Distraction Osteogenesis for Craniofacial Defects

Number: 0549

Policy

1. Aetna considers distraction osteogenesis (distraction histogenesis) medically necessary for the correction of functional impairments accompanying the following congenital craniofacial skeletal deformities:
    
   
   • Cleft lip and palate; 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
   • Correction of severe micrognathia (such as accompanying Pierre Robin syndrome or Treacher Collins syndrome) in infants and children with airway obstruction; 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
   • Widening of a narrow mandible or maxilla.

   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), obstructive sleep apnea, and all other craniofacial indications because of insufficient evidence regarding the clinical value of this approach for these indications.
   
   
3. Aetna considers enhancement of bone formation by means of bone morphogenetic proteins and local injection of bone marrow aspirate and platelet gel at the osteotomy site during distraction osteogenesis experimental and investigational because of insufficient evidence in the peer-reviewed literature.
   
   
4. Aetna does not cover distraction osteogenesis (distraction histogenesis) in preparation for dental implants or orthodontic care under plans that exclude dental implants or orthodontic care.  Please check benefit plan descriptions.  See CPB 0082 - Dental Services and Oral and Maxillofacial Surgery - Coverage under Medical Plans.
   
   
5. Aetna considers distraction osteogenesis for the sole purpose of improving individual appearance and profile cosmetic.

Background

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.  Mal-occlusion 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.

Distraction osteogenesis, initially developed by Ilizarov for limb lengthening 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 re-shaping of deformed bone by surgical fracture and gradual separation of bony segments.  The surgeon lengthens and re-shapes 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 pre-determined 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 6 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 uni-directional 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, peri-operative 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:

• 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
• 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.
• 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.

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 2 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 un-radiated 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.

Ow and Cheung (2008) stated that mandibular distraction osteogenesis has been used effectively to treat syndromic craniofacial deformities.  In recent years, its scope of application has widened to include treatment of airway obstruction in adults and children as well as non-syndromic class II mandibular hypoplasia.  So far, there has been no evidence-based review of mandibular distraction osteogenesis for mandibular lengthening.  These investigators carried out a meta-analysis of mandibular distraction osteogenesis.  Two rounds of searches were performed by 2 independent assessors.  The first-round PubMed search used the keywords "mandible" and "distraction osteogenesis".  In the second-round search, the reference lists of the articles were retrieved.  For both rounds, abstracts and then full articles were reviewed and selected on the basis of a set of inclusion and exclusion criteria.  The 178 retrieved articles yielded 1,185 mandibular distraction osteogenesis patients: 539 received unilateral mandibular distraction osteogenesis and 646 received bilateral mandibular distraction osteogenesis.  Mandibular distraction osteogenesis was reported to improve facial asymmetry and retrognathia (50.1 %), correct the slanted lip commissure (24.7 %), and improve or level the mandibular occlusal plane (11.1 %) in unilateral asymmetry cases, whereas bilateral mandibular distraction osteogenesis was shown to be effective in preventing tracheostomies for 91.3 % of neonates or infants with respiratory distress, and in relieving symptoms of obstructive sleep apnea for 97.0 % of children and 100 % of adult patients.  The authors concluded that mandibular distraction osteogenesis is effective in treating craniofacial deformities, but further clinical trials are needed to evaluate the long-term stability and to compare the treatment with conventional treatment methods, especially in cases of obstructive sleep apnea or class II mandibular hypoplasia.

In a retrospective medical review spanning a 9-year period, Kolstad and colleagues (2011) examined if there is a difference in mandibular distraction osteogenesis (MDO) treatment success rates and adverse outcomes in newborns, early infants, and older pediatric patients.  Ten newborn (less than or equal to 35 days old), 5 early infant (36 days to 5 months) and 8 older pediatric (greater than 5 months) patients underwent MDO for treatment of micrognathia with a severe tongue-based obstruction.  Success was defined as avoidance of tracheostomy or continuous positive airway pressure, and de-cannulation of patients with tracheotomies.  Post-operative complications were grouped into minor and major.  MDO successfully treated 90 % of newborns, 100 % of early infants and 100 % of older pediatric patients.  There was no difference in the rates of success (p = 0.48), minor (p = 1.00) and major (p = 1.00) post-operative complications between newborns and early infants.  Older pediatric patients had no treatment failures, tended to have fewer minor (p = 0.18) and significantly fewer major (p = 0.04) post-operative complications compared to younger patients.  The distractor pin mobility (9 %) and scar revisions (13 %) were uncommon.  The authors concluded that MDO is a reliable method for relieving severe tongue-based obstructions in pediatric patients.  When comparing newborns and early infant patients, treatment success rates and the occurrence of complications were not found to be different.  Older pediatric patients had no treatment failures, and tended to have fewer post-operative complications compared to younger patients.

Pluijmers et al (2014) provided an overview of the surgical correction of the mandible in unilateral craniofacial microsomia (UCM) performed in the growing patient, and its long-term outcome and stability.  The following databases were searched: PubMed, Embase, Cochrane, and Web of Science.  Articles reporting prospective and retrospective studies of patients not older than 16 years (n ≥ 4) who had undergone surgical correction of a craniofacial microsomia spectrum condition using grafts, osteotomies, distraction, or combinations of these, were reviewed.  The period of follow-up was selected to be greater than or equal to 1 year.  After inclusion, the articles were evaluated on short- and long-term outcomes, relapse, and any increase in asymmetry following treatment; 30 of 1,611 articles were included in the qualitative synthesis.  Analysis of the surgical mandibular correction of UCM showed that the outcome is not so much treatment-dependent, but patient-dependent, i.e., deformity gradation-dependent.  The type I and type IIa Pruzansky-Kaban patient had the best results with regard to minimal relapse and/or minimal increase in asymmetry.  Single-stage correction of the asymmetry should be postponed until the permanent dentition stage.  The authors concluded that in the treatment of the severely hypoplastic mandible, the patient will benefit from a multi-stage treatment protocol if indicated for functional or psychological problems.

Tahiri et al (2014) stated that distraction osteogenesis is an effective technique for elongating the deficient mandible.  These investigators evaluated its effectiveness in the treatment of airway obstruction in pediatric patients with mandibular hypoplasia.  A comprehensive literature review of the National Library of Medicine (PubMed) database was performed.  English-language studies involving isolated distraction of the pediatric mandible (younger than 18 years) with descriptive reporting of airway changes were included.  Extracted data included demographics, initial diagnosis, distractor type, distraction protocol, pre-distraction and post-distraction airway status, and complications.  A total of 74 articles met the inclusion criteria, resulting in 711 patients with craniofacial abnormalities who underwent mandibular distraction osteogenesis.  Mean age at the time of distraction was 18.1 months.  The most common diagnoses were isolated Pierre Robin sequence (52.9 %), syndromic Pierre Robin sequence (7 %), and Treacher Collins syndrome (6.8 %).  Mandibular distraction osteogenesis successfully treated airway obstruction in 89.3 % of cases.  Success was defined as either de-cannulation of tracheostomy, avoidance of tracheostomy or continuous positive airway pressure, or alleviation or significant improvement of obstructive sleep apnea (OSA) symptoms.  A total of 171 (84.2 %) of the 203 tracheostomy-dependent patients were successfully de-cannulated.  Among the 181 patients with OSA, mandibular distraction osteogenesis successfully allowed for either complete resolution or significant improvement of symptoms in 95.6 %.  A 23.8 % overall complication rate was noted.  The mean follow-up time was 28.7 months.  The authors concluded that in addition to its positive effect on facial appearance, mandibular distraction osteogenesis is an effective procedure for the treatment of airway obstruction associated with congenital craniofacial defects involving mandibular hypoplasia in appropriately selected patients.

Bone Morphogenetic Proteins

Sabharwal and colleagues (2011) notd that delayed bone healing during distraction osteogenesis negatively affects clinical outcome.  In addition to autologous bone grafting, several mechanical, chemical, biologic, and external treatment modalities may be employed to promote bone growth during distraction osteogenesis in the pediatric patient.  Mechanical approaches include compressive loading of the distraction regenerate, increased frequency of small increments of distraction, and compression-distraction.  Intra-medullary nailing and sub-muscular plating can reduce the time in external fixation; however, these techniques are associated with technical difficulties and complications.  Exogenous application of low-intensity pulsed ultrasound or pulsed electromagnetic fields may shorten the duration of external fixation.  Other promising modalities include diphosphonates, physician-directed use (off-label use) of bone morphogenetic proteins, and local injection of bone marrow aspirate and platelet gel at the osteotomy site.  The author concluded that well-designed clinical studies are needed to establish safe and effective guidelines for various modalities to enhance new bone formation during distraction osteogenesis in children.

Terbish and colleagues (2015) evaluated the effect of recombinant human bone morphogenetic protein-2 (rhBMP-2) on the quality and quantity of regenerated bone when injected into distracted alveolar bone. A total of 16 adult beagle dogs were assigned to either the control or rhBMP-2 group.  After distraction was completed, an rhBMP-2 dose of 330 μg in 0.33 ml was injected slowly into the distracted alveolar crest of the mesial, middle, and distal parts of the alveolar bone in the experimental group.  Histologic and micro-computed tomography analyses of regenerated bone were done after 2 and 6 weeks of consolidation.  After 6 weeks of consolidation, the vertical defect height in the middle of the regenerated bone was significantly lower in the rhBMP-2 group (2.2 mm) than in the control group (3.4 mm) (p < 0.05).  Additionally, the width of the regenerated bone was significantly greater in the rhBMP-2 group (4.3 mm) than in the control group (2.8 mm) (p < 0.05).  The bone density and volume of regenerated bone in the rhBMP-2 group were greater than in the control group after 6 weeks of consolidation (p < 0.001).  The authors concluded that injection of rhBMP-2 into regenerated bone after a distraction osteogenesis procedure significantly increased bone volume in the dento-alveolar distraction site and improved both the width and height of the alveolar ridge and increased the bone density.  These preliminary findings from a canine model need to be examined in human subjects.

Distraction Osteogenesis of the Irradiated Craniofacial Skeleton

Momeni and colleagues (2017) stated that craniofacial DO is a common treatment modality today.  Despite its numerous advantages, however, concerns have been expressed regarding the use of DO in the irradiated setting.  A systematic review was performed to identify all published reports of patients who underwent DO of the irradiated craniofacial skeleton.  The following parameters were of particular interest: post-operative complications, specifically, insufficient bone formation, fracture, and hardware exposure (intra-oral and cutaneous), as well as the need for additional bone grafting.  The initial search retrieved a total of 183 articles of which 20 articles (38 patients) met pre-determined inclusion criteria.  The most common site of distraction was the mandible (76.3 %).  The median radiation dose was 50.7 Gy (range of 30 to 70 Gy).  Bone defects ranged from 30 to 80 mm (median of 42.5 mm).  Complications were encountered in 19 patients (50 %), with insufficient bone formation being most common (9 patients; 23 %).  The overall incidence of complications was not significantly associated with radiation dosage (p = 0.79).  The remaining procedural and demographic variables also failed to meet statistical significance when compared against the overall complication rate (p = 0.27 to 0.97).  The authors concluded that the complication rate associated with craniofacial DO of the irradiated skeleton did not appear to be substantially higher than what was reported for DO in the non-irradiated setting.  As such, patients should be offered this treatment modality, particularly in light of the fact, that it offers the option to decrease patient morbidity as well as treatment complexity.

The above policy is based on the following references: