Temporomandibular joint (TMJ) dislocation is defined as an excessive forward movement of the condyle beyond the articular eminence with complete separation of the articular surfaces and fixation in that position. The aim of this study was to describe a modified miniplate designed for treating chronic mandibular dislocations and evaluate the results of its placement in one patient, who was followed for 18 months. The treatment of chronic mandibular dislocation using this modified miniplate was shown to be efficient in relation to the postoperative maximal mouth opening, recurrence and articular function.
Temporomandibular joint (TMJ) dislocation is defined as an excessive forward movement of the condyle beyond the articular eminence with complete separation of the articular surfaces and fixation in that position . A variety of therapeutic approaches designed to limit the forward excursion of the condylar head have been applied; each has advantages and disadvantages. The placement of a titanium miniplate in the articular eminence aims to prevent hyperexcursion of the condyle, thereby avoiding its displacement, but there is a possibility of the plate fracturing, possibly owing to material fatigue where the plate was bent during adaptation to the articular eminence during surgery . This article describes a modified titanium miniplate to be used in the articular eminence for the treatment of chronic mandibular dislocation, to avoid the possibility of the plate fracturing.
Materials and methods
The study was conducted at the Division of Oral and Maxillofacial Surgery of Oswaldo Cruz Hospital and Pernambuco Dental School – University of Pernambuco, Pernambuco, Brazil. A prospective evaluation of cone-beam computed tomography (CBCT) studies of 20 TMJs (10 patients) was used to measure the articular eminence in relation to the mandible to design the plate. Four measures were made ( Fig. 1 ): vertical distance (v), from the most inferior point of the articular eminence to the sigmoid notch; horizontal distance (h), from the most anterior point of the articular eminence to the most posterior; articular eminence height (aeh), from the most superior point of the articular eminence to the most inferior; articular eminence width (aew), from the most lateral point of the articular eminence to the most medial.
TMJ measurements were made on the right and left with the aim of obtaining a single plate that could adapt to either side of the eminence. The plate was manufactured in titanium for this case.
The TMJ was exposed using the preauricular approach under general anaesthesia. After exposure and identification of the articular eminence, the modified miniplate was used. The short arm of the plate was fixed with three 6 mm, 2.0 mm diameter screws and the long arm served as a mechanical obstacle in the condylar path. The plate was placed inferior and anterior to the articular eminence and anterior to the capsule of the joint in order to prevent hyperexcursion of the condyle, thereby avoiding its displacement and avoiding the intra-articular region ( Figs. 2 and 3 ). The jaw movements were checked for interference and any required adjustments made.
After the data evaluation the plate had a base for its fixation in the articular eminence and an arm, like a drop, serving as a mechanical obstacle in the condylar path, placed inferior and anterior to the articular eminence. The plate measurements (mean ± standard deviation in mm) obtained were: vertical distance (10.46 ± 3.13), horizontal distance (14.88 ± 1.79), articular eminence height (5.99 ± 2.00), and articular eminence width (11.27 ± 1.80). Based on these measurements the plate had a vertical distance of 4.20 mm (mean − (2× SD)), a horizontal distance of 13.09 mm (mean − SD), an articular eminence height of 3.99 mm (mean − SD) and an articular eminence width of 7.70 mm (mean − (2× SD)).
The patient had episodes of at least three dislocations per day and was unable to perform jaw movements, to smile, speak or eat. The patient was followed for 18 months, when she was clinically and radiographically re-evaluated ( Figs. 4 and 5 ). Her preoperative maximum mouth opening was 55 mm and after surgery it was 48 mm. No pain was related at either evaluation. No recurrence or miniplate fracture were observed.