horizontal or outward traction.
NOE fracture (naso-orbito-ethmoid fracture): Particularly often accompanied by medial canthal tendon avulsion.
Iatrogenic injury: Can also occur during dacryocystorhinostomy (DCR) or after surgical removal of tumors around the eye.
There are two types of injury. The main differences are shown in the table below.
Type of injury
Mechanism
Features of the tear site
Indirect injury
Excessive outward traction on the eyelid due to blunt trauma to the eye area
Tear on the nasal side, making repair difficult
Direct injury
Direct force to the inner corner of the eye
Relatively easy to repair
The following tendencies are seen in the areas and parts that are more likely to be injured.
The lower eyelid is more likely to be injured than the upper eyelid.
Canalicular lacerations are most common in the lower canaliculus > upper canaliculus > both upper and lower canaliculi.
The posterior limb of the medial canthal ligament is relatively weak against lateral traction and is easily avulsed.
QWhat kinds of trauma are likely to injure the medial canthal ligament?
A
It is often associated with blunt trauma, animal bites, traffic accidents, and naso-orbito-ethmoid fractures. It can also occur as an iatrogenic injury after dacryocystorhinostomy. In indirect injuries, traction of the eyelid outward often causes a nasal canalicular laceration, which is often difficult to repair.
The diagnosis of medial canthal ligament avulsion is a clinical diagnosis. A thorough understanding of the injury mechanism and a detailed medical history are important, and medial upper facial injuries involving the brow, nose, and cheek should raise suspicion for medial canthal ligament trauma.
First, perform a complete ophthalmic examination to check for eye injury. Confirm whether there is globe rupture, corneal perforation, orbital fracture, extraocular muscle injury, or associated head and facial trauma. If a retained foreign body such as wood, glass, stone, or metal is suspected, perform a CT scan.
General anesthesia is preferred. This is because tissue swelling from infiltration of local anesthetic makes it difficult to find the cut ends. If the procedure is done under local anesthesia, combine it with an infratrochlear nerve block.
Insert a bougie through the punctum to estimate the site of the tear. Expose the wound with a fishhook hook and traction suture (4-0 silk).
Stump exploration: While controlling bleeding and suctioning with Bosmin forceps, bipolar cautery, and a suction tip, search for the cut end. After confirming the end, perform irrigation and insert a bougie to confirm that it is the canaliculus.
Silicone tube placement: Insert a silicone lacrimal tube through the punctum.
Stump suturing: Suture the stump ends together with 2 to 3 stitches using 8-0 absorbable suture (such as Vicryl). Also suture the surrounding tissue, including Horner’s muscle, together. Suturing Horner’s muscle is important for restoring the lacrimal pump function.
② Medial canthal tendon suturing
After suturing the canaliculus, suture the medial canthal tendon. If this step is omitted, the punctum may heal in a laterally deviated position after surgery, causing disfigurement.
When both ends can be identified by cutting the medial canthal tendon: perform a horizontal mattress suture with 4-0 polyester thread (non-absorbable).
When the periosteum is intact and the distal end is unknown: pass a 5-0 braided multifilament absorbable suture through the periosteum of the medial wall and the medial canthal tendon to secure it.
In complete avulsion: perform bony fixation of the medial canthal tendon using a microplate, or transnasal wiring.
③ Eyelid suturing
Using the medial canthus as the reference point, suture the surrounding lacerations.
The eyelid skin has a rich blood supply and is resistant to infection, so it is easy to take with suturing. Do not perform debridement because it would create tissue loss.
If there is a marginal eyelid laceration: temporary sutures with 6-0 nylon → tarsal plate suturing → suture the skin, orbicularis oculi muscle, and conjunctiva layer by layer.
Do not perform irrigation testing for 2–3 weeks after surgery. The tube is usually removed after 1–2 months.
Even after tube removal, confirm patency by irrigation every 2 weeks for 2–3 months.
Prescribe steroid eye drops (to prevent inflammation and foreign-body reaction) and antibiotic eye ointment. Use oral antibiotics if needed.
Remove skin sutures in about 1 week. The scar is most noticeable 2–3 months after surgery, but becomes less noticeable after 6 months to 1 year.
Examine the patient at 1 week and at 4–6 weeks after surgery, and provide long-term follow-up if needed.
QIn cases with a canalicular laceration, in what order is the surgery performed?
A
First repair the canalicular laceration (suture the cut ends and insert the lacrimal tube), then suture the medial canthal tendon, and finally suture the eyelid laceration. Following this order helps prevent displacement of the lacrimal punctum and deformity of the medial canthal area.
QWhen should the tube be removed after surgery?
A
Usually it is removed 1 to 2 months after surgery. Do not perform irrigation testing for 2 to 3 weeks after surgery. Even after removal, irrigation checks are needed every 2 weeks for 2 to 3 months. The lacrimal tube should be left in place for at least 6 weeks, and if there are no problems, leaving it in place for 4 to 6 months may also be considered.
6. Pathophysiology and detailed mechanism of onset
The anterior limb of the medial canthal tendon passes in front of the lacrimal sac and attaches to the frontal process of the maxilla and the anterior lacrimal crest, maintaining the position of the punctum. The posterior limb passes behind the lacrimal sac and attaches to the posterior lacrimal crest, contributing to the position of the inner eyelid and its close contact with the eye. Because the posterior limb is relatively weak against lateral traction, avulsion tends to occur from the posterior limb.
There are two routes for blunt trauma.
Indirect injury: A blow to the eye causes the eyelid to be pulled excessively outward, tearing the medial eyelid. In indirect injury, the canaliculus is prone to rupture on the nasal side, making repair difficult.
Direct injury: Caused by a direct external force to the medial canthus.
In blunt trauma, lacerations that tear the tarsal plate are uncommon; instead, lacerations with canalicular rupture tend to occur at the innermost part of the eyelid. Because the canaliculus runs on the posterior side of the medial canthal tendon, avulsion of the medial canthal tendon and canalicular rupture are anatomically linked injuries.
When canalicular rupture occurs, the medial canthal tendon also tears, and the punctum shifts outward. As a result, rounding of the medial canthal angle and telecanthus appear. In addition, tearing of the medial canthal tendon and Horner’s muscle impairs the tear-drainage pump function that accompanies blinking, and epiphora persists.
7. Latest research and future prospects (reports at the research stage)
A method has been reported in which repair is performed using only placement of a Crawford-type bicanalicular stent, without reconstruction of the medial canthal ligament.
It was reported to be effective in 35 of 37 patients who underwent stent-only repair, with almost no tearing and good cosmetic results (as described in Source C). It is thought to help reattach the medial canthal ligament complex by providing a pull toward the postero-medial side.
A system in which a screw hole is created in the medial orbital wall, an anchor device is inserted, and sutures are placed to the cut end of the medial canthal ligament. In cadaver studies, it was reported to have 97% of the holding strength of the contralateral medial canthal ligament.
A technique in which two drill holes are made at the medial canthal insertion, non-absorbable suture is passed through them, and it is tied from the same-side nostril. It is relatively simple and inexpensive, and good outcomes were reported in two cases.
Seo MG, Chung KJ, Kim YH. Post-traumatic Telecanthus Induced by a Missed Diagnosis of Avulsion Fracture of the Medial Canthal Tendon.J Craniofac Surg. 2023;34(5):e486-e488. PMID: 37150876
内眥部の浮腫や損傷では孤立性 MCT 剥離骨折を疑うべきこと、bowstring test と画像評価の重要性を強調。本記事「4. 診断と検査方法」の根拠。
Chu YY, Lim E, Liao HT. Ipsilateral transnasal medial canthopexy to correct secondary telecanthus after naso-orbito-ethmoid fracture.J Plast Reconstr Aesthet Surg. 2020;73(5):934-941. PMID: 32151558
Abdelmegeed AG, Haredy MM, Mazeed AS, Hifny MA. Transnasal Medial Canthopexy Supported with Autogenous Bone Graft: A New Method for Repair of Traumatic Telecanthus.J Craniofac Surg. 2022;33(5):1494-1497. PMID: 35119403
