Executive Editor: Daniel Buchbinder General Editor: Daniel Buchbinder

Authors: S Fusetti, B Hammer, R Kellman, C Matula, EB Strong, Co-author: A Di Ieva

Skull base & Cranial vault Frontal sinus, frontal recess

back to CMF overview

Glossary

1 Introduction top

Fractures of the floor of the sinus that involve the frontal recess and interfere with the drainage apparatus may render the sinus non functional. In this situation, frontal sinus obliteration may be required. This involves exposure of the entire sinus, fastidious removal of all sinus mucosa and obliteration of the sinus cavity with autologous tissue.

2 Choice of tissue top

Many different autologous materials have been used for sinus obliteration. These include:

  • Fascia
  • Abdominal fat
  • Muscle
  • Pericranium
  • Spontaneous osteoneogenesis
  • Bone

Fascia

Regardless of what other material will be used to fill the sinus, fascia will generally be the graft of choice for plugging the recess. Some surgeons add additional fascia to fill the sinus.


Choice of tissue enlarge

Abdominal fat

Abdominal fat is readily available and the graft harvest results in low morbidity. This material has a long and successful track record in the otolaryngology literature.


Muscle

Nonvascularized muscle can also be used successfully to obliterate the sinus cavity. The morbidity of harvesting muscle is often greater than abdominal fat.


Choice of tissue enlarge

Pericranium

A pericranial flap can be used to obliterate small to medium size sinuses.


Choice of tissue enlarge

It has the advantage of being a vascularized flap. When using an osteoplastic bone flap, the bone flap may compress the blood supply to the pericranial flap thereby devascularizing it.


Choice of tissue enlarge

The pericranial flap must be inserted over the orbital rims and into the sinus. The reduced anterior table bone fragments must not strangulate the flap as it enters the sinus. A small bone defect (2-3 mm) must be generated to allow passage of the flap into the sinus.


Spontaneous osteoneogenesis

The mucosa is stripped, the recess is plugged, and the sinus is left empty.


Choice of tissue enlarge

Bone

Cortical and cancellous bone can be harvested from the previously exposed skull (coronal approach) with minimal morbidity.
Large sinuses can be more challenging to fill with bone.

3 Exposure top

Exposure enlarge

While elevating the coronal flap, it is important to maintain the integrity of the pericranial flap whenever possible. This flap may be used for obliteration of the sinus when the posterior table is intact. It is however most critical to maintain the pericranial flap integrity when posterior table fractures are present and there is greater probability of a dural tear. In these cases the pericranial flap will be used to repair the dura and reline the anterior cranial fossa.


Exposure enlarge

Pearl: identification of explanted bone fragments
Final orientation of any removed bone fragments can be challenging. Placing the explanted segments on a rough sketch of the skull made with a sterile pen will maintain orientation until re-implantation. Outline each segment and the overall shape of the defect.
The bone fragments should be kept moist until they are re-placed.

4 Defining the sinus margin top

Defining the sinus margin enlarge

The margins of the frontal sinus are irregular and may not be visible through the fracture.


Defining the sinus margin enlarge

It is however critical to determine the precise margins of the sinus to allow for an accurate osteotomy and complete exposure of the sinus. There are several ways to accomplish this:

  • Bayonet forceps
  • Transillumination
  • 6-foot (1.83 m) Caldwell x-ray with coin reference
  • Intraoperative navigation

Defining the sinus margin enlarge

Bayonet forceps

One tine of the bayonet forceps (or bipolar cautery) can be inserted into the defect. The other tine spans the anterior table. The internal tine is then “walked” around the periphery of the sinus. The external tine is then used to guide markings which will outline the periphery of the sinus on the outer table bone. The outline can be marked with ink or electrocautery (the electrocautery should be placed at a low setting to coagulate overlying blood and avoid excessive bone injury).


Defining the sinus margin enlarge

Transillumination

Alternatively, a light source (such as an endoscope) can be inserted through the anterior table bone defect. The light will transilluminate the sinus and delineate its margins.
Beware of pitfalls such as soft-tissue and blood present in the sinus.


Defining the sinus margin enlarge

6-foot (1.83 m) Caldwell x-ray with coin reference

A 6-foot (1.83 m) Caldwell x-ray with  (anterior-posterior Caldwell x-ray with the patient placed 6 feet from the x-ray tube) can be used to delineate the margins of the sinus. The 6-foot penny Caldwell generates a “life-size” representation of the sinus cavity. It is imperative that the orientation (ie, right and left) is clearly documented on the x-ray.


Defining the sinus margin enlarge

Scissors are then used to cut along the margins of the sinus. Lateral “wings” that project along the orbital rims are also cut out to help with orientation. A second copy of the sinus template is generated from the first in case one is contaminated during the procedure. An “R” is scratched into the right side of both templates to record orientation. Both copies are sterilized and brought onto the surgical field.


Defining the sinus margin enlarge

The template is then placed over the sinus using the orbital rim “wings” to help with orientation. The template is held in place. The sinus periphery can then be outlined using ink or electrocautery as previously described.


Defining the sinus margin enlarge

Intraoperative navigation

Intraoperative navigation can be used to outline the periphery of the sinuses using the preoperative CT scan. A reference array must be fixed to the skull (or Mayfield head holder) to allow for accurate navigation.


Defining the sinus margin enlarge

The navigation system is used to guide the probe along the periphery of the sinus.


Defining the sinus margin enlarge

Ink or electrocautery can be used to mark the outline.

5 Osteotomy top

Plate application enlarge

Plate application

After the proposed osteotomy has been marked at the periphery of the sinus, thin plates are applied spanning the sinus margin. An adequate number of plates should be applied to provide stability when the anterior table segment is osteotomized. The plates should be pre-applied prior to the osteotomy. This allows for accurate repositioning of the anterior table bone.


Plate application enlarge

Each plate should be rotated away from the proposed osteotomy line. This can be accomplished by removal all but one screw located on stable bone outside the sinus. The plate can then be rotated away from the sinus.


Plate application enlarge

Perforating the anterior table

A sagittal saw can be used to perform the osteotomy. However, a side-cutting burr (as illustrated) is more controlled and accurate. The bit is used to drill sequential holes along the superior border of the sinus. Individual holes are separated by several millimeters.


Plate application enlarge

The handpiece should be angled approximately 45° towards the sinus and away from the cranial vault to avoid violation of the posterior table.


Plate application enlarge

Completion of superior osteotomy

The holes are then connected to create a single osteotomy on the superior margin of the sinus.


Plate application enlarge

Osteotomizing the orbital rims/glabella

Next, the drill is used to osteotomize the orbital rims and glabella in a similar fashion. Care should be taken to protect the orbital contents and supratrochlear/supraorbital neurovascular pedicles.


Plate application enlarge

Intersinus septum osteotomy

If the intersinus septum is intact, it may be necessary to insert a curved osteotome through the superior osteotomy site and fracture the intersinus septum just deep to the anterior table bone. Care must be used to avoid injuring the posterior table.


Plate application enlarge

Bone removal

A curved osteotome is then inserted through the superior osteotomy to cantilever the anterior table and generate a controlled fracture of any remaining attached bone. A clamp should be used to control the anterior bone fragment as the osteotomy fracture is completed.

6 Mucosa removal top

Mucosa removal enlarge

The sinus cavity is then suctioned free of any blood or mucous. An elevator and/or forceps are used to remove the sinus mucosa.


Mucosa removal enlarge

Diamond burrs of various sizes (1-6 mm) are then used to meticulously remove the sinus mucosa and a thin layer of bone from the entire sinus surface. All septations are drilled down to generate a single smooth sinus cavity.


Mucosa removal enlarge

Particular attention must be paid to the scalloped areas at the periphery of the sinus. In the supraorbital region this can be challenging. Extra time should be spent to assure that  mucosa is removed from this area.
Rarely, a small amount of bone from the orbital roof may be removed to gain access to the deepest portions of the sinus.


Mucosa removal enlarge

A clamp is used to stabilize the free anterior bone segment(s) that were previously removed. A large diamond burr is then used to remove the mucosa from the inner surface.

7 Closure of the outflow tract top

Closure of the outflow tract enlarge

An elevator is then used to circumferentially elevate the mucosa in the frontal recess bilaterally. The mucosa is then inverted and pushed inferiorly to obstruct the outflow tract. Free fascia is used for obliteration of the outflow tract.


Closure of the outflow tract enlarge

Alternatively, a sharp 1-2 cm straight osteotome can be used to harvest a thin layer of outer layer calvarial bone. If the graft can be harvested from a region with Intact periosteum, this will help maintain the integrity of the graft.


Closure of the outflow tract enlarge

Each bone graft is trimmed to fit into the frontal sinus infundibulum using a fine bone rongeur. The graft is then wedged into place to obstruct the sinus outflow tract.

8 Sinus obliteration top

Sinus obliteration enlarge

Harvesting fat

Fat can be readily harvested from the abdomen. An incision can be placed around the umbilicus (better cosmesis) or in the left lower quadrant.


Sinus obliteration enlarge

To maintain maximum graft viability, one adequately sized piece should be obtained without the use of electrocautery.


Sinus obliteration enlarge

The fat graft is then placed in the sinus cavity and ...


Sinus obliteration enlarge

... distributed to fill the entire defect.


Sinus obliteration enlarge

The anterior surface should be trimmed so that the fat does not extrude from the osteotomy gap.


Sinus obliteration enlarge

The anterior table bone fragments are then repositioned and the pre-applied plates are rotated back into position to fixate the fragments. Replace any remaining fragments and fix them with small plates.


Sinus obliteration enlarge

This clinical photograph shows the fixation.

v1.0 2011-05-14