Outcome of Management of Mandibular Sub condylar Fractures Based on Classification System Using Cone-Beam Computed Tomography

Abstract

Purpose

The purpose of this study is to determine the amount of ramal height shortening and degree of displacement of sub condylar fracture that should be considered for effective management of mandibular sub condylar fractures using cone-beam computed tomography.

Patients and Methods

A prospective study of forty-two patients, who presented with unilateral sub condylar fracture was done. All patients were classified into Class I, II and III based on the degree of displacement of fractured segment and amount of ramal height shortening measured using cone-beam computed tomography. The treatment protocol was closed reduction and maxillomandibular fixation for Class I patients and open reduction and internal fixation for Class II and III patients. Outcomes of treatment were measured postoperatively 2 weeks, 1 and 3 months clinically. The variables, such as mouth opening, lateral and protrusive movements, deviation, pain and occlusion were studied.

Results

Among forty-two patients, twenty had Class I fractures, twelve had Class II fractures and ten had Class III fractures. Overall, no statistically significant differences were found between Class I and Class II groups in terms of functional outcomes and there were statistically significant differences between Class I and III groups. Class I fractures can be considered for closed method and open reduction is recommended for Class II and III fractures. The sample was composed of 42 patients grouped as follows: Class I (n = 20), Class II (n = 12), and Class III (n = 10) for treatment of sub condylar fractures. There were no significant differences between the three groups for the study variables at baseline, except for mouth opening and pain. There was significant difference in mouth opening between Class I and III cases (p 0.001) and insignificant difference in mouth opening in Class I and II cases (p 0.98). Persistent pain was elicited more in surgical Class II and III (n = 5) than non-surgical cases Class I (n = 0) on 3 months follow-up.

Conclusion

The study emphasises on use of three-dimensional diagnostic modality like cone-beam computed tomography for accurately classifying sub condylar fractures. The results favour closed reduction for mildly displaced Class I cases and surgical management of significantly displaced Class III fractures. The need for open reduction for Class II patients classified using CBCT is negligible assessing risks associated with surgical procedure which is contradictory to our protocol which requires a further comparative evaluation among Class II group.

Introduction

Mandibular condyle fractures are uncommon, accounting for 17.5–52% of all mandibular fractures [1]. The main causes of this type of fracture are road traffic accidents (approximately 50%), falls (30%) and inter personal violence (20%) [2]. This region is clinically significant because of the presence of important anatomical structures like the temporomandibular joint, vessels like maxillary artery and nerves like facial and auriculotemporal nerve and parotid gland, which may be functionally impaired by the fracture itself or by the surgical treatment with advances in diagnostic and surgical armamentarium, understanding of anatomy and exploration in the field of internal fixation, has made surgical management of this complex fracture feasible. But, the real challenge for a surgeon is to clearly demarcate between surgical and non-surgical cases. Although a giant leap from conventional radiography to CBCT has occurred in the field of craniofacial diagnosis over the years, surgeons still adhere to two-dimensional radiographs for assessing and classifying fracture of most complex three-dimensional region TMJ. The study emphasises on a novel classification using advanced diagnostic tool, such as CBCT for sub condylar fractures.

CBCT and 3D CT images provide the precise orientation and angle of the fractured sub condyle, which is important to determine when deciphering what treatment is indicated. Kaeppler et al. [3] did a study on mandibular fractures and stated that CBCT is superior to panoramic radiography as condylar, coronoid fractures and the anterior part of the mandible were more difficult to detect due to superimposition in a panoramic view. The purpose of this study is to reveal a classification system for management of unilateral sub condylar fracture by quantifying the amount of ramal height shortening and degree of displacement of fractured condylar segment using CBCT.

Materials and Methods

Forty-two patients reported to the department of Oral and Maxillofacial Surgery with sub condylar fracture (as classified by Lindahl [4] and illustrated by Ellis et al. [5]) between Jan 2017 and June 2018 were selected for the study after obtaining informed written consent. The study design and method of randomization were approved by the Ethics Committee of Government Dental College, Kottayam.

Inclusion criteria
1. The patient is over the age of 18 years
2. Unilateral sub condylar fracture as classified by Lindhal and illustrated by Ellis et al.
3. Teeth are present to assess occlusion
4. Patient’s written informed consent

Exclusion criteria
1. Currently existing temporomandibular disorders
2. Severe pre-traumatic dysfunction
3. Other associated fractures

Procedure

CBCT was performed on patients who had a unilateral sub condylar fracture that had been diagnosed clinically and confirmed radiographically with a panoramic radiograph. On the basis of cone-beam computed tomography (CBCT) images, the unilateral mandibular sub condylar fractures were categorized into 3 classes as described by Bhagol et al. [6]:

1. Class I (minimally displaced)-fracture with ramal height shortening, < 2 mm and/or degree of fracture displacement; < 10°.

2. Class II (moderately displaced) fracture with ramal height shortening; 2–15 mm and/or degree of fracture displacement; 10°–35°.

3. Class III (severely displaced)-fracture with ramal height shortening; 15 mm and/or degree of fracture displacement > 35°.

The greater value among these two radiographic parameters was used to determine the class of the fracture.

The following method was used to measure the degree of displacement and amount of ramal height shortening of the fracture in the cone-beam computed tomography (CBCT) image:

According to Ellis and Throckmorton, the measurement of degree of displacement of fractured sub condylar segment and the amount of ramal height shortening can be done using imaginary lines drawn on the panoramic radiograph and reverse Towne’s view. Similarly, the lines were measured using cone-beam computed tomography rather than conventional plain radiograph. The accurate digital linear measurements were recorded.

Measurement of degree of displacement of the fractured sub condylar segment (Fig. 1):

Fig. 1.

Measurement of angulation of displaced fracture using CBCT. R: Right, L: Left

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 angles on the non-fractured and the fractured sides were used as a measure of coronal displacement.

Measurement of ramal height shortening (Figs. 2, 3).

Fig. 2.

Reference line drawn from gonion to gonion using CBCT. Go: Gonion (Left), Go’: Gonion (Right)

Fig. 3.

Calculation of distance between the most superior point on the condyle and reference line. A: Anterior, P: Posterior, Go’: Gonion (Right)

A reference line was drawn through both gonial angles. The 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 difference in ramal length (loss of ramal height).

Based on the above-mentioned classification, a treatment principle was formulated as:

1. Closed treatment (Maxillo-mandibular fixation) for Class I fractures.

2. Open treatment for Class II fractures.

3. Open treatment for Class III fractures.

Closed reduction was done with Erich arch bar and no. 26 gauge arch wire were used for maxillomandibular fixation. Open reduction and internal fixation were done via retromandibular approach using titanium plates and screws. A follow-up examination was performed at 2 weeks, 1 month and 3 months postoperatively after the trauma and included assessment of the following clinical parameters:

1. Range of motion of the injured joint together with the contra lateral joint as given by the mouth opening (maximum interincisal distance) and by the extent of lateral excursion and of protrusion was measured using ruler.

2. Deviation or deflection during mouth opening was assessed clinically.

3. Pain assessment was done with a visual analogue scale from 0 (no pain) to 10 (strongest pain or discomfort).

4. Occlusion was assessed clinically comparing with pre-traumatic status (1-identical to pre-traumatic, 2-slight difference, 3-functional malocclusion, 4-requires occlusal adjustment, 5-gross malocclusions).

5. Motor nerve function was observed clinically using a grading scale (1-no deficit, 2-mild weakness, 3-moderate weakness, 4-severe weakness, 5-absence of function).

6. Sensory perception was elicited clinically by various accepted clinical tests (1-full sensation, 2-can distinguish cotton/wood/pin, 3-not full but not distracting, 4-can discern pressure, 5-profoundly numb).

The accuracy of fracture reduction and the stability of fixation were assessed on the basis of panoramic radiograph obtained preoperatively, 2 weeks, 1 month and 3 months postoperatively.

Statistical Analysis

An ethical clearance was obtained before starting the study from the Institutional Ethics Committee, Government Dental College, Kottayam. A written informed consent and willingness to participate was obtained from all patients participating in the study. The data were analysed using SPSS software. Chi-square test was used for qualitative data and one-way ANOVA for quantitative data.

Results

47.6% of patients were in the age group of 19–30 years. Among 42 patients, 34 was male and 8 were female. Road traffic accidents led to majority of fractures that is 40 patients. Among 42 patients, 20 had Class I fractures (47.61), 12 had Class II fractures (28.57) and 10 had Class III fractures (23.80).

Clinical Outcomes

All groups of patients were evaluated pre-treatment and post treatment (at 2 weeks, 1 month and 3 months).

Range of Motion

The range of pre-operative mouth opening measured across the groups was in the range of 14–34 mm. The data were tested for significance using one-way ANOVA for difference in post treatment mouth opening among three groups. Class III patients had better recovery in first 3 months postoperatively than the other patients. There was a statistically significant difference in value of mouth opening measured post treatment, at 2 weeks (p 0.026; < 0.05), 1 month (p 0.002; < 0.05) and 3 months (p 0.001; < 0.05) among all groups. Using Post hoc Tukey’s analysis, Class I and II patients showed no significant difference in mouth opening on comparison (p 0.981) (Table 1).

Table 1.

Comparison of mouth opening (mm) in three Classes

Mouth opening (mm)	Pre-op (MO) Mean ± SD	Post-op 2 weeks (MO1) Mean ± SD	Post-op 1 month (MO1) Mean ± SD	Post-op 3 months (MO1) Mean ± SD
Class I	24.55 ± 5.59	25.85 ± 5.52	28.85 ± 4.84	31.31 ± 3.86
Class II	19.38 ± 2.87	22.15 ± 3.82	26.69 ± 3.70	31.77 ± 3.67
Class III	18.30 ± 3.19	31.40 ± 3.19	34.80 ± 3.19	38.90 ± 3.19

Significantly, there was improvement in range of protrusive movement in all three groups at post-op 2 weeks (p 0.027; < 0.5), 1 month (p 0.018; < 0.5) and 3 months (p 0.037; < 0.5) (Table 2).

Table 2.

Comparison of protrusion (mm) in three Classes

Protrusion (mm)	Pre-op (PO) Mean ± SD	Post-op 2 weeks (PO1) Mean ± SD	Post-op 1 month (PO2) Mean ± SD	Post-op 3 months (PO3) Mean ± SD
Class I	3.5 ± 3.0	4.0 ± 3.0	4.0 ± 3.5	5.5 ± 3.5
Class II	4.0 ± 3.9	5.0 ± 3.5	5.5 ± 4	5.5 ± 3.6
Class III	4.0 ± 0.62	4.35 ± 0.47	4.8 ± 0.42	5.7 ± 0.67

Lateral excursion was measured as the sum of extreme right and left lateral excursive movement of mandible. The lateral excursive movements ameliorated with time (p 0.004; < 0.05). There was statistically significant difference between lateral excursive movements when surgical (Class II and III) and non-surgical group (Class I). There was no statistically significant difference between Class II and III patients’ post treatment at 2 weeks and 1 month (p 0.007; > 0.05). This may be attributed to the fact that both the groups were managed surgically (Table 3).

Table 3.

Comparison of lateral excursion (mm) in three classes

Lateral excursion (mm)	Pre-op (LO) Mean ± SD	Post-op 2 weeks (LO1) Mean ± SD	Post-op 1 month (LO2) Mean ± SD	Post-op 3 months (LO3) Mean ± SD
Class I	12.0 ± 2.5	13.0 ± 2.3	13.0 ± 2.0	15.0 ± 2.0
Class II	14.17 ± 2.66	15.17 ± 2.70	16.38 ± 2.36	17.42 ± 1.45
Class III	11.45 ± 1.44	14.70 ± 1.63	16.80 ± 2.18	19.35 ± 1.09

Other Parameters

Deviation on mouth opening is a characteristic finding in unilateral condylar fractures which usually results in ipsilateral premature contact and a contralateral open bite of the posterior teeth. All patients had deviation on mouth opening in Class II and III groups preoperatively. At 2 weeks post treatment, 50% patients in Class III group had deviation on mouth opening which reduced to 30% after 3 months. 25% of Class II patients had mandibular deviation at 2 weeks which remained after 3 months. In 75% of Class I patients with deviation on mouth opening prior to treatment, only 20% had this after 3 month follow-up. The recovery was statistically significant (p 0.002; < 0.05) for observed values among groups using Chi-square analysis.

Pain was an important clinical parameter because our study compared surgical and non-surgical groups. It was measured using visual analogue scale (VAS) taking into account of the ordinal quantitative values. In 70% of Class I patients, mild pain was elicited on 2 weeks follow-up which nullified by the end of 3 months. Mild pain persisted in 3% of Class II patients at the three-month post-operative follow-up. 10% of Class III patients had moderate pain after 3 months. Pain was elicited more in surgical cases. Intensity of pain was relatively more in surgical cases (Fig. 4).

Fig. 4.

Intensity of pain in Class I, II and III patients over a period of 3 months. Class I (minimally displaced)-fracture with ramal height shortening; < 2 mm and/or degree of fracture displacement; < 10° (Closed reduction). Class II (moderately displaced) fracture with ramal height shortening; 2–15 mm and/or degree of fracture displacement; 10°–35° (Open reduction). Class III (severely displaced)-fracture with ramal height shortening; 15 mm and/or degree of fracture displacement > 35° (Open reduction). Blue: percentage of patients with pain post treatment at 2 weeks in each treatment category. Orange: percentage of patients with pain post treatment at 1 month in each treatment category. Grey: percentage of patients with pain post treatment at 3 months in each treatment category

Hence, from the patient’s perspective, sub condylar fractures managed non-surgically were considered as a superior treatment option. The satisfaction and compliance achieved with conservative management inarguably made the patient prefer it over surgical treatment in case of mildly displaced fractures retrospectively.

Occlusion was graded using an ordinal scale clinically, by observing the extent of deviation from normal occlusion that was present post treatment. In Class I patients, the slight occlusal disturbance was present in 25% of patients three months post treatment which was corrected using guiding elastics. In Class II and III patients, preoperatively, 50% and 60% of patients had functional deviation of occlusion, respectively. After surgical management, near to pre-treatment occlusion was attained which remained stable after 3 months postoperatively. Minor occlusal disturbances in Class II and III patients was rectified using guiding elastics for 2 weeks. MMF wasn’t required for cases treated with ORIF postoperatively.

Regarding surgical complications, 47.61% of patients categorized as Class II and III underwent surgical management via retromandibular approach. One patient (Class III) had transient facial nerve weakness which reduced gradually after 6 months by medical management. One out of 22 patients developed sialocele as a surgical complication which was managed with serial aspiration, isotonic saline injection and pressure dressings.

Discussion

Even though globally, several studies have been conducted on mandibular sub condylar fracture, still diagnosis, classification and management remain controversial. Literature shows that shortening of ramal height and angulation of fractured condylar segment are the two definitive quantitative measures to be considered for evaluating these fractures. The classifications were based on the techniques, materials and scientific reports available in that particular era. A paradigm shift has evolved with the development of improved diagnostic tools like cone-beam computed tomography and refinement of treatment strategies. The objectives of treatment of mandibular sub condylar fractures are to re-establish pre-anatomic position, occlusion and masticatory function with minimal disability and complications.

According to Bhagol et al., sub condylar fractures were classified on the basis of Towne’s and panoramic radiograph into 3 classes: Class1 (minimally displaced) fracture with ramal height shortening, 2 mm and/or degree of fracture displacement, < 10°, Class 2 (moderately displaced) fracture with ramal height shortening; 2–15 mm and/or degree of fracture displacement; 10°–35°, Class 3 (severely displaced) fracture with ramal height shortening > 15 mm and/or degree of fracture displacement; > 35°.

The limitations of the mentioned classification were lessened in our study that classified sub condylar fractures into Class I, II and III using cone-beam computed tomography as a diagnostic tool. CBCT has a cone-shaped beam which can obtain multiplanar images of Condyle with minimal radiation doses. Especially, in fractures with smaller comminuted bone fragments, the degree of displacement are often misdiagnosed with two-dimensional imaging techniques. CBCT images for complex sub condylar fractures can avoid the need of conventional CT which requires high radiation doses and cost.

Closed reduction was historically considered the standard treatment for mildly displaced sub condylar fractures due to fewer complications. According to Strobel et al. [7], the duration of maxillomandibular fixation (MMF) ranges from 2 to 6 weeks in order to avoid temporomandibular joint ankylosis. But in cases of severe displacement or dislocation, they prefer surgical management.

In the present study, Class I patients (47.6%) were treated with closed treatment with a period of MMF for 2 weeks. After this period of MMF, guiding elastics were used for a variable period to maintain proper occlusion and at the same time, to enable mouth opening. Class II (28.5%) and III (23.8%) patients were managed with open reduction and internal fixation by a single surgeon via retromandibular approach.

Our findings favour closed reduction for Class I cases and open reduction for Class III cases. The argumentative finding inferred from this study is that indication for open reduction for Class II patients can be avoided by weighing the risks of surgical complications. There is insignificant difference between Class I and II patients in basic functional parameter, such as mouth opening. The amount of pain and surgical complications can be lessened by considering closed reduction in Class II cases too.

The surgical complications like neurological, functional and occlusal disturbances can be avoided in patients by clearly assessing the displacement of a three-dimensional structure using CBCT. The surgeon should feel comfortable using the mentioned classification system that delineates the location and description of the sub condylar fracture in a manner that affords the understanding of the injury sustained by the patient. Once the determination has been made regarding the location and anatomic components of the injury, the surgeon can then appropriately discuss the inherent risks and benefits of open versus closed operative management with the patient and decide on a course of action.

Till date, most of the classification systems for sub condylar fracture are based on manual measurements of ramal height shortening and angulation of deviated fractured segment, traced using two-dimensional radiography which is prone to intra and inter-observer errors. This study utilises accurate digital measurements for classification which can be standardized easily, is less time-consuming and reduces human error in the first place. This also helps in analysing the three-dimensional view of complex fracture at the time of diagnosis itself, with minimal radiation exposure to patients. The controversy of open versus closed reduction persists even after having multiple classifications. One of the reasons is the lack of precision with which the fractures are placed into different classes using conventional methods which is nullified to an extent by this classification system.

In conclusion, the novel classification can guide maxillofacial surgeons to simplify the decision-making process and effectively group patients into surgical and non-surgical cases using an advanced diagnostic method. The study was conducted in a small group of patients and further multi centre studies are required on larger population to analyse the validity of this classification. Novel researches are also needed to assess other factors contributing to the systematic approach to management of sub condylar fractures. Considering the debate between open and closed treatment modalities, a prospective study may offer a consensus. A comparative study regarding open or closed treatment among Class II patients classified accurately using CBCT can be done in the future.