1.The average distance between the medial canthus in the same age group
Medial canthus distance (mm)
Age
Mean
Standard deviation
0 20 4
1 25 5
3 26 4
5 27 5
7 28 4
12 29 5
Adulthood
30 5
2.Orbital distance widening and medial canthus distance widening criteria
n Widening of orbital distance: orbital distance greater than 30mm
n Mild 30mm~35mm
n Moderate 35mm～40mm
n Severe 40mm
n Widening of the medial canthus: medial canthal distance greater than 35mm
3.Morphology and position of the inner and outer canthus
The position of the outer canthus is in the line of the two inner canthi or 1-3 mm above the line is the normal range. If it is lower than the inner canthus within 2 mm and symmetrical on both sides, it is also acceptable. If it is greater than 3 mm, surgical correction is usually required.
5. Causes of abnormal position of the medial canthus
n
Congenital causes.
Abnormal position of the medial canthus due to bony widening, such as orbital spur widening disorder.
Non-bony causes such as microphthalmia, cleft face, canthus, etc.
n
Acquired craniofacial deformities.
Benign tumors such as lymphangiectasia, hemangioma, fibrous tissue abnormalities, and other extrusion-induced displacements.
Displacement caused by traumatic injury to the medial canthal ligament
II. Anatomy of the medial canthal ligament
n
The medial canthal ligament is located in the subcutaneous area of the medial canthus and is in a transverse position, with a tough cord-like structure that can be palpated from outside the skin.
n
It is generally believed that the medial canthal ligament is divided into two branches, the anterior and posterior, and wraps around the lacrimal sac, anchoring the lid to the anterior and posterior tear crests for tear collection and excretion, and playing a supportive and stabilizing role for the attachment of the orbicularis oculi muscle and eye opening and closing movements.
n
The fibers of the anterior and superior branches of the medial canthal ligament travel nasally and terminate on the frontal process of the maxilla and the superior and inferior periosteum of the nasofrontal suture. The fibers of the upper branch penetrated into the frontomandibular suture, while the fibers of the posterior branch traveled along the surface of the lacrimal sac fascia and terminated at the posterior lacrimal crest of the lacrimal bone, where the fibers were neatly arranged and migrated with the periosteum on both sides after reaching the posterior lacrimal crest.
Clinical significance of the anatomical findings of the medial canthus
n
The anterior branch alone is loose, and there is no medial canthus deformity.
n
If the superior branch and the anterior branch are released together, the distal medial canthus deformity is evident, so at least the anterior and superior branches of the medial canthal ligament together maintain the normal shape of the medial canthus.
n
The role of the posterior branch needs to be further investigated.
n
In the correction of postfracture medial canthus deformity, the combined action of the branches of the medial canthal ligament should be taken into account, and the direction of suspension should be in the direction of their combined force.
n
The anterior, superior, and posterior branches of the medial canthus are directed to the anterior lacrimal crest, the frontomandibular suture, and the posterior lacrimal crest, respectively. The combined force must be directed from the beginning to a point on the orbital rim within the range of attachment of the three.
n
Clinical experience shows that the best results are obtained by suspending the ligament over the posterior aspect of the anterior lacrimal crest or the posterior lacrimal ridge.
n
In the medial canthus, the orbicularis oculi muscle and the medial canthal ligament are closely related. Therefore, when the medial canthal ligament is released, the medial canthus is displaced outward by the temporal force of the orbicularis oculi muscle, resulting in a distal medial canthus deformity.
C. Surgical treatment of medial canthal ligament injury
Characteristics of medial canthal ligament injury
n
Directly severed by the fracture fragment or injury-causing object.
n
direct separation of the ligament from the bone surface, along with the attached bone fragment
n
Collapse of the bone scaffold with subsequent displacement and release of the ligament.
Classification and clinical manifestations of medial canthal ligament injuries
n
Type I.
Partial or complete severance or avulsion of the medial canthal ligament from its point of attachment: increased distance between the medial canthus of both eyes, tearing, blunting of the medial canthus, and reduction in the size of the eye fissure.
n
Type II
Unilateral comminuted fracture and displacement of the medial orbital wall. The clinical presentation is similar to type I. There may be a combination of entrapment of the internal rectus muscle, cerebrospinal fluid leakage and possible optic nerve injury
n
Type III
Bilateral medial orbital wall fractures, nasal and septal fractures, including nasal bone, septum and frontal sinus injuries. Clinical manifestations include flattening and widening of the nasal root, poor airway ventilation and rhinorrhea, widening of the medial canthal spacing, blunting of the medial canthus, smaller eye fissures, and tearing.
Internal fixation of the displaced medial canthal ligament
1: In situ suturing of the medial canthal ligament.
2: Fixation of the medial canthal ligament to the anterior tear ridge.
3: Fixation of the medial canthal ligament to the posterior lacrimal crest.
Surgical method
1: A curved incision is made on the medial side of the eye, the subcutaneous tissue is separated, the periosteum of the medial orbital wall is incised, and the medial orbital wall is peeled off with a peeler to reveal the lacrimal crest and the lacrimal sac fossa.
2, Find the rupture of the medial canthal ligament under the skin, then make a small notch at the corner of the eye, and use a round needle with a fine wire to pass through the ruptured medial canthal ligament, through the small incision in the corner of the eye with the true subcutaneous tissue, and back through the medial canthal ligament.
3.Drill a hole behind the anterior lacrimal crest or at the posterior lacrimal ridge, pass through the nasal bone to the lateral side of the contralateral nasal bone, a small incision can be made on the contralateral nose, bluntly separate to the nasal bone, and drill two holes on the lateral side of the nasal bone.
4. A large curved needle with a wire with the severed end of the medial canthal ligament is passed from the anterior lacrimal crest foramen on the affected side through the nasal bone to the contralateral side of the nose, and another large curved needle with another wire from the anterior lacrimal crest foramen through the nasal bone to the other hole on the contralateral side of the nose, so that the severed medial canthal ligament is planted on the anterior lacrimal crest foramen, pulled tightly and then tightened and fixed to reset the transplanted medial canthal ligament.
Caution
n
The hole must be drilled posteriorly above the lacrimal fossa, not just on the lateral nasal bone, with a larger hole so that the severed end of the medial canthal ligament is planted into the hole.
n
The position of the medial canthal ligament implant (i.e., the location of the hole) is generally preferred to be downward rather than upward. If the medial canthal ligament is planted higher than the lateral canthus, the appearance is not good.