By Tyler Scoresby, MD

Auricular reconstruction is the surgical rebuilding of the external ear with local flaps, skin grafts and autologous cartilage or other materials. Such a procedure would be required because of congenital malfomations of the external ear or damage to the ear later in life, as in trauma, cancer or burns.

Relevant Anatomy

In order to understand the need for and the process of auricular reconstruction, a review of basic external ear anatomy is required.   The outer rim of the ear is called the helix, and the groove just under this rim is the scaphoid fossa.  The next ridge of cartilage is termed the antihelix and this typically divides into two folds in the upper ear called the antihelical crus. The hollow between these folds is called the triangular fossa.  The bowl of the ear is the concha and this is divided by the root of the helix into the concha cymba superiorly and the concha cavum inferiorly.  The triangular outcropping of cartilage anterior to the ear canal is the tragus and just opposite the ear canal is the antitragus.  The lobule lies inferiorly and has no underlying cartilage framework. 

The external ear is generously vascularized.  Anteriorly, it is supplied and drained by the superificial temporal artery and vein respectively.  The posterior auricular artery and vein supply the ear from behind.  The skin of the ear is innervated anteriorly by the auriculotemporal nerve.  The posterior superior skin is innervated by the lesser occipital nerve and inferiorly by the great auricular nerve.

Microtia

The external ear develops around the 5th week of gestation beginning with 6 buds of tissue called the Hillocks of His.  Over the next several weeks, these hillocks develop into normal external ear structures: the tragus arises from the first hillock, the helical crus from the second, the helix from the third, the antihelix from the fourth and fifth and the antitragus from the sixth.

Microtia is the congenital poor formation of the ear during this process. Several systems exist to classify and grade microtia, but most are based on grades close to the following.  In Grade I microtia, the pinna is malformed and smaller than normal but most of the characteristics of the pinna, are present with relatively good definition.  In Grade II, the pinna is smaller and less developed and the triangular fossa, scaphae, and antihelix have much less definition. In Grade III the pinna is essentially absent except for a vertical nub of a skin remnant. There is typically some underlying unorganized cartilage in the superior aspect of this remnant, while the inferior portion consists of a relatively well-formed, though malplaced lobule.  This is the most common grade in which reconstruction is performed.  Grade VI microtia is the total absence of the pinna and is also termed anotia.
 
The right ear is affected twice as often as the left. Fifty percent of patients with microtia have associated syndromes such as goldenhar syndrome, branchiootorenal syndrome, branchial cleft cysts, holoprosencephaly, treacher collins syndrome, and Robinow syndrome, and a bilateral defect in these cases is much more common.

Microtia Repair

Surgial repair of microtia typically consists of 3-4 stages, separated by about 3-6 months and beginning at around the age of 5.  This age is ideal because the opposite ear, which will be used as a template for reconstruction of the affected ear, is at or close to adult size.  Additionally, the costal cartilage which will be used as reconstructive material has formed well by this time. Furthermore, the child has not yet entered school and will not face the stigma of a malformed ear.

In stage 1, the main portion of the auricular framework is created from the contralateral costal cartilage. The synchondrosis of ribs 6-7 is harvested and carved to create the antihelix, the crus, and the concha. The 8th rib cartilage is harvested separately and carved to create the helix, which is then sutured to the carved synchondrosis.  The carving is based off a template drawn of the opposite ear, if normal.  The cartilage framework is then placed in a skin pocket in the appropriate location for the newly formed ear.  Because the skin must drape and conform to the contours of the carved cartilage, the appropriate plan of dissection of the skin pocket is extremely important.  The correct plane is superficial to the temporoparietal fascia. Excess fat and hair follicles should be removed as much as possible in the overlying skin to ensure a good result. Any remaining cartilage is banked along with the carved cartilage for use in future stages.

As stated above the lobule in Grade 3 microtia is present but malplaced.  In stage 2, the lobule rotated inferiorly. The inferior aspect of the buried cartilage is delivered and the lobule is filleted open to accept the cartilage.  This ensures a better contour in later stages.

Stage 3 involves creating the postauricular sulcus.  An incision is made posteriorly from the root of the helix to the lobule, such that the skin and cartilage is hinged anteriorly.  The cartilage is propped up to the appropriate angulation from the head with banked cartilage from Stage 1. An autologous skin graft is then placed in the posterior sulcus and a bolster dressing placed.

The tragus is formed in Stage VI with either local remnants, if any remain, or from a composite skin/cartilage graft from the contralateral conchal bowl.

These stages are followed, if necessary, by reconstruction of the external auditory canal by an otologist.  This process is beyond the scope of this article.

Acquired Defects

Ninety percent of all skin cancers occur on the head and neck and twelve percent of these occur on the ear.  Local destruction by the cancer itself, as well as any treating surgery, leaves auricular defects that can be repaired with acceptable cosmetic results.  '

Likewise, because of its protrusion off the head, the external ear is especially susceptible to trauma.  Forty two percent of traumatic injuries to the external ear are from human bites, twenty percent from falls, sixteen percent from motor vehicle collisions, and 14% from dog bites.  The extent of injury varies widely, including blunt trauma causing hematomas or seromas, burns and frostbite, lacerations, or composite defects.

Clearly, each injury must be assessed and dealt with individually but several general principles should be considered.  For blunt trauma, the surgeon should aspirate or incise the hematoma or seroma and apply a pressure dressing to prevent necrosis and deformation of the underlying cartilage.  Ear wounds, as any other wound, should be cleaned with saline and betadine, and debrided of macerated and non-viable tissue and foreign bodies. Perichondrium is typically sutured with small absorbable monofilament sutures such as PDS.  The skin is closed with non-absorbable suture, antibiotic ointment and a pressure dressing is placed.

Acquired Defect Reconstruction

Several reconstructive techniques are available to the surgeon repairing an auricular defect from trauma or cancer.  These include skin grafting, cutaneous flaps, fascial flaps, and condrocutaneous flaps.

Cutaneous Flaps

Cutaneous flaps include the thin tubed flap, the Banner flap, the tunnel procedure, as well as several other variations.

The thin tubed flap is ideal for superior helical rim defects. Two parallel incisions are made in the postauricular skin adjacent to the helical rim defect. The skin is undermined between the inciisions and the bipedicled flap is tubed in the center. Next, one pedicle is divided and transposed on to the adjacent defect. 2 weeks later, the second pedicle is excised the the tubed flap is inset. The postauricular  incision is closed primarily.

The Banner flap is also effective for superior helical rim defects.  In this flap, a wedge of  preauricular skin is elevated with its pedicle close to the superior sulcus.  The flap is then helical defect and the preauricular skin is then closed primarily.   A wedge of supraauricular skin with a pedicle in the same place can also be used.

In the tunnel procedure, a cartilage graft is shaped to the size of the helical defect and then tunneled under the skin of the mastoid area, and joined to the corresponding ends of the defect. In a second stage, the auricle is separated from the mastoid area with the cartilage and skin and then a full thickness skin graft is used to cover the resulting mastoid and postauricular defect. This can be used for a helical or larger defect anywhere along the rim of the auricle.

Fascial Flap

The temporoparietal fascia flap is useful in ear reconstruction if there is a significant area of denuded cartilage lacking its perichondrium, prior to skin grafting.  It is ideal because it is well vascularized, but thin and pliable and will drape well over cartilage, allowing its shape to still be seen.

Chondrocutaneous Flaps

For some composite defects, chondrocutaneous flaps will be necessary and desirable.  These include the Antia-Buch flap, the island postauricular flap (the flip-flop flap).

The Antia-Buch flap is used for a defect in the helix and antihelix.  The anterior skin and cartilage along the conchal bowl or antihelix are incised and the posterior skin left intact to serve as its pedicle. The flap is rotated along this incision to close the helical defect and sutured together. Although this flap does result in some loss in ear height, it provides less buckling than with a typical wedge excision and closure.

The island chondrocutaneous flap, or the "flip-flop flap" is commonly used for chonchal bowl defects.  In this procedure, postauricular skin is incised in a manner to match and anterior conhcal defect.  The flap is then rotated along the axis of the postauricular sulcus into the anterior defect.  It is based on the tissue in that axis of the postauricular sulcus.  The posterior skin defect is then closed primarily or with a skin graft.

Repair and reconstruction of the pinna is challenging and rewarding for the surgeon, requiring an aesthetic eye and honed sense of spatial orientation.  It is also of great benefit to the patient, whose self perception is frequently affected by these noticeable defects.