**8. Surgical approaches to frontal bone**

### **8.1. Traumatic wounds**

conditions to assess the integrity of the underlying bone. Through-and-through injuries of the frontal sinus have high morbidity, and prompt surgical treatment is indicated. Conscious patients should be questioned regarding the presence of watery rhinorrhea or salty-tasting postnasal dripping suspicious for CSF leak. Suspicious fluid can be grossly evaluated bedside with a "halo test". The bloody fluid is allowed to drip onto filter paper. If CSF is present, it will diffuse faster than blood and result in a clear halo around the blood. Glucose or β2-

Plain radiographs do not adequately characterize FS fractures. Computed tomography (CT) is the gold standard for the assessment of FS injuries. Advances in the equipment used for CT imaging can now produce reformatted images of a very high quality. Patients are scanned in one axial plane, in a supine position with thin cut spiral CT, creating data set allowing generation of reformatted and reconstructed diagnostic images. Sagittal reconstructions can be made to evaluate the posterior wall defect. Special importance belongs to evaluation of the

Gross outflow tract obstruction (fracture fragments lying in the tract) can be observed in some cases. FSOT injury is strongly suggested when the CT scan demonstrates the involvement of the base of FS, the anterior ethmoid complex, or both. Fracture in the floor of the sinus can be seen best with sagittal and coronal views, anterior ethmoid cell injury with coronal more than axial views, and obstruction best with the coronal view (occasionally axial).Thus, the naso‐ frontal tract complex should be evaluated in the axial, coronal and sagittal planes. Unfortu‐ nately, the involvement of the FSOT is not always easily discernible with CT imaging. [16] Three-dimensional (3D) reconstructions may help to visualize the external contour deformity

The evolvement of surgical methods dealing with diseased or injured FS is described in several publications. The following summary is based on synopsis of two of them [1, 13]. In the preantibiotic era frontal sinusitis and its complications were fearsome, with high morbidity and mortality secondary to intracranial spread. The first reported procedure on FS for a mucopyocele was performed by *Wells* in 1870. Operations of limited extent involved punc‐ turing the anterior table, some with limited removal of the mucosa, packing of the sinus or

In 1898 *Reidel* first described ablation of the anterior sinus wall. This radical, disfiguring operation involved removal of the frontal bone and supraorbital bar to the posterior table of the frontal sinus. *Killian* modified this approach in 1904 by preserving the supraorbital rims to improve the patient's appearance but still removing the anterior table and contents of FS and then collapsing the skin to the posterior table of FS. The Killian procedure produced less disfigurement but had significant rates of failure because of persistent disease at the naso‐

transferrin are the laboratory tests to confirm a CSF leak. [27]

442 A Textbook of Advanced Oral and Maxillofacial Surgery Volume 2

**6.2. Radiological examination**

involvement and severity FSOT. [28]

as well as associated facial skeleton injuries.

creation of an external draining sinus tract.

**7. Historic development of operative methods**

Only in exceptional cases an existing traumatic wound can be used to address an isolated fracture of the anterior FS wall. It can be considered in limited injuries without involvement of the FSOT and/or the medial orbital rim, in the absence of other associated regional cranio‐ facial injuries (Figure 4). [13]

#### **8.2. Coronal incision**

The main purpose of coronal approach is to avoid visible facial scars. Coronal incision more or less follows the course of the coronal suture of the neurocranium, which joins FB to the parietal bones. Therefore in the literature frequently encountered term *bicoronal incision* is a misnomer, because there is just one coronal suture on the skull. Acceptable alternative term is *bitemporal incision*. The extent and design of the incision depends on the targeted anatomic area and intended surgical procedure. A fully developed coronal flap with preauricular or post‐ auricular extensions provides access to FB, zygomatic arches, bodies of the zygomatic bones,

**Figure 4.** Industrial accident; re-opening of traumatic wound for fracture exposure

medial, superior and lateral orbital margins and much of the corresponding orbital walls, as well as nasal bones. Via preauricular extension it is possible to address the temporomandibular joint and the upper neck of the condylar process of the mandible. Coronal incision also allows harvesting of calvarial bone grafts. There is general agreement that it is not necessary to shave the hair, however shaving facilitates wound closure. In female patients with long hair, who are understandably more distressed by prospect of hair shaving, the hair can be divided by a comb and braided. Alternatively, 2 cm wide strip of shaven skin is sufficient. In consenting male patients there is no harm in a complete hair shave, which makes suturing of the flap much more comfortable and subsequent wound care easier and more hygienic (Figure 5).

**Figure 5.** Scalp preparation for coronal incision: hair braiding, strip shaving and full head shave.

After proper skin disinfection and draping the planned line of incision is marked with a surgical pen. The incision line runs from ear to ear across the top of the head in either straight, anteriorly curved, sinusoid or zigzag fashion. There is always some hair loss in the incision line and the scar is much less prominent if it is not straight, especially in a patient with a short hair-cut and when the hair is wet (Figure 6).

**Figure 6.** Straight incision is more prominent in closely cropped hair, while zigzag incision gives good results even in bald scalps.

medial, superior and lateral orbital margins and much of the corresponding orbital walls, as well as nasal bones. Via preauricular extension it is possible to address the temporomandibular joint and the upper neck of the condylar process of the mandible. Coronal incision also allows harvesting of calvarial bone grafts. There is general agreement that it is not necessary to shave the hair, however shaving facilitates wound closure. In female patients with long hair, who are understandably more distressed by prospect of hair shaving, the hair can be divided by a comb and braided. Alternatively, 2 cm wide strip of shaven skin is sufficient. In consenting male patients there is no harm in a complete hair shave, which makes suturing of the flap much

**Figure 4.** Industrial accident; re-opening of traumatic wound for fracture exposure

444 A Textbook of Advanced Oral and Maxillofacial Surgery Volume 2

more comfortable and subsequent wound care easier and more hygienic (Figure 5).

**Figure 5.** Scalp preparation for coronal incision: hair braiding, strip shaving and full head shave.

hair-cut and when the hair is wet (Figure 6).

After proper skin disinfection and draping the planned line of incision is marked with a surgical pen. The incision line runs from ear to ear across the top of the head in either straight, anteriorly curved, sinusoid or zigzag fashion. There is always some hair loss in the incision line and the scar is much less prominent if it is not straight, especially in a patient with a short The inferior extent of the incision depends on the target region. When desired exposure is limited FB, it is sufficient to confine the incision to the level of upper ear attachment. The placement of the incision line should take into consideration future balding patterns in men, and anterior migration of the scar due to growth of the cranium in young children. There is no advantage in placing the incision more ventrally, because the extent of exposure is given by the caudal extent of the incision: the lowest points define the axis around which the flap will rotate. Sufficient dorsal extension will also preserve the deep branch of the supraorbital nerve and avoid sensory loss behind a too-anteriorly placed incision. It is desirable to make the incision of the scalp parallel to the hair follicles. Avoiding the transection of hair follicles avoids alopecia at the edges of the wound. [13]

Vascularization of the scalp is very rich and due to the presence of subcutaneous fibrous septa the vessels gape and bleed profusely when cut. To reduce the initial bleeding and make establishment of the proper dissection level easier, the sub-galeal layer is infiltrated with saline or diluted local anesthetic with vasoconstrictor (e.g. adrenalin 1:200 000). The incision starts on the top of the head and progresses step by step latero-caudally to both sides, while arresting bleeding after each step. Hemostasis is mainly achieved by compression of wound margins by Raney clips, Tessier scalp clamps, or running interlocking silk sutures. Use of electrocautery should be minimized and only bipolar coagulation should be employed to protect hair follicles.

The three superficial layers of the scalp (skin, subcutaneous layer and galeal aponeurotica) make up one functional unit. [29] The incision penetrates through these layers and stops just above the pericranium inside the fourth layer of loose areolar tissue (subgalea fascia). Dissec‐ tion inside this level is initially facilitated by undermining the incision line with a spreading hemostat. Below the superior temporal line the galea continues as temporoparietal fascia. The dissection should be kept below this fascia, just on the top of temporalis fascia, which can be identified as a tough white glistening layer. Branches of superficial temporal artery and vein are usually transected here and need to be ligated or cauterized. After the whole length of the incision has been developed to the proper depth, the scalp is pulled forward with a pair of cat paw retractors and the flap is dissected further by reverse cutting with a large blade until it can be turned inside out (Figure 7).

**Figure 7.** Dissection of coronal flap: subperiosteal dissection over top of skull, dissection under temporalis fascia below the level of the temporal line. In this case pericranial flap is not developed.

Anterior dissection progresses to the point where the base of the flap dissected so far reaches a 45º angle with the zygomatic arches. The temporal and zygomatic branches of the facial nerve leave the parotid gland and cross close to the periosteum of the zygomatic arch into the temporoparietal fascia, 15–28 mm ventral to the external acoustic meatus. [30] To protect them, further dissection in the temporal areas must continue under the temporalis fascia. The temporalis fascia is incised over the root of the zygoma and the incision progresses firstly through the external leaflet of fascia, just over the temporal fat pad. Above the line of fusion of external and deep layer of temporalis fascia the dissection progressed just above the temporalis muscle fibers, alongside the base of the developing flap, to the superior temporal line. At this point it is necessary to consider if a pericranial flap will be needed for anterior cranial fossa repair or sinus obliteration. If this is the case, its design must be incorporated into the periosteal dissection instead of cutting the periosteum straight across the frontal bone. If pericranial flap is not needed, right and left incisions in the temporalis fascia are connected by incising the pericranium between them. The forward dissection of the coronal flap continues in the subpericranial level, then subfascial level over the temporalis muscles and temporalis fat pads. The connection between the periosteum and temporalis fascia at the superior temporal line is firmly adherent to the underlying bone and requires sharp dissection, which is best done by diathermy in cutting mode (Figure 8).

When the dissection reaches the orbital margins, careful attention is paid to identification and freeing of the supraorbital neurovascular bundles. This is easy if only supraorbital notches are present. If the bundles pass through supraorbital foramina, these must be converted into notches by resecting the foramina's inferior margins with a fine chisel. The periosteum must be subsequently elevated beyond the orbital margin and inside the orbital cavity to allow free retraction of the flap. [31] The contentious point of the above described technique is the dissection in the temporal area. If the dissection proceeds as described, it jeopardizes inner‐ vation and vascularization of the temporal fat pad. It can lead to postoperative temporal hollowing as a consequence of a fat atrophy. [13] For this reason some authors prefer to keep the dissection completely above temporalis fascia, but "maintaining the integrity of tempor‐

**Figure 8.** Elevation of pericranial flap and release of supraorbital nerve.

oparietal fascia" to protect the facial nerve branches. [32] To overcome this dilemma between jeopardizing either the facial nerve or temporal fat pad, *Luo et al.* recently described an alternative dissection technique: the supratemporalis approach. The temporal fascia was incised 5-6 cm up the zygomatic arch. The flap was composed of skin, subcutaneous fat, temporoparietal fascia, temporal fascia, and temporal fat pad on the surface of the temporalis muscle. The authors operated 40 cases with no temporal fossa depression observed in any of them. [33]

#### **8.3. Alternative skin incisions**

paw retractors and the flap is dissected further by reverse cutting with a large blade until it

**Figure 7.** Dissection of coronal flap: subperiosteal dissection over top of skull, dissection under temporalis fascia below

Anterior dissection progresses to the point where the base of the flap dissected so far reaches a 45º angle with the zygomatic arches. The temporal and zygomatic branches of the facial nerve leave the parotid gland and cross close to the periosteum of the zygomatic arch into the temporoparietal fascia, 15–28 mm ventral to the external acoustic meatus. [30] To protect them, further dissection in the temporal areas must continue under the temporalis fascia. The temporalis fascia is incised over the root of the zygoma and the incision progresses firstly through the external leaflet of fascia, just over the temporal fat pad. Above the line of fusion of external and deep layer of temporalis fascia the dissection progressed just above the temporalis muscle fibers, alongside the base of the developing flap, to the superior temporal line. At this point it is necessary to consider if a pericranial flap will be needed for anterior cranial fossa repair or sinus obliteration. If this is the case, its design must be incorporated into the periosteal dissection instead of cutting the periosteum straight across the frontal bone. If pericranial flap is not needed, right and left incisions in the temporalis fascia are connected by incising the pericranium between them. The forward dissection of the coronal flap continues in the subpericranial level, then subfascial level over the temporalis muscles and temporalis fat pads. The connection between the periosteum and temporalis fascia at the superior temporal line is firmly adherent to the underlying bone and requires sharp dissection, which

When the dissection reaches the orbital margins, careful attention is paid to identification and freeing of the supraorbital neurovascular bundles. This is easy if only supraorbital notches are present. If the bundles pass through supraorbital foramina, these must be converted into notches by resecting the foramina's inferior margins with a fine chisel. The periosteum must be subsequently elevated beyond the orbital margin and inside the orbital cavity to allow free retraction of the flap. [31] The contentious point of the above described technique is the dissection in the temporal area. If the dissection proceeds as described, it jeopardizes inner‐ vation and vascularization of the temporal fat pad. It can lead to postoperative temporal hollowing as a consequence of a fat atrophy. [13] For this reason some authors prefer to keep the dissection completely above temporalis fascia, but "maintaining the integrity of tempor‐

the level of the temporal line. In this case pericranial flap is not developed.

is best done by diathermy in cutting mode (Figure 8).

can be turned inside out (Figure 7).

446 A Textbook of Advanced Oral and Maxillofacial Surgery Volume 2

The coronal scalp approach provides excellent operative field exposure and results in a hidden scar. However, it is also associated with certain disadvantages and complications. These include longer operating times, increased blood loss, scalp hematoma, postoperative infection, a large scar with related alopecia, potential injury to the branches of the facial nerve with frontalis muscle paresis and brow ptosis, injury to auriculotemporal, supraorbital and supratrochlear nerves with numbness and paresthesia, parietal scalp pain, temporal fossa depression, scar irregularities and ptosis of facial soft tissues. [13, 34, 35] In attempts to avoid these problems different simplified methods of surgical access were reported for management of uncomplicated anterior table FS fractures. If the posterior table is involved then the technique is contraindicated. Also FSOT must be intact. Careful selection of patients is vital. A small skin incision can be made parallel to the margin of the eyebrow to approach the fracture. It is often possible to introduce a small periosteal elevator through the inferior edge of the fracture. If this is not possible, a 5 mm burr hole is created near or on the fracture site. A narrow periosteal elevator is introduced into FS and fracture is reduced with careful pressure. The bony opening may be used to confirm adequate reduction endoscopically. [34] A similar technique with wider exposure of fracture utilizes an upper blepharoplasty incision. [44] Another alternative approach is incision through the frontalis rhytid crease. [36]
