Infraorbital rim





The upper midface skeleton has direct and indirect influences on the appearance of the face and, particularly, the eyes. The relationship between the globe and the orbital rims will determine if the eyes appear prominent or deep set. Because the infraorbital rim and upper midface skeleton support the lower eyelids and the cheek soft tissues, their projection impacts on lid and cheek position. Patients with deficient skeletons are more likely to undergo premature lower lid and cheek descent with aging. This lack of skeletal support predisposes to lower lid malposition after blepharoplasty and limits the efficacy and longevity of midface lifting. This chapter demonstrates the impact that infraorbital rim augmentation alone, or together with other soft tissue manipulations, has on periorbital appearance. It includes techniques not only for augmenting the infraorbital rim with alloplastic implants, but also for elevating the midface soft tissues as well as repositioning the lower lid and lateral canthus.


Globe–Rim Relations


The relationship of the globe to the orbital rims is a primary determinant of the appearance of the upper third of the face. Normal values, that is, averages calculated from a cohort of young, healthy adults, have been published. They are presented in Fig. 8.1 . On average, the surface of the soft tissues overlying the supraorbital rim lies 10 mm anterior to the cornea, and the surface of the soft tissues overlying the infraorbital rim lies 3 mm behind the anterior surface of the cornea. This implies that the supraorbital rim usually projects 13 mm beyond the infraorbital rim. When the orbital rims have a greater projection beyond the anterior surface of the cornea, the eyes appear “deep set.” When the orbital rims project less, the eyes appear “prominent.” In addition to being predisposed to corneal exposure-related problems, overly prominent eyes are usually considered less attractive.




Fig. 8.1


Sagittal relations of the anterior surface of the cornea to the soft tissues overlying the supraorbital and infraorbital rims. On average, in the young adult, the supraorbital rim projects 10 mm beyond, the infraorbital rim lies 3 mm behind, and the cheek prominence projects 2 mm beyond the anterior surface of the cornea.


Jelks’ vector analysis


Jelks and Jelks categorized globe–orbital rim relationships and the tendency for the development of lower lid malposition after blepharoplasty ( Fig. 8.2 ). On sagittal view, they placed a line or “vector” between the most anterior projection of the globe and the malar eminence and lid margin. A “positive vector” relationship exists when the most anterior projection of the globe lies behind the soft tissues overlying the midface skeleton in the parasagittal plane. A “negative vector” relationship exists when the most anterior projection of the globe lies beyond the soft tissues overlying the midface skeleton in the parasagittal plane. This relation reflects a deficiency in midface projection. Jelks and Jelks warned, similar to Rees and LaTrenta, that patients whose orbital morphology has a “negative vector” relationship are morphologically prone to lid malposition after lower blepharoplasty.




Fig. 8.2


Jelks and Jelks categorized globe–orbital rim relationships by placing a line or “vector” between the most anterior projection of the globe and the soft tissues overlying the midface skeleton in the parasagittal plane. (A) Positive vector relationship. (B) Negative vector relationship. (C) “Reversed” negative vector relationship resulting from increasing the sagittal projection of the infraorbital rim with an implant.

After Yaremchuk 2003.


There is a considerable variability in globe–orbital rim relations as a result of the wide variations in human facial skeleton morphology. It is influenced by ethnicity and sex, and changes with aging.


Migliori and Gladstone determined the normal range of globe protrusion for white and black adults. Using the Hertel exophthalmometer, which measures projection of the anterior surface of the cornea beyond the lateral orbital rim, they found that the range for white adults was 10 mm; for black adults it was 12 mm. In addition to determining a range of normal values, they documented racial and sexual differences in globe projection. When globe projection was measured relative to the lateral orbital rim, men’s globes, on average, were 2 mm more prominent than women’s, and black men’s and black women’s globes were 2 mm more prominent than those of white men and white women.


Pessa et al. showed that the globe–orbital rim relationship changes with age. Retrusion of the infraorbital rim with aging makes the eyes appear more prominent by changing globe–rim relations, and exaggerates lower lid fat prominence, particularly in those who tend toward maxillary hypoplasia. These findings and surgical maneuvers to rejuvenate this anatomy are described in Chapter 14 .




Altering Globe–Rim Relations: Reversing the “Negative Vector”


Augmentation of the infraorbital rim with an alloplastic implant in patients with midface deficiency can bring it into a better relationship with the globe, thereby “reversing the negative vector” ( Fig. 8.2 ).


Indications for reversing the negative vector


Blepharoplasty


The relative prominence of the eyes impacts on the position and shape of the lower lid; therefore it is an important consideration in aesthetic blepharoplasty. Eye prominence results from a deficiency in skeletal support, as has been discussed, but may also result from excess of orbital soft tissue volume. Eye prominence correlates with a more inferior position of the lower lid (resulting in scleral show) and a more medial position of the lateral canthus. Descent of the lower lid increases the height of the palpebral fissure, while a more medial position of the lateral canthus decreases its width. Hence, patients with poorly projecting upper midface skeletons have “round eyes” as compared to the long, narrow eyes characteristic of young people with a normal periorbital morphology. Furthermore, in the skeletally deficient, the lack of infraorbital rim projection and cheek prominence often allows their lower lid fat compartments to be visible – giving them “early bags” ( Fig. 8.3 ). Patients with this morphology can benefit from reversing their “negative vector” at the time of their blepharoplasty, together with resuspension of their midface soft tissue envelope.



Pearl


Deficient infraorbital rim projection predisposes to lower lid descent with aging.




Fig. 8.3


(A) Frontal and (B) lateral views of a woman with midface skeletal morphology (negative vector) predisposing to lower lid and cheek descent resulting in a “round eye” appearance with prominent bags. On lateral view (B) , the artist has drawn in the underlying deficient facial skeleton.

Reproduced from Yaremchuk 2004, with permission.



Fig. 8.4


Midface skeletal anatomy with muscle origins and nerve foramina.


After blepharoplasty


Patients with prominent eyes have long been recognized to develop symptomatic lower lid descent (with exaggeration of their “round eyes”) after conventional lower blepharoplasty. Negative vector patients who develop lid malposition after conventional blepharoplasty can have their lid position and palpebral fissure shape improved by increasing their skeletal support by alloplastic augmentation of the infraorbital rim together with midface soft tissue elevation and lateral canthopexy.



Pearl


Deficient infraorbital rim projection predisposes to lower lid descent after blepharoplasty.



Graves’ disease


Eye prominence results from a deficiency in sagittal skeletal projection, as has been discussed, but may also result from excess of orbital soft tissue volume as occurs with thyroid ophthalmopathy. Infraorbital rim augmentation together with midface soft tissue elevation can be a useful adjunct to orbital decompression in patients with Graves’ disease.


As will be described, infraorbital rim augmentation is part of the strategy for normalizing the appearance in patients who are “morphologically prone.” It can be adapted for morphologically prone patients who are first seeking improvement in their periorbital appearance or for those whose lid malposition and round-eye appearance have been exaggerated by previous lower blepharoplasty.




Surgical Anatomy ( fig. 8.4 )


The infraorbital rim has lateral zygomatic bone and medial maxillary bone contributions. The zygomaticomaxillary suture is situated approximately at the midpupillary line. Approximately 8 mm beneath the orbital rim (or 3 to 6 mm in severely hypoplastic midfaces) and along the zygomaticomaxillary suture exits the infraorbital nerve. The infraorbital nerve travels beneath the levator superioris and above the levator anguli oris. Its branches supply the skin of the lower lid, the side of the nose, most of the cheek, and upper lip. The zygomaticofacial nerve exits through its small foramen located on the lateral aspect of the zygoma, approximately 8 to 10 mm beneath the infraorbital rim and in line with the lateral orbital rim. It supplies a small portion of the skin of the upper cheek. Whereas the infraorbital nerve must be protected, the zygomaticofacial nerve is routinely sacrificed during infraorbital rim augmentation, with the ensuing sensory loss rarely noted by the patient.


In exposing the surface of the infraorbital rim area for implant augmentation, the origins of the upper lip elevators are detached from their skeletal origins. The zygomaticus major muscle originates from the lateral surface of the zygoma just medial to the zygomaticotemporal suture and sometimes intermingles with the orbicularis oculi. It passes obliquely downward and forward to the corner of the mouth where it inserts into skin and mucosa. The zygomaticus minor lies medial to the zygomaticus major. It originates from the malar surface of the zygoma immediately lateral to the zygomaticomaxillary suture and passes downward and medially to insert into the lip just medial to the corner of the mouth. The levator labii superioris originates from the lower margin of the orbit just above the infraorbital foramen. It travels downward and medially to insert into the orbicularis oris as well as the skin of the lip. The levator labii superioris alaequae nasi originates from the frontal process of the maxilla lateral to the nose. It inserts into the skin and alar cartilage of the nose and, more significantly, into the skin and musculature of the lip. Branches of the infraorbital nerve are adherent to the underside of the levator muscles.


The orbicularis oculi originates from the nasal process of the frontal bone, the frontal process of the maxilla, and from the anterior surface of the medial canthal tendon. The fibers are directed laterally to surround the entire circumference of the orbit. The orbicularis oculi’s maxillary origins are elevated during the placement of an infraorbital rim implant. The manipulation of this muscle may lead to a transient decrease in lower lid tone.




Preoperative Evaluation


As depicted in Fig. 8.1 , in young, healthy adults, the average projection of the soft tissues overlying the supraorbital rim beyond the surface of the cornea is about 10 mm, and the projection of the cornea beyond the soft tissues overlying the infraorbital rim is 2 mm. These relations are the approximate goals of augmentation of the orbital rims. A disproportion in sagittal globe–rim relations is usually obvious and correction is made by clinical judgment.

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Feb 9, 2020 | Posted by in Craniofacial surgery | Comments Off on Infraorbital rim
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