Step 4 Elevation of the Coronal Flap and Exposure of the Zygomatic Arch

After elevation of the anterior and posterior wound margins for 1 to 2 cm, hemostatic clips (Raney clips) are applied or bleeding vessels are isolated and cauterized. Indiscriminate cauterization of the edge of the incised scalp can result in areas of alopecia and should be avoided. A technique to expedite clip removal before closure involves positioning an unfolded gauze sponge the cut edge of the scalp before clip application. The gauze can be pulled off the scalp before closure, removing the accompanying row of clips. In some instances, bleeding encountered during the procedures is from small emissary veins exiting through the pericranium or exposed skull. Cauterization, bone wax, or both are useful for these vessels.

Figure 6- 12 Two methods of dissecting the flap in the subgaleal plane. Left, finger dissection readily cleaves the areolar tissue in the subgaleal plane. Several centimeters above the orbital rims, however, the pericranium is more tightly bound to the frontalis muscle and the periosteum may strip from the bone when using this technique in this location. Right, dissection with a scalpel. The flap is lifted gently with retractors and/or hooks to maintain gentle tension. The back (dull) edge of the scalpel rests on the pericranium and is swept back and forth, allowing the point of the scalpel to incise the subgaleal tissue. This technique is especially useful in flaps elevated for a second or third time, where adhesion in the subgaleal layer are more common and must be sharply incised.

Figure 6- 12 Two methods of dissecting the flap in the subgaleal plane. Left, finger dissection readily cleaves the areolar tissue in the subgaleal plane. Several centimeters above the orbital rims, however, the pericranium is more tightly bound to the frontalis muscle and the periosteum may strip from the bone when using this technique in this location. Right, dissection with a scalpel. The flap is lifted gently with retractors and/or hooks to maintain gentle tension. The back (dull) edge of the scalpel rests on the pericranium and is swept back and forth, allowing the point of the scalpel to incise the subgaleal tissue. This technique is especially useful in flaps elevated for a second or third time, where adhesion in the subgaleal layer are more common and must be sharply incised.

The flap may be elevated atop the pericranium with finger dissection, with blunt periosteal elevators, or by back-cutting with scalpel (Fig. 6-12). As dissection proceeds anteriorly tension develops because the flap is still attached laterally over the temporalis muscles. Dissecting that portion of the flap below the superior temporal line from the temporalis fascia relieves this tension and allows the flap to retract farther anteriorly. Along the lateral aspect of the skull, the glistering white temporalis fascia becomes visible where it blends with the pericranium at the superior temporal line. The plane of dissection is just superficial to this thick fascial sheet.

Dissection of the flap continues anteriorly in the subgaleal fascial plane to a point 3 to 4 cm superior to the supraorbital rims. A finger is used to palpate and locate the superior temporal lines, and a horizontal incision is made through pericranium from one superior temporal line to the other (Fig. 6-13). The surgeon should not extend the incision beyond the superior temporal line or the temporalis muscle will be cut and begin to bleed. A subperiosteal dissection then continues to the supraorbital rims.

Figure 6-13 Incision of periosteum across the forehead from one superior temporal line to the other. The tension through periosteum should be 3 to 4 cm superior to the orbital rims.

Figure 6 -14 Anatomic dissection showing incision through the superficial layer of temporalis fascia (forceps) several centimeters above the zygomatic arch. Note the underlying fat between this layer of fascia and the deep layer of temporalis fascia. The tempoparietal fascia with the temporal branch of the facial nerve is folded inferiorly (below).

Figure 6 -14 Anatomic dissection showing incision through the superficial layer of temporalis fascia (forceps) several centimeters above the zygomatic arch. Note the underlying fat between this layer of fascia and the deep layer of temporalis fascia. The tempoparietal fascia with the temporal branch of the facial nerve is folded inferiorly (below).

The lateral portion of the flaps is dissected inferiorly atop the temporalis fascia. Once the lateral portion of the flap has been elevated to within 3 to 4 cm of the body of the zygoma and zygomatic arch, these structures usually can be palpated through the covering fascia. Near the ear, the flap is dissected inferiorly to the root of the zygomatic arch. The superficial layer of temporalis fascia is incised at the root of the zygomatic arch, just in front of the ear, and continues anteriorly and superiorly at a 45o angle, joining the cross-forehead incision previous made through pericranium at the superior temporal line. Incision of the superficial layer of temporalis fascia reveals fat and areolar tissue (Fig. 6-14). Further dissection inferiorly within this layer provides a safe route of access to the zygomatic arch, because the temporal branch of the facial nerve is always lateral to the superficial layer of temporalis fascia (Fig. 6-15). Metzenbaun scissors are used to bluntly dissect just under the superficial layer of temporalis fascia, within the space containing the superficial temporal fat pad (see Fig 6-15). Once the superior surface of the zygomatic arch and posterior border of the body of the zygoma are palpable or visible, an incision through periosteum is made along their superior surface. The incision progresses superiorly along the posterior border of the body of the zygoma and orbital rim, ultimately meeting the cross-forehead horizontal incision through pericranium. Subperiosteal elevation exposes the lateral surfaces of the zygomatic arch, body of the zygoma, and a lateral orbital rim (Fig. 6-16). To allow the flap to fold anteriorly, it may be necessary to continue the preauricular component inferiorly and to dissect the flap from the TMJ capsule.

Figure 6-15 Incision made through the superficial layer of the temporalis fascia. Incision begins at the root of the zygomatic arch (above the temporomandibular joint) upward and forward to join the incision made across the forehead in periosteum. One method to approach the posterior portion of the lateral orbital rim and superior surface of the zygomatic arch is also demonstrated. Dissection with incisors is continued deep to the superficial layer of temporalis fascia (see inset), within the superficial temporal fat pad, until bone is encountered. Sharp incision is then made through the periosteum on the superior surface of the zygomatic arch and the posterior surface of the zygoma.

Figure 6-15 Incision made through the superficial layer of the temporalis fascia. Incision begins at the root of the zygomatic arch (above the temporomandibular joint) upward and forward to join the incision made across the forehead in periosteum. One method to approach the posterior portion of the lateral orbital rim and superior surface of the zygomatic arch is also demonstrated. Dissection with incisors is continued deep to the superficial layer of temporalis fascia (see inset), within the superficial temporal fat pad, until bone is encountered. Sharp incision is then made through the periosteum on the superior surface of the zygomatic arch and the posterior surface of the zygoma.

Figure 6-16 Anatomic dissection showing the zygomatic arch (ZA) and body (ZB). The superficial layer of the temporalis fascia and periosteum is retracted inferiorly and anteriorly. Note the masseter muscle (MM) attachment to the inferior portion of the zygomatic arch.
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