Microtia (a smaller than normal, usually misshapen auricle) is one of the more common congenital anomalies of the external ear. It occurs with a frequency of one in every 7000-8000 births in the general population. Males and right ears are affected more often. Bilateral microtia occurs I none in every twenty thousand births. The majority of cases are sporadic; less than 15% of individuals have a family history of ear anomalies.
Three grades according to severity are typically described in the Weerda classification. Grade I microtia represents a smaller than expected but generally well formed pinna with recognizable landmarks. Grade II microtic ears have rudimentary, misshapen pinnae. The cranial end is usually curved representing a crude helix. Grade III describes the worst manifestation of microtia: severe attenuation of the pinna, represented only by a small nodule of misshapen tissue that distinguishes it from the anotia, or a complete absence of the external ear.
Conventional surgical treatment id the Tanzer-Brent technique, a multistaged procedure that usually does not restore hearing and requires multiple autogenous rib grafts. The drawback of this approach is that there are only a few physicians who can reliably obtain an acceptable and detailed auricular shape at the completion of the multistaged surgeries. The usual result is a thickened, poorly contoured mass on the side of the head. Additionally, the procedure requires a mutilating donor site at the six-year old child's chest, with a 3cm by 6cm block of rib being harvested for the auricular body framework, and a 9cm portion of rib taken for the helix. Absorption of the autogenous rib framework with loss of auricular detail has also been well documented in the medical literature.
I prefer to utilize a prefabricated auricular prosthesis made of porous polyethylene and covered with an ipsilateral temporoparietal fascia (TPF) flap and contralateral postauricular full thickness skin graft. I utilize this approach in primary Grade II and Grade III microtia patients as well as in failed microtia reconstructions that had utilized local skin and autogenous rib grafts. This approach to microtia reconstruction eliminates the chest donor site morbidity and allows surgeons with less exacting carving skills to produce an elegant and detailed auricular reconstruction. (Baha System)
Children with bilateral microtia receive bone conduction hearing aids at birth and auricular reconstruction at four years of age. Unilateral cases usually start reconstruction when five years old. Before reconstruction all children receive a full evaluation by an experienced audiogram and temporal bone CT scan if warranted. Hearing restoration is attempted after reconstruction whenever possible in appropriate patients.
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