Both the incidence and etiology of facial fractures in children evolve with age.
Understanding the stage of dentition of the patient can have significant implications in the treatment management.
The development of the alveolus is tooth dependent and the absence of developing teeth will significantly impact the growth and development of the maxilla and mandible, thus impacting treatment.
The sphenoid and frontal sinuses are not present at birth.
The paranasal sinuses all develop at different rates and times.
Pediatric zygomatic fractures are rare.
The orbit reaches bony maturity at approximately age 7 and can present with entrapment which is a surgically urgent scenario requiring immediate attention to prevent long-term sequelae.
1.1 Background/Introduction
A discussion of pediatric facial fractures requires a solid foundation in understanding the development of the facial skeleton. As the facial skeleton develops it will be prone to different fracture patterns depending upon the direction of the forces applied. This chapter discusses the development of the following facial skeleton subunits: the developing dentition, mandible, maxilla and paranasal sinuses, zygoma, and orbits.
1.2 Epidemiology of Facial Fractures in Children
As children develop, both the patterns of fracture and mechanisms of injury change. The incidence of facial fractures is small, but increases with age. One retrospective single-center study over 5 years indicated that children of ages 0–5 comprised 20.2% of facial fractures, ages 6–11 totaled 32.8%, and the largest group was 12–18-year-olds which accounted for almost half of the pediatric facial fractures (47%) [1]. The mechanisms of injury evolved with the age group as well. Young children aged 0–5 years were injured with activities of daily living, while the 6–11-year-old group were most consistently injured from motor vehicle collisions, play, and bicycle accidents. As anticipated, the 12–18-year-old group had violence and sports as the leading cause of injuries [1]. This distribution of fractures with increased incidence with age has been confirmed in multiple studies [2–4]. The reason that fractures increase can be explained with several arguments. First, as children age, they become more engaged in activities that have a higher risk for fracture. A youth playing hockey or even basketball is much more likely to fracture his/her mandible than a child playing with building blocks. Second, a young child’s bones have increased elasticity due to a larger proportion of organic to inorganic components of bone [5, 6]. Thus the younger the patient, the more likely the bones are to bend and not break—with no resultant fracture or greenstick fractures. Finally, as the facial skeleton develops, there are inherent weak points that act as fracture points with various applied forces. Some examples of this are third molars leading to mandibular angle fractures or development of the frontal sinus with increased frontal bone fractures [7]. Thus, understanding the development of the facial skeleton is paramount, and it aids the practitioner in developing and executing a treatment plan.
1.3 Developing Dentition
The maxilla and mandible can be viewed as the housing of tooth buds. As early as 8 weeks in utero, the dental lamina in both the maxilla and mandible can be seen to develop swellings that will continue on to form the enamel organs and eventually teeth [8]. In general, a tooth develops beginning at the crown and progressing inferiorly with the apex of the root being the last area to develop. Teeth also develop from the midline first, extending to the posterior molars as the patient continues to grow and develop. Thus, the central incisors (mandibular) are generally the first teeth to erupt at around 6–7 months of age. The lateral incisors generally follow the central incisors and this process continues posteriorly until the second primary molars are the final teeth to erupt at approximately 2–3 years of age. Fractures of the mandible or maxilla in the primary dentition phase are rare, but can pose significant challenges with bulbous primary crowns creating difficulty with attaining intermaxillary fixation and an alveolar structure that is rife with tooth buds which can create difficulties with both reduction and (if necessary) fixation.
The first permanent teeth to erupt are typically the first permanent molar at the age of 6—thus termed the “six-year molar.” This then begins the mixed dentition phase. The mixed dentition phase continues until the 12 or 13th year of life when all of the permanent dentition has erupted. However, a patient that is in the early permanent phase of dentition continues to have key differences, including open root apices, which can alter both treatment and prognosis when dealing with dentoalveolar trauma.
1.4 Alveolar Bone
The alveolar bone in the maxilla and mandible develops in conjunction with tooth development and eruption. By definition, this bone is the housing structure for the teeth. Thus, in patients with anodontia or oligodontia (such as ectodermal dysplasia), the alveolar bone remains undeveloped. Alveolar bone develops by intramembranous ossification and is comprised of three layers in cross section. There is buccal/labial and lingual/palatal cortical bone which is dense in nature and has a periosteal layer in direct contact. Between the two cortical plates exists cancellous bone with trabecular patterns. Within these layers lie the tooth sockets, which are comprised of bundle bone. This alveolar bone is constantly being remodeled due to the constant stresses placed on this bone with normal function.
1.5 Mandible
The mandible is made up of two rami, the mandibular body (including the symphysis) and the alveolar process. It develops from the first pharyngeal arch where its precursor, Meckel’s cartilage, aids in the development of the mandible. As the mandible develops it evolves from birth to maturity, and the gonial angle decreases as the ramus increases and thus increases the mandible’s vertical dimension from condyle to gonial angle. The mandible continues to remodel based on the stresses applied and the development of the dentition and associated alveolus. It is important to note that this is the final facial bone to reach maturity. Therefore, trauma to the mandible can result in asymmetry if growth is affected as a result of the trauma. This is rare, but when it occurs it is most often due to condylar trauma that affects the ipsilateral growth.
1.6 Maxilla
Developmentally, the maxilla is comprised of the premaxilla (primary palate) and the two palatal shelves (secondary palate). Overall growth is inferiorly and anteriorly. Like the mandible, the overall growth is greatly impacted by the developing dentition as evidenced by patients with oligodontia or anodontia where the maxilla remains hypoplastic and looks more severe due to a lack of alveolar bone. The maxilla reaches skeletal maturity in late adolescence. It is extraordinarily rare to have a growth disturbance as a result of maxillary trauma. More often, a maxillary cant in the absence of pathology is a dental compensation for an asymmetry spawned by a unilateral mandibular growth disturbance.
1.7 Paranasal Sinuses
The paranasal sinuses comprise the maxillary, ethmoid, sphenoid, and frontal sinuses. Each differs in regard to its overall growth and development. The sphenoid and frontal sinuses are not present at birth, while both the maxillary and ethmoid sinuses are present but not radiographically evident. The earliest radiologic evidence of each sinus is as follows:
Maxillary sinus—4–5 months of age
Ethmoid sinus—age 12 months
Sphenoid sinus—4 years of age
Frontal sinus—6 years of age
Each of the sinuses continues to develop into the teenage years, with the ethmoid sinuses completing growth in the early teen years, the maxillary and sphenoid sinuses around age 15, and the frontal sinus completing its growth in the late teenage years. This can have an effect on fracture patterns as the frequency of midface fractures does increase with the development of the paranasal sinuses [9].
1.8 Zygoma
The malar bone grows into late adolescence and approximates that of the nasomaxillary complex. The malar bone moves posteriorly relative to the nasomaxillary complex. It also grows laterally along its proximal aspect including the arch. This is accomplished by resorption of bone on the medial aspect with deposition of bone on the lateral surface. Trauma to this region is often a result of activities that are not engaged in until late adolescence. As such, malar fractures are rare prior to the teenage years when sporting accidents, MVC, and interpersonal violence are more common and thus increase the chance of sustaining a zygomaticomaxillary complex (or tripod) fracture [10].
1.9 Orbits
The bony orbit is comprised of several bones including the lacrimal, sphenoid, frontal, zygomatic, palatine, and ethmoid bones. Orbital growth is complete around the age of 7. Orbital floor fractures begin to surface in conjunction with the development of the maxillary sinus. Of utmost importance is the recognition that pediatric populations are more likely to have greenstick fractures and this can result in inferior rectus entrapment and a “white-eye” blowout fracture that is a surgically urgent case to avoid long-term sequelae associated with fibrosis of the inferior rectus.
1.10 Summary/Conclusion
Understanding the growth and development of the facial bones helps to illuminate the fracture patterns incurred based on age and mechanism of injury. In the growing patient, it is important to remember that it is not only important to understand how to treat the fractures, but also crucial to follow the growing patient to ensure that there are no sequelae that require attention and/or treatment. The following chapters are meant to act as a guide in this decision-making process. It is our aim to increase the practitioner’s ability to manage pediatric fractures to avoid long-term sequelae (where able) and to address the complications that can arise from the trauma and its treatment.