Surgical Approaches to the TMJ to Avoid Facial Nerve Injury
There are several incisions for approaching the TMJ. The difficulty with any approach is the ability to provide for adequate exposure without injuring the facial nerve. The preauricular incision is most commonly used. In this approach, the skin incision line is drawn (Fig. 5.7) by making use of any previous incision scars or strategically located fine skin wrinkles. Once the skin incision is made, the avascular plane immediately anterior to the perichondrium of the external
Fig. 5.7 Preauricular skin incision line. Many surgeons prefer an endaural incision placed at variable distances posterior to the dotted line where it is less visible (Adapted from Ness ; with permission) auditory canal wall’s anterior surface is opened bluntly, beginning just deep to the skin at the base of the tragus. Once the cartilage surface is located, the dissection must be directed medially and anteriorly, not perpendicular to the skin surface, to follow the path of the auditory canal cartilage and avoid injury to the ear. When in the correct plane, this initial dissection creates a clean, bloodless pocket immediately anterior to the tragus that ends bluntly at the depth of the parotidomasse- teric fascia. Dissection continues through the superficial temporal fascia until the smooth, white, well-defined surface of the deep temporal fascia is exposed. Dissection continues deeply until the zygomatic arch is palpable under the superficial layer of the deep temporal fascia, which divides 1-2 cm above the arch to surround it. The tissues anterior and superficial to this plane are retracted gently to minimize any traction on the temporal branch of the facial nerve, and only a narrow band of the fascia over the zygomatic arch is exposed just superior to the auditory canal cartilage and connecting the two initial dissections. A scalpel blade is then used to make an incision in the superficial layer of the deep temporal fascia in the same plane as the dissection to expose the area, beginning about 1 cm above the zygomatic arch. The incision is then extended inferiorly across the zygomatic arch, and then a periosteal elevator is used to dissect under the superficial layer of the deep temporal fascia; retracting from beneath this layer protects and retracts branches of the facial nerve. The overall goal of this approach is to dissect and elevate a continuous layer from superior to inferior containing the temporal fascia, the superficial layer of the temporal fascia, and the periosteum to prevent injury to the nerve .
Modifications of this technique have been described. A deep subfascial approach offers an additional protective layer for the facial nerve (the deep layer of the deep temporalis fascia and temporal fat pad). In comparison to the traditional technique described above, the incision of the upper and lower layer of the deep temporalis fascia is completely through the fat tissue, exposing the fibers of the temporal muscle and producing this subfascial layer (under the deep temporal fascia) .