Reconstruction of orbital floor/wall defects

There is a linear correlation between intraorbital volume and axial globe position. 1ml of orbital volume enlargement will lead to (approximately) 1mm enophthalmos.

A 2 ml increase in orbital volume will result in noticeable enophthalmos.

Orbital wall defects are either isolated or associated with orbital rim deformities.

High resolution CT-scan with fine cuts is obtained and the DICOM data processed in suitable planning platform.

Serial axial, coronal, and sagittal cuts are visualized to determine the extent and location of the defect.

If a titanium implant is used, the shape of the defect is outlined on a standard skull and the plate preshaped to reconstruct the defect. The plate is then sterilized prior to the surgery.

If preshaped orbital plates are available, they are an excellent option for complex orbital floor/medial wall defects.

If custom made implants are available, the defect is outlined on a virtual 3D-model and mirrored from the unaffected side. The implant can be designed to accurately reproduce the normal anatomy.

Navigation, when available, can be very useful in orbital wall reconstruction. Further details can be found in the section on computer assisted surgery.

Transconjunctival incisions are preferred by most surgeons.

A coronal incision is also used to treat associated naso orbital ethmoidal and/or orbito zygomatic deformities.

Special attention is paid to protect the globe, cornea, and conjunctiva.

Use of corneal protectors, ointments, or temporary tarsorrhaphy techniques are recommended.

Appropriate exposure of the orbit requires adequate visualization through gentle retraction of the soft tissues and lighting. The posterior orbit is ideally visualized using headlights or illuminated retractors.

Magnification by using surgical loupes is helpful.

Special malleable orbital retractors (straight or anatomically shaped) are available with metric markings providing the surgeon additional information regarding the extent of the defect and the depth of the orbital dissection. Specific orbital retractors have been developed to improve orbital retraction and minimize prolapse of soft tissue during insertion of implants.

It is important to consider the unique contours of the orbital anatomy.

The key areas of the orbit involve mainly the posterior orbital floor and medial orbital wall which bulge towards the orbit resulting in an S-shape of the orbital floor in the posterior third (seen in a sagittal view along the axis of the optic nerve). Before bulging in the posterior third, the contour of the orbital floor slopes down directly behind the infraorbital rim before ascending towards the posterior aspect. This contour has to be restored in order to provide appropriate orbital volume and shape.

Inadequate/insufficient reconstruction of the orbital floor may lead to a hammock-shape contour. The latter can be observed in cases where resorbable implants were used or in cases where a thin wafer of silicone or porous polyethylene was used for reconstruction of large orbital wall defects.

The challenge of orbital floor reconstruction is particular in the most posterior part and in the transition zone with the medial wall.
The transition zone between the medial orbital wall and the orbital floor is difficult to visualize intraoperatively. This becomes even more difficult to visualize in dissection further posteriorly.
Repair of the transition zone between medial orbital wall and floor is vital and determines the position of the orbital contents and the globe.
Coronal slice of a CT scan shows a non-affected left orbit with normal anatomy of the transition zone. (The arrow indicates the buttress of the transition zone between medial orbital wall and orbital floor).

Coronal slice of a postoperative CT scan taken after transconjunctival reconstruction of the complete left medial orbital wall and orbital floor.
The overlying colored line in the medial wall and orbital floor area indicates the preoperative virtual planning that is superimposed on the implant reconstructed area.
This X-ray shows the classic transition zone.

Reconstruction of the orbital floor has to respect the course of the infraorbital nerve in the orbital floor.
A careful sharp dissection separating the infraorbital nerve from the orbital contents is usually required.

The forced duction test should be performed to determine ocular motility as soon as general anesthesia is induced.

As soon as the periorbita has been dissected another forced duction test should be performed to determine ocular motility.

After the insertion of any implant material, it is imperative to perform a forced duction test to assure that the implant has not created a decrease in ocular motility.

Click here for details on the forced duction test.

The unique and complex anatomy of the orbit, unless prebent plates are used, requires significant contouring of the implants to restore the proper anatomy.

The majority of cases require reconstruction of the orbital floor to support the globe position and restore the shape of the orbit. There is hardly any anatomic region in the human body that is so controversial in terms of appropriate material used reconstruction. Most common reconstructive options in secondary cases include:

• Autogenous/allogenous/xenogenous versus alloplastic material
• Non-prebent versus preformed (anatomical) plates
• Standard versus custom-made plates
• Nonporous versus porous material
• Noncoated versus coated plates

Many surgeons recommend using materials that allow bending to an anatomical shape, that are radiopaque (to allow for intra- or postoperative radiologic confirmation of placement), and stable over time.
Reconstruction of the dislocated orbital walls is demanding. There is a paucity of evidence to support the ideal choice for an orbital implant. Modern imaging analysis offers a unique chance to quantitatively asses the surgical result and stability over the time. This can provide valuable information for future recommendation.

Advantages:

• Availability
• Stability
• Contouring (facilitated by the artificial sterile skull)
• Adequate in three-wall reconstructions (the pre-bent plate is limited to medial wall and orbital wall fractures only).
• Radiopacity
• Spaces within the implant to allow dissipation of fluids
• No donor site needed
• Tissue incorporation may occur

Disadvantages:

• Costs
• Possible sharp edges if not properly trimmed

Note: The extensive use of titanium implants for orbital reconstruction in traumatized orbits has been shown to be safe, with few problems due to infections and no problems with secondary displacement due to additional trauma, on condition of proper handling, contouring, and fixation of the implant.

Illustration shows an example of a calvarial bone graft.
Advantages:

• Low material costs
• Smooth surface
• Variability in thickness
• Radiopacity
• Maximal biocompatibility
• Periorbita readily dissects off of the bone in secondary reconstructions

Disadvantages:

• Additional donor site needed (necessitating additional surgery time for harvest, pain, scar, and possible surgical complications)
• Possible contour and dimensional changes due to remodeling
• Difficult to shape according to patients anatomy
• Less drainage from the orbit than with titanium implant

Advantages:

• Availability
• Contouring (facilitated by the artificial sterile skull)
• Smooth edges
• Allows tissue ingrowth

Disadvantages:

• Not radiopaque (not visible on postoperative images)
• Lack of rigidity when a very thin wafer of PPE is used. When a thicker rigid wafer is used there is a risk of causing a dystopia
• Less drainage from the orbit than with titanium implant

By combining titanium plates with porous polyethylene the material becomes radiopaque, and more rigid than porous polyethylene of a similar thickness. Some surgeons also believe that there is less risk of having retained sharp barbs, which can lead to an entrapment of soft tissues during placement.

Advantages:

• Availability
• Stability
• Contouring (facilitated by the artificial sterile skull)
• Adequate in large three-wall reconstruction (the pre-bent plate is limited to medial wall and orbital floor reconstruction only).
• Radiopacity
• No donor site needed

Disadvantage:

• Less drainage from the orbit than with titanium implant

Advantages:

• Radiopacity
• Smooth surface
• Minimal or no contouring necessary

Disadvantages:

• Cost
• Designed to fit Caucasian orbits

Multiplanar and 3-D view showing a preformed plate placed prior to surgery into patient CT dataset.

Extensive subperiosteal orbital wall dissection (270°-360°) is usually needed to adequately mobilize the orbital contents.

The following pages provide general information regarding orbital anatomy and dissection

• Preoperative considerations
• Anatomy of the bony orbit
• Correlation of surface and cross sectional anatomy
• Introduction to periorbital dissection
• Orbital floor dissection
• Medial orbital wall dissection
• Lateral orbital wall dissection
• Orbital roof dissection
• Adjunctive access procedures (orbitotomies)
• Retrobulbar hemmorage

Adequate exposure and illumination (headlight, illuminated retractor) of the surgical area is imperative prior to fixation.
Adequate hemostasis has to be achieved. Bipolar coagulation is useful.
Gentle retraction of the intraorbital soft tissues is essential.

A foil template (or sheet of other material) may help with a retractor to avoid prolapse of soft tissues, improve visualization, and prevent entrapment of soft tissues during implant placement.
The illustration shows the insertion of this foil below the retractor.

The retractor is removed, placed under the foil, and the orbital soft tissues are properly retracted.

Note: Do not forget to remove the foil template following implant placement.

This illustration shows the foil template larger than the size of the retractor.

If adequate preoperative planning is performed, only minor adaptations of the implant shape will be necessary.

Note: special attention is paid to properly approximate the layers of the eyelid and resuspend the soft tissue of the midface.

CT-Scan shows the extent of a post traumatic two wall defect in coronal view.

Postoperative CT scan shows the reconstruction of the defect.

When indicated, the implant is tailored to the specific defect and any sharp edges are trimmed off to avoid soft tissue injury.

The implant is contoured to achieve the required shape, and accommodate key anatomical structures (nasolacrimal duct and infraorbital nerve).
It is advisable to keep the posterior edge of the implant at least 1 cm anterior to the optic canal.

A sterile artificial skull allows proper anatomical contouring of the implant. This is not required when using the prebent option.

Note:

1. When using the fan-shaped plate, the outer circumference of the implant is widest in the area of the infraorbital rim. The implant should be trimmed so that the outer circumference is as small as possible but still provides enough width to cover the defect.
2. It is important to use a plate large enough to span the entire defect.

Regardless of the implant chosen, the insertion process must prevent its deformation. Under adequate retraction of the intraorbital soft tissues the implant has to be positioned so that proper and stable recontouring of the orbital walls results. Care has to be taken that neither orbital fat nor muscles are entrapped. During the insertion process, the implant may require rotation in order to be properly positioned.

Additionally, navigation may serve for intraoperative control of implant position. Modern 3D C-arm technology will further improve on intraoperative quality control of fracture reduction and implant positioning. Endoscopic modalities may also be helpful in confirming proper implant placement.

One screw will suffice in most cases. The screw can be placed into the floor of the orbit just posterior to the infraorbital rim.

After the insertion of any implant material, it is imperative to perform a forced duction test to assure that the implant has not created a decrease in ocular motility. Click here for details on the forced duction test.

Note: Pupils should be checked; however pupillary function might be compromised by drugs or mechanical force to the orbital contents.

According to the dimension of the defect the bone has to be adapted and fixed with micro plates and screws (as illustrated).

Evaluation of the patient's vision and pupillary response are performed as soon as awakened from anesthesia and then at regular intervals until they are discharged from the hospital.

Head of bed elevation may significantly reduce edema and pain.
A cooling mask may be used to further reduce edema.

To prevent orbital emphysema, nose-blowing should be avoided for at least 14 days following surgery.

The use of the following perioperative medication is controversial.

• Analgesia as necessary
• Antibiotics (many surgeons use perioperative antibiotics. There is no clear advantage of any one antibiotic, and the recommended duration of treatment is debatable.)
• Steroids may diminish postoperative edema. Some surgeons have noted increased complications with perioperative steroids.
• Ophthalmic ointment should follow local and approved protocol. This is not generally required in case of periorbital edema. Some surgeons prefer it. Some ointments have been found to cause significant conjunctival irritation.

The following signs and symptoms are usually evaluated:

• Visual acuity
• Extraocular motion (motility)
• Diplopia
• Globe position
• Lid position

Postoperative imaging has to be performed within the first days after surgery. 3-D imaging (CT, cone beam) is recommended.

Remove sutures from skin after approximately 5 days if non resorbable sutures have been used.
Avoid sun exposure and tanning to skin incisions for several months.

Clinical follow-up depends on the complexity of the surgery, and whether the patient has any postoperative problems. In most patients one week, four weeks, six months and one year follow up is recommended.
Additionally, ophthalmological, ENT, and neurological/neurosurgical examination may be necessary. A regular follow-up CT scan is recommended 3-6 months after surgery.
Travel in commercial airlines is permitted following orbital surgery. Commercial airlines pressurize their cabins. Mild pain on descent may be noticed. However, flying in non-pressurized aircrafts should be avoided for a minimum of six weeks.
No scuba diving should be permitted for at least six weeks.