Otoplasty - Surgical Anatomy of The External Ear - The Angles of The Ear

The Angles of The Ear

Cephaloauricular and scaphoconchal angles

The degrees of angle between the head and the ear, and the degrees of angle between the scapha and the concha, determine the concept of prominent ears. The study, Comparing Cephaloauricular and Scaphaconchal Angles in Prominent Ear Patients and Control Subjects (2008) reported that the comparisons of the head-to-ear angles and the scapaha-to-concha angles of a 15-patient cohort with prominent ears, with the analogous ear angles of a 15-person control group, established that the average head-to-ear angle was 47.7 degrees for the study group, and 31.1 degrees for the control group; and that the average scapha-to-concha angle was 132.6 degrees for the study cohort, and 106.7 degrees for the control group.

I. Antihelix

The antihelix normally forms a symmetric Y-shaped structure in which the gently rolled (folded) crest of the root of the antihelix continues upwards as the superior crus, and the inferior crus branches forwards, from the root, as a folded ridge. The root of the inferior crus of the antihelix sharply defines the rim of the concha. Moreover, the inferior crus also forms the wall that separates the concha from the triangular fossa. The root and superior crus of the antihelix form the anterior wall of the scaphoid fossa, and the helix forms the posterior wall. The triangular fossa dips within the Y-arms of the superior and inferior crura. The corrugated contours of these auricular crests and valleys provide a pillar effect (support) that stabilizes the pinna. The vertical walls of the conchal cup translate to a semi-horizontal plane as the concha merges with the folded crest of the antihelix. The scapha–helix is nearly parallel to the plane of the temporal surface of the head. If the roll of the antihelix and its crest are effaced and flat, rather than rolled or folded, the steep pitch of the conchal wall continues into the un-formed antihelix and scapha and ends at the helix, with little interruption. Said planar orientation places the scapha–helix complex nearly perpendicular to the temporal plane of the head — because of which the ear appears prominent, thus, such an ear also lacks the stability provided by the pillar effect, and so allows the superior auricular pole to protrude. In the literature, effacement (deficiency) of the antihelical fold is the foremost subject of most discussions of the prominent ear, because it is an aurical deformity manifested as a spectrum of defects and deformities — ranging from an indistinguishable antihelix (with a confluent concavity, from antihelix to scapha and the helical rim projected outwards and forwards) to loss of definition solely of the superior antihelix (with prominence of the upper pole of the ear).

II. Concha

The concha of the ear is an irregular hemispheric bowl with a defined rim. The normal scapha–helix surrounds the posterior part of the bowl (much as the brim of an inverted hat surrounds the crown). The pitch at which the scapha–helix projects from the conchal cup is determined: (i) by the acuteness of the fold of the crest of the antihelix, (ii) by the height of the posterior wall of the conchal bowl, and (iii) by the completeness of the hemisphere formed by the concha. If the posterior wall of the concha is excessively high, and the concha is excessively spherical, then there is an excessive angle and distance between the plane of the scapha–helix and the plane of the temporal surface of the head. Such protrusion usually is evenly distributed around the posterior conchal wall, however, the cephalad part of the concha can protrude disproportionately, another cause for a protruding upper pole. Similarly, the caudal part of the concha can project disproportionately, and cause a protruding lower auricular pole, therefore, these deformational features require special attention in the operating room.

Moreover, regarding the shape and projection of the ear, the importance of the concha must be considered in relation to the three-tiered configuration of the auricular cartilage framework, because the more delicate antihelix and helical complex are mounted upon the sturdier concha; therefore, changes in conchal size and shape greatly influence the overlying tiers, hence it is rare to see prominence of the ear that does not have a conchal element. The concha affects the prominence of the ear three-fold ways: (i) the overall enlargement of the concha projects the ear away from the mastoid surface; (ii) an extension of the helical crus across the concha creates a firm cartilage bar that pushes the ear outwards; (iii) the effect of the angulation of the cartilage, at the junction between the cavum concha; and the sweep of cartilage up to the antitragal prominence, affects the position and prominence of the lobule (earlobe) and lower third of the ear.

Understanding the first deformational element is well recognized, and, despite limited attention to the second element, once seen, it is easily understood. Therefore, understanding the third element leads to understanding the surgical-technical approach to correcting the isolated lower-pole and lobule prominence. The latter feature of conchal shape, while not the sole cause of lobular prominence, appears to play a key role. As the cartilage angle, between the concha cavum and the antitragus, becomes more acute (i.e. as the antitragus tips closer towards the concha), this supporting structure outwardly projects the lobule and the lower-third of the ear. This feature has a greater influence upon the lobule position than does the commonly described helical tail.

III. Protruding antihelix and protruding concha combined

The combined effects of an effaced antihelix and a deep concha also contribute to severe auricular protrusion, that is, a very prominent ear.

IV. Protruding mastoid process
Auricular prominence

The occurrence of a prominent mastoid process tends to push the concha forward, which extends the pinna (external ear) away from the side of the head. The external ear is mounted upon the bony base of the underlying temporal bone, therefore, anomalies and asymmetries of the skeletal shape can cause either pinna, or both pinnae, to become prominent. In relation to the protruding mastoid process, the most recognizable skeletal anomaly is the change in the position and in the projection of the pinna, as associated with non-synostotic plagiocephaly (the positional flattening of the side of the head, not caused by the inappropriate union of two bones). Hence, in the occurrence of a flattening of the skull (parallelogram deformation of the cranial vault), the side of the head afflicted with occipital plagiocephaly presents a prominent ear. In subtle cases, the prominent ear might be more readily evident in an elder patient, whose ears are asymmetrically positioned, reason for which the residual occipital flattening (occipital plagiocephay), and mild facial asymmetry, are unapparent at first view. This effect, of the shape of the patient’s head, upon the outward and extended position of the ear is notably indicated in the 19th-century illustrations that describe the Ely otoplasty technique (1881).

Hemifacial microsomia

The undersized development of one side of a person’s face, demonstrates the influence of skeletal development upon the position of the external ear on the head, as caused by the deficient morphologic development of the temporal bone, and by the medial positioning of the temporomandibular joint, the synovial joint between the temporal bone and the mandible (upper jaw). Moreover, in severe cases of hemifacial microsomia, without the occurrence of microtia (small ears), the normal external ear might appear to have been sheared off the head, because the upper half of the pinna is projecting outwards, and, at the middle point, the lower half of the pinna is canted inwards, towards the hypoplastic, underdeveloped side of the face of the patient. A similar type of asymmetric development of the head and face features a relatively broad head, a narrow face, and a narrow mandible; when observed from the front perspective, the head and face of the person present a triangular configuration. Such wide-to-narrow skeletal sloping, from the head to the face, might create the bone promontory upon which rests and from which projects the upper anatomy of the pinna, which otherwise is an external ear of normal proportions, size, and contour.

V. Protruding cauda helicis

The cauda helicis (tail of the helix) is bound to the fibrofatty tissues of the earlobe by a network of connective tissue. The tail of the helix (cauda helicis), which projects outwards from the concha, carries the earlobe with it, causing it to protrude, which physical condition contributes to prominence of the lower pole of the pinna, the external ear.

VI. Protruding earlobe

Given the morphological diversity of the earlobes found among men, women, and children, some earlobes are large, some earlobes are pendulous, and some earlobes are large and pendulous, but some are prominent because of the structure and form of the dense, interlacing connective tissue fibers that shape the earlobe anatomy independent of the tail of the helix (cauda helicis).

VII. Soft tissues

Functionally, the external ear is served by three (3) ear muscles, the auricularis posterior muscle (rear ear-muscle), the auricularis superior muscle (upper ear-muscle), and the auricularis anterior muscle (front ear-muscle), the most notable of which is the auricularis posterior muscle, which functions to pull the ear backwards, because it is superficially attached to the ponticulus (bridge) of the conchal cartilage, and to the posterior auricular ligament (rear ligament of the ear). The posterior muscle of the ear is composed of 2–3 fascicles (skeletal-muscle fibers contained in perimysium connective tissue), originates from the mastoid process of the temporal bone and is inserted to the lower part of the cranial surface of the concha, where it is surrounded by fibroareolar tissue deep within the temporal fascia. The posterior auricular artery irrigates the ear tissues with small, branch-artery blood vessels (rami). Likewise, the rear muscle of the ear is innervated with fine rami of the posterior auricular nerve, which is a branch of the facial nerve. Deep within these muscle and ligament structures lie the mastoid fascia and the tendinous origin of the sternomastoid muscle.

Read more about this topic:  Otoplasty, Surgical Anatomy of The External Ear