TMJ ankylosis of any etiology is an intolerable problem, and appropriate treatment is important to help patients return to normal life. Trauma to the TMJ and infection are the most common etiologic factors of TMJ ankylosis, and patients with a history of these problems should be examined regularly to prevent future ankylosis (
5). The key to appropriate treatment is an exact clinical and paraclinical examination.
There are several treatment plans presented in the literature for each type of ankylosis. Interference of the coronoid process with the zygomatic is a rare but important ankylosis type (
7), and some studies have been done in these cases, but there is no sole treatment approach that is advocated ( 10). The treatment of these patients may be difficult, requiring several surgeries, and in some cases, there may be relapse after surgery. Conservative therapy is usually unsuccessful in these patients, who will eventually need surgical treatment ( 10).
According to the available investigations, coronoidectomy is an appropriate treatment for zygomatico-coronoid ankylosis (
6, 7). The aim of this treatment plan is to eliminate the interference of the coronoid process with the zygomatic arch by cutting the coronoid process. The case presented by Guven in 2012 is one of the 14 reports of zygomatico-coronoid ankylosis presented in the literature ( 7). Guven treated the patient with coronoidectomy via an intraoral approach, and postoperative examinations did not show recurrence or coronoid process regrowth ( 7).
Although coronoidectomy in cases similar to Guven’s may be successful, in some cases, such as ours, the overgrowth of the coronoid and displacement of the zygomatic body lead to the failure of coronoidectomy alone. In the present case report, interference between the coronoid process and the zygomatic arch was the etiology of the limitation in mouth opening. This interference was the result of downward and inward displacement of the zygomatic arch and body. The mouth opening of the patient after bilateral coronoidectomy via an intraoral approach was insufficient (approximately 20 mm), so we attempted to reach to the right zygomatic arch via a preauricular incision, and to split the arch. We were able to open the mouth to approximately 40 mm after the splitting and osteotomy of the zygomatic arch.
The main concept of the present study underscores the importance of the clinical examination. Condylectomy is not always the best treatment choice for mandibular ankylosis. The current case report suggests that condylectomy is not a successful treatment plan for extracapsular ankylosis and that there may be important complications, such as hematoma or damage to the anatomical structures. Inspection and palpation are required in a patient who has limitation of mandibular movement. In our case, the flattened right malar eminence, vertical dystopia of the right eye, and asymmetry of the middle one-third of the face suggested that the cause of the ankylosis may be related to the right zygomatic bone. In this case, both temporomandibular joints had slight movement and the patient was able to open her mouth approximately 3 - 4 mm, suggesting that the interference was extracapsular and the function of the joint was normal. After clinical examination, radiographic assessment is useful to detect the main cause of ankylosis. Panoramic x-ray views and CT scans are excellent paraclinical studies for detecting extra- or intracapsular ankylosis.
After the examination and the detection of the main etiology of the ankylosis, an appropriate treatment plan should be decided upon that has the fewest complications and the easiest approach. In our case, condylectomy was not necessary, since the ankylosis was extracapsular. According to the available articles in the literature, bilateral coronoidectomy has been performed to eliminate interference between the coronoid process and the zygomatic arch, and we chose this approach. After coronoidectomy, we were unable to open the mouth completely, so we decided to split the zygomatic arch and to perform an osteotomy in order to omit the interference because the downward and inward displacement of the zygomatic bone was excessive and the interference could not be eliminated by coronoidectomy alone. After arch-splitting, we were able to open the mouth approximately 40 mm. There are no exact reports of arch-splitting to solve this problem in similar cases in the literature. Arch-splitting may be a good method to eliminate interference between the zygomatic arch and the coronoid process, and simultaneous coronoidectomy may be the best option for the treatment of zygomatico-coronoid interference due to displacement of the zygomatic arch and body.
According to the present report, it seems that coronoidectomy, and in severe cases, simultaneous zygomatic arch osteotomy, may be appropriate treatment approaches in zygomatico-coronoid ankylosis.