True vertical maxillary deficiency is a characteristic of short face syndrome. In these patients, inferior repositioning of the maxilla (IRM) is indicated to improve facial aesthetics and function, but this procedure has been described as the most unstable. The aim of this study was to evaluate the long term, post surgical stability of IRM, fixed with four 2.0 mm L-shaped miniplates, without any type of graft. A cephalometric study was performed, analysing linear measurements (anterior nasal spine, the A point, top of the incisor, top of the buccal-mesial cusp of the first molar, and posterior nasal spine on an X – Y coordinate system) traced immediately preoperatively, immediately postoperatively and at least 6 months post operatively. Eight young adult patients who underwent IRM were studied. The average results of this study were: surgical movement of 4.65 mm at I point, 5.32 mm at anterior nasal spine (ANS) point, and 4.70 mm at A point and relapses of 1.60 mm (35%), 2.23 mm (43%) and 2.10 mm (46%), respectively. It was concluded, that IRM using this type of internal rigid fixation without graft is unstable.
True vertical maxillary deficiency is relatively rare compared to other dentofacial deformities , but it is the main characteristic of short face syndrome (SFS) . Inferior repositioning of the maxilla (IRM) is often the procedure of choice for these patients; but it involves a therapeutic challenge due to the maxillary instability resulting from the surgery . Data on the stability of inferior maxillary repositioning are scarce, with skeletal relapse varying from 0.4% to 64% . Several factors are thought to contribute to this instability.
W essberg & E pker studied masticatory muscle activity before and after IRM and concluded that in SFS patients electromyographic activity is higher, either in activity or at rest, when compared to that in patients with normal morphology. Similar results were obtained by S ong et al. showing that the bite force is reduced after surgery, but remains higher than that of patients with normal morphology. W ardrop & W olford listed some factors contributing to instability, including inappropriate preoperative orthodontic therapy, peri-operative complications, inadequate maxillary mobilisation during downfracture, inadequate stabilisation techniques, lack of bone grafts, and inadequate bone-grafting techniques. P roffit et al. suggested that SFS patients need a sagittal split ramus osteotomy to reduce muscle masticatory activity.
Most studies report the use of iliac crest bone graft for Le Fort I osteotomy . Other authors successfully used hydroxyapatite (HA) blocks . Only two studies addressed the stability of the IRM in non-cleft patients after Le Fort I osteotomy using miniplates . The present study reports the long-term stability of IRM in non-cleft patients who had undergone Le Fort I osteotomy using miniplates, without graft.
Material and methods
The data analysed in this retrospective study were collected from the database of the Department of Oral and Maxillofacial Surgery at Piracicaba Dental School – State University of Campinas (UNICAMP), from January 1990 to July 2009. Inclusion criteria were: patients had vertical maxillary deficiency due to a maxillary hypoplasia treated with Le Fort I osteotomy, without segmentation; patients had been operated on by the same senior surgeon, using the same surgical technique; patients had undergone orthodontic and surgical treatment; patients needed a minimum inferior maxillary repositioning of 3.0 mm; and maxillary fixation was done using four L-shaped plates (two plates on canine buttress and two plates on maxillary–zygomatic buttress; Fig. 1 ).
To evaluate the stability of the IRM, lateral cephalograms were evaluated considering the three periods of image taking: preoperatively (T0), immediately postoperatively (T1), and at least 6 months postoperatively (T2). All cephalograms were taken at a similar focus distance and all images were traced and analysed by the same individual ( Figs 2 and 3 ).
Vertical and horizontal tracing measurements were made using digital callipers, on an X – Y coordinate system, where the X axis was established by a line 7° downward from the S–N line. A vertical reference line perpendicular to the X axis crossing the S point was drawn and labelled the Y axis ( Fig. 4 ). The X – Y axes were drawn on the preoperative image (T0) of each patient. The two subsequent tracings were carried out for T1 and T2. All the tracings were handmade and repeated twice.