Author Affiliations: Cleft and Craniofacial Program, Facial Plastic and Reconstructive Surgery, Department of Otolaryngology–Head and Neck Surgery, UC Davis Medical Center, Sacramento, California.
To evaluate whether mandibular distraction osteogenesis relieves tongue-based airway obstruction in patients with severe micrognathia.
Retrospective medical review spanning a 7-year period in a tertiary care hospital. The inclusion criterion was defined as micrognathia associated with a severe tongue-based obstruction. The patients included 11 neonates and infants (mean age, 4.3 months) and 2 pediatric patients (mean age, 5.4 years). Two patients had already received tracheotomies, 11 had not. The intervention was bilateral mandibular osteotomies with distraction osteogenesis. The outcome measures were avoidance of tracheotomy and decannulation.
Ten of 11 patients avoided tracheotomy. Two of 2 patients who had already undergone tracheotomies were successfully decannulated.
Mandibular distraction osteogenesis is an acceptable treatment alternative to tracheotomy in select pediatric patients with micrognathia and severe tongue-based obstruction.
Pierre Robin was not the first to describe the well-known triad of micrognathia, glossoptosis, and a U-shaped cleft palate. This anatomical constellation was written about in 1822 by Saint-Hilaire and later by Fairbain in 1846 and Shukowsky in 1911.1 However, it was Robin who dedicated years to publishing articles and monographs describing the embryology, complications, and management of this disorder. In 1923, Robin2 associated this anatomical constellation with upper airway obstruction. The initial insult in the sequence is failure of anterior growth of the mandible. Consequently, the tongue physically blocks the fusion of the palatine shelves, typically resulting in a U-shaped cleft palate. In children with micrognathia, the muscular attachments of the tongue are held in a less anterior position than in nonaffected children. The tongue base is retrodisplaced, resulting in oropharyngeal narrowing. This tongue-based obstruction can be life threatening without appropriate management.3
Fortunately, a large percentage of patients with mandibular deficiency have an obstruction that can be relieved with supportive measures. Prone positioning and nasal continuous positive airway pressure are noninvasive treatments that are sufficient for most newborns with Pierre Robin sequence.4 However, up to 23% of patients with micrognathia have a tongue-based obstruction that requires intervention beyond these noninvasive, supportive measures.5 For such patients, tracheotomy remains the “gold standard.” Tracheotomy relieves the upper airway obstruction, but it is not without its own limitations. Several articles have described a tracheotomy-specific mortality of 1% to 4%.6- 8 In addition to swallowing dysfunction, speech and language development are also adversely affected by the presence of a tracheotomy tube.9- 11 Patients requiring tracheotomies for treatment of tongue-based obstruction are typically not decannulated until an average age of 3.1 years.12,13 Tongue-lip adhesion procedures were introduced as an alternative to tracheotomy. A glossopexy, in which the tongue is attached to the lower lip and mandible, is typically performed in infancy and reversed around 12 months of age. Although it is frequently effective in relieving a tongue-based airway obstruction, it can result in language developmental delays and permanent articulation deficits.14
Mandibular distraction osteogenesis (MDO) was first described by McCarthy et al15 in 1992 for the treatment of hemifacial microsomia. The indications have expanded to include treating tongue-based obstruction in patients with micrognathia. The present study reviewed the UC Davis Medical Center (UCDMC), Sacramento, California, experience from 2001 to the present using MDO to treat tongue-based obstruction in patients with micrognathia. The effectiveness of MDO and any associated adverse outcomes from surgery were analyzed both perioperatively and for an average of 33 months postoperatively.
The medical and radiographic records of 13 consecutive patients who underwent MDO for tongue-based obstruction were evaluated during this retrospective chart review. Permission to pursue the study was granted by the institutional review board at UCDMC. Informed consent was obtained from the parent or legal guardian before surgery. Twenty-six mandibular distractors were placed bilaterally in 13 patients with micrognathia and severe tongue-based airway obstruction. During a 7-year period originating in 2001, 5 girls and 8 boys met the criteria for bilateral mandibular distraction surgery at UCDMC. The patients were evaluated by multidisciplinary specialists, including neonatologists, pediatric otolaryngologists, oral surgeons, dentists, and pediatricians. Preoperative assessment included awake flexible fiberoptic laryngoscopy, oxygen saturation provided by pulse oximetry, oral intake, and weight gain.
Candidacy for MDO was defined as a micrognathia with an associated severe tongue-based obstruction. A severe obstruction was defined as a persistent pCO2 greater than 50 mm Hg or a life-threatening event related to upper airway compromise. A total of 11 neonatal and infant patients and 2 pediatric patients were included in the study. Two had already received tracheotomies, 11 had not. Twelve of 13 patients had Pierre Robin sequence, and 9 of them had other congenital anomalies. One patient had micrognathia and glossoptosis without a cleft palate. Table 1 lists the clinical features of the study participants.
Intraoperatively, the posterior border of the mandibular ramus and the inferior border of the angle were palpated and marked. An external (modified Risdin) approach was used to access the inferior mandibular border after injection of a topical anesthetic and vasoconstrictor. The marginal mandibular branch of the facial nerve was protected by a Hayes-Martin maneuver after the submandibular gland was encountered.
After the inferior mandibular border was identified, wide subperiosteal elevation of the lingual and buccal cortices was performed to create a plane for the osteotomy and pin sites. The ideal distraction vector was correlated with the preoperative imaging, and osteotomy sites were marked on the buccal cortex (Figure 1). In general, the osteotomy extended from the external angle of the mandible to the internal mandibular angle. Two central and 2 distal pin sites were marked 4 mm and 8 mm from the line of intended osteotomy. A reciprocating saw was used to make monocortical osteotomies, first through the buccal cortex and then by the lingual cortex. The superior 5 to 10 mm of the lingual cortex could not be adequately reached with the reciprocating saw without risking injury to the tooth buds and the inferior alveolar nerve and was temporarily left intact. The inferior 5 mm of the mandibular border was cut in a bicortical fashion because the inferior alveolar nerve and tooth roots are not at risk in this location.
Ideal distraction vector with osteotomy, pin sites, and tooth bud markings (reprinted with permission from the University of California–Davis Otolaryngology Illustration Library, Sacramento).
A No. 15 scalpel was used to make an incision in the facial skin at the planned pin sites. A curved hemostat was placed through the periosteum and, with blunt dissection, guided through the incision. A drill pilot was grasped between the hemostat tips and brought to the mandibular surface. Four monocortical pin sites were then drilled. Two screws with 15-mm threads and 2 with 10-mm threads were introduced through the pilot hole and placed into the mandibular body and ramus pin sites, respectively. A small, sharp osteotome was used to complete the bicortical osteotomy, with special attention given to the superior aspect of the lingual cortex (Figure 2).
Completion of the osteotomy using a 2-mm osteotome.
After mobilization of the mandibular fragments, the external, multiplanar, mandibular distractor (Stryker Leibinge Inc, Kalamazoo, Michigan) was placed into position and secured. The segments were distracted several millimeters to verify the osteotomy. A 1- to 2-mm gap was left between the segments. The screws were trimmed with a heavy pin cutter. Soft plastic, cylindrical, suture boots were placed onto the cut screws for protection. The neck incisions were reapproximated in multiple layers using absorbable suture for the deep soft tissue. The skin was closed with 6-0 fast-absorbing gut (Ethicon Inc, Somerville, New Jersey). Later in the study, the skin was reapproximated with cyanoacrylate glue to avoid the suture tracking that may be seen when fast-absorbing gut suture is used. Xeroform gauze was wrapped around the device pin sites. This procedure was repeated on the contralateral side.
Distraction was initiated on postoperative day 1 or 2. Neonates and infants were distracted at a rate of 2.0 to 2.5 mm/d. Older patients were distracted at a rate of 1.5 mm/d. The total daily distraction was divided equally into twice-daily regimens. The vector and symmetry of distraction were determined preoperatively using 3-dimensional computed tomography and adjusted when clinically appropriate. Binding was relieved periodically by adjustment of the transverse angulation. When possible, the mandible was distracted until it projected 2 to 3 mm beyond the maxillary alveolar ridge. Overdistraction allows for bony relapse or differential maxillary to mandibular growth. Typical distraction is represented radiographically in Figure 3. Distraction was performed by the surgical team while the patient was in the hospital. When the patient was discharged home, distraction was performed by the primary caregivers, with frequent follow-up. Patients with a tracheotomy were discharged from the hospital on postoperative day 2. Those without a surgical airway remained intubated for approximately 1 week. Four to 6 weeks of bony consolidation were allowed after the distraction was complete. The hardware was then removed at the bedside or in a clinic setting. The patients were followed up at regular intervals by a multidisciplinary cleft and craniofacial panel.
Overdistraction of the mandible, 2 to 3 mm beyond the maxilla.
After MDO, 12 of 13 patients (92%) successfully met the goal of surgery. Two of 2 patients with preoperative tracheotomies underwent decannulation. Ten of 11 patients who had not yet received tracheotomy avoided tracheotomy. One patient was later diagnosed as having central hypoventilatory syndrome and required a tracheotomy after MDO. Patients without tracheotomies underwent extubation after an average of 8 days of distraction (range, 0-20 days).
Table 2 summarizes the adverse outcomes and rates. Two patients (15%) had pin-site infections that required antibiotic administration. There was 1 technical failure (8%) (greenstick fracture) that required surgical revision on postoperative day 5. One patient required early removal of the distractor for loose pins after 4.5 weeks of consolidation. There was no apparent sequelae from the early removal. There was 1 paresis (8%) of the marginal mandibular branch of the facial nerve that developed during distraction. There were no cases of temporomandibular joint ankylosis. One patient had trismus due to coronoid process hypertrophy, without evidence of ankylosis or condylar atrophy on computed tomography. At completion of the study, there were no tooth bud injuries resulting in loss of permanent dentition on physical examination. There were no premature bony unions that required reosteotomy. There were no nonunions.
The results of distraction are presented in Table 3. Six patients were younger than 30 days at the time of surgery; the youngest was 5 days old. The mean total distance distracted was 20 mm (range, 12 to 28 mm). Figure 4 and Figure 5 illustrate a micrognathic mandible before surgery and after 13 days of distraction. Most patients had favorable scarring and did not require additional treatment (Figure 6). Two patients (15%) required revision of facial and neck scars (Figure 7). If a patient had a cleft palate, revisions were typically performed during the patient's scheduled palatoplasty. Figure 5 represents a patient with favorable scarring.
Preoperative micrognathic mandible.
Micrognathic mandible after 13 days of distraction.
Example of favorable pin site and neck scars.
Example of unfavorable pin site and neck scars.
Follow-up duration averaged 32.7 months (range, 5.4 months to 7.2 years). During this period, 4 patients (31%) were noted to have either persistent or recurrent obstructive symptoms. Two patients (15%) had persistent obstruction due to laryngomalacia, with 1 requiring supraglottoplasty. Three patients (23%) later experienced obstructive symptoms and were successfully treated with tonsillectomy and adenoidectomy. The surgical treatments relieved the obstructive symptoms in all 4 patients.
Mandibular distraction osteogenesis can be used to relieve tongue-based obstruction in patients with micrognathia. Before MDO, the infants in this study would have received tracheotomies. Rather than living with a tracheotomy for several years, these patients underwent extubation an average of 8 days after distraction. Furthermore, 2 patients who had been living with tracheotomies for years underwent decannulation after MDO. As evidenced by the 1 failure in our study, MDO cannot alleviate respiratory compromise in everyone with micrognathia. Patients with concomitant neurologic disorders may not ever realize the true surgical benefits. Even those who gain relief from a tongue-based obstruction may continue to experience airway compromise from other anatomical areas or the inability to clear pharyngeal secretions. In the present study, 4 patients (31%) had either persistent or recurrent obstruction after MDO and were successfully treated with other surgical techniques.
Although the efficacy of MDO is gaining acceptance, the method of distraction continues to be debated. Proponents of an intraoral uniplanar distractor extol the advantages of this device. The absence of facial pin-site scars and the decreased risk of dislodgement are frequent claims. However, as in this study, patients who require a surgical scar revision can have one performed in conjunction with their palatoplasty. Although only 15% of the patients in our study received scar revisions, parents are told that typically 50% of patients will be candidates for this therapy. In this series, there were no instances of patient-related distractor dislodgments. The single device that became mobile was likely attributable to poorly located mandibular ramus pins rather than to postoperative trauma. External distractors have the ability to perform multiplanar distraction and to eliminate binding. Most patients in this study received differential advancements of the vertical and horizontal vectors. These adjustments accommodated mandibular asymmetries or slight asymmetries in pin placements. Also, adjustments were made with ease during the course of distraction. This fine tuning takes advantage of the external distractor potential for multiplanar advancement. One of the main disadvantages of internal devices is that the mandible can only be distracted in a single vector. Consequently, the ability to obtain symmetrical mandibular distraction requires near-perfect placement of osteotomies and distractors. Another limitation of internal distractors is the need to remove them with the patient under general anesthesia. Their removal also requires another incision and disruption of the mandibular periosteum. This second periosteal trauma may adversely affect the repair, nutrition, and long-term growth of the mandible.
Patients with micrognathia and tongue-based obstruction are now treated with MDO very early in life. In this series, 46% of patients were neonates, with the youngest being 5 days old. Advancements in experience and surgical expertise have made MDO a successful treatment for even the youngest patients. The benefits of early treatment are numerous. Fewer days in the intensive care unit and earlier discharges from the hospital are potential advantages of relieving significant upper airway obstruction in neonatal patients.
Several other studies have findings that support using MDO to treat upper airway obstruction in patients with micrognathia.16- 18 However, given the relatively recent use of this therapy in the neonatal and infant population, there is limited knowledge of the long-term results. Maxillomandibular occlusal relationships and persistence of upper airway obstruction are only beginning to be reported.
In conclusion, MDO can relieve tongue-based obstruction in select pediatric patients with micrognathia. This procedure can relieve upper airway obstruction in neonatal patients who are only several days old. It can also be used to decannulate pediatric patients who have been living with tracheotomies for several years. Subsequent research in this patient population should focus on the need to pursue subsequent orthognathic surgery, dental relationships, and injury to permanent dentition.
Correspondence: Craig W. Senders, MD, Cleft and Craniofacial Program, Department of Otolaryngology–Head and Neck Surgery, UC Davis Medical Center, 2521 Stockton Blvd, Ste 7200, Sacramento, CA 95817 (firstname.lastname@example.org).
Accepted for Publication: April 7, 2009.
Author Contributions:Study concept and design: Senders and Kolstad. Acquisition of data: Kolstad and Tollefson. Analysis and interpretation of data: Senders, Kolstad, and Sykes. Drafting of the manuscript: Kolstad. Critical revision of the manuscript for important intellectual content: Senders, Kolstad, Tollefson, and Sykes. Statistical analysis: Kolstad. Administrative, technical, and material support: Senders and Tollefson. Study supervision: Senders, Tollefson, and Sykes.
Financial Disclosure: None reported.
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