Otoplasty - Surgical Anatomy of The External Ear

Surgical Anatomy of The External Ear

The pinna

The external ear (pinna) is a surgically challenging anatomy composed of a delicate and complex framework of shaped cartilage that is covered, on its visible surface, with thin, tightly adherent, hairless skin. Although of small area, the surface anatomy of the external ear is complex, consisting of the pinna (the auricle) and the external auditory meatus (auditory canal). The outer framewok of the pinna is composed of the rim of the helix, which arises from the front and from below (anteriorly and inferiorly), from a crus (shank) that extends horizontally above the auditory canal. The helix merges downwards (inferiorly) into the cauda helices (tail of the helix), and connects to the lobule (earlobe). The region located between the crura (shanks) of the antihelix is the triangular fossa (depression), while the scapha (elongated depression) lies between the helix and antihelix. The antihelix borders in the middle (medially) to the rim of the concha (shell) and the concha proper, which is composed of the conchal cymba above (superiorly) and the conchal cavum below (inferiorly), which are separated by the helical crus, and meet the antihelix at the antihelical rim. The tragus (auditory canal lobule) and the antitragus (counterpart lobule) are separated by the intertragal notch; the auditory canal lobule does not contain cartilage, and displays varied morphologic shapes and attachements to the adjacent cheek and scalp.

Blood supply and innervation

The superficial temporal and posterior auricular arteries preserve the arterial blood supply of the external ear. The sensory innervation involves the front and back (anterior and posterior) branches of the greater auricular nerve, and is reinforced by the auricular temporal and lesser occipital nerves. The auricular branch of the vagus nerves supplies a portion of the posterior wall of the external auditory canal.

Otoplastic praxis

The support framework of the reconstructed pinna must be more rigid than the natural cartilage framework of a normal ear, in order for it to remain of natural size, proportion, and contour. If the reconstructed pinna framework were as structurally delicate as the cartilage framework of a natural pinna, its anatomic verisimilitude as an ear would gradually be eroded by a combination of the pressure of the tight skin-envelope in the temporal region of the head, and of the pressure of the progressive contracture of the surgical scar(s).

Prominent ears

In the practice of otoplasty, the term prominent ears describes external ears (pinnae) that, regardless of their size, protrude from the sides of the head. The abnormal appearance exceeds the normal head-to-ear measures, wherein the external ear is less than 2.0 cm, and at an angle of less than 25 degrees, from the side of the head. Ear configurations, of distance and angle, that exceed the normal measures, appear prominent when the man or the woman is viewed from either the front or the back perspective. In the occurrence of prominent ears, the common causes of anatomic defect, deformity, and abnormality can occur individually or in combination; they are:

(i) Underdeveloped antihelical fold

This anatomic deformity occurs consequent to the inadequate folding of the antihelix, which causes the protrusion of the scapha and the helical rim. The defect is manifested by the prominence of the scapha (the elongated depression separating the helix and the antihelix) and the upper-third of the ear; and occasionally of the middle third of the ear.

(ii) Prominent concha

This deformity is caused either by an excessively deep concha, or by an excessively wide concha-mastoid angle (<25 degrees). These two anatomic abnormalities can occur in combination, and produce a prominent concha (the largest, deepest concavity of the pinna), which then causes the prominence of the middle third of the external ear.

(iii) Protruding earlobe

This defect of the earlobe causes the prominence of the lower third of the pinna. Although most prominent ears are anatomically normal, morphologic defects, defromities, and abnormalities do occur, such as the:

• Constricted ear which features an abnormally small pinna, and protrudes from the head because of the inadequate development of the circumference of the helical rim, which, in turn, causes the pinna to collapse forwards, and form a cup ear.

• Cryptotic ear which is hidden in the side of the head. The condition of a hidden ear is produced when the developed helix of the pinna is contained under the skin of the scalp in the temporal region. (see Cryptotia)

• Macrotic ear, a prominent external ear that features an oversized pinna, but is otherwise morphologically normal. (see Macrotia)

• Question mark ear describes the ear that features a deformity of the supralobular region (upper area of the pinna), and has the appearance of a question mark (?).

• Stahl’s ear deformity describes the presence of a third crus (shank) in the pinna, which produces a pointed elfin ear. The third crus is additional to the two crura (shanks) of the normal triangular fossa (depression), which traverses the scapha (elongated depression separating the helix and the antihelix).