Maxillary Distraction Osteogenesis

Christina Tragos, Alexander L. Figueroa, Alvaro A. Figueroa, John W. Polley

KEY POINTS

○ Maxillary distraction is indicated for severe maxillary hypoplasia and skeletal clefting.

○ It is an alternative for patients with negative overjet of more than 8 mm.

○ Maxillary distraction osteogenesis creates autologous bone and expands soft tissues.

○ For maxillary distraction, an orthodontic splint is used, with a cranially fixed halo or internal device.

○ The three phases of treatment are latency, activation, and consolidation.

○ This procedure results in angular, linear, and dental changes.

Patients with severe maxillary deficiency as a result of orofacial clefting present multiple challenging problems for the reconstructive team. These patients exhibit multidimensional maxillary hypoplasia and skeletal clefting, with absence of maxillary and alveolar bone, as well as scarring, residual fistulas, and dental anomalies. Although sometimes successful in obtaining adequate occlusal relationships, the traditional surgical and orthodontic approaches to treat these patients often fall short of expectations with respect to facial balance and stability. The application of maxillary distraction osteogenesis in the treatment protocol of patients with severe maxillofacial anomalies offers a powerful alternative for the reconstructive team. In this chapter we present the use of maxillary distraction osteogenesis for the treatment of patients with severe maxillary deficiency resulting from orofacial clefts. The technique of rigid external distraction, based on the well-known concept of cranial fixation, has enabled rigid control over the distraction process, allowing predictable and highly successful outcomes.1

HISTORY

Maxillary hypoplasia is a common finding in patients with orofacial clefting. It has been estimated that 25% to 50% of all patients born with orofacial clefts will be potential candidates for maxillary advancement to correct functional deformities and improve aesthetic facial proportions.2 The majority of patients with orofacial clefts have morphologically normal or slightly smaller than normal mandibles.^3,4 Patients with severe cleft maxillary deficiency are difficult to treat with standard surgical and orthodontic approaches. These patients present with maxillary hypoplasia in the vertical, horizontal, and transverse dimensions and thin or structurally weak bone. The issue of maxillary hypoplasia in cleft patients is compounded by residual palatal and alveolar fistulas, absent and aberrant dentition, and scarring of the palatal and pharyngeal soft tissues. The physical deformities of patients with severe maxillary hypoplasia contribute to multiple functional deficiencies. These include severe malocclusions, which result in compromised mastication, speech abnormalities, and nasal pharyngeal airway constriction.⁵ The severe concave facial profiles in these patients result in highly detrimental psychosocial ramifications as well.⁶

Traditional protocols for treatment of maxillary hypoplasia in cleft patients rely on a surgical/orthodontic approach, including a LeFort I maxillary advancement with concomitant fistula closure and maxillary and alveolar bone grafting. This surgery includes rigid internal fixation hardware for stabilization of the repositioned maxilla in the postoperative period. In the past, it has been difficult to consistently and successfully treat patients with severe maxillary deficiency with maxillary advancement alone. Patients with large anteroposterior maxillomandibular discrepancies may require mandibular setback surgery in addition to maxillary advancement for correction of their severe horizontal deficiency.

It is well known that cleft patients with maxillary deficiency treated with traditional surgery have relapse rates of 0% to 50% in the long term.^7–12 The rigid external distraction (RED) technique results in improved relapse rates. Aksu et al⁷ reported on seven adult cleft patients who underwent maxillary distraction osteogenesis with a RED device for a mean 37 months and found horizontal maxillary relapse rate of 22%. Gursoy et al⁸ found that maxillary position remained stable over 60 months. Cho and Kyung⁹ followed nine cleft distraction patients for 60 months and found a 23% relapse rate. Figueroa et al¹⁰ studied 17 cleft patients over 3 years who underwent maxillary advancement with RED; these patients had a mean advancement of 9.6 mm. At follow-up, the maxilla was found to be stable. Similar horizontal relapse rates after maxillary advancement with rigid internal fixation in cleft patients have been reported by others as well^7–12 (Table 74-1).

Table 74-1 Review of Long-Term Results of Maxillary Relapse in Cleft Patients After Maxillary Advancement

Authors	Number of Cleft Patients	Mean Follow-up (mo)	Mean Maxillary Advancement (mm)	Mean Relapse Rate (%)
Aksu et al⁷	7	37	9	22
Gursoy et al⁸	13	60	13	—
Cho and Kyung⁹	9	60	13.6	23
Rachmiel et al¹¹	19	12	15.8	Minimal
Daimaruya et al¹²	6	12	8	13.4
Polley and Figueroa¹	14	4	11.6	—

Fig. 74-1 Histologic section of a bone biopsy specimen obtained from the pterygomaxillary region when a LeFort I surgery was completed in a patient who had undergone previous maxillary advancement with rigid external distraction. Note the well-ossified dense lamellar bone.

With the use of rigid external distraction, we can gradually reposition a severely hypoplastic maxilla to the exact horizontal and vertical position desired. The patients create autologous bone along osteotomy lines during this process, eliminating the need for a bone grafting and rigid internal fixation hardware (Fig. 74-1). The use of RED has enabled us to correct maxillary skeletal and soft tissue deficiencies with concomitant expansion of the soft tissue facial mask.^13,14

In our initial consecutive series of 18 patients, we used two different techniques for maxillary distraction. One group (four patients) underwent maxillary distraction with the use of orthodontic facemask and elastic traction.¹⁵ Using elastic distraction, horizontal maxillary deficiencies were partially corrected, and we considered our facemask patients to have failed their surgical treatment. Subsequently we changed the design of the distraction technique and developed a RED system. The RED system uses the cranium as an anchorage point for stabilization of the distraction device, from which traction is delivered to the hypoplastic maxilla. Cranial stabilization devices for maxillofacial trauma reconstruction, as well as for elective maxillofacial surgery, have been reported.^16,17 In addition, neurosurgeons have used the cranium as a fixation point for the stabilization of cervical injuries and reconstructions for decades.

The halo distraction device is adjustable, offering vertical and horizontal control during the distraction process. The rigidity of the RED system allowed greater maxillary advancement when compared with patients who underwent facemask elastic distraction. In our initial series of patients who underwent distraction with the RED device (14 patients), the mean effective horizontal maxillary movement at the upper incisal edge was 11.7 mm. A point advancement was 8.3 mm. In Rachmiel’s series of patients with facemask traction,¹⁸ the change in the skeletal angle of convexity was 5.0 degrees, compared with a change of 17.2 degrees in our series using RED. Diner et al¹⁹ obtained 3 mm of horizontal maxillary advancement at A point in patients using facemask and elastic traction. The experience of Hung et al²⁰ was similar: the mean horizontal maxillary advancement was 5.2 mm. Maxillary distraction with facemask and elastic traction is unpredictable and unreliable and only allows horizontal advancement in the 4 to 6 mm range. In our practice, patients who require only 4 to 6 mm of maxillary advancement are treated with traditional surgery and are not routinely considered for treatment with distraction osteogenesis.

Internal distraction devices have also been reported for cleft maxillary advancement.^21,22 Internal devices may require multiple surgical approaches for their placement, a second operative procedure for their removal, and the necessity for an exit port for the activating arm of the device. The vectors of distraction with the use of internal devices will be limited by the placement of each device as well as its finite mechanics. Additionally, with internal distraction devices, the location of the osteotomy is limited, as it must be designed so that there is enough stable bone above and below the osteotomy line to allow appropriate placement and fixation of the distraction hardware. This is not the case with RED. The osteotomy design with the external device is based on the aesthetic requirements of each individual, not on the placement of internal hardware. The transverse maxillary osteotomy can be carried as high as indicated along the piriform aperture, as well as in the malar regions, allowing maximal correction of preoperative facial concavity. Maxillary advancement with RED permits control of the direction and amount of maxillary distraction. The vectors of distraction can be changed at any time during the distraction process. In addition, no additional surgical procedure is required for removal of the rigid external device.

RECONSTRUCTIVE PRINCIPLES

The advantages of maxillary RED are numerous. This technique is an excellent modality for correcting, at any age, the severe midface deficiency present in patients with orofacial clefting and other conditions in which maxillary and midface hypoplasia is present. Rigid external distraction follows the important principles of aesthetic maxillofacial surgery by treating only the affected jaw and offers the multiple benefits of distraction osteogenesis, including not only orthotopic bone generation with expansion of the facial skeleton, but also soft tissue expansion. As a result of maxillary distraction, nasal projection increases, resulting in a more favorable nasolabial angle.23–25

There is no age limitation for treatment with RED. Contemporary surgical orthodontic approaches depend on the patient’s having reached skeletal maturity before reconstructive surgery can be performed. Treating patients in the transitional dentition stage with autologous bone grafting and rigid internal fixation plates and screws, is technically difficult to perform without injury to the developing permanent tooth buds. The RED technique eliminates negative technical factors associated with traditional orthognathic surgery in patients in transitional dental development. With maxillary RED, an osteotomy is performed, but repositioning skeletal segments, internal fixation hardware and bone grafting are not required. The only limitations with RED include adequate dentition, either primary or secondary, for fixation of the intraoral splint, as well as the ability of the patient to wear the device. In special circumstances in patients with craniosynostosis (Crouzon and Apert syndromes), we have used the technique for monobloc advancement as early as 18 months of age, using the second or even the first primary maxillary molar to support the intraoral splint. In addition, special plates have been developed to connect the edentulous maxilla to the RED device.²⁶

PATIENT SELECTION AND EVALUATION

Patients with severe maxillary hypoplasia, as defined as a negative overjet of 8 mm or more, are considered candidates for treatment with maxillary distraction osteogenesis. Criteria for patient selection include the following: unilateral or bilateral cleft lip and palate, severe maxillary hypoplasia (vertical, horizontal, and transverse planes), patients requiring horizontal maxillary advancement in excess of 8 mm, normal mandibular morphology and position, patients with severe palatal and pharyngeal scarring, and patients with airway obstruction and sleep apnea.

All patients undergo a thorough history and clinical examination and a complete dental and orthodontic examination. Preoperative and postoperative photographic and cephalometric records are obtained. Time is spent with the patient and the patient’s family, explaining the distraction process in detail with the use of prediction photographs as well as discussions with other patients and their families who have undergone the procedure. The patient and parents are thoroughly familiarized with the distraction apparatus and its mechanics before the procedure is performed.

MANAGEMENT ALGORITHM

Distraction is an alternative surgical technique to treat severe maxillary and midface deficiencies that are difficult to manage with conventional orthognathic surgery. Patients with unilateral or bilateral cleft lip and palate and severe maxillary hypoplasia are considered for treatment. For patients with mild deformities in which significant paranasal improvement is not required, internal devices could possibly be used for treatment, and patients with milder maxillary hypoplasia may be candidates for traditional surgical/orthodontic treatment. Additionally, patients must be able to undergo complete dental and orthodontic examination, have access to orthodontic treatment, and comply with routine postoperative visits during the activation period.

SURGICAL TECHNIQUE

A custom-made intraoral orthodontic splint, which acts as the link between the maxillary skeleton and distraction apparatus, is manufactured and inserted for each patient. This intraoral splint is constructed with rigid 0.045 or 0.050 stainless steel orthodontic wire (Fig. 74-2, A and B). In the anterior region, two square tubes are soldered just medial to the oral commissures. These tubes are used to house removable traction hooks made of heavy rectangular wire (Fig. 74-2, C and D), which remain in place throughout the distraction process. With this design, the external traction hooks are not present at the time of surgery, facilitating anesthesia management and intraoral surgical manipulation. For ease of management, or where orthodontic support is limited, a splint can be manufactured by a dental lab (such as AOA Laboratories).