A case of prolonged unilateral temporomandibular joint (TMJ) dislocation, which was treated by open surgical reduction and post-surgical orthodontic therapy, is presented. A 58-year-old woman presented complaining of facial asymmetry and malocclusion. She had received surgery for a malignant tumour in the right retromolar region 7 years previously. It was considered that contraction of the pterygoid muscle by surgical injury caused anterior meniscal displacement and TMJ dislocation. Since manual manipulation failed, direct open reduction was performed after separation of the lateral pterygoid muscle from the condylar head and removal of the intra-articular scar tissues. Although the condylar head was returned to the glenoid fossa, optimal occlusion was not obtained because of compensatory tooth movement and inclination. Satisfactory occlusion and symmetric facial appearance were brought about by post-surgical orthodontic therapy.
Dislocation of the temporomandibular joint (TMJ) usually occurs as an acute event and prolonged dislocation is comparatively rare. Although the causes of acute TMJ dislocation include trauma, excessive mouth opening, drugs, and psychogenic and neurological disorders, prolonged dislocation commonly occurs when an acute dislocation is left untreated or is inadequately treated . In most acute dislocations, manual reduction is effective. The management of prolonged dislocations is more difficult because of severe muscular spasm and periauricular fibrotic changes . Cases of prolonged dislocation frequently require surgical methods such as open reduction, condylectomy, and several types of osteotomy . This article reports a rare case of long-standing dislocation of the TMJ caused by contracture of the lateral pterygoid muscle following resection of a mucoepidermoid carcinoma that developed in the retromolar region. The patient received an open reduction, followed by orthodontic treatment because sufficient occlusion was not obtained after surgery.
A 58-year-old Japanese woman presented complaining of malocclusion due to marked deviation of the mandible to the left side. She had undergone surgery for a mucoepidermoid carcinoma in the right retromolar region in contact with the ramus of the mandible 7 years ago ( Fig. 1 ). The surgery was performed with incision from angle of the mouth to the cheek (Velpeau’s incision) and the tumour was resected with the anterior part of the mandibular ramus, coronoid process, and the inferior part of the temporal muscle. After surgery, the condyle head located in a slightly anterior position within glenoid fossa ( Fig. 2 ). Although she had noticed the progressive change in her bite during the 2-year follow-up after the surgery, the patient had missed her scheduled appointment.
A clinical examination revealed deviation of the mandible to the left side and facial asymmetry ( Fig. 3 A ). Her occlusion was Class III on the right and Class II on the left, and a crossbite from the right incisor to the left molar (overjet, −5.0 mm; overbite, +2.0 mm) was observed. The midline between the lower central incisors was shifted 13.0 mm to the left side relative to the midline between the upper central incisors. Her maximum mouth opening was 30 mm. Panoramic radiography showed the location of the right condyle in front of the articular eminence ( Fig. 4 ). A mixture of high and low signals was seen in the glenoid fossa in T2-weighted magnetic resonance images.
Manual manipulation was attempted for reduction without success. Therefore, the patient underwent an attempt at reduction under general anaesthesia. An initial attempt at manual manipulation under general anaesthesia with muscle relaxants failed. The lateral pterygoid muscle and scar tissues attached to the condylar process were intraorally detached, but manipulation failed again. Consequently, a preauricular incision was made and the fibrous tissues in the glenoid fossa were removed. Open reduction was then performed successfully ( Fig. 5 ). To prevent postoperative relapse, an intermaxillary fixation with nine bone screws was applied for 1 week. At this time, the slight deviation remained (the deviation of the lower incisor midline was 3 mm), and a slight open-bite was observed (overjet, +2.0 mm; overbite, −2.0 mm; Fig. 3 B). Cephalometric and cast analyses revealed bite interference on the left molars because of the movement and inclination of the lower teeth that occurred during the prolonged TMJ dislocation. Orthodontic treatment with a multi-bracket appliance and intermaxillary training elastics was performed for 1 year. After orthodontic therapy, good occlusion and a symmetric appearance were obtained ( Fig. 3 C). Occlusal retention therapy was followed by dynamic orthodontic therapy, and the occlusion has been stable for 3 years.