Step 5 Dissection to the TMJ Capsule

Blunt dissection with periosteal elevators undermines the superior portion of the incision (that above the zygomatic arch) so that a flap can be retracted anteriorly for approximately 1 to 1,5 cm (Fig. 12-7). This flap is dissected anteriorly at the level of the superficial (outer) layer of temporalis fascia. This layer is usually hypovascular. The superficial temporal vessels and auriculotemporal nerve may be retracted anteriorly in the flap. Failure to develop the flap close to the cartilaginous external auditory canal increases the risk of damage to these structures.

Below the zygomatic arch, dissection proceeds bluntly adjacent to the external auditory cartilage. Scissor dissection proceeds along the external auditory cartilage in an avascular plane between it and the glenoid lobe of the parotid gland (see Fig. 12-7). The external auditory cartilage runs anteromedially and the dissection is parallel to the cartilage. The depth of the dissection at this point should be similar to that above the zygomatic arch.

Figure 12 7 Dissection above the zygomatic arch to the level of the superficial layer of the temporalis fascia. Dissection below the zygomatic arch along the external auditory meatus to the same depth.

Attention again turns to the portion of the incision above the zygomatic arch. With the flap retracted anteriorly, an incision is made through the superficial (outer) layer of temporalis fascia beginning from the root of the zygomatic arch just in front of the tragus anteroposteriorly toward the upper corner of the retracted flap (Fig. 12-8). The fat globules contained between the

Attention again turns to the portion of the incision above the zygomatic arch. With the flap retracted anteriorly, an incision is made through the superficial (outer) layer of temporalis fascia beginning from the root of the zygomatic arch just in front of the tragus anteroposteriorly toward the upper corner of the retracted flap (Fig. 12-8). The fat globules contained between the

Temporalis Fascia Periosteum
Figure 12 8 Oblique incision through the superficial layer of the temporalis fascia. Fat is visible deep to the fascia.

incision can be through both the superficial layer of temporalis fascia and periosteum of the zygomatic arch. The sharp end of a periosteal elevator is inserted in the fascial incision, deep to the superficial layer of temporalis fascia, and swept back and forth to dissect this tissue from the incision can be through both the superficial layer of temporalis fascia and periosteum of the zygomatic arch. The sharp end of a periosteal elevator is inserted in the fascial incision, deep to the superficial layer of temporalis fascia, and swept back and forth to dissect this tissue from the

Figure 12 9 A periosteal elevator inserted beneath the superficial layer of the temporalis muscle is used to strip periosteum off the lateral portion of the zygomatic arch, and continues the dissection below the arch just superficial to the capsule of the temporomandibular joint

the zygomatic arch, where the sharp end of the periosteal elevator cleaves the attachment of the periosteum at the junction of the lateral and superior surfaces of the zygomatic arch, freeing the periosteum from its lateral surface. The periosteal elevator can then be used to continue bluntly dissecting inferiorly with the black-and-forth motion, taking care not to dissect medially into the TMJ capsule (Fig. 12-10). Blunt dissection with scissors can also be used to dissect inferiorly to the zygomatic arch. Once the dissection is approximately 1 cm below the arch, the intervening tissue is sharply released posteriorly along the plane of the initial incision (Fig. 12-11).

The entire flap is then retracted anteriorly, and blunt dissection at this depth proceeds anteriorly until the articular eminence is exposed. The entire TMJ capsule should then be revealed. Because of subperiosteal dissection along the lateral surface of the zygomatic arch, the temporal branches of the facial nerve are located within the substance of the retracted flap (see Fig. 12-10). To help determine the location of the articular space, the mandible can be manipulated open and closed._i

Temporalis Fascia
Figure 12 10 Coronal section showing the layer of dissection. VII = relative position at temporal branch during dissection.
Figure 12 11 Vertical incision made through intervening tissues just in front of the external auditory meatus to the depth of the periosteal elevator.
Figure 12 12 After retraction of tissues superficial to the temporomandibular joint (TMJ) capsule, scissors are used to enter the capsule. Initial point of entry is just below the zygomatic arch, continuing parallel to the contour of the TMJ fossa.

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