Clinical outcomes of three different types of hardware for the treatment of mandibular angle fractures: a comparative retrospective study

Abstract

A retrospective study was conducted to compare the clinical outcomes of three different types of hardware that are used in mandibular angle fracture fixation. Thirty patients were selected from the hospital database. The patients were categorized into the following groups: group A, in which a single 2.0-mm locking miniplate was used; group B, in which a single rigid 2.3-mm plate was used; and group C, in which a single lag screw was inserted. All patients were followed for 6 months. With regard to intraoperative variables, significant differences were found among the groups in the duration of surgery and cost. Group C had the shortest surgical time, followed by group A and then group B. Two patients, one in group A and one in group B, suffered an occlusal discrepancy after surgery. Of the group A patients, two exhibited wound dehiscence and one had an infection. One patient in group B had an exposed plate. Sensory nerve involvement was noted in three group C patients and one group B patient. The lag screw was associated with the fewest complications and exhibited all of the advantages of plating systems in the treatment of angle fracture. The lag screw involved the least hardware and a short operating time, however the differences were not significant.

Mandibular fractures are frequent injuries that are treated in maxillofacial departments and are caused primarily by assault and traffic accidents. Mandibular angle fractures require particular attention because they make up 23–42% of all mandibular fractures and have the highest postsurgical complication rate, which ranges from 0% to 32%; these are the most difficult mandibular fractures to treat.

The ideal method for the treatment of mandibular fractures should have the objectives of a perfect anatomical reduction, functional stable fixation and painless mobilization of the injured segments, minimization of complications, and the achievement of immediate function. The treatment of mandibular angle fractures requires an adequate understanding of the surgical anatomy, biomechanical forces at the angle, the state of occlusion, and the presence of a third molar in the fracture line. Additionally, the angle has limited intraoral access, which makes its treatment difficult. All of these factors may cause problems in the attainment of stable fixation of the fractured segments.

Despite progress in treatment methods and fixation systems for maxillofacial trauma, the optimal method for the treatment of mandibular angle fractures remains controversial. Variable sizes, shapes, designs, numbers, and biomechanics of plates and screws with different combinations have been used for the treatment of mandibular angle fractures, but even with the most popular methods, satisfactory results may not be achieved because the pterygomasseteric sling and masticatory forces can displace the fractured segments.

Rigid plates (2.7-mm and 2.4-mm) were introduced for placement at the inferior border of the mandible for the treatment of mandibular fractures. Such plates provide sufficient rigidity to the fragments, adequate neutralization of functional forces even in the absence of compression, and prevent interfragmentary mobility and distraction in the tension zone and thus decrease the incidence of complications. A study by Assael et al. compared different types of plates and screws and reported that 2.7-mm diameter screws with 2.0-mm thick plates carried greater functional loads than 2.4-mm diameter screws with 1.6-mm thick plates. Additionally, the use of three screws on each side of the angular fracture and a single rigid plate has been claimed to provide adequate neutralization of functional forces and to prevent segment displacement in another study.

The locking plate/screw system offers many advantages over other plating systems, including the ease of plate adaptation, minimal alterations in osseous and occlusal relationships during screw tightening, less screw loosening, and enhanced stability without transmitting excessive pressure to the underlying bone, which decreases the impairment of the blood supply. It has been reported that intentional maladaptation of the plates affects the non-locking systems but does not affect the locking plates.

Lag screw fixation is the best means of providing axial compression and load sharing across the fracture site, because all of the fixation forces are directed across the long axis of the screw with no metal-to-metal friction, providing better stability than any other method of fracture fixation because its effectiveness relies on securing the tension zone during function. A unique advantage of the lag screw over single plate fixation is that it can be inserted more rapidly.

The purpose of this study was to identify any differences in postoperative clinical outcomes after fixation of mandibular angle fractures with single 2.3-mm rigid plates, single 2.0-mm locking plates, and the lag screw technique.

Patients and methods

Thirty patients with either isolated mandibular angle fractures or angle fractures with concomitant fractures elsewhere in the mandible were included in this study. The patients attended Al Zahraa University Hospital, Al Azhar University between October 2007 and October 2013. The indications for open reduction and internal fixation were displaced mandibular angle fractures and angle fractures associated with condylar fracture for which mobilization was necessary. Patients with infected fracture lines, comminuted fractures, or a systemic disease that could have interfered with healing (e.g., diabetes, chemotherapy) were excluded from this study.

All patients were informed about the proposed mode of treatment and provided written informed consent to undergo surgery. The local ethics review committee of Al Azhar University for Girls approved the identification and selection of patients who met the inclusion criteria from the hospital database to accomplish this study. Prior to surgery, full histories and clinical examinations were performed and recorded on a standardized sheet. Preoperative digital panoramic radiographs were used for the initial assessments of the following: the line or lines of the fractures, the location of the inferior alveolar canal, the presence of a tooth in the fracture line, and the degree of displacement ( Fig. 1 ). Other necessary views, such as postero-anterior views or computed tomography (CT) ( Fig. 2 ) were requested as necessary for each case. The diagnosis was established on the basis of each case’s history and clinical and radiographic examinations, and the treatment plan was selected accordingly.

Fig. 1
Preoperative panoramic radiograph showing a severely displaced left angle fracture with right parasymphyseal fracture.

Fig. 2
Three-dimensional CT showing a displaced right angle fracture and left parasymphyseal fracture.

The selected patients were categorized into three groups, with 10 patients in each group, according to the type of hardware used for fracture fixation, as follows: group A included patients who were treated with single 2.0-mm locking miniplates, group B included patients who were treated with heavy non-locking 2.3-mm plates, and group C included patients who were treated with the single lag screw technique. In the process of allocating patients to the different groups, gender, medical histories, smoking habits, and the type and location of the fractures were matched, with the exception of a predominance of right angle fractures in group C ( Table 1 ). All patients received intravenous antibiotics from the time of admission until discharge, followed by a 5- to 7-day course of oral antibiotics.

Table 1
Demographic preoperative findings for patients with a mandibular angle fracture.
Characteristic Group A Group B Group C P -value
Age, years, mean ± SD 26.1 ± 2.34 26.3 ± 2.44 26 ± 2.64 1.000
Gender (%) 1.000
Male 70% ( n = 7) 70% ( n = 7) 80% ( n = 8)
Female 30% ( n = 3) 30% ( n = 3) 20% ( n = 2)
Medical history Free Free Free
Smoking (%) 40% ( n = 4) 30% ( n = 3) 40% ( n = 4) 1.000
Injury to admission interval, days, mean (range) 3.6 (0–15) 3.5 (0–20) 3.4 (0–15) 1.000
Injury to surgery interval, days, mean (range) 9.8 (7–22) 9.8 (7–27) 10.4 (7–22) 1.000
Mechanism of injury (%) 1.000
Motor accident 60% ( n = 6) 60% ( n = 6) 60% ( n = 6)
Assault 10% ( n = 1) 20% ( n = 2) 10% ( n = 1)
Fall 30% ( n = 3) 20% ( n = 2) 30% ( n = 3)
Signs and symptoms (%) 1.000
Swelling 100% 100% 100%
Pain 100% 100% 100%
Haematoma 10% ( n = 1) 20% ( n = 2) 10% ( n = 1)
Malocclusion 100% 100% 100%
Displacement 100% 100% 100%
Preoperative inter-incisal opening 10–20 mm 14–22 mm 10–21 mm 1.000
Numbness (%) 10% ( n = 1) 10% ( n = 1) 0% ( n = 0)
Soft tissue injury (%) 0.286
Intraoral 100% 100% 100%
Extraoral 30% ( n = 3) 10% ( n = 1) 0% ( n = 0)
Loss of consciousness 20% ( n = 2) 10% ( n = 1) 10% ( n = 1)
Side of angle fracture (%) 0.249
Right side 30% ( n = 3) 20% ( n = 2) 60% ( n = 6)
Left side 70% ( n = 7) 80% ( n = 8) 40% ( n = 4)
Degree of displacement (%) 0.917
Mild 30% ( n = 3) 40% ( n = 4) 50% ( n = 5)
Moderate 40% ( n = 4) 30% ( n = 3) 30% ( n = 3)
Severe 30 ( n = 4) 30% ( n = 3) 20% ( n = 2)
Concomitant mandibular fractures (%) 1.000
None 20% ( n = 2) 20% ( n = 2) 20% ( n = 2)
Symphyseal 10% ( n = 1) 10% ( n = 1) 10% ( n = 1)
Parasymphyseal 40% ( n = 4) 30% ( n = 3) 40% ( n = 4)
Body 30% ( n = 3) 30% ( n = 3) 30% ( n = 3)
Angle 0% 10% ( n = 1) 0%
Ipsilateral subcondylar (3rd line) 10% ( n = 1) 10% ( n = 1) 10% ( n = 1)
Contralateral subcondylar 0% 0% 0%
Other injuries (%) 1.000
None 80% ( n = 8) 90% ( n = 9) 90% ( n = 9)
Midface 0% 0% 0%
Orthopaedic 20% ( n = 2) 10% ( n = 1) 10% ( n = 1)

SD, standard deviation.

Surgical procedures

Under general anaesthesia, the fracture was exposed using an intraoral extended third molar incision. The third molars were not removed during the surgical interventions unless they were loose, fractured, luxated, or prevented an appropriate reduction. Arch bars with maxillomandibular fixation (MMF) were applied preoperatively in every patient, and if the occlusion was not perfect, manipulation of the fractured segments was performed after the exposure of the fracture line until proper occlusion was achieved. The MMF was secured, and reduction of the fractured segments was then performed. The lingual cortices of all study cases were also checked to ensure that they were firmly approximated; this was done by dissecting the tissues below the inferior border of the mandible in the area of the fracture to allow their direct exposure and ensure their accurate reductions, particularly in cases of concomitant fractures.

In group A, medium-sized 2.0-mm locking miniplates (AO/ASIF Arbeitsgemeinschaft für Osteosynthese Fragen; Synthes Maxillofacial, Paoli, PA, USA) with threaded holes were adapted along the inferior border of the mandible and secured with 2.0-mm locking self-tapping screws with threaded heads. The lengths of the screws ranged between 10 and 18 mm and allowed for the bicortical fixation of the basal bone. The bicortical screws provided sufficient rigidity to the fragments to prevent interfragmentary mobility during active use of the mandible and to overcome the biomechanical forces in the mandibular angle, which tend to bend and torque the angle and may lead to pseudarthrosis in what is considered the ‘lever’ area. The locking miniplates had locking screws and non-locking screws that could be inserted obliquely such that the fracture site could be penetrated from cortex to cortex. The plate was contoured to match the anatomy of the angular region, and at least two locking screws were inserted on either side of the fracture. Accurate adaptation of the locking plate was not required because the plate stability was not dependent on plate-to-bone contact. Care was taken to place the screws inferior to the roots and the neurovascular bundle ( Fig. 3 ).

Jan 17, 2018 | Posted by in Oral and Maxillofacial Surgery | Comments Off on Clinical outcomes of three different types of hardware for the treatment of mandibular angle fractures: a comparative retrospective study
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