Prolonged mandibular hypomobility patient with a "square mandible" configuration with coronoid process and angle hyperplasia.

The objective of this study was the surgical management of chronic severe mandibular hypomobility patients associated with square mandible morphology with coronoid process and angle hyperplasia, and one-year follow-up data is reported. Ten patients were studied. All patients were female and had a history of gradual severe jaw hypomobility. Clinical findings were similar to those of a "closed lock" patient. However, the facial appearance in these patients showed a characteristic square mandible facial configuration. Coronoid process thickening and overgrowth of the mandibular angle was evident in the radiographic findings. Diagnostic imaging scarcely depicted any disk derangement, but a severely limited jaw opening was noted in spite of acceptable excursive jaw movements. Bilateral coronoidotomy or coronoidectomy was done initially, and then masseter muscle stripping via the intraoral approach. After successful reduction of jaw hypomobility, a selective mandibular anglectomy was completed. Physical therapy began within three to five days after the surgery. Postoperatively, all patients were questioned about their jaw function and their subjective assessment of the treatment. Interincisal jaw opening was recorded with a ruler marked in millimeters. Bilateral coronoidotomy or coronoidectomy and masseter muscle stripping were done for all patients; the mandibular anglectomy was performed in seven of the cases at 13 sites. Simultaneous TMJ surgery was done on three joints for three patients. Most patients reported improvement of jaw function, and the patients' subjective assessment revealed an average satisfaction rate of 74.6%. A preoperative mean jaw opening distance of 25.6 mm increased to 36.6 mm postoperatively at a one-year follow-up (p < 0.05). The conclusion was that surgical intervention is indicated when nonsurgical treatment is unsuccessful. Etiology is unknown, but masseter and temporal muscle contracture associated with mandibular coronoid and angle hyperplasia may be a strong component of the pathophysiology.