Construction of Zygomatic arch and Glenoid fossa

When the zygomatic arch and the glenoid fossa are missing in whole or in part, they should be constructed as symmetrically as possible. The key is to try to place the glenoid fossa in as similar a position and distance as possible from the midline in all three dimensions.

Mirror imaging of the normal side to the abnormal side using 3D-CT software can provide a guide to the shape and position of the graft required.

The construction of the zygomatic arch and the glenoid fossa is generally carried out during childhood although the same principles apply when a patient presents as an adult.

The surgical approach is via a coronal or hemi-coronal/extended preauricular incision (illustrated)

This enables exposure of the temporo- mandibular joint area, including the:

• mastoid bone posteriorly
• body of the zygomatic bone anteriorly
• lateral orbital rim

It is generally possible to reconstruct the zygomatic arch and glenoid fossa using autogenous rib grafts. Usually one rib graft is sufficient but sometimes two have to be harvested.

The rib is molded using rib benders to the required shape.

In the region of the glenoid fossa, multiple layers of rib are assembled with screws and the fossa is carved out with a drill.

The construct is then stabilized with two screws (eg, 1.5 mm), one anteriorly and one posteriorly. Screw fixation is generally into the body of the zygomatic bone anteriorly and the mastoid process of the temporal bone posteriorly.

It is important to ensure that the bony construct especially of the glenoid fossa is covered with soft tissue to prevent TMJ ankylosis. This can either be carried out during this procedure or at the time of mandibular condyle construction.

The best material to cover the fossa is fascia. Sometimes temporal fascia is available and can be turned over the construct as a pedicle flap. Sometimes it needs to be used as a free graft. In the absence of suitable local tissue (muscle should be avoided because it does have the potential to ossify) fascia lata can be harvested from the lateral aspect of the thigh.

Apply ice packs (may be effective in a short term to minimize edema).

The sterile dressing placed over the incisions is maintained for a minimum of 48 hours. Thereafter routine wound care should be instituted.

Antibiotic prophylaxis is continued for 1-5 days depending on the nature, complexity, and duration of the surgical procedure.

Remove sutures from skin after approximately 5 days if nonresorbable sutures have been used.

Regular follow up examinations to monitor healing are required.

Avoid sun exposure and tanning to skin incisions for several months.