Ear Reconstruction




Abstract


Ear reconstruction can be challenging but also very rewarding due to its complex topography. Retaining the essential curvature of the helical rim is a key element in reconstructing the ear. Though flaps for ear reconstruction don’t have named vascular pedicles, it is important to understand the vasculature in order to successfully mobilize these flaps. Dividing the auricle into superior middle and inferior regions will help choose the appropriate repair. For superficial defects, full-thickness skin grafts play a key role. Because of the ear’s flexibility, it is important to provide a strong pressure dressing or bolster for a skin graft. While wedge repairs are useful, in many cases the chondrocutaneous advancement flap will be the better choice since it reduces the risk of cupping. For larger defects, the staged retroauricular flap is an excellent flap and can be combined with a cartilage graft to retain the shape of the helix. For defects that involve more than half of the superior portion of the auricle, a prosthesis or referral to a head and neck surgeon may be appropriate.




Keywords

helix, occipital artery, temporoparietal, retroauricular, island pedicle

 




Introduction


Repair of the auricle can be traced back to India (600 bce ), with subsequent contributions by the Egyptians, Renaissance Italians, 19th-century surgeons, and finally German surgeons such as Diffenbach, who played a major role in refining auricle reconstruction. Much of the literature has focused on providing a reliable framework either after trauma or for microtia repair. These techniques range from harvesting costal cartilage buried in the abdomen to using porous polyethylene.


Because the auricle framework gives the ear its characteristic shape and orientation, until recently little emphasis has been placed on the cutaneous defects of this cosmetic unit. With the increased incidence of skin cancer, these defects have become commonplace. Reconstructive technique that does not restore the natural shape and curvature of the ear will invariably be noticed, particularly when compared with the contralateral ear.




Ear Aesthetics


Although auricle length is somewhat dependent on ethnicity (with African being the shortest and Asian being the longest), the length to width of the auricle should be slightly less than 2 : 1. Generally, the auricle protrudes from the scalp at a 20- to 30-degree angle. A smooth contour outlined by the helical rim and bilateral symmetry are important universal aesthetic norms ( Fig. 14.1 ).




Fig. 14.1


The aesthetic proportions of the ear.


The superior aspect of the helical rim, defined by a horizontal line from its attachment to the scalp, needs to maintain a gentle curve without any acute angles. As the rim descends it almost approaches a 90-degree angle through its midportion. The lower third of the auricle curves at approximately a 45-degree angle as it descends into the earlobe. The lobule has great variability in its length and curvature. In general, its width is one-third to one-half of the width of the superior portion of the helix. Earlobe length depends on ethnicity but is approximately 2 cm on average. Earlobe thickness or “fleshiness” also varies from barely discernable from the helical rim to a very defined and separate structure. Earlobes tend to be asymmetrical and elongate with age. Aesthetically, the most important aspect of the earlobe is its independence as a separate cosmetic unit while maintaining the curved continuity of the helical rim.




Embryology


Embryologically, the ear develops from the first and second branchial arches. These arches arise as hillocks from the neck. During the early gestational period, they migrate cephalad. The outline of the ear is apparent early in the fetus at approximately the sixth week. Following birth, the external auricle grows quickly. By the age of 6 years, it has attained nearly adult size and proportions.




Topography


With its numerous ridges and valleys designed to improve acoustic reception, the external ear possesses the most complex topography of any cosmetic unit of the head and neck. The auricular framework is formed by cartilage. The earlobe like the nasal alar lobule is made of fibrofatty tissue. The medial-anterior facet of the auricle is characterized by perichondrium and thin skin tightly adherent to cartilage. The posterior-medial aspect has looser skin and some subcutaneous fat overlying the cartilaginous framework ( Fig. 14.2 ).




Fig. 14.2


The topography of the ear.


The major anterior landmarks of the external ear are the helix, scapha, antihelix, concha, and tragus and antitragus. Posteriorly, there are eminences that correspond to these anterior landmarks. Laterally, the helix actually begins with the crus, which originates at the superior aspect of the conchal bowl. The helix extends superiorly in a gentle curve. As it descends, there is a slight prominence known as the Darwinian tubercle. The helix continues its descent uninterrupted to the lobule. Proceeding medially from the helical rim is the scaphoid fossa. This is bounded by superior and inferior crura of the antihelix. As these two limbs of the antihelix stretch to meet the helical rim, a depression known as the triangular fossa bounded by these two limbs and the rim is created. Medially, these ridges bound the concha. This bowl-like structure can be divided into the cymba, which is bounded superiorly by the anterior crus of the antihelix and inferiorly by the crus of the helical rim. Inferior to the crus is the cavum, which has a more concave nature. Although the recessed nature of the concha makes it appear less important to the structure of the auricle, it actually acts as a brace between the mastoid and the remainder of the auricle. Medial-posteriorly, the concha leads to the external auditory canal. Lateral to the canal is the tragus, a roundish prominence. Opposing the tragus, across the conchal valley, is the antitragus, a linear prominence at the origin of the antihelix. The posterior aspect of the ear is marked by various ridges and named prominences known as eminences, which correspond to the anterior anatomic landmarks. Aside from the intrinsic rigidity produced by the cartilaginous framework, the auricle is held in placed by small muscles and ligaments. The musculature can be divided into three extrinsic and three intrinsic bands.


Vasculature


The blood supply is mainly supplied by the superficial temporal and the posterior auricular arteries. Both are branches of the external carotid. The superficial temporal artery and its branches, including the direct auricular, supply the anterior (lateral) surface of the ear, particularly the superior half. The posterior auricular artery supplies the entire medial (posterior) surface and has branches that perforate to the opposing surface, mainly supplying the lower half of the ear including the conchal bowl ( Fig. 14.3 ). The postauricular region is also supplied by the occipital artery. A recent cadaver study demonstrated the robust anastomoses in the mastoid and postauricular space. This study is particularly relevant to staged retroauricular flaps because it appears that flaps up to 5 cm from the external auditory canal would have a sufficient vascular supply. Venous drainage occurs via corresponding named veins in addition to the retromandibular vein. These three veins flow into the external jugular vein.




Fig. 14.3


The vasculature of the ear. (A) Superficial temporal artery and branches. (B) Posterior auricular artery and branches. (C) Regions of the auricle supplied by these two arteries.


Innervation


The external ear possesses an intricate sensory supply. The innervation is supplied by branches of the cervical nerve, 10th cranial nerve, trigeminal nerve, and lesser occipital nerve. The greater auricular nerve, which originates from C 2 and C 3 , extensively innervates the cranial aspect of the ear, including the earlobe. It also branches out to the anterior surface and innervates most of the upper half of the auricle. The auriculotemporal nerve, a branch of V 3 , supplies the lateral aspect of the superior portion of the helix. The posterior surface of the helix and the eminences of the scapha and fossa triangularis are innervated by the mastoid branch of the lesser occipital nerve. Finally, the Arnold nerve, a branch of the vagus (CN 10 ), supplies sensory nerves to the concha.




General Principles


The most important principle of reconstructing the ear is to maintain the natural contour and shape as defined by the helical rim. The auricle should appear within the range of expected shapes, be in close approximation to the scalp, and be symmetrical to the contralateral ear. Although not as important as the shape, the height of the auricles should be similar. Unlike the shape, a minor discrepancy in height will be imperceptible to the casual observer. If the shape, particularly the curve of the helical rim, is not smooth, it will be instantly noticeable.


As with other regions of the head and neck, second intent healing is a viable option for many wounds. It is particularly useful in concavities such as the conchal bowl and scaphoid fossa. Because of the robust blood supply, the healing is usually rapid with excellent cosmetic results. If there is exposed cartilage, it may be prudent to provide coverage rather than allowing second intent healing. The coverage will reduce pain, minimize distortion due to wound contraction, and lessen the risk of chondritis.


Tumor extirpation with Mohs micrographic surgery is the treatment of choice in this area for providing the highest possible cure rate and minimal sacrifice of normal tissue. In tumors that are well defined, wedge excisions may be acceptable with proper en face examination of the margin. Unlike the lip, a simple wedge excision may lead to an uneven closure and notching of the helical rim because of the complex topography of the ear cartilaginous framework. The addition of two perpendicular Burow triangles will facilitate a wedge excision closure by removing the redundant cartilage. Another important reconstruction pearl to maintain the smooth curve of the helix is the use of the Z-plasty to prevent retraction of the wound edge and notching.




Reconstructive Options


Skin Grafts


Full-thickness skin grafts have a wide application in resurfacing small to medium auricular defects. Grafts will have the highest chance of surviving if there is intact perichondrium. If the wound base consists of cartilage, multiple full-thickness perforations of the cartilage with a 2-mm punch can be used to facilitate the blood supply. Common donor areas include the preauricular and postauricular sulci. The postauricular region is desirable because the scar will be hidden and it can heal by second intent or be closed primarily ( Fig. 14.4 ). The preauricular region may provide a slightly thicker graft. This site is a good choice when there are significant creases in which to hide the scar. It is rare that this donor site is left to heal by second intention. In general, the donor site is from the ipsilateral side because this will decrease the need for patient repositioning.




Fig. 14.4


A common donor site for full-thickness skin grafts: the postauricular region.


For helical rim defects that do not involve cartilage, a full-thickness skin graft will restore the contour without placing tension on the delicate cartilaginous framework. For medium-sized defects of the scaphoid fossa or conchal bowl in which second intent healing may require several weeks, a full-thickness skin graft will minimize wound care and possible chondritis. These grafts can be sewn in with 6-0 absorbable or nonabsorbable sutures. Sutures can be placed through the center of the graft to secure it to the underlying tissue to obliterate a potential space for a hematoma or seroma. The postoperative dressing is as important to a good outcome as securing the graft. It can take the form of a bolster dressing and be stabilized with sutures. The use of a dental roll to maintain well-distributed pressure may improve graft survivability. Alternatively, a secure pressure dressing will most likely be as effective as the most complex bolster. It can also be more easily removed to inspect the graft should that be necessary. The variability in skin graft healing and inosculation may alter how long a dressing is kept in place. However, it is usually prudent to leave a dressing undisturbed for 1 week.


Adjacent Tissue Transfer


As in other head and neck defects, well-vascularized flaps with bulk that can be contoured are excellent reconstruction options for auricular defects. Random vascular pattern flaps based on the generous and redundant blood supply of the ear have a high survival rate. For larger defects, flaps may be staged, either from the preauricular or postauricular regions ( Fig. 14.5 ) or from the temporal scalp. Wide undermining is necessary on the ear because there is minimal skin laxity, particularly on the lateral aspect of the external ear. Flaps may include cartilage, such as the chondrocutaneous helical advancement flap and the conchal bowl transposition flap for partial helical defects. Flaps may also be “tubed” to rebuild the helical rim from the preauricular or postauricular sulci ( Fig. 14.6 ). For full-thickness conchal bowl or antihelix defects, posterior-based flaps may be bivalved to resurface both the lateral and medial side of the defect ( Figs. 14.7 and 14.8 ).










Fig. 14.5


A postauricular staged flap for reconstruction of the superior helical rim. (A) Post-Mohs micrographic surgery. (B) Cartilage attached. (C) Postauricular flap attached. (D) Long-term postoperative result. The helix is smooth and retains its original shape.





Fig. 14.6


A “finger” or banner transposition flap for helical reconstruction. (A) Mohs defect and marking for superior-based finger transposition flap. (B) Flap attached.

Mar 3, 2019 | Posted by in Dermatology | Comments Off on Ear Reconstruction
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