Contralateral coronoid hyperplasia in patients undergoing hemimandibulectomy with disarticulation: a case series

The purpose of this article is to evaluate whether hemimandibulectomy with disarticulation predisposes the patient to the development of contralateral coronoid hyperplasia, thereby justifying a coronoidectomy procedure for these patients to improve jaw function and mouth opening and decrease the length of postoperative physical therapy.

Five patients who had hemimandibular resection with disarticulation for odontogenic cysts and benign tumors followed by hemimandibular graft reconstruction with either a cadaveric hemimandible or an iliac crest bone graft, or both, were retrospectively reviewed. The Levandoski panoramic radiograph analysis, which has been proven to be useful in evaluating facial asymmetry and hyperplasia of the coronoid process in adults, was used to analyze preoperative panoramic radiographs as well as those obtained at postoperative months 3 and 6.

All patients performed postoperative range-of-motion exercises for treatment of limited mouth opening in a range between 12 to 24 mm lasting up to 3 or 4 months. Two patients had prolonged trismus with a maximum interincisal opening of about 30 mm. The mean preoperative Kr' (koronion')-Go' (gonion')/Cd' (condylion')-Go' ratio was 0.92. A minimal increase in the Kr'-Go'/Cd'-Go' ratio was noted at postoperative months 3 and 6, with mean values of 0.95 and 0.96, respectively. Only 3 patients showed minimal elongation of the coronoid process, with 1 having a notable increase from 0.91 to 1.04.

Trismus, the clinical sign of restricted jaw movement, can result from pathology in a variety of structures around the oral cavity. Among the general population, the normal Kr'-Go'/Cd'-Go' ratio was found to be less than 1.07, which coincides with the preoperative mean Kr'-Go'/Cd'-Go' ratio of 0.92 in our series. Our study sample showed a minimal increase in the Kr'-Go'/Cd'-Go' ratio over the first 6 postoperative months, but the number of patients was not sufficient to conclude causality. The etiology of coronoid hyperplasia remains unclear, but the role of increased temporalis muscle activity cannot be excluded. We recommend the Levandoski analysis for patients who had hemimandibulectomy with disarticulation who complain of prolonged limited mouth opening. We also recommend considering coronoidectomy as a treatment option for those with persistent trismus and radiographic signs of coronoid hyperplasia.