Two-piece orbitozygomatic craniotomy

The two pieces fronto temporal orbitozygomatic craniotomy, involves the removal of the standard pterional bone flap, represented here in black, followed by the orbitozygomatic osteotomy, and the removal of the second bone flap, represented here in blue.

This figure shows the creation of four burr holes, one at the level of the keyhole, one on the frontal bone, just next to the supraorbital foramen. The other burr holes are placed, one superior to the zygomatic arch, at the temporal basal level, and one at the level of the posterior part of the superior temporal line.

A craniotome was then used for the first three bone cuts, to connect the burr holes, in order to perform a pterional craniotomy. This image shows the pterional craniotomy that was performed using four burr holes and a craniotome. This bone flap is elevated to allow preparation towards orbitozygomatic osteotomy.

The orbitozygomatic osteotomy sites are then prepared to perform the second step of the two pieces bone flap. The temporal muscle is put back to its original position. And we continue the dissection of the zygomatic process of the frontal bone, the frontal process of the zygomatic bone, and the zygomatic arch up to the posterior root of the zygoma.

Inferiorly, the deep fascia of the temporalis muscle is identified at its attachment to the zygomatic arch, and carefully dissected. For wide exposure of the zygoma, the skin flap must be reflected downwards by further dissection of the masseteric fascia overlaying the masseter muscle.

The masseter muscle is then detached at the inferior edge of the zygomatic arch. The roof of the orbit is then dissected on both sides. In the intracranial side, dura is dissected away from the roof, and on the orbital side, the periorbita is dissected off the roof.

Here we can identify two important landmarks, the supraorbital foramen, at the medial limit of the orbital craniotomy, and the inferior orbital fissure, after detachment of the periorbita along the inferior portion of the lateral orbital wall, and detachment of the temporalis muscle in the infratemporal fossa. Once those bony landmarks are visualized, the four additional bone cuts for the orbitozygomatic removal, represented on this drawing, can be performed.

The fourth cut here, is already done, and was performed using a foot-plate at the posterior root of the zygomatic arch, slightly oblique to ensure stabilization after final fixation.

Here the foot-plate is also used for the fifth cut, which starts in the temporal fossa, and extends anteromedially across the zygomatic bone, just above the malar eminence, towards the lateral orbital wall. This cut is more safely performed in two steps. One half of the cut is performed from the infratemporal fossa to the midpoint of the malar eminence, and the other half, from the intraorbital part of the inferior orbital fissure.

The sixth cut is performed using a long straight drill bit, which is placed perpendicular to the orbital roof. It starts just lateral to the supraorbital foramen, perpendicular to the superior orbital rim, and extends superiorly across the orbital roof, to connect the pterional craniotomy defect. The orbital rim is cut one centimeter lateral to the frontal medial edge of the craniotomy, so that a bone step is left to support the replacement of the bone flap at closure. The cut can be extended posteriorly by placing the drill bit parallel to the orbital roof.

For the seventh cut, the osteotome is then used to drill through the anterolateral part of the orbital roof, from the inferior orbital fissure, to the superior orbital cut. The orbital content is protected by a spatula during this osteotomy, with all efforts taken to keep the periorbita intact.

This second piece of the bone flap can then be removed, and additional bone from the anterolateral aspect of the orbital roof towards the small wings of the sphenoid, and superior orbital fissure can be removed for wider exposure.

Dural retention sutures placed anteriorly, allow the retraction of the periorbital and orbital contents. At this point we have a wide basal frontotemporal craniotomy, that allows an extended access to the lesion.