Comparison Between Internal and External Distractors in Osteogenesis

Distraction osteogenesis is a powerful technique for creating new bone during significant lengthening of the mandible without the need for bone grafting and associated donor site morbidity.

The idea of distraction osteogenesis was largely abandoned by many until the 1950s. Ilizarov minimized complications by performing a corticotomy with minimal disruption of the surrounding blood supply and using a system of tension ring fixators to control the distraction in multiple planes. Through a series of experimental studies and clinical applications, Ilizarov established the foundation of distraction osteogenesis and its role in orthopedic management.

Applications in craniofacial surgery were first seen in 1973, when Synder et al applied the approach to mandibular lengthening in a canine animal model. Almost another 20 years passed before McCarthy and colleagues published, in 1992, the first report of mandibular lengthening in 4 children with congenital mandibular deficiency, 3 with hemifacial microsomia, and 1 with Nager syndrome. Thereafter, its role rapidly expanded to the midface and nearly all classic approaches to craniofacial reconstruction.

In general, mandibular distraction can be performed in the ramus for ramus lengthening, in the mandibular angle for downward and forward advancement, or in the mandibular body. Ramus or gonial angle distraction are mainly used to treat facial asymmetries as in hemifacial macrosomia.

Severe mandibular retrognathia can be classified as congenital or acquired. Congenital abnormalities that are associated with severe mandibular retrognathia or micrognathia include craniofacial syndromes such as hemifacial microsomia, Pierre-Robin syndrome, Treacher-Collins syndrome, and Nager syndrome. Adult patients with craniofacial syndromes may have undergone previous surgery at an earlier age, but unfavorable postsurgical growth or skeletal relapse may have occurred.

Severe mandibular retrognathia also can develop following maxillofacial trauma and mandibular fractures, which may have occurred in an adult or as a child Condylar fractures occurring at an early age can result in subsequent bony and/or fibrous temporomandibular joint ankylosis and/or deficient mandibular growth, also adult patients with complications from previous mandibular tumor resection and reconstruction can also present with acquired severe mandibular retrognathia that may require distraction osteogenesis as well.

Despite the advantages of extra-oral distraction devices in the hands of clinicians (application for very small children, simplicity of attachment, ease of manipulation, bidirectional and multidirectional dis- traction), patients are apprehensive about wearing bulky external appliances because of the social inconvenience and the potential of permanent facial scars, these disadvantages and limitations were the primary force driving the evolution of mandibular lengthening and widening toward the development of intra-oral devices.

However nowadays both internal and external distractors are used in a variety of indications in these cases each of the two types of distractor devices has its own advantages and disadvantages.

Aim of the work:

The aim of this study is to compare external and internal distraction devices for mandibular lengthening in terms of bone lengthening, patient comfort, and complications.