Impingement of the enlarged coronoid processes against the medial surfaces of the zygomatic arches and posterior surfaces of the body of the zygomatic bones results in mechanical restriction of the mouth opening. The authors introduce a helpful tool for easy assessment and estimatation of the length of the coronoid process, measured on the CT scans of 40 patients (20 adults, 20 adolescents) and report a case of a 13-year-old boy suffering from restricted mouth opening caused by bilateral hyperplasia of the coronoid process. The CT based analysis resulted in a mean length of the coronoid process of 13.02 mm in adults and 12.43 mm in adolescents. The 13-year-old boy had a length of nearly 2 cm. For comparison, a coronoid/condyle ratio was developed. This ratio showed a value of 0.78 for all patients compared with a value of about 2.0 for the boy. The literature review revealed comparable results to the reported case. Most of the patients were adolescent, male and presented a median history of 2 years until correct diagnosis.
Enlargement of the coronoid process was first described by L angenbeck in 1853 . Impingement of the enlarged coronoid processes against the medial surfaces of the zygomatic arches and posterior surfaces of the body of the zygomatic bones results in painless, yet mechanical restriction of mouth opening . Subsequently, enlargement of the coronoid process has been reported in some cases. The most consistent clinical condition of the patients is restricted mouth opening. The diagnosis of elongated coronoid process is confirmed radiographically. The condition of the elongated coronoid process is often missed and the patients are treated as suffering from temporomandibular joint (TMJ) disorder because of the history, which includes a subtle clinical manifestation. The only helpful treatment is resection of the elongated coronoid process by means of a transoral or extraoral approach. There are no previous data describing the normal length of the coronoid process. The authors introduce a helpful tool for easy assessment and estimatation of the length of the coronoid process, measured on the CT scans of 40 patients (20 adults; 20 adolescents) and report a case of a 13-year-old boy suffering from restricted mouth opening caused by bilateral hyperplasia of the coronoid process. A literature review compares the present case with published data.
A 13-year-old boy was referred to the authors’ department with a history of limitation of mouth opening of only 10 mm that began 18 months previously and was initially diagnosed by a dentist as a TMJ disorder. The patient underwent TMJ stretching under general anaesthesia at another institution 10 months previously. This procedure was not successful so the patient was referred for CT and MRI scans. The diagnostic analysis of the radiologist (10 months ago) revealed a normal configuration of the TMJ on both sides. No ankylosis or dislocation of the disc could be found. For the next 10 months, the patient underwent functional treatment supervised by an orthodontist, who referred the patient to the authors because there were no signs of success. At the time of introduction to the authors’ department, clinical examination showed restricted mouth opening of 10 mm ( Fig. 1 A and B ), but there were no signs of pain or infection. The patient presented without the previous panoramic radiograph but with a CT and MRI scan. To reduce radiation exposure, the authors decided use the pre-existing CT scan. Re-examination of the pre-existing and pre-assessed CT scan showed a previously unobserved elongated coronoid process on both sides, which were locking above the zygomatic arch ( Fig. 1 C).