Auricular anatomy
Mastery of auricular anatomy is a prerequisite for achieving successful reconstruction. The majority of the auricle is composed of an intricate cartilaginous framework with an overlying taut skin envelope, creating distinct topographical landmarks ( Fig. 3.1 ). The lobule lacks underlying cartilage and is made up of thin skin overlying fibrofatty tissue. Between the cartilage and skin along the posterior surface of the auricle exists a minimal amount of intervening adipose tissue, which is absent on the anterior surface of the auricle. The rich vascular supply to the auricle is derived from two branches of the external carotid artery: the superficial temporal artery and the posterior auricular artery. Venous drainage occurs via the superficial temporal, posterior auricular, and retromandibular veins into the external and internal jugular veins.
The average height and width of the adult auricle is 5–6 cm and 3–4 cm, respectively. In the Frankfort horizontal plane, the root of the adult helix is 6–7 cm posterior to the lateral canthus. The superior and inferior most points of the auricle align with the superior orbital rim and subnasale, respectively. The longitudinal axis of the auricle is inclined 15–20 degrees off the true vertical axis. The auriculocephalic angle, defined as the protrusion of the auricle from the scalp, is between 25 and 35°. The ear protrudes from the postauricular skin approximately 1.5–2 cm. Despite these established anthropomorphic standards for the ideal ear, auricular reconstruction is best modeled on the patient’s contralateral ear to ensure symmetry and facial harmony.
Primary survey
Primary survey of the auricular injury should include assessment of the size, location and depth of the defect, viability of any avulsed segments and adjacent tissue, and patient goals based on comorbidities and trauma burden. A complete head and neck examination should be performed with special attention to evaluation of the tympanic membrane, presence of cerebrospinal fluid otorrhea, temporal bone fractures, facial nerve function, and external auditory canal (EAC) edema and lacerations. For lacerations extending into the EAC, a wick is placed to prevent canal stenosis, and otic drops are initiated until wick removal. All auricular injuries in the acute setting should be copiously irrigated and debrided of foreign bodies and visibly necrotic tissue. Tetanus and rabies vaccines should be administered if necessary. Topical antibiotic ointment is applied to all lacerations and open wounds. With regard to systemic prophylactic antibiotic therapy, superficial lacerations with intact perichondrium can be covered with a first-generation oral cephalosporin. For wounds with exposed cartilage in adults, oral fluoroquinolones are recommended to reduce the risk of auricular chondritis.
Principles of auricular reconstruction
The primary goal of auricular reconstruction is to restore the function of the auricle to converge, amplify, and transmit sound to the middle ear. The secondary, more formidable goal is to recreate the complex topographic landmarks and three-dimensional structure of the auricle and to maintain symmetry in its position, protrusion, height, and width when compared to the contralateral ear. For minor skin lacerations with intact perichondrium, the wound can often be closed primarily. If cartilage is exposed, the framework is reestablished either by primary repair or with use of cartilage grafts, with the most common donor sites being the conchal bowl, septum, and autologous rib. Any exposed or grafted cartilage must be covered with vascularized tissue. A multilayered, composite closure is performed with use of cartilage grafts, local advancement flaps, and skin grafts. Bolsters are applied to prevent hematoma or seroma formation and resultant auricular deformity.
Minor auricular trauma
Auricular hematoma
Auricular hematomas ( Fig. 3.2 ) result from accumulation of blood in the subperichondrial plane ultimately forming a dense, fibrin clot. A delay in clot evacuation can lead to an unsightly cauliflower ear deformity. Auricular hematomas are drained via a small, dependent incision down to cartilage overlying the area of fluctuance and hidden within a concavity of the lateral auricle. Dental roll or xeroform bolsters are contoured and secured to the anterior and posterior surface of the auricle via through-and-through large, nonabsorbable monofilament sutures in a quilting fashion to obliterate potential dead space and to prevent reaccumulation of the hematoma.
Auricular lacerations
Auricular lacerations should be repaired with a layered primary closure within the first 24 hours of injury to prevent infection, cartilage devascularization, scar contracture and an unfavorable aesthetic outcome. The site of injury should first be copiously irrigated of debris. A regional peripheral nerve block will facilitate primary repair without the anatomical distortion associated with direct infiltration. Local anesthetic is infiltrated just inferior to the lobule to block the great auricular nerve and posterosuperiorly within the auriculocephalic sulcus to block the auriculotemporal branch of the mandibular division of the trigeminal nerve (V3). Nonviable tissue should then be debrided prior to performing a layered closure. If there is no cartilage exposure, a simple skin closure with minimal tension and wound edge eversion should be performed using fast-absorbing plain gut or nylon sutures. If there is cartilage exposure or involvement, 4-0 or 5-0 long-lasting absorbable monofilament suture should be used to reapproximate the cartilage framework. Extra care should be taken during repair if the laceration involves the helical rim, where slight imperfections in cartilage reapproximation can result in a noticeable soft tissue step-off deformity. A bolster dressing should be applied for relatively large and complex lacerations to prevent auricular hematoma formation.
Lobule tears
Due to the round, smooth contour of the ear lobe, repair of lobule tears can present a significant reconstructive challenge. To prevent notching of the inferior border of the ear lobe, lobule tears can be repaired with a small Z-plasty such that the resultant scar lies parallel to the inferior border of the ear lobe. Given that the lobule is composed of thin skin and subcutaneous tissue with lack of rigid structural support, lobule tears with substantial skin loss can result in significant contraction and lobule deformity. A small cartilage graft harvested from the conchal bowl or septum can therefore be placed in a subcutaneous pocket to reduce contraction. , A full-thickness skin graft (FTSG) or vascularized local flap can be placed over the cartilage graft if additional skin coverage is needed.
Classification of auricular trauma: depth of defect
Skin defects and auricular burns
Superficial skin defects of concave auricular surfaces with intact perichondrium and cartilage framework can heal by secondary intention with diligent wound care. Larger, lateral skin defects left to heal by secondary intention, however, can contract and cause forward-folding of the auricle. FTSGs can be harvested from the pre- or postauricular skin for a close color match. FTSGs intended for the ear should be thinned aggressively before placement to optimize graft survival and to accentuate the underlying auricular contour. Fast-absorbing gut suture is used to tack down the edges of the FTSG, and quilting sutures can be added along natural lines of concavity.
Due to its superolateral position on the cranium, the auricle is also highly susceptible to thermal injury. Early debridement of burns is crucial for preventing irreversible cartilage damage and deformity. Based on the depth and size of the burn injury and viability of adjacent tissue, options for repair include healing by secondary intention with meticulous wound care, FTSG coverage, and postauricular advancement flaps.
Perichondrium defects
Superficial defects involving both skin and perichondrium with resultant cartilage exposure will not support skin graft survival. Small, 2-mm fenestrations through the exposed cartilage can be created to accelerate the growth of granulation tissue and to promote neovascularization. Subsequent delayed repair of the defect can be performed with a FTSG placed overlying the vascularized bed of granulation tissue overlying the cartilage. If perichondrium defects are present in a location that is not vital to the auricular framework, such as the conchal bowl or scaphoid fossa, the exposed cartilage can be excised and a FTSG can then be placed within the defect. The blood supply for the FTSG will be derived from the opposing perichondrium or subcutaneous tissue. A better aesthetic outcome can be achieved for particular skin and perichondrium defects—such as those located along the sharp contour of the helical rim—with conversion to a composite defect via excision of the underlying cartilage.
Composite defects
Composite defects of the auricle—those that involve skin, perichondrium and cartilage—can be repaired via conversion of the defect to a wedge or star excision ( Fig. 3.3 ). Small composite defects of the middle third of the helical rim can be closed via wedge resection. A triangular full thickness wedge is excised such that the base encompasses the rim defect and the apex lies within the conchal bowl. No more than 1 cm of the conchal rim should be excised to maintain the overall proportions of the auricle. The defect is closed primarily in layers with a staggered closure of the cartilage and skin, referred to as “tongue and groove” fashion. A star resection should be utilized for larger composite defects of the middle third of the helical rim in cases where a traditional wedge resection would cause unsightly distortion. A traditional wedge is first drawn to encompass the defect. Two smaller triangles are then added with their axis oriented parallel to the antihelix. The composite defect is thereby repaired primarily via chondrocutaneous advancement of the adjacent tissue. The entirety of the auricle is slightly reduced in size via the star resection technique while maintaining normal proportions for the individual subunits. ,
