1. Aetna considers distraction osteogenesis (distraction histogenesis) medically necessary for the correction of functional impairments accompanying the following congenital craniofacial skeletal deformities:
   • Correction of severe micrognathia (such as accompanying Pierre Robin syndrome or Treacher Collins syndrome) in infants and children with airway obstruction; or
   • Correction of hemifacial microsomia, in children with sufficient bone to allow for a corticotomy and/or osteotomy and placement of pins for external or internal distraction devices (i.e., Pruzansky Grade I and IIa type mandibular deformity); or
   • Correction of severe congenital mandibular deficiency requiring lengthening of the mandible of greater than 10 mm (orthognathic surgery is able to correct smaller mandibular deformities); or
   • Widening of a narrow mandible or maxilla; or
   • Lengthening of a short mandibular ramus (stretching of pterygomasseteric sling); or
   • Non-syndromic craniosynostosis - coronal (bilateral or unilateral) or sagittal; or
   • Syndromic craniosynostosis - Apert, Crouzon, and Pfeiffer syndromes; or
   • Cleft lip and palate.

   Upon review by Aetna's Oral and Maxillofacial Surgery (OMS) Unit, distraction osteogenesis may be considered medically necessary for correction of functional impairments accompanying other congenital craniofacial anomalies where it is determined that distraction osteogenesis can uniquely produce a degree of improvement unavailable with other standard techniques.

2. Aetna considers distraction osteogenesis experimental and investigational for acquired craniofacial defects (e.g., reconstruction of defects following tumor (e.g., osteosarcoma) resection, or ablative head and neck surgery), and for all other craniofacial indications because of insufficient evidence regarding the clinical value of this approach for these indications.

Orthognathic surgery is the surgical correction of skeletal anomalies or malformations involving the midface, mandible and maxilla. These malformations may be present at birth, or may become evident as the patient grows and develops. Jaw malformations can cause chewing and eating difficulties, abnormal speech patterns, early loss of teeth, and disfigurement and dysfunction of the maxilla and mandible. Malocclusion may be caused by a deficiency or excess of bony tissue in one or both jaws, or by trauma to the facial bones.

In orthognathic surgery, an osteotomy is made in the affected jaw, and the bones are repositioned in a more physiologic alignment. Generally, the bones are held in their new positions with plates, screws and wires. The patient may also need arch bars placed on both jaws to add stability (a procedure called intermaxillary fixation). For patients with deformities affecting both jaws, either simultaneous or staged osteotomies may be undertaken to achieve correction. Patients with deficient bone tissue may require grafts from their ribs, hips or skull. Alloplastic replacement of missing bone may also be required.

Indications for orthognathic surgery include: (1) mandibular prognathism; (2) mandibular retrognathia; (3) maxillary excess; (4) maxillary deficiency; and (5) apertognathia (open bite deformity). In some cases, adjunctive procedures such a reconstructive rhinoplasty, malar and chin osteoplasty, and bone grafting are needed to correct deformities; however these procedures require evaluation by the Oral and Maxillofacial surgery unit to determine coverage. These adjunctive procedures are typically considered cosmetic in nature. (For information regarding orthognathic surgery, see Aetna CPB 095 - Orthognathic Surgery).

Distraction osteogenesis, initially developed by Ilizarov for limb lengthening (see Aetna CPB 220 - Ilizarov Method for Distraction Osteosynthesis), has recently been applied to the correction of severe congenital or acquired craniofacial deformities as an early alternative to orthognathic surgery. Distraction osteogenesis involves the lengthening and reshaping of deformed bone by surgical fracture and gradual separation of bony segments. The surgeon lengthens and reshapes deformed bone by surgically fracturing the bone and slowly separating (distracting) the resultant segments with specially fabricated hardware. The bony fragments are held in place during the first week following surgical fracture to allow callus to form between the fragments. During the next several weeks, the fragments are gradually separated at a rate of 1 to 2 millimeters per day, up to a predetermined length (e.g., 20 days for 20 millimeters or 5/8 inches). The bone segments are moved gradually to allow callus formation and adaptation of fibromuscular attachments. Once the desired length and shape is achieved, the hardware is left in place for an additional six weeks until the newly formed bone calcifies.

The specially fabricated hardware used for the distraction process can be internal or external. Advantages of external devices include ease of placement and removal. In addition, some external devices allow multi-dimensional control. External devices, however, are very conspicuous and are more likely to cause traction scars than internal devices. Internal devices are less visible than external devices, and directly transmit force to the bone. Internal devices, however, are only unidirectional and require a subsequent surgical procedure for their removal.

The primary advantage claimed in connection with distraction osteogenesis is that it allows major reshaping of the facial bones without bone grafts or jaw wiring. Proponents claim that distraction osteogenesis may be safer than other methods of facial reconstruction, since it can involve less blood loss and a lower risk of infection. However, according to available literature, distraction osteogenesis has several drawbacks. If the bone ends are moved apart too slowly, callus may calcify too soon, preventing further distraction. If the bone ends are moved apart too rapidly, callus may become too fibrous and fail to mature into solid bone. Therefore, the rate and rhythm of distraction is important to the quality and quantity of bone that is formed.

The published literature regarding the effectiveness of distraction osteogenesis for craniofacial anomalies has focused on its use in repair of congenital conditions in young children. The published clinical literature on distraction osteogenesis for developmental and acquired craniofacial deformities is more limited, and consists primarily of case series reporting on its technical feasibility, perioperative morbidity, and short-term outcomes. Orthognathic surgery is the established method of correcting developmental mandibular deficiencies, maxillary deficiencies and other developmental and acquired craniofacial deformities. More investigation is necessary to refine distraction osteogenesis technique, to help define its role in craniofacial surgery, and to improve the design and reliability of distraction devices in repairing developmental and acquired deformities in older children and adults whose growth is at or near completion. Moreover, there are insufficient published data on the long-term effectiveness of this procedure for these indications, especially on the rate of skeletal relapse.

According to a position statement from the American Association of Oral and Maxillofacial Surgeons (AAOMS, 2003), “the indications for distraction involving the jaws are limited to conditions in which this technique may be uniquely able to produce significant improvement over more traditional therapy.” According to the AAOMS (2003), examples of these situations are as follows:

• Severe deficiency of either jaw with early correction indicated, e.g., an infant with Pierre Robin with mandibular deficiency so severe that tracheostomy is required and advancement of the mandible is the only way to correct an obstructive situation.
• Severe mandibular deficiency requiring lengthening of the mandible of greater than 10 mm. Growth modification via orthodontics generally produces no more than 5 mm differential growth and conventional orthognathic procedures become more difficult and less predictable when greater than 8 to 10 mm advancement is needed.
• Need for lengthening of a short mandibular ramus. According to the AAOS, the nature of distraction osteogenesis is well suited for stretching of the pterygomasseteric sling, which is not easily overcome by conventional procedures.
• Narrow mandible that must be widened. There has been little success in widening the mandible with conventional surgery prior to the advent of distraction. Distraction techniques offer a better way to address this problem.

The AAOMS guidelines also list alveolar deficiency among examples of established indications for distraction osteogenesis for craniofacial anomalies. However, there is insufficient published evidence of the effectiveness of distraction osteogenesis for vertical augmentation of the alveolar ridge in comparison with grafting techniques for this indication.

The AAOMS guidelines list “[w]idening of the maxilla in an adult” among established indications for distraction osteogenesis. However, surgically assisted palatal expansion, which is analogous to distraction osteogenesis, has been utilized to overcome this problem for decades with very desirable and stable results.

AAOMS guidelines note that, “[a]s with any procedure, distraction osteogenesis should be utilized primarily when superior results can be achieved compared to conventional techniques” (AAOMS, 2003).

Although the AAOMS guidelines do not distinguish between congenital and developmental and acquired conditions, the published evidence to date has focused on repair of congenital conditions. There is insufficient evidence of the effectiveness of distraction osteogenesis for developmental and acquired craniofacial anomalies.

Schreuder et al (2007) noted that bilateral sagittal split osteotomy (BSSO) and distraction osteogenesis are the most common techniques currently applied to surgically correct mandibular retrognathia. These investigators reviewed the literature on BSSO and mandibular distraction osteogenesis with emphasis on the influence of age and post-surgical growth, damage to the inferior alveolar nerve, and post-surgical stability and relapse. Although randomized clinical trials are lacking, some support was found in the literature for distraction osteogenesis having advantages over BSSO in the surgical treatment of low and normal mandibular plane angle patients needing greater advancement (greater than 7 mm). In all other mandibular retrognathia patients the treatment outcomes of distraction osteogenesis and BSSO seemed to be comparable. Distraction osteogenesis is accompanied by greater patient discomfort than BSSO during and shortly after treatment, but it is unclear if this has any consequences in the long term. There is a need for randomized clinical trials comparing the two techniques in all types of mandibular retrognathia, in order to provide evidence-based guidelines for selecting which retrognathia cases are preferably treated by BSSO or distraction osteogenesis.

Sacco and Chepeha (2007) stated that earlier work has reported encouraging results regarding the translation of distraction osteogenesis from animal studies to human uses, with particular success in the unradiated setting. The major challenge surrounding the use of this technology in head and neck oncological reconstruction will be the effect of radiotherapy on the regenerate bone in patients who have received or will need radiotherapy as part of their treatment. Although distraction osteogenesis provides an attractive option for reconstructing mandibular defects, large human studies are needed to further evaluate the use of this technology and its role in the treatment for mandibular neoplasms.