Mandibular fractures in children long term results☆

1. Introduction 

Pediatric bone fracture is a particular pathology because it occurs on a rapidly growing bone. In child face, the most common sites of fracture are the nasal bones and the mandible, which is the site of dental buds development. The management of mandibular fractures in children continues to be a subject of many debates because of its effect on mandibular growth and on temporomandibular joint (TMJ) mobility. Usually, pediatric mandibular and alveolar fractures are managed according to the same basic principles applied to adult fractures. Some authors advocated for conservative approach only in maxillofacial trauma in pediatric age group [1]. However, there are specific aspects related to the pediatric dentition and to anatomical differences. For instance, the maxilla and mandible of the child are usually full of unerupted teeth or there is a mixed dentition. This produces a more stable structure requiring greater force to cause a fracture and makes fixation more difficult [2]. Some reported that a shorter period of maxillomandibular fixation was needed for children [3] but results of long term follow-up after such fractures have rarely been reported. The purpose of this retrospective study was to determine prognosis factors that might interfere with therapeutic procedures and long term results.

2. Material and methods 

The charts of all pediatric mandibular fractures patients in our department over a 7 years period (from March 1994 to January 2001) were retrospectively reviewed. Nineteen patients under 18 with 30 fractures of the mandible were studied. Fractures were assessed by physical examination and documented radiographically. The data studied were age, etiology, anatomic site of fracture, treatment, short term and long term complications. All patients were monthly followed up for 6 months and clinically reviewed every year. They were all reexamined for this study. TMJ mobility, maximal mouth opening, occlusion were recorded.

Patients were divided into three groups, according to the development of dentition, group A1 (from 1.5 to 5-years-old) and group A2 (from 6 to 11 years) and group B (from 12 to 18 years). From 12 years, canines and second molars finish setting up and the biomechanic of the face acquire a real stability. The age and sex distribution of the population appears on Fig. 1.

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Fig. 1. Age and sex distribution of our studied population.

3. Results 

Our series included 19 patients (from 1.5 to 18-years-old) with 30 fractures treated in our department from March 1994 to January 2001. The mean age of the population was 10±8 years. There were 12 boys and 7 girls; M/F=1.7: 1. The mean follow-up period was of 28±6 months. Causes are summarised on Fig. 2.

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Fig. 2. Causes of mandibular fractures in this series (TA, traffic road accidents).

Six patients were less than 11 years (i.e. two in group A1 and four in group A2), 13 were 12–18-years-old (i.e. group B). The peak incidence was at 12±5 years with few cases (16%) occurring under 10 years.

In group A1, two children with deciduous dentition sustained three fractures of the subcondylar area secondary to traffic accident (children being passenger in car). Associated injuries were severe (cervical spine injury, as shown on Fig. 4). All fractures were treated by physiotherapy only.

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Fig. 4. Profil cephalogram X-rays showing the subcondylar fracture (white arrow) and the anterior luxation of the atlas (black arrow) in a child victim of a traffic road accident (passenger in a safety seat with safety belt).

In group A2, four children in mixed dentition presented seven fractures. The sex ratio was M/F=1:1. The most common cause of mandibular fractures in group A2 was bicycle falls (40%) and common falls (20%). Familial violence were noted in one case. There were no fracture of the condyle. Most fractures were parasymphiseal, and angular (Fig. 3). Multiple fractures represented only 40% in this group. One patient presented three sites of fractures. Associated injuries concerned only one child (dental traumatism). Two children with subcondylar fractures were treated by physiotherapy only. In other cases, rigid maxillomandibular fixation with open or closed reduction was performed.

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Fig. 3. Anatomic distribution of mandibular fractures in group A (n, number of children with this fracture location on this side of the mandible).

In group B, 13 children presented 20 fractures. The sex ratio was M/F=2:1. The causes of the fractures varied according to the age. Traffic accidents represented 61% of the etiologies of the mandibular fractures (children being pedestrian or passenger). Multiple fractures were more common in this group (53%) than in group A1 and A2 (40%). The most common sites were subcondylar, parasymphiseal and angular (Fig. 5). Associated injuries occurred in 69% of the patients, commonly fractures of extremities and dental traumatism. Children presenting condylar and subcondylar fractures were treated by physiotherapy. In other cases, rigid maxillomandibular fixation with open or closed reduction was used. When present, orthodontic arch bar were used for closed reduction (Fig. 6). Treatment protocol according to the sites of fractures as well as the age of children are shown on Table 1, Table 2.

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Fig. 5. Anatomic distribution of mandibular fractures in group B (n: number of children with this fracture location on this side of the mandible).

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Fig. 6. Left lateral oblique view X rays showing parasymphyseal fracture (white arrow) and orthodontic arch bar (white arrowhead) that was used for closed reduction.

Table 1. Treatment according to the site of fractures (OR, open reduction; MMF, maxillomandibular fixation; PT, physiotherapy)

	Sites	Closed reduction (%)	MMF (%)	OR+MMF (%)	PT (%)
	Body	12	24	64	–
	Condyle	–	25	–	75
	Body+Condyle	–	–	100	–

Table 2. Treatment according to the age of children (OR, open reduction; MMF, maxillomandibular fixation; PT, physiotherapy)

	Age (years)	Closed reduction (%)	MMF (%)	OR+MMF (%)	PT (%)
	0–11	–	50	17	33
	12–18	8	16	46	30

No infection, no retarded facial growth were recorded. Maximal mouth opening was not reduced in patients but a partial unilateral ankylosis of the condyle was seen in one patient of group B. Two children presented a minimal deviation of the mandible (one in group A1, one in group B). One child in group B presented a TMJ syndrome. Compared with the sequels of the associated injuries (cervical spine injury, fractures of the extremities, of the knees), complications of the mandibular fractures appear to be minor.

Maximal mouth opening was normal in all children when compared to children of same age and sex. Malocclusion was present in 3 children of group B only.

4. Discussion 

In children, cranial traumatism are more frequent than facial traumatism because of the relative importance of the cranial skeleton volume compared with the facial bones. Elasticity of young bones is a factor of protection. The lack of pneumatization, a high cancellous-to-cortical bone ratio and mixed dentition contribute to elasticity and stability of the mandible. Thus, the force required to produce a fracture in children is greater than in adults. Thus, concomitant intracranial and cervical spine injuries are more frequently associated to maxillofacial trauma in children [2]. Due to the facial bones of the child heal much more rapidly than those of adult, stabilisation is required at an earlier time, usually between 5 and 10 days [2]. From these principles, it can be stated that children are a unique subpopulation of maxillofacial fractures patients.

Mandible is a membranous bone which growth is done by two mechanisms: cartilaginous tissue which undergo of a secondary calcification (condylar growth centre for instance) and forces developed by facial muscles like masticator muscles [4]. Progressively the growth of the mandible depends on dental occlusion obtained by the traction realised by muscles.

This study confirms findings from earlier studies that mandibular fractures are rare in children [5], [6]: over a 7 years period, only 19 children have been treated in our department for these fractures, representing less than 10% of the activity for pediatric maxillofacial traumatism during the same period.

In our study, the incidence of mandibular fractures increased with the age of the group: only six patients were less than 12 years and the peak incidence was around 17 years of age. Our population is relatively older than in other studies [7].

In fact, the lifestyle of children changes after 12 years because of introduction of sports and outdoors activities. For patients between 16 and 18, the causes of mandibular fractures are the same than in adults. Mandibular fractures should be prevented in children by wearing protections and helmet adapted to the age and the outdoor activities.

Traffic accidents are the main cause of mandibular fractures in children in various publications [8], [9], [10]. In our study, we found a majority of traffic accidents (61%) being the mechanism of the mandibular fractures in group B but only in few cases in group A1 and A2 (16%). Actually, for a child from 2 to 12 years, the first cause of mandibular fractures are the falls (bicycle falls in 40% and common falls in 20%). It seems that young children are more protected in cars than on their bicycles. Seat belts, safety seats are more present in cars for young children security but safety helmets with chin protections are still neglected in bicycle use. In our study, children did not wear these protections. Bicycle falls were the cause of multiple fractures in 77% of the cases.

For teenagers, traffic accidents are responsible for the most part of mandibular fractures. Associated injuries go with 20% of the mandibular fractures before 12 years of age as compared with 69% before 18 years old. In group B, we found a majority of fractures of the extremities. Among children who presented associated injuries, 77% were victims of traffic accidents.

Treatment of mandibular fractures in children is usually conservative: physiotherapy in condylar fractures and often maxillomandibular fixation in other cases. Various authors agree that a short period of immobilisation (2 weeks) and an early mobilisation are necessary [11], [12], [13]. Indications of surgical treatment are limited. This attitude is guided by prevention of ankylosis of the TMJ and of damage in developing teeth.

In children, mandibular fractures have few complications [14], [15]. In our study, among 19 children, five only presented complications. A boy victim of a traffic accident presented a partial ankylosis of the TMJ. A girl of the group B, who underwent maxillomandibular fixation during 3 weeks and open reduction presented a TMJ disorder few months later. Postoperative malocclusions (lateral deviation of the interincisive line, without any functional perturbations and with spontaneous partial resolution) were recognised in three patients with alveolar bone fractures. There is a growth centre in the condyle, it was then expected that condylar fractures in children may cause abnormal growth and development of the mandible. It did not happened in our study. Mandibular body fractures rarely influenced the growth of the bone if treatment is performed rapidly and correctly. TMJ disorders or partial ankylosis were the main complications in this study. In these cases, traffic accident was the mechanism, associated injuries were presents and the fracture was localised in a subcondylar area.

Some stated that the degree of precision required in a child is not quite as great as in an adult, since the replacement of deciduous teeth by permanent teeth and the adaptive potential of alveolar bone can bring about a various degree of self correction. In our experiment, it may be true if a correct dental occlusion is achieved postoperatively. We should remain modest, the high osteogenic potential of the pediatric mandible is responsible for a low complication rate.

Our mean time of follow-up is 28 months. This is the major limitation of this study. This makes impossible to draw conclusions about alterations in facial growth. Moreover, a multicentric study only would allow statistical tests.

Miniplates was recommended for pediatric maxillofacial fractures for a long time [16], [17]. This technique did not influenced the degree of complications [18], [19], [20]. Resorbable bone fixation plates are now used in craniosynostosis surgery [21] as well as in cranio-maxillofacial trauma [22] with apparently good results but long time survey remain essential to assure the persistence of the results. This new material could avoid the removing of the plates and would decrease the number of general anesthesia needed.

Other authors have encouraged the use of three dimensional CT reconstruction in order to evaluate facial fractures in children as well as adults [23]. We don't have access to that technology in emergency in our hospital but it could be of great interest when facial fractures are associated to cranial fractures in order to perform the surgical planning.

5. Conclusion 

Treatment of mandibular fractures in children is usually less aggressive than in adults. Traffic accidents are at risk of complication because of the mechanism of the traumatism usually brings associated injuries. In these cases, surgical treatment is frequently performed. Bicycle falls are underestimated. Facial protection must be worn by younger kids to prevent mandibular fractures. We recommend to consider the mechanism of mandibular fractures in children as a major prognosis factor.