TMJ Ankylosis

When the lower jaw fuses with the skull bone at its joint (the condyle of the mandible fuses with the glenoid fossa of the temporal bone), it is called Temporomandibular joint ankylosis. It leads to the obliteration of normal articulation and finally immobile lower jaw (mandible).

TMJ ankylosis limits the ability of the person to open the mouth. This creates difficulty in eating food, maintaining hygiene, and even speaking.

It can also lead to impaired growth of the lower jaw and various dental problems.

Normal full mouth opening is around 4-5 cm as measured from the edge of lower front teeth to the edge of upper front teeth.

It may be one-sided or both-sided, with different types of appearance on the face.

1. TMJ ankylosis may be due to any injury over the TMJ region like

• condyle fracture
• collection of blood
• injury during childbirth

2. TMJ ankylosis may be due to any inflammatory condition (like arthritis).

3. TMJ ankylosis may be due to any infection of the ear or due to post-operative complications of TMJ surgery.

It is very commonly seen in children. Usually, they come with zero mouth opening and deformity of the lower jaw. Ankylosis leads to arrest of growth of the lower jaw, so facial asymmetry is common in children

Most of the time, patients or parents of the affected children would have consulted many physicians but the correct diagnosis would not have been reached.

• Painless limitation of lower jaw movement.
• Decreased mouth opening.
• Varying degrees of lower jaw deformity.
• Nutritional deficiencies.
• Malalignment of teeth.
• Halitosis and caries in teeth.
• ‘Bird’ like face with retruded or underdeveloped chin.

Diagnosis of TMJ ankylosis is mostly clinical but it is supplemented with a few investigations like

• Orthopantomogram of the mandible (OPG X-ray)- This X-ray will show the bony fusion between both bones.
• A 3D CT Scan of the face- is the gold standard investigation for TMJ Ankylosis. It not only shows the Bone fusion but also the extent of the Bone block and the jaw deformity.

Intra-articular (true) ankylosis must be distinguished from extra-articular (false) ankylosis.

False ankylosis may be caused by

• enlargement of the coronoid process,
• depressed fracture of the zygomatic arch, or
• scarring resulting from surgery, irradiation, or infection.

In most cases of true ankylosis, x-rays of the joint show loss of normal bony architecture around the TMJ region.

TMJ Ankylosis is completely treatable with surgery. Restoration of mouth opening is the primary aim of treatment. The lower jaw (mandibular) deformity, if present, is usually corrected later during second-stage surgery.

The patient is admitted one day before surgery and all preoperative investigations are done.

• Anesthetizing the patient with TMJ ankylosis is very challenging as mouth opening is nil and nasal intubation must be done. We have a very competent intensivist and anesthetist in our team who has managed an innumerable number of such cases till now.
• During surgery, an incision is given in front of the ear within its folds so that the incision is very well hidden and not visible to the human eye.
• The Bony block is removed and space is created between the mandible below and the temporal bone above to achieve a normal mouth opening of 4 cm.
• This gap between the bones is usually filled by a facial flap harvested from the scalp region so that the ankylosis does not recur. If TMJ Ankylosis is present on both sides, then the same procedure is repeated on the other side.
• The incision is closed over a drain which is removed on postoperative day 2.
• The patient is discharged from the hospital after the drains are removed.
• Sutures are removed on the 7 th day after the surgery.

• Regular Jaw-opening exercises must be done for a minimum of 6 months to maintain the surgical correction.
• There are chances of temporary paresis or paralysis of the facial nerve or one of its branches during the surgery leading to paralysis of one side of the face which happens in 5 to 10% of cases. The recovery takes around 3 to 6 months and is usually complete. Permanent damage to the facial nerve occurs in only 1 to 2% of the cases with abnormal anatomy and a more widespread diseased segment.

Correction of mandibular deformity can be done with orthognathic surgery procedures notably Bilateral Saggital Split Osteotomy (BSSO) and genioplasty or chin surgery . These patients also require orthodontic treatment for correction of the alignment of their teeth.

Orthognathic surgery is usually done as a second-stage procedure when the children have completed their skeletal maturity i.e., 14 to 16 years for girls and 16 to 18 years for boys.

Bilateral Saggital Split Osteotomy (BSSO) should be done when the whole lower jaw is underdeveloped and requires advancement or to be brought forward.

Genioplasty or chin surgery is a single cosmetic procedure that gives the maximum cosmetic correction in boys and girls with receding chins. It is usually combined with BSSO.