Pediatric facial fractures are uncommon, and fortunately, the majority can be managed with conservative measures. Rigid fixation of the pediatric facial skeleton can potentially be associated with delayed hardware issues and growth inhibition. When appropriate, resorbable fixation is most commonly used for this purpose. Titanium plates and screws are advantageous when rigid fixation is a priority because properly placed hardware that respects natural suture lines is not thought to significantly inhibit growth. Furthermore, titanium fixation may be removed following healing.
Key points
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Pediatric facial fractures do not often require internal fixation. Conservative management or closed reduction can be used for many situations.
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Internal fixation in children less than 10 years of age is complicated by the presence of reduced bone stock and permanent tooth buds.
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Nonresorbable hardware has superior mechanical properties; however, there are concerns associated with implant size, implant strength, translocation, and, less so, growth restriction.
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Resorbable hardware obviates elective removal and is a reasonable alternative to traditional titanium implants in non–load-bearing regions.
Introduction
Pediatric patients are distinct from adults. Children exhibit different facial fracture patterns; their bones are incompletely ossified; their dentition is constantly evolving; and their skeleton is actively growing. Furthermore, when considering pediatric care, the social concerns of both patients and their families may affect the timing and type of treatment rendered. Pediatric facial fractures are uncommon. Fortunately, the majority of these injuries are amenable to conservative management and do not require internal fixation. Due to ongoing growth considerations, many providers elect to avoid internal skeletal fixation in children whenever possible. Persistent plates and screws can potentially tether bony fragments and mechanically inhibit normal facial growth. It is important to recognize that hardware itself is not the sole culprit. Experiences borrowed from cleft surgery have demonstrated that there are multiple contributions to craniomaxillofacial growth restriction. Simple periosteal elevation disrupts the vascularity and the nutritional state of bone. Wound contracture and scar formation, which are part of normal healing, are well-described risk factors for subsequent bony hypoplasia. Furthermore, fractures or osteotomies can directly disrupt ossification centers. Even in the presence of these iatrogenic disturbances, growth is rarely arrested. As such, orthognathic surgery must be delayed until after adolescence to avoid skeletal relapse. It is difficult to parse out the contribution of each individual risk factor to growth restriction. This has led to uncertainty regarding the precise role that hardware fixation plays in altering pediatric craniofacial growth, with some arguing that internal fixation plays a minimal role in inhibiting normal bone formation. Regardless, within many disciplines, there is hesitancy and preference against internal fixation in pediatric patients. The goal of this article is to present the principles of pediatric rigid fixation and to discuss the merits of nonresorbable and resorbable hardware options.
Principles of rigid fixation
Fracture immobilization is required to achieve bony union. Primary bone healing occurs when precise anatomic reduction allows for direct lamellar contact. Once the defect is narrowed, osteogenic elements are then able to traverse the fracture line and restore continuity. If there is misalignment or movement across a fracture, the body will form a bony callus in an attempt to bridge and/or stabilize the bony segments ( Fig. 1 ). Excessive gaps or movement can overwhelm the body’s ability to heal secondarily and therefore increase the risk of fibrous or nonunion.
The concept of rigid fixation first originated in the orthopedic literature but was subsequently adapted for use in craniomaxillofacial surgery. Rigid fixation achieves complete immobility across a fracture such that there is no micromovement during function. In contrast, nonrigid fixation lacks sufficient strength to entirely prevent movement of bone fragments under function. Although rigid fixation is the preferred treatment strategy, the body can still achieve bony union with nonrigid fixation through secondary healing. Of note, when comparing fixation techniques, some surgeons will consider rigidity on a spectrum rather than as an all-or-none event. In this context, techniques that are better at reducing interfragmentary motion are considered to be “more rigid.” The concept of rigid versus nonrigid fixation should not to be confused with the concept of load bearing and load sharing, the latter of which are properties inherent to the hardware that is used. With load-bearing fixation (reconstruction plate), the hardware absorbs all of the external force, whereas with load-sharing fixation (miniplate), the external force is distributed between both the hardware and the underlying bone. Load-bearing fixation is always rigid; however, load-sharing fixation may be either rigid or nonrigid depending on how it is applied.
Because the mandible is subject to both muscular and occlusal forces, the principles of rigid fixation are particularly important in the management of mandibular fractures. The upper and midface are not subject to the same functional loads, and therefore fixation strength poses less of a concern in those regions. Before the advent of modern skeletal fixation, closed reduction with maxillomandibular fixation (MMF) was the mainstay of treatment of mandible fractures. When situations were not amenable to MMF, external pins were used for rigid stabilization. Intraosseous wiring was helpful for aligning and reducing the bony segments; however, this technique was only semirigid and lacked sufficient strength to be used by itself in the mandible. Despite these and other early efforts at internal fixation, the end result always lacked sufficient rigidity. MMF was therefore still required as an adjunct to immobilize the fracture and eliminate masticatory forces. The first attempts at plate and screw fixation were met with high rates of failure because surgeons at the time did not respect the biomechanics of the mandible. In 1978, Maxime Champy published his ideal zones of osteosyntheses for load-sharing fixation in the dentate mandible. Champy’s techniques improved treatment success by optimizing areas of compression and tension to ensure adequate rigidity across the fracture line. A Champy-style plate for mandibular angle fractures is an example of “nonrigid” or “semirigid” fixation ( Fig. 2 ) that functions with success because it respects the mandibular lines of osteosynthesis ( Fig. 3 ). Ellis subsequently expanded on Champy’s work and proposed his own decision algorithm for managing non–condylar mandible fractures that incorporated both closed and open reduction. This algorithm can be applied to pediatric fractures as well.
Pediatric craniomaxillofacial fractures are subject to the same treatment principles as adult fractures. Namely, the mandible preserves its role as a load-bearing bone, and therefore, any treatment should incorporate the aforementioned fixation guidelines. Children do have the benefit of improved osteogenic capacity, and therefore, they can tolerate shorter durations of MMF. In fact, prolonged MMF and temporomandibular joint disuse are contraindicated because they increased the risk of ankylosis. Their superior wound healing abilities and tendency to “greenstick fracture” also present a larger opportunity for conservative management. The designation of plates as either load bearing or load sharing by manufacturers is based on the ability to resist forces applied by the adult mandible. Children have lower peak bite forces, which places less demand on the hardware. As such, plates designed to be load sharing in adults may provide sufficient strength to achieve load-bearing fixation in a child. There is also a decreased need to obtain completely rigid internal fixation in children because dental splints and other external adjuncts are often used in combination to stabilize the fracture. The effectiveness of semirigid internal fixation for pediatric patients also opens the possibility of using resorbable materials not only in the upper midface but also in the mandible.
Pediatric anatomic considerations
Pediatric proportions exhibit a larger cranium to face ratio (8:1) than that of adults (2.5:1). ( Fig. 4 ). As a result, the face is relatively protected from trauma at the expense of the cranium. Pneumatized sinuses and unerupted tooth buds compromise the structural integrity of the facial skeleton. , Stereotyped patterns of injury occur based on the stage of development and the location of these breakage points. Midface fractures are extremely uncommon in children aged younger than 6 years because of the recessed bony anatomy, thicker subcutaneous fat pads, and clinical irrelevance of the paranasal sinuses. The mature paranasal sinuses allow the face to absorb and dissipate forces away from the skull base. The maxillary and ethmoid sinuses are present at birth and complete development sooner than the frontal and sphenoid sinuses that form postnatally. Once the maxillary sinus reaches a meaningful size, around the age of 7 years, the risk of orbital roof injury decreases and the risk of orbital floor injury increases proportionally with the extent of pneumatization. The pediatric mandible occupies a more vulnerable position in the facial skeleton than the midface and is most susceptible to fracturing at the condylar and the parasymphyseal regions. , The developing permanent mandibular canine creates a unique stress point that disappears once dental eruption and bone substitution are completed.
The distinct anatomy of children also poses unique considerations for internal fixation. Most anatomic differences converge by 10 years of age, after which point many surgeons will manage both pediatric and adult patients in a more uniform fashion. , Until the eruption of the permanent second molars at 13 years, tooth buds occupy much of the intercortical volume within the mandibular body and symphysis. Even with grossly displaced fractures, bicortical fixation is generally unnecessary and relatively contraindicated during primary and mixed dentition ( Fig. 5 ). Any internal fixation during this stage of development should be placed along the inferior border so that the screws are housed entirely within cortical bone. This avoids damage to the inferior alveolar nerve and the developing dentition. The pediatric maxilla is short and retruded, and before 6 years of age, much of the maxillary volume is similarly occupied by the permanent tooth buds. These maxillary tooth buds may be at risk when attempting to plate the zygomaticomaxillary (ZMC) buttress for the rare pediatric zygomatic complex fracture. In such instances, Kaban and colleagues have justified using 1-point of fixation at the zygomaticofrontal suture because of the shorter lever arm generated by the smaller zygoma. Every effort should be made to ensure that any internal fixation does not traverse suture lines or the mandibular midline. Multiple animal studies have demonstrated that rigid fixation across active sutures in both the skull and the face mimics premature fusion and does significantly restrict growth potential. ,
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