42. Reconstruction of a Microtic Ear, an outline
The following text is about the creation of the main cartilaginous framework of the ear. Detailed steps are covered in the next chapter including how a template is made to facilitate cutting the cartilage of the exact shape and size. Some photographs in this chapter show a reconstructed ear lobule. The exact chronology of all the steps including the creation of the ear lobule will also be detailed in the next chapter.
1. The kind of cartilage that gives the human ear its unique appearance is not found elsewhere in the body. Maternal homografts as well as other irradiated homografts are known to absorb and synthetic material tends to extrude from under the thin local skin employed to cover the implant. Small pieces of the cartilage of the opposite normal ear have been used for reconstruction but that is only for partial defects. In established cases of Microtia where most of the external ear fails to develop, surgeons now use costo-chondral cartilage (fifth, sixth and seventh rib) which is the next best option. The cartilage is cut and carved in situ and then given the desired shape to prepare the final assembly on a separate trolley. This is called bench work. Occasionally cartilage from a free adjacent rib is harvested to add to the cartilaginous framework that is being prepared (Fig. 1-3).
The assembly of the costo-chondral cartilage in recent times is being done by a thin gauge 5/0 stainless steel wire mounted on a needle (28 gauge). This is considered a major advance. All previous materials were either not strong enough or did not last for a sufficient duration leading to dismantling of the cartilage assembly over a period of time. Autologous chondrocyte culture in the laboratory, followed by these cells being put in a biodegradable synthetic dye resembling the ear’s shape and then implanted in the skin, is being tried in animals but its use in man belongs to the future.
2. The distinctive feature of the ear is its uniquely prominent ridges and valleys and in reconstructing the ear a thin skin envelope is essential so that these features are distinctly visible. Such a thin flap is difficult to import but fortunately in most cases of Microtia just about adequate skin is available locally to bury the cartilage. If the hair line is low, as happens in some cases, a laser can be employed to increase the area of hairless skin (Fig. 4-5).
Tissue expanders have been tried but have the disadvantage of formation of a capsule under the expanded skin which is collagenous in nature and this capsule obliterates the fine architecture of the cartilaginous framework. In order that the cartilaginous framework is distinctly seen, the skin flap that is raised in the auricular area has to be very thin, yet the pocket underneath has to be capacious enough to accommodate the framework. A hematoma following this step is a disaster (as also a seroma). Both lead to deposition of collagen and might also adversely affect the overlying thin skin flap. That is why an effective continuous, strong suction drainage forms a crucial part of this surgical step.
The drain needs to be observed closely and hourly and a blocked drain constitutes an emergency and must be replaced. The suction also helps to drape the skin snugly over the cartilage. It might be left in place even when drainage is stopped for a firmer approximation of the skin and cartilage. Only in the event when the skin flap over the cartilage undergoes necrosis is tissue imported in the form of a temporal fascial flap and is covered by a split skin graft (Fig. 6-8).
3. Once the implanted cartilage settles down (six months) it requires to be lifted to create the auriculocephalic sulcus. This step must ensure that the cartilage is adequately covered by soft tissue to prevent exposure as well as to able to receive and accept the split skin graft. The raw area left behind by lifting the auricle from the cranium should also have enough soft tissue to accept a graft. Between the two, the posterior surfaces of the ear receives precedence and should the cranial surface appear bare and not of a quality to be able to accept a graft, a temporo-facial flap might be used to cover this area which in turn can be covered with a split skin graft (Fig. 9,10).
For a good colour match split skin grafts from the scalp are considered superior. Because all split skin grafts contract a splint in the form of a mould is worn over and in the sulcus for a period of several weeks. A new technique that has been added is to place a cartilage strut under the soft tissue in the sulcus to prevent recontracture (Fig. 11-13).
In reconstructing the ear, the lobe (or lobule) also forms an important part of the whole. Prachi Bhalerao, a senior resident from Nair hospital who presented the anatomy of the ear during a workshop on Microtia has sent these two photographs of the earlobe that show the two main types. Wonderful that nature is, the two lobes are identical on both sides. It helps the surgeon look at the opposite lobe in reconstructing the ear because that part is almost invariably exposed in most cultures.