Cosmetic Otoplasty and Related Cosmetic Ear Surgery

Embryology

To be a successful surgeon, understanding embryology in anatomy is crucial. All mammals have external ears. The internal, middle, and external ear development is a beautiful and complex embryologic orchestration. The classic description by His is as follows: The external ear forms from tissues of the first and second pharyngeal arches, which can be seen at 5 weeks ( Fig. 8.1 ). Six tissue elevations termed auricular hillocks of His become apparent at 6 weeks in utero. Three hillocks form from the first arch, and three form from the second arch. Each of the auricular hillocks forms a distinctive portion of the definitive external ear. For example, hillock #1 forms the tragus, and hillock #6 forms the antitragus and part of the helix ( Fig. 8.2 ). The lobule of the ear is not derived from the hillocks. The developing external ears are initially more caudal than the lower jaw. Growth of the lower jaw places the external ear in a relatively higher and more vertical orientation.

Normal Anatomy

The developed external ear has evolved to capture and focus vibrations through the middle ear canal to the inner ear. In humans, many of the functions remain vestigial. Anyone who has ever witnessed animals whose life depends on detecting predators in nature such as deer has a better understanding of the complex movements and function of the mammalian external ear. Fig. 8.3 shows the normal anatomic components of the developed ear.

Other common measurements include the long axis of the ear, which inclines posteriorly at an approximately 20-degree angle from the vertical. The anterolateral aspect of the helix protrudes at a 21- to 30-degree angle from the scalp. The ear is positioned at approximately one ear length (5.5–7 cm) posterior to the lateral orbital rim between horizontal planes that intersect the eyebrow and columella.

The average length of the auricle is 63.5 mm in males and 59 mm in females. The average width of the auricle is 35.5 mm in males and 32.5 mm in females. The helix should project 2–5 mm more laterally than the antihelix on frontal view ( Fig. 8.4 ).

A very important measurement estimate is the distance that the auricle sits from the cranium. This will become paramount when diagnosing, planning, and performing cosmetic otoplasty. Although it varies from patient to patient, these distances are similar in the normal ear. I personally find the following specific measurements most useful: I measure with a caliper from the temporal skin to the center of the helical rim at the top of the helix. The average measurement in my experience is about 11 mm, with a range of 10–12 mm ( Fig. 8.5 ). The second measurement is taken from the mastoid skin to the back of the mid ear (see Fig. 8.5 ). This measurement is also generally about 11 mm (measured to the posterior of the ear at the mastoid region). I find measurements from the back of the lobe to the mastoid skin to be considerably more variable. When setting a protruding ear back to normal position, I usually use the 11-mm top measurement and the 11-mm posterior mastoid measurement. This may vary in either direction by several millimeters, but 11 mm seems to be the most common for each measurement. For comparison sake, the little finger width is about 10–12 mm.

Classic otoplasty texts discuss complex angles of where the various components of the ear are in relation to other structures. These include the conchomastiod angle, conchocephalic angle, and auriculocephalic angle (also called the cephaloauricular angle ). These are often described differently in various texts, and although they are important for understanding normal and abnormal ear posture, they are rarely used in treatment planning in my experience. I liken this to a facelift surgeon who realizes that a normal cervicomental angle is 90–110 degrees but does not use this measurement in any way intraoperatively when performing facelift surgery. I rely much more on actual millimeter measurements than angles for otoplasty planning and surgery. I am not saying that these numbers are irrelevant, but that they are not that clinically relevant.

Auricular Neuroanatomy

The auriculotemporal nerve is a branch of the mandibular division of the trigeminal nerve and supplies sensation to the tragus and helical crus. The anterior branch of the greater auricular nerve (from the cervical plexus) innervates most of the ear including the helix, scapha, antihelix, concha, antitragus, external acoustic meatus, and lobule. The posterior branch of the greater auricular nerve also innervates some of the posterior ear. The mastoid branch of the lesser occipital nerve (from the cervical plexus) also innervates the posterior region of the external ear ( Figs. 8.6 and 8.7 ). The external auditory meatus also receives innervations from branches of the vagus nerve (Arnold’s nerve) and the glossopharyngeal nerve. The entire ear can be anesthetized by injecting local anesthesia along the base anteriorly and posteriorly. Supplemental anesthesia may be needed at the posterior wall of the external ear canal supplied by the auricular branches of the vagus nerve. For other supplemental local anesthesia, a “ring block” is performed by injecting circumferentially around the ear (see Fig. 8.7 ).

Auricular Vascular Anatomy

The arterial supply to the external ear includes the posterior auricular artery from the external carotid artery, the anterior auricular artery from the superficial temporal artery, and a branch from the occipital artery.

The anterior arterial blood supply to the ear is primarily derived from the external carotid artery via the superficial temporal branch. The superficial temporal vessel exits the parotid capsule, passes under the anterior auricular muscle, and then divides into superior, medial, and inferior branches to supply the anterior surfaces of the auricle. The posterior auricular artery branches from the external carotid artery and runs parallel to the posterior auricular crease, deep to the posterior auricular muscle and greater auricular nerve. The posterior auricular artery (a branch of the external carotid artery) supplies the posterior surface of the ear and also has superior, medial, and inferior branches. The posterior ear also has arterial contribution from the mastoid branch of the occipital artery (a branch from the external carotid artery) ( Fig. 8.8 ).

The veins accompany the corresponding arteries. Venous drainage is from the superficial temporal and posterior auricular veins, and lymphatic drainage is from the parotid preauricular nodes (anterior), the superficial cervical nodes (inferior), and the retroauricular (mastoid) nodes posteriorly and mirrors the arterial distribution.

Muscular Anatomy

The muscles of the auricle consist of two sets. The extrinsic muscles connect the auricle with the skull and scalp and move it as a whole, and the intrinsic muscles extend from one part of the auricle to another.

The extrinsic muscles are the anterior, superior, and posterior auricular muscles ( Fig. 8.9 ). The anterior auricular muscle, the smallest of the three, is thin and fan-shaped with pale and indistinct fibers. It arises from the lateral edge of the galea aponeurotica, and its fibers converge to be inserted into a projection on the front of the helix. The superior auricular muscle, the largest of the three, is thin and fan-shaped. Its fibers arise from the galea aponeurotica and converge to be inserted by a thin, flattened tendon into the upper part of the cranial surface of the auricle. The posterior auricular muscle consists of two or three fleshy fascicules that arise from the mastoid portion of the temporal bone by short aponeurotic fibers. They are inserted into the lower part of the cranial surface of the concha.

The temporal branch of the facial nerve (cranial nerve VII) supplies the anterior and superior auricular muscles. The posterior auricular branch of cranial nerve VII supplies the posterior auricular muscle and the intrinsic auricular muscles. In humans, these muscles possess very little action. The anterior auricular muscle draws the auricle forward and upward, the superior auricular muscle slightly raises it, and the posterior auricular muscle draws it backward. Some people have increased activity of this musculature and can wiggle their ears.

Cartilaginous Anatomy

The delicate and complex ear cartilage is one of the most unique anatomic forms in the body. The entire external ear possesses a cartilaginous framework, with the exception of the lobe and the tragal incisura ( Fig. 8.10 ).

Aberrant Anatomy and Protruding Ears

Prominauris is the condition of protruding ears. Growth disturbances of the auricle have been described to occur in 1 in 12,500 births or 5% of the population. The ear grows proportionally at a rapid rate; 85% of the development occurs by 3 years of age, and the ear is fully developed at 7–8 years of age. Protruding ears can be present at birth or develop over the first year. The only difference between the neonatal ear and the adult ear is that, in the neonate, the cartilage is more malleable and softer. Otherwise, the anatomy is the same. Ear width reaches its mature size in boys at 7 years of age and in girls at 6 years of age. Ear length matures in girls at 12 years of age and in boys at 13 years of age. Ear cartilage becomes stiffer and calcified with age. Heredity plays an obvious part in the growth and development of protruding ears and is an autosomal dominant trait ( Fig. 8.11 ). Approximately one-third of ear deformities may self-correct.

Anatomic Causes of Protruding Ear Deformities

The absolute key to diagnosis and treatment of protruding ears is thorough knowledge of the anatomic contributions to the deformity. Many cases of mistreatment stem from the fact that the surgeon either does not recognize the singular or combination deformities or fails to properly treat the specific deformity. Ear deformities can be from singular or combined factors ( Figs. 8.12–8.14 ).

Combination Deformities

In my experience, the majority of patients exhibit a hypoplastic AHF and conchal bowl hypertrophy simultaneously ( Figs. 8.15 and 8.16 ). This combination deformity is very common and is present in the majority of patients I have treated, as opposed to a sole deformity of undefined AHF or posterior conchal wall excess.

Many more complex deformities exist as a result of development. These include microtia (the external ear does not form properly and is small), cryptotia (the upper ear is pulled against the side of the head and buried under the skin as a result of abnormal muscle positioning), Sthal’s deformity (a lack of superior helical rim), lop ears (helix is folded over), and branchial arch syndrome (skull and facial bones fuse early and prevent normal bone growth). Treatment of these deformities is beyond the scope of this text.