Abstract
Maxillary hypoplasia is a common outcome in patients with cleft lip and palate after surgical and orthodontic interventions, and maxillary distraction osteogenesis has become a useful procedure for patients with extensive maxillary deformities. The aim of this study was to evaluate long term (two years) stability after maxillary advancement of more than 10 mm by distraction osteogenesis in cleft patients using internal devices. We organised a retrospective study on 42 patients with cleft lip and palate using cephalometric analysis before and after maxillary distraction osteogenesis and evaluated them for 24 months. Postoperative measurements showed a marked advancement with an increase of 13.3 mm and 10.8° in the length of the maxilla (Co-A) and SNA, respectively, including a shift from Angle class III to class I in dental relations. Follow-up observations showed preservation of maxillary length with a relapse of only 6.0 % (mean (SD) 0.8 (0.7) mm) and 10% relapse in SNA angle (mean (SD)1.1 (1.4) °) one year postoperatively and a negligible regression at the two years’ follow up. This large-scale study shows stable results of skeletal advancement using distraction osteogenesis, indicating safe and reliable outcomes among patients with cleft lip and palate.
Introduction
Maxillary hypoplasia is a common outcome in patients with cleft lip and palate (CLP) after surgical interventions. Intrinsic effects may also cause the posterior height of the basal maxilla to be reduced in patients who have not been operated on. Primary repair of CLP in early childhood improves facial appearance, speech, and deglutition. However, the inevitable impairment in maxillary growth that results from surgery may cause malocclusion, and aesthetic deformities. In our experience, between 25% and 60% of patients with CLP need surgical advancement of the maxilla to treat these complications.
A conventional Le-Fort I osteotomy with rigid fixation has proved to be a reliable treatment for patients with mild to moderate malformations such as isolated cleft lip and palate, but because of formation of postoperative scar tissue among these patients, the maxilla is difficult to mobilise and relapse rates are high. Large sagittal discrepancies between bony segments also expose patients to a higher risk of velopharyngeal insufficiency. These limitations may be overcome by maxillary distraction.
Maxillary distraction osteogenesis has become a common procedure for patients with maxillary hypoplasia, and is considered to be safe and efficient. Distraction osteogenesis (DO) results in gradual formation of bone in the osteotomy line and in the pterygomaxillary region by the use of traction. The advantages of this technique include the ability to treat growing and adult patients, and an additional elongation of adjacent soft tissues including muscles, nerves, and skin. The disadvantages include physical and emotional difficulties for the patient as a result of prolonged fixation of the devices, particularly the external ones. Other disadvantages include a second intervention for removal in the case of internal devices, and difficulty in controlling the vector of elongation.
Our primary objective was to evaluate long-term stability (two years) after maxillary advancement of more than 10 mm by distraction osteogenesis in patients with clefts using internal devices. We hypothesised that maxillary advancement by distraction osteogenesis among patients with CLP is a stable and safe technique.
Patients and methods
For the present retrospective study 236 patients treated for cleft lip and palate and maxillary retrognathism between January 2000 and January 2015 were identified and evaluated for inclusion criteria. These included a repaired cleft lip and palate, and maxillary advancement of more than 10 mm using distraction osteogenesis. Patients who had had conventional orthognathic surgery were excluded. Patients with significant maxillomandibular canting and transversal asymmetries who required additional surgical procedure were also excluded.
All patients included were operated on according to our well-established protocol of reconstruction of the cleft lip and palate (including repair of the lip and palate in infancy and early childhood, and bone grafting to the cleft maxillary alveolus between the ages of 8-11). The preoperative dental characteristics of the patients are shown in Table 1 , and include typical features including missing lateral or central incisor for most and Angle class III dental relations. All patients were treated preoperatively by an orthodontic team to achieve alignment of the teeth in the dental arch and levelling to the occlusal plane. Radiographic imaging before distraction osteogenesis, included panoramic radiograph, lateral cephalometric radiograph, and cone-beam computed tomography (CT), followed by an evaluation of the hard and soft tissues. The surgical plan, including anticipated elongation of the hypoplastic maxilla, was based on measurements made on radiographic cephalograms, and clinical photographs. All patients had substantial midface depression ( Figs. 1 and 2 ) and were treated using internal distraction devices.
| Dental characteristic | No. (% of patients) |
|---|---|
| Missing teeth: | |
| Single tooth | 21/42 (50%) |
| Up to three teeth | 14/42 (33.3%) |
| Dental relations: | |
| Class III malocclusion | 42/42 (100%) |
| Crowding: | |
| None | 23/42 (54.7%) |
| Mild | 19/42 (45.2%) |
| Open bite | 28/42 (66.7%) |
Surgical technique
The patients were operated on under general anaesthesia. An intraoral circumferential horizontal incision was made 5 mm superior to the mucogingival junction between the second molar regions on both sides of the maxilla. The maxillary bone was then exposed and both infraorbital nerves identified. A Le-Fort I osteotomy was completed, and the maxilla down-fractured and fully mobilised. Two internal distraction devices (KLS-Martin) were positioned and fixed to the maxillary alveolar bone and the zygomatic buttresses in a dual inferior and anterior vector according to the preoperative plan and using two parallelisation instruments.
Distraction devices were then placed under the mucoperiosteal flap while distraction arms remained exposed, and a latency period of three days preceded the phase of active distraction. This is calculated beforehand according to the planned length of elongation, or usually around three weeks with a twice-daily elongation of 0.5 mm. We made a slight over-correction of 2-3 mm. Throughout a consolidation period of about 16 weeks, weekly follow-ups were made to prevent postoperative complications and to monitor the patient’s weight and oral hygiene.
Both internal distractors were removed at a second operation. Postoperatively all patients had continued orthodontic treatment for postoperative adjustment, and achieved maximal intercuspidation with stable Angle class I dental relations. Most of the patients continued speech therapy after operation.
Cephalometric analysis
All patients had lateral cephalograms preoperatively (T1), at the time of removal of the internal devices (T2), 12 months after removal (T3), and 24 months after removal (T4).
For our retrospective study, we chose four skeletal and two dental landmarks. To evaluate skeletal changes, the following measurements were used: nasion-sella line to A point (SNA angle), A point to nasion-sella line perpendicularly (A-SNLP line), and condylion to A point (Co-A line). Dental relations were evaluated by horizontal overjet. Data were then documented and analysed. The study was approved by Rambam Health Care Campus Ethics Committee Approval No. 0423-09-RMB.
Statistical analysis
We used SPSS Statistics for Windows (version 17.0 SPSS Inc.) software for statistical analysis. All variables were divided into continuous and categorical, and the changes between T1 and T2, T2 and T3, and T3 and T4, were compared for each variable. For all statistical tests, p < 0.05 was accepted as significant.
Results
The final group consisted of 42 patients; 21 male and 21 female, whose ages ranged from 16 – 29. All patients treated by maxillary distraction osteogenesis had pronounced forward advancement of the maxilla ( Fig. 3 ). There was no intraoperative morbidity. The consolidation period ranged between 4 – 6 months, usually about 16 weeks. Postoperative observation (T2) showed a mean maxillary advancement of 13.3 mm (range 9 −17 mm) and 10.8° measured by maxillary length (Co-A) and SNA, respectively. Dental relations improved from Angle class III malocclusion to class I with a mean (SD) change of 10.7 (4.17) mm in the horizontal overjet, followed by final orthodontic adjustment to complete the normalisation of maxillomandibular relations. All patients with a unilateral cleft palate had a unilateral cross-bite. Patients with bilateral cleft palate had a bilateral cross-bite. All patients had orthodontic correction to resolve the cross-bite during puberty. The first follow up measurements were made 12 months postoperatively ( Figs. 4 and 5). As shown in Table 2 , maxillary length was preserved with only 6.0% (mean (SD) 0.8 (0.7) mm) posterior relapse. SNA angle was decreased by 1.1° (10%). A regression of 1 mm in the horizontal over-jet maintained the Angle class I dental relations achieved by the operation. Twenty-seven patients attended the second follow-up two years postoperatively. Skeletal measurements showed a minimal additional posterior regression of 0.5 mm and 0.4° in maxillary length (Co-A) and SNA, respectively, and a non-significant decrease in dental relations (over-jet).
