Abstract
A modified technique of horseshoe osteotomy combined with Le Fort I osteotomy for superior and posterior repositioning of the maxilla is presented. Eight patients with maxillary excess associated with retrogenia or microgenia were treated with this technique in combination with genioplasty. The maxillary segment was repositioned a maximum of 5.0 mm posteriorly and 7.0 mm superiorly at point A. The mandible autorotated anterosuperiorly to achieve sound occlusion. Point B moved 2.0–10.0 mm anteriorly and 5.0–10.0 mm superiorly. The pogonion moved 7.0–17.0 mm anteriorly in combination with genioplasty. All patients obtained sound occlusion and a good profile after the operation. Almost no skeletal relapse was observed during 1 year of postoperative follow-up. Patients with long faces with maxillary excess and retrogenia often have small, unstable condyles. In these cases, because surgical intervention to the ramus can result in postoperative progressive condylar resorption, maxillary single-jaw surgery with a horseshoe osteotomy, thereby avoiding ramus intervention, is a less invasive option.
Interventions for maxillary vertical excess or protrusion require superior and/or posterior repositioning of the maxillary segment. Superior and/or posterior movement of the maxilla as a single segment after Le Fort I osteotomy is often made difficult by intrusion of the posterior maxillary bone around the descending palatine artery (DPA) and the anterior part of the pterygoid plates. Thus, removal of the maxillary tuberosity and/or the anterior part of the pterygoid plates is often necessary in these cases. There is a risk of injuring the DPA or pterygoid venous plexus, which can result in massive intraoperative haemorrhage and aseptic necrosis of the maxilla, if an incorrect osteotomy is performed. Additionally, relatively large impaction of the maxilla results in abutting of the nasal conchae and nasal floor, decreasing the volume of the nasal chamber.
To overcome these problems, Wolford and Epker, in 1975, described the total maxillary alveolar osteotomy for the management of maxillary excess. In 1977, Bell and McBride introduced the total alveolar osteotomy in combination with Le Fort I osteotomy, named the horseshoe palatal osteotomy. This study group has recently described a modified horseshoe osteotomy technique for superior and/or posterior repositioning of the maxilla and have confirmed the accuracy of the technique in repositioning the maxilla.
Some cases of maxillary excess with retrogenia or microgenia have a nearly normal-sized mandibular dental arch. These patients can theoretically be managed with single-jaw maxillary surgery, i.e., maxillary impaction and/or setback with mandibular autorotation. However, an extremely precise repositioning technique is needed because even a small error will result in malocclusion and relapse. Therefore, two-jaw surgery (Le Fort I and ramus osteotomy) is often used to achieve sound occlusion. A modified horseshoe technique with Le Fort I to achieve sufficient mobilization of the dentoalveolar component is introduced. This technique was applied for the correction of maxillary excess, thus avoiding ramus intervention. Postoperative skeletal stability was also evaluated.
Materials and methods
Patient selection
Eight Japanese females (mean age 26.4 years, range 21–35 years) who underwent maxillary single-jaw surgery with genioplasty for the correction of maxillary excess at the authors’ institution were included in this study. They received pre- and post-surgical orthodontic treatment. All were followed for at least 1 year after surgery.
The patients displayed maxillary excess without asymmetry of the maxilla and mandible. Although they had a nearly normal-sized mandibular dental arch, most had a long face and some degree of anterior open bite with retrogenia or microgenia. With the use of cephalometric prediction, all of the patients were predicted an optimal maxilla–mandibular complex position and a good profile through impaction and/or setback of the maxilla and mandibular autorotation combined with genioplasty ( Fig. 1 ). Specifically patients in whom the optimal repositioning of the maxilla would result in point A being consistent with the McNamara line and the cusp tip of upper tooth number 1 (U1) being at the same level or up to 2 mm below the predicted stomion were selected. The chin position was determined by consent between the patient and the orthodontist based on the predicted Ricketts’ aesthetic line (E-line). The cephalometric analysis used was mainly Burstone’s planning.
Exclusion criteria were previous mandibular surgery other than genioplasty, periodontal disease judged to be severe by the surgeon, previous maxillomandibular surgery, and any history of trauma or craniofacial syndrome.
Surgical technique
A conventional Le Fort I osteotomy was performed in the standard fashion. After down-fracture of the maxilla, the horseshoe osteotomy and additional paramedian osteotomies were performed according to the technique described previously. Briefly, in the horseshoe osteotomy, the down-fractured maxilla is separated into dentoalveolar and palatal components to avoid injury to the DPA and dental roots. The DPA is included in the palatal component. The palatal component is then further split into three segments with two paramedian osteotomies ( Figs 2 and 3 ). More recently, this study group has begun to use an ultrasound scalpel for these steps to prevent injuries to the vessels and the palatal mucosa. The osteotomized palatal segments provide flexibility, which assists the impaction of the dentoalveolar component.
In cases of posterior repositioning, the maxillary tuberosity in the dentoalveolar component is carefully reduced using a round bur, with sub-periosteal stripping of the tuberosity, while protecting the DPA ( Fig. 4 ). The anterior margin of the palatal component can be reduced so that the dentoalveolar component can be repositioned posteriorly. To make the dentoalveolar component more mobile, a small amount of the bony edge of the osteotomized margin of the dentoalveolar component is detached sub-periosteally, preserving the periosteum of the palatal component.
After maxillomandibular fixation is performed and the maxillomandibular complex (MMC) is rotated and seated without any bony interference, two miniplates are adapted to the anterior buttress of the maxilla and the MMC is transitionally fixed with several screws. Maxillomandibular fixation is then released to ensure accurate repositioning of the maxilla. After releasing the maxillomandibular fixation, the mandible should open smoothly. After confirmation of optimal positioning of the maxilla, maxillomandibular fixation is again performed and completion of the internal fixation is done with an additional two miniplates at the posterior buttress. Maxillomandibular fixation is then released, and proper mandibular positioning is reconfirmed by tapping the jaw. Finally, a conventional genioplasty is performed.
Method of analysis
Subjects were evaluated 1 week before surgery (T0) and at 1 week (T1), 6 months (T2), and 1 year (T3) postoperatively. Lateral cephalograms were taken with the patient oriented to the Frankfort horizontal plane with the teeth in centric occlusion. Postoperative changes in U6 and the upper first molar (UMT), as well as point A, point B, and the pogonion, were evaluated. Linear measurements are illustrated in Fig. 1 . Measurements for the x -axis were obtained using a line parallel to the Frankfort horizontal plane. A perpendicular line intersecting the first line at the sella was defined as the y -axis. These x and y axes were transcribed onto each successive radiograph by superimposition on the best fit of the sella, nasion, and anterior and posterior cranial base landmarks.
The relevant points were identified on the x and y axes. Movements of these points were represented as linear measurements in millimetres on both axes. On the x -axis, anterior movement was indicated as a positive value and posterior movement as a negative value. On the y -axis, superior movement was indicated as a positive value and inferior movement as a negative value.
Pre- (T0) and postoperative (T3) patient profiles were also evaluated by the distance of the tip of the upper and lower lips to E-line.
Results
All patients underwent concomitant horseshoe osteotomy with Le Fort I and genioplasty. Recent studies have reported that Japanese people prefer a more posterior position of the lips in orthodontic treatment in comparison to studies performed several decades ago. The preferred position of the upper lip is reported to be on or 1–2 mm posterior to the E-line and the preferred position of the lower lip is reported to be on or 1 mm anterior to the E-line. The postoperative results obtained for patient profile were almost within the range preferred by modern Japanese females ( Table 1 ). Surgeons and orthodontists subjectively judged the postoperative aesthetic condition both frontally and laterally to be good, and all patients expressed satisfaction with their appearance.
| Case No. | T0 | T3 | ||
|---|---|---|---|---|
| Upper lip to E-line | Lower lip to E-line | Upper lip to E-line | Lower lip to E-line | |
| 1 | 2 | 5 | 0 | 1 |
| 2 | 4 | 8 | −1 | 0 |
| 3 | 5 | 5 | −1 | −1 |
| 4 | 1 | 6 | 0 | 1 |
| 5 | 3 | 8 | 1 | 1 |
| 6 | 4 | 6 | −1 | 0 |
| 7 | 5 | 6 | −1 | −1 |
| 8 | 3 | 6 | 1 | 2 |
| Mean | 3.4 | 6.3 | −0.3 | 0.4 |
a Positive results are anterior to the E-line; negative results are posterior to the E-line. T0: 1 week before surgery; T3: 1 year postoperative.
There were no severe complications such as intraoperative haemorrhage, partial or total avascular necrosis of the maxilla, devitalization of teeth, or oro-antral or oronasal fistulas. No patient or orthodontist identified malocclusion after surgery.
Tables 2 and 3 show the movements of the relevant points during the follow-up period. The maxilla repositioned itself 3.0–7.0 mm superiorly and 0–5.0 mm posteriorly. In three cases, the maxilla was affected equally bilaterally, in another three cases the molar side was affected more, and in the remaining two cases the U1 side was affected more. Depending on the new position of the maxilla, the mandible autorotated anterosuperiorly. Point B moved 2.0–10.0 mm anteriorly and 5.0–10.0 mm superiorly. The pogonion moved 7.0–17.0 mm anteriorly and 4.0–9.0 mm superiorly. Chin advancement with the genioplasty ranged from 3.0 to 7.0 mm.
| Case No. | T1–T0 | ||||
|---|---|---|---|---|---|
| U1 | U6 | A-point | B-point | Pogonion | |
| 1 | 0 | 0 | 1 | 10 | 17 |
| 2 | −1 | 0 | −3 | 3 | 10 |
| 3 | −3 | −3 | −3 | 4 | 11 |
| 4 | 0 | 0 | 0 | 4 | 7 |
| 5 | −2 | −3 | 0 | 3 | 7 |
| 6 | −5 | −3 | −2 | 2 | 8 |
| 7 | −5 | −5 | −5 | 3 | 9 |
| 8 | −1 | −1 | −2 | 3 | 9 |
| Mean | −2.1 | −1.9 | −1.8 | 4.0 | 9.8 |
a Positive results are anterior movements; negative results are posterior movements. T0: 1 week before surgery; T1: 1 week postoperative.
| Case No. | T1–T0 | ||||
|---|---|---|---|---|---|
| U1 | U6 | A-point | B-point | Pogonion | |
| 1 | 5 | 6 | 3 | 5 | 4 |
| 2 | 7 | 7 | 7 | 5 | 5 |
| 3 | 7 | 5 | 7 | 9 | 5 |
| 4 | 5 | 5 | 5 | 8 | 8 |
| 5 | 4 | 5 | 3 | 10 | 6 |
| 6 | 4 | 5 | 2 | 7 | 6 |
| 7 | 4 | 4 | 4 | 7 | 9 |
| 8 | 4 | 3 | 4 | 6 | 8 |
| Mean | 5.0 | 5.0 | 4.4 | 7.1 | 6.4 |
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