Clinical and radiological outcomes of transoral endoscope-assisted treatment of mandibular condylar fractures

Abstract

Fractures of the mandibular condyle are one of the most common craniofacial fractures. However, the diagnosis and treatment of these fractures is controversial because of the multiple surgical approaches available. The purposes of this study were to identify surgery-related technical tips for better outcomes and to evaluate the results as well as complications encountered during 7 years of endoscope use to supplement the limited intraoral approach in the treatment of mandibular condylar fractures. Between 2005 and 2012, 50 patients with condylar fractures underwent endoscope-assisted reduction surgery. Postoperative facial bone computed tomography and panoramic radiography demonstrated adequate reduction of the condylar fractures in all patients. No condylar resorption was detected, and most patients displayed a satisfactory functional and structural recovery. There was no facial nerve damage or transitory hypoesthesia, and there were no visible scars after the surgery. Transoral endoscope-assisted treatment is a challenging but reliable method with lower morbidity and a rapid recovery.

Fractures of the mandibular condyle are one of the most common craniofacial fractures. However, there are differing opinions among surgeons regarding the optimal treatment and management of these fractures. Although closed reduction is the most useful method, it can be more difficult to achieve an anatomical reduction compared with the use of open reduction and internal fixation (ORIF). In most cases, ORIF provides good alignment, establishes facial symmetry, and restores function and the anatomical environment; however, it does not always provide sufficient operative exposure.

The pre-auricular, submandibular, intraoral, and retromandibular approaches are the most commonly used routes of access for ORIF of condylar fractures. Most surgeons prefer to treat condylar fractures by extraoral approaches rather than intraoral approaches because extraoral approaches provide good visualization of the operative field. However, extraoral approaches are associated with a high rate of surgical complications, such as salivary fistula formation, visible scarring, and facial nerve injury, compared with intraoral approaches. The intraoral route is a good approach because it prevents facial scarring; however, it offers limited exposure and a worse visual field compared to the other surgical approaches. More recently, endoscope-assisted transoral approaches have been performed to overcome the limited visibility of intraoral approaches and have led to satisfactory results. Although excellent visibility in areas of limited exposure can be obtained using an endoscope, the technique is technically challenging and there is a steep learning curve.

The purpose of this study was to identify surgery-related technical tips for better outcomes of mandibular condylar fracture treatment using endoscopy. Refinements of the endoscopic transoral technique are reported, along with the postoperative results obtained over a 7-year period.

Materials and methods

Patients

The records of 50 patients who underwent the surgical repair of condylar fractures by endoscope-assisted reduction between 2005 and 2012 at a university medical centre in Korea were reviewed retrospectively.

The following indications were the inclusion criteria required for endoscopic treatment: adult patients with displaced unilateral condylar fractures, malocclusion and/or inability to achieve adequate occlusion with closed reduction, and vertical shortening of the ascending ramus. Patients with high condylar fractures such as intracapsular and condylar head fractures, non-displaced fractures, or fractures without functional impairment were treated by means of ORIF with an extraoral approach or closed reduction with intermaxillary fixation (IMF).

Radiological imaging, which included facial bone computed tomography (CT) and panoramic radiography, was performed prior to the surgery. IMF using an arch bar was performed in all patients under local anaesthesia on admission day 2, prior to the reduction. One surgeon performed all of the surgical procedures.

Surgical technique

A preoperative injection of 2% dental lidocaine was administered along the intraoral incision line for haemostasis. A 5-cm intraoral S-shaped incision was made from the ascending ramus to the vestibular mucosa, lateral to the second molar region. Dissection using Bovie electrocautery was performed before exposing the periosteum of the anterior border of the ramus. After achieving sufficient dissection, an endoscope was inserted to identify the fracture site. However, visualization was often difficult as the mandibular bone is not flat. For better visualization, the convex area of the mandibular angle was shaved with a burr or a rasp ( Fig. 1 ).

Fig. 1
A three-dimensional reconstructed CT image of the mandible illustrating a left-side condylar neck fracture. The red arrow points to a prominent area that interferes with the visualization of condylar fractures using an endoscope. For a better operative field via an intraoral endoscopic approach, surface shaving using a burr is needed.

After adequate visualization of the fracture line was achieved using endoscopy, the reduction was performed ( Fig. 2 A) . Reduction was facilitated by releasing the IMF and pulling downward on the angle of the mandible. The surgeon used a trocar to reach the angle of the mandible for wire fixation, which facilitated a better reduction. A 0.5-cm stab incision was made in the nearby submandibular skin; the trocar was inserted percutaneously, and drilling of the mandibular angle was performed ( Fig. 2 B). An 8-mm screw was fixed through the trocar, and a double-folded 1–0 wire was inserted to hang on the fixed screw ( Fig. 2 C). Once the wire was hanging on the screw, the wire was twisted through the trocar. After removing the trocar, the wire was pulled downward to move the distal mandibular segment while an endoscope enabled visualization of the fracture site. Other options to access the mandibular angle for placement of a screw included an angulated drill and screwdriver system. The use of an 18-gauge needle inserted through the skin over the angle will allow placement of a wire without the need for the submandibular trocar; the wire is then hooked over the screw and pulled inferiorly.

Fig. 2
An endoscopic view of the surgical procedure used for a subcondylar mandibular fracture. (A) A subcondylar fracture line is seen. (B) Drilling is performed on the angle to hang a wire. (C) A fixed screw with a twisted wire is shown at the mandibular angle. (D) A hinged plate-holding device with a plate is shown at the fracture site. (E) A screw fixation is seen on the proximal fracture segment. (F) A dynamic compression plate fixation is shown in the correct position.

After the distal mandibular segment was pulled downward, the proximal condylar segment was positioned in the correct place or manipulated into position using a bone hook. This is a good time to position the transbuccal trocar that is used for drilling and screw placement. Improper placement of this trocar made screw placement extremely difficult. A stab incision was made through the skin parallel to the anticipated direction of the facial nerve. Extraoral dissection is limited to the small stab incision required for the placement of the trocar. Proper placement ensures that it will be possible to place all of the screws using a single stab incision and trocar placement. The trocar itself may prove helpful for pushing the proximal fragment into place ( Fig. 2 A). A hinged plate-holding device with a plate was then inserted into the intraoral incision site; the slotted screw portion of the device could be rotated to release it from the plate ( Fig. 2 D). When the plate appeared appropriately positioned under the endoscope, drilling and screw fixation was performed through the trocar ( Fig. 2 E).

One or two 2.0-mm miniplates with 6-mm screws were commonly used. With the plate in position, the first screw was always placed in the proximal fragment. During internal fixation with a plate, an assistant should pull the fixed wire on the distal mandibular segment (mandibular angle) downward. After endoscopic control of the fracture reduction, the second screw was inserted in the distal segment. When pre-injury occlusion and anatomical reduction were obtained, osteosynthesis was completed. The IMF was usually reapplied before screw placement. If there was a sufficient bone surface, two miniplates could be placed. The endoscope ensured correct reduction and positioning of the plate ( Fig. 2 F). During the reduction of mandibular condylar neck fractures, one may need to detach the surrounding ligaments and muscles ( Fig. 3 ).

Fig. 3
An endoscopic view of the surgical treatment of a condylar mandibular fracture. (A) Dissection to expose the condyle. (B) Condylar fracture exposure. (C) A curved elevator dissection of the medial part of the condyle. (D) Ligaments and muscles released by the elevator.

The wound was irrigated and closed with absorbable sutures. Any external stab incisions were closed, usually with a single non-absorbable suture. The IMF was generally released at the completion of the procedure, although arch bars were retained for the application of elastics during the early postoperative period in order to retrain the musculature.

Evaluation

Postoperative complications were recorded and follow-up examinations included clinical and radiological assessments. The following clinical parameters were assessed: range of motion of the injured joint together with the contralateral joint as determined by the mouth opening (maximum inter-incisal distance) and by the extent of lateral excursion, deviation on mouth opening, occlusion, and nerve function. Radiological examination consisted of the Towne’s view, panoramic radiographs, and a facial bone CT. Preoperative, postoperative, and follow-up radiographs were obtained.

Postoperative radiographs were used to assess the adequacy of reduction by measuring the coronal displacement of the condyle and loss of ramus height. The method used to measure the degree of condyle fragment displacement in the Towne’s radiograph was as follows: a line was drawn between the medial and lateral poles of the condyle. Another line was drawn tangent to the ramus. The inner angle formed by the intersection of the two lines was calculated. The difference between the angle on the non-fractured side and the angle on the fractured side was used as a measure of coronal displacement. The loss of ramus height was measured on the panoramic radiograph: a reference line was drawn through both gonial angles. The perpendicular distance between the most superior point on the condyle and the reference line was calculated. The difference between the non-fractured and the fractured sides was used as a measure of the difference in ramus length. An adequate reduction was defined as follows: correct anatomical shape of the condyle, coronal displacement ≤4°, and difference in ramus height ≤4 mm.

Panoramic follow-up radiographs were used to assess condylar resorption. Condylar resorption was defined as a flattening of the condyle and marked irregularity of the condylar surface. These evaluations were recorded by a single plastic surgery resident who was not involved in the treatment planning or subsequent operative procedures on the patients.

Results

There were 35 male and 15 female patients. The mean age of the patients was 44.5 ± 14.7 years (range 21–71 years), and the mean follow-up duration was 6.7 ± 1.5 months (range 3–11 months). Among these 50 patients, 34 had subcondylar fractures and 16 had fractures involving the neck of the condylar process. Six out of the 16 condyle fractures were comminuted. Thirteen patients had additional mandibular fractures, which were first reduced. Most of the injuries resulted from physical assaults, motor vehicle accidents, or other blunt trauma. Surgery was normally performed within 4 to 15 days after the injury (average 7.2 days)

Osteosynthesis was performed in all patients. The mean operating time was 1 h 41 min, excluding the time required for IMF. In this study, follow-up data for up to 5 months were recorded. The results of the clinical and radiological examinations were entered on a data sheet.

The range of movement was assessed by maximum mouth opening and lateral excursion. The average inter-incisal distance postoperatively was 41.3 ± 4.1 mm. The average range of lateral excursion was 7.0 ± 1.2 mm. None of the patients presented clicking of the temporomandibular joint (TMJ) during the physical follow-up examination. Deviation of the mandible during mouth opening was observed in three patients, without any functional disturbances. Six patients complained of a mild open bite; these patients were referred to the department of dentistry for an evaluation. However, no significant complications such as malocclusion or TMJ dysfunction were observed. The remaining 44 patients showed their habitual occlusion. There was no postsurgical facial nerve damage or transitory hypoesthesia.

The postoperative radiographs confirmed adequate reduction in all patients. The average degree of postoperative fracture angulation was 1.5 ± 1.7° and the average loss of ramus height was 0.8 ± 0.9 mm. No condylar resorption was observed on follow-up panoramic radiographs.

The outcomes of this surgical technique using an endoscope were favourable, and most of the patients were satisfied with their results. The patients also demonstrated a good occlusion and mouth opening of >40 mm. Moreover, there were no complications such as nerve damage, TMJ dysfunction, or facial scarring. In two patients, removal of the osteosynthesis material was indicated because of an infection at 6 months postoperatively. Uneventful healing and good TMJ function were noted in both patients ( Figs. 4 and 5 ) .

Jan 16, 2018 | Posted by in Oral and Maxillofacial Surgery | Comments Off on Clinical and radiological outcomes of transoral endoscope-assisted treatment of mandibular condylar fractures
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