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Surgical Approach to the Patient with Bimaxillary Protrusion
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CLINICS IN PLASTIC SURGERY Clin Plastic Surg 34 (2007) 535–546
Surgical Approach to the Patient with Bimaxillary Protrusion Yong-Ming Chu, MDa, Roger Po-Hsun Chen, DDSb, David E. Morris, MDc,d, Ellen Wen-Ching Ko, DDS, MSb, Yu-Ray Chen, MDa,* -
Discussion Patient evaluation and treatment planning Surgical technique Lower anterior segmental osteotomy (Kole procedure) Upper anterior segmental osteotomy (Wassmund procedure)
The patient who has bimaxillary protrusion often is treated using a combination of orthodontics and orthognathic surgery, and the general approach is dental extraction with retraction of the incisors and/or anterior segmental osteotomies. In certain cases, maxillary excess may be corrected solely with LeFort I osteotomy and setback and without dental extraction or anterior segmental osteotomies. This article discusses (1) treatment evaluation and planning and (2) the specific surgical techniques, primarily anterior segmental osteotomies and the technical details for setback of the LeFort I osteotomized segment (more than 5 mm), as they relate to the surgical approach of the patient who has bimaxillary protrusion.
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LeFort I osteotomy with setback Complications Errors in planning Errors in surgical technique Summary References
Discussion Patient evaluation and treatment planning Bimaxillary protrusion is a common dentofacial pattern in the Asian population. It is characterized by protrusive dentoalveolar position of the maxillary and mandibular dental arches. The perioral soft tissues demonstrate protrusive upper and lower lips, lip incompetence, excessive exposure of frontal teeth, a gummy smile, and mentalis strain. Improvement in facial aesthetics is the primary reason adult patients who have bimaxillary protrusion seek treatment. The treatment consists of orthodontic correction with extraction of four premolars and orthognathic surgery if skeletal
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Craniofacial Center, Department of Plastic and Reconstructive Surgery, Chang Gung Memorial Hospital, Chang Gung Medical College and Chang Gung University, 5 Fu-Shin Street, Kweishan, Taoyuan 333, Taiwan b Department of Craniofacial Orthodontics, Chang Gung Memorial Hospital, Chang Gung Medical College and Chang Gung University, 6F, 199 Dung Hwa North Road, Taipei 105, Taiwan c Division of Plastic, Reconstructive, and Cosmetic Surgery, The Craniofacial Center, University of Illinois at Chicago, 811 S. Paulina, Chicago, IL 60612, USA d Shriners Hospital for Children, 2211 N. Oak Park Avenue, Chicago, IL 60707, USA * Corresponding author. E-mail address: [email protected] (Y-R Chen). 0094-1298/07/$ – see front matter ª 2007 Elsevier Inc. All rights reserved.
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doi:10.1016/j.cps.2007.05.006
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problems are significant. To determine which cases are suitable for surgical correction, pretreatment skeletal, dental, and soft tissue evaluation is essential for diagnosis and treatment planning. The skeletal assessment evaluates facial symmetry, the sagittal position of maxillary and mandibular skeletal base, and the vertical proportion of lower facial height. Dental assessment includes occlusion type, alignment of dentition, and incisor inclination. Soft tissue evaluation should include both static and dynamic assessment, whether the incisors show at rest and during smiling, interlabial gap, nasolabial angle, and mentolabial fold. Cephalometric and panoramic radiographs are useful for identifying the skeletal and dental relations, demonstrating the condition of the temporomandibular joint, and identifying any pathologic lesions. The patient’s main concern and aesthetic considerations should be the first priorities in decision making and formation of a treatment plan; understanding the importance of these considerations is the key factor in treatment success and patient satisfaction. If the skeletal problems of bimaxillary protrusion involve only sagittal excess and protrusion of both jaws, the condition can be corrected by anterior segmental osteotomies and extraction of premolars of the affected jawbones (Fig. 1). The anterior segment can be set back by segmental movement or by palatal tipping of the incisors; depending on the original sagittal incisor inclination. If the anterior segment
is retracted and tipped palatally, there will be vertical discrepancy between the canines and premolars. This vertical discrepancy can be corrected orthodontically if it is less than 3 mm. A distance exceeding 4 mm predisposes the patient to potential periodontal problems during subsequent orthodontic correction. Aside from anterior segmental osteotomy of the jawbones, simultaneous genioplasty (vertical elongation or advancement) is usually required to further improve facial profile and proportion. For the patient who has bimaxillary protrusion combined with maxillary vertical hyperplasia (excess), the concomitant problems of long lower facial height, lip incompetence, and unaesthetic gummy smile should be addressed. Maxillary LeFort I osteotomy with superior impaction may be considered in the surgical plan (Fig. 2). The smiling arc can also be improved by proper maxillary posterior impaction [1]. Overimpaction of the anterior maxilla, however, widens the alar base and leads to insufficient show of the upper front teeth during smile or resting lip posture. It is important that patients have realistic expectations before surgical correction of bimaxillary protrusion. All patients should be informed of the anticipated subtle soft tissue changes such as upper lip lengthening, deepening of the nasolabial fold, and widening of the nasal base that will result from surgery. It is essential to avoid overcorrection of the anterior segment and to preserve some lip fullness, especially in older patients. It is an art for the
Fig. 1. 29 year-old woman with bimaxillary protrusion. (A, B) Preoperative views. (C, D) Fourteen months after Wassmund and Kole procedures and genioplasty.
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Fig. 2. 30 year-old man with bimaxillary protrusion. (A, B) Preoperative views. (C, D) One year after three-piece LeFort I osteotomy, Kole procedure, bilateral sagittal split-ramus osteotomy, and genioplasty.
surgeon and orthodontist to achieve the very fine balance between optimal anterior dentoalveolar retraction and preservation of a youthful appearance that is associated with a certain degree of bimaxillary fullness.
Surgical technique A number of factors, as discussed previously, determine the surgical treatment plan for the patient who has bimaxillary protrusion. More specifically, the decision as to which procedure(s) are to be used is based on clinical examination of the patient, patient desires, radiographic analysis and prediction tracing, and pretreatment and preoperative model studies. At our centers, the orthodontists perform the tracing and model tasks and then proceed to preoperative model surgery to construct the surgical splint(s). Thus the plan may include some combination of LeFort I osteotomy, bilateral sagittal split-ramus osteotomy (BSSO) of the mandible, and upper and lower anterior segmental osteotomies (Wassmund and Kole procedures, respectively). The surgical techniques for LeFort I osteotomy and BSSO are well described elsewhere for the former, the authors prefer the method described by Bell and colleagues [2,3] and for the latter they prefer that described by Hunsuck [4] with modifications that they have developed. Several points related to these procedures warrant further discussion. For BSSO, the authors routinely perform full detachment of the pterygomasseteric muscle sling and ostectomy of the pterygoid
protuberance (Fig. 3). They believe that this modified technique allows a greater amount of mandibular advancement or setback with probable better long-term stability [5,6]. In addition, it allows concomitant contouring to reduce the mandibular angle, with results that are aesthetically quite pleasing for some Asian women who desire a softer, gentler contour of the mandibular angle [7,8]. Finally, this approach provides a useful source of bone graft if needed [9]. For the LeFort I osteotomy, the authors prefer to use a 90 oscillating saw to cut the pterygomaxillary junctions initially and then complete the disjunction using a curved thin-blade osteotome (Fig. 4). In this manner, the maxilla is downfractured with relatively little effort and minimal risk [10–14]. The authors believe that this technique has the advantage of being less traumatic and requires no special instrumentation. The following discussion focuses on the authors’ surgical approach to performing upper and lower anterior segmental osteotomies and the details of their approach to setback of a LeFort I osteotomized segment greater than 5 mm. For patients who have bimaxillary protrusion, anterior segmental osteotomies are sometimes performed in isolation; in other cases these are combined with a LeFort I osteotomy or BSSO. In the latter scenario, specific points should be noted regarding both intraoperative osteotomy sequence and osteotomy design. Finally, an isolated LeFort I osteotomy with setback can be a useful alternative for correcting maxillary excess (eg, in patients
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Fig. 3. Bilateral sagittal split-ramus osteotomy. The drawing demonstrates the technique described by Hunsuck with the authors’ modifications. (A) Configuration of osteotomy lines. (B) Full detachment of the pterygomasseteric muscle sling. (C, D) Ostectomy of the pterygoid protuberance facilitates concomitant angle contouring and is a good source of bone grafts if needed. (From Honda T, Lin CH, Yu CC, et al. The medial surface of the mandible as an alternative source of bone grafts in orthognathic surgery. J Craniofac Surg 2005;16(1):123–8; with permission.)
previously compromised by extraction orthodontic treatments) (Fig. 5). When upper and/or lower anterior segmental osteotomies are to be performed, the surgeon usually extracts the bilateral first premolars at the time of the surgical procedure; alternatively, this extraction may be done early in treatment. If extractions are not necessary or feasible (eg, when teeth have been extracted previously), interdental osteotomies can be performed safely between parallel roots of the canines and premolars or the canines and lateral incisors. The authors rarely find it necessary to extract teeth just for the purpose of the surgery if there is no specific orthodontic reason for extraction. Before surgery the orthodontist removes the brackets from teeth to be extracted and segments the upper and lower arch wire that spans them so that there is discontinuity across these
teeth. This procedure makes extraction easier and also prevents extraction of the wrong teeth.
Lower anterior segmental osteotomy (Kole procedure) The upper and lower anterior gingivobuccal sulci are infiltrated with 2% xylocaine with 1:100,000 epinephrine for hemostasis. The authors use ropivacaine (Naropin), a long-acting local anesthetic, for probable better-controlled hypotensive anesthesia and less postoperative pain [15]. In general, they prefer to use only a final splint and to perform the mandibular osteotomy first. Turning first to the lower arch, the lower first premolars are extracted (Fig. 6). A gingivobuccal incision is made extending from the region of the first molar across to the contralateral first molar, and the soft tissues are elevated caudally in the
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Fig. 4. Useful pearls in performing the LeFort I osteotomy. (A) Essential instruments are a 90 right-angle saw and a curved thin-blade osteotome. (B) Placement of oscillating saw for the initial cut of the pterygomaxillary junction. (C) Completion of the pterygomaxillary disjunction with a curved thin-blade osteotome.
subperiosteal plane. Care is taken to identify and preserve the bilateral mental nerves during the subperiosteal dissection both in the symphyseal region and posterior to the nerves along the mandibular body. A small elevator is used to lift a gingival bridge buccally where the first premolars have been extracted and where the interdental osteotomy will be performed. The authors prefer to preserve continuity of this gingival bridge to maintain one additional source of vascularity to the segment and to avoid a vertical scar and recession along the gingiva that may be apparent when the patient smiles. Gingival dissection is also performed adjacent to the first premolar on the lingual side (Fig. 6A & 6C). The planned osteotomy lines are marked with a pencil. The roots of the canines are identified, and the horizontal osteotomy line is drawn at least 5 mm inferior to this level, usually at about at the level of the mental foramina (Fig. 6B). At this point it must be decided whether a genioplasty will be performed; if so, care must be taken not to draw this line too low, because an adequate intervening segment of bone must be maintained to provide stable points of fixation for both the anterior segment and the genioplasty segment and to avoid an unplanned fracture. The blood supply enters the canine root about 2 mm inferior to the tip of the root, so the horizontal osteotomy must, at the very least, be below this point. Two lines relatively perpendicular to this horizontal osteotomy line are drawn on each side that delineate the segment of bone to be removed in setting back the segment (Fig. 6A & 6C). This line is designed to not
encroach within 5 mm of the mental nerve, and care also must be taken to preserve adequate bone to support the roots of the adjacent canine and second premolars (usually at least 1 mm). Using a 3mm round burr, the vertical segments of bone where the premolars had been extracted are excised in a buccal-to-lingual fashion. In doing so the burr is maintained perpendicular to the curve of the mandibular surface, and a Ragnel retractor is used to lift the intervening gingival bridge gently. The segment can be set back about 5 to 6 mm, so the 3-mm–wide burr serves as a guide in determining how wide of a segment to resect. For an interdental osteotomy, a 1-mm round burr or even a reciprocating saw with a thin blade should be used. A reciprocating saw then is used to make the horizontal osteotomy. The blood supply to the osteotomized segment is derived primarily from the remaining lingual attachments (genioglossus muscle and gingival attachments); the maintained bridges of gingiva on the buccal side may supply a minor contribution. After the segment has been mobilized completely, reference is made to the models and splint(s) to position the segment optimally. The final position of the segment in relation to the second premolars should be noted. Typically a few areas of bony contact remain that must be identified and burred further to allow setback of the osteotomized segment into its final position. Initially attention is paid to positioning the segment appropriately horizontally with respect to the position of the bilateral second molars and to achieving inclination identical to that in the model.
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Fig. 5. A 28-year-old woman who had bimaxillary protrusion after compromised extraction orthodontic treatment performed at an outside institution. (A, B) Preoperative views. (C, D) Seven months after a LeFort I osteotomy with 5-mm setback, 3-mm intrusion, and 2.5-mm advancement genioplasty.
Additional burring of bone on one or both sides may be needed, and here care should be taken not to expose the dental roots. The surgeon also must be aware of the degree of preoperative pro/ inclination of the incisors and the desired postoperative inclination. This precaution is necessary because in cases that require a true horizontal setback (ie, no change in pro/inclination) the surgeon must avoid torquing the segment into the splint, which will result in a change in inclination. Once the ideal horizontal position is achieved, any vertical discrepancy is corrected to level the teeth of the segment in relation to those of the
adjacent stable arch (Fig. 6D). To accomplish this leveling, additional bone may be burred from the inferior edge of the segment, from the adjacent upper mandibular border, or from both. The lower teeth are placed into the splint to estimate whether the position is adequate. With the splint in place, a horizontal interdental wire is placed around the canine and second premolar bilaterally to secure the segment in place temporarily, preventing avulsion while attention is turned to the upper arch. If BSSO is necessary, the authors prefer to perform the BSSO initially but without complete splitting.
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Fig. 6. Lower anterior segmental osteotomy (Kole procedure). Markings for (A) the right vertical, (B) horizontal, and (C) left vertical components of the osteotomy. Arrows designate the canine roots. Note that the gingival bridges remain intact and are retracted. (D) The osteotomized segment is mobilized, and any bony interference preventing proper seating of the segment into the splint is burred. (E) Configuration of the fixation hardware.
The split is completed after the Kole procedure, providing better control of the segment.
Upper anterior segmental osteotomy (Wassmund procedure) As in the lower arch, upper teeth (generally the first premolars) are extracted first (Figs. 7 and 8). The authors prefer the technique relying on the use of the palatal pedicle (Fig. 7D & 8E). The palatal mucosa is elevated in the subperiosteal plane to form a tunnel between the site of each extracted tooth, converging at the midline. This tunnel should be about twice the width of the 6-mm diameter of the extracted tooth so that the palatal mucosa does not kink with setback. Anterior segmental osteotomies may be performed without concomitant LeFort I osteotomy; however if a LeFort I osteotomy is part of the surgical plan, it is completed at this time (ie, after exposure of the anterior segmental osteotomy, but before it is cut). It is much easier to perform the LeFort I osteotomy before the segmental osteotomy than the reverse. The tip of the canine root lies at about the same horizontal level as the nasal floor, and the anterior component of the
LeFort I osteotomy should be kept at least 5 mm above this. After the LeFort I osteotomy has been completed and the segment has been mobilized completely, the osteotomy lines for the anterior segmental osteotomy are drawn. The width of the bone that will be excised with burrs should be planned meticulously. Patients who have bimaxillary protrusion usually have proclined upper incisors, which should be corrected. For this correction, more bone should be removed from around the tooth level than from the upper edge of the segment (ie, the marked ‘‘ostectomy’’ segment should look roughly trapezoidal or wedge-shaped) (Fig. 8F). Parallel excision of the bone probably will result in poor bony contact along the upper edge, which may affect long-term stability. On the other hand, too much clockwise rotation of the segment into the splint secondary to inadequate bone removal must be avoided also. Hence, the surgeon must be flexible in performing the complete osteotomies and select carefully the burrs or thin-bladed reciprocating saws that are most appropriate for a given case. Again, the burr should be maintained perpendicular to
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Fig. 7. General surgical approach to a maxillary anterior segmental osteotomy (Wassmund procedure) and mandibular anterior segmental osteotomy (Kole procedure) in a patient who has bimaxillary protrusion. (A) Patient demonstrates typical skeletal and soft tissue features. (B) Extraction of the bilateral upper and lower first premolars. (C) Vertical bony segments (light blue) to be resected and site of concomitant LeFort I osteotomy (dotted line) if indicated. (D) A subperiosteal tunnel along the palate is raised to allow the osteotomy. (E) Initial LeFort I osteotomy facilitates completion of anterior segmental osteotomy. (F) The osteotomized segment has been posteriorly repositioned and set upright. (G) Resultant change in skeletal and soft tissue appearance.
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Fig. 8. Intraoperative steps in a maxillary anterior segmental osteotomy. (A–C) Preoperative radiographs of the patient in this figure. (D) Right first premolar has been extracted. (E) Subperiosteal tunnel is dissected across the hard palate between the bilateral extraction sites. (F) The gingivoperiosteal flap is left intact and retracted inferiorly while the right vertical maxillary osteotomy lines are marked. Note the trapezoidal or wedge-shaped ostectomy area. (G) Both LeFort I and anterior segmental osteotomies are completed. (H) The LeFort I posterior segment is split bilaterally in the paramedian fashion. (I) Final fixation of both segments.
the maxillary arch at all times to avoid injury to the dental roots. Both the intervening gingival bridge and the palatal mucosa are retracted away from the bone to avoid soft tissue injury. The osteotomy proceeds from laterally to the midline on one side and then laterally to the midline on the contralateral side. When a three-piece LeFort I osteotomy is indicated, unilateral paramedian split of the LeFort I posterior segment is performed if the patient does not require significant expansion or torque of the posterior arch. Bilateral paramedian split is not performed routinely if the segments fit into the splint very well after only a unilateral split (Fig. 8H). Once all segments are mobilized fully, reference is made to the surgical models and splint(s), and tooth positions are compared. Additional bone is burred from the anterior segment or from the adjacent maxilla to eliminate any bony interference that prevents the anterior segment from coming into its desired position. Each segment of the upper
dentition is placed and wired into the splint. Next, each segment of the lower arch is wired into the splint. Temporary wire fixation of the maxilla is applied first, to judge the sagittal, transverse, and vertical dimensions of the facial appearance including the profile, dental, and facial midlines and gingival and dental display. The superior aspects of the anterior and/or posterior segments may need to be burred if the maxillary excess in the vertical dimension should be corrected also (ie, too much gingival show during smile and excess dental display at rest). For correction of sagittal maxillary excess, additional LeFort I en bloc setback sometimes is necessary even after the intervening portions between the anterior and posterior segments have been removed entirely and the spaces have been closed. This situation is encountered more frequently when LeFort I osteotomy with impaction is undertaken and the sagitally longer portion of the segment has been raised, introducing additional bony interference between
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the maxillary tuberosity and pterygoid process. Clockwise rotation of the occlusal plane will worsen this situation further if it has not been included in the surgical design, because this maneuver might not be predicted precisely during preoperative surgical planning. For this reason the authors prefer to use only a final splint, with both surgeon and orthodontist taking equal responsibility for the fine adjustment of patients’ facial appearances. They do not argue against the value of two-splint designs or discount the orthodontic effort in planning two-splint cases, realizing that there is no other surgical option in these circumstances if no concomitant BSSO is performed. The coordinated effort of the orthodontist and surgeon is of utmost importance.
LeFort I osteotomy with setback For setback of LeFort I osteotomized segments, the authors would like to share their experience with several helpful nuances that facilitate this somewhat difficult procedure. First, although the authors usually prefer not to fracture or even penetrate the pterygoid process because of the associated increase in intraoperative bleeding, reducing the pterygoid process remains an alternative. When left intact, they feel that the pterygoid process provides some support while posteriorly repositioning the maxilla. Second, posterior segments of the maxillary tuberosity can be resected. Third, extraction of the third molars facilitates greater setbacks (especially > 5 mm). This procedure requires resecting more maxillary tuberosity and even the posterior palatine plates of the maxilla. An oscillating saw can be used in this scenario for controlled partial fracture laterally, quite similar to the technique the authors use in pterygomaxillary disjunction. Then the same curved thin-blade osteotome used during pterygomaxillary separation and a small curved elevator are used to take out the excess. Although limited visibility makes this procedure difficult, it can be performed meticulously and safely without tearing the palatal mucosa. For large setbacks, the descending palatine neurovascular bundles are not routinely cauterized or ligated. They can be dissected carefully from the canal and well protected. If injured, however, they are cauterized or ligated because of the risk of significant postoperative bleeding. With proper design and technique, the palatal mucosa can provide adequate blood supply even after multiple segmental osteotomies [16]. Based on this technique, the authors believe that solitary LeFort I osteotomy with setback is an alternative for treating maxillary excess without any extraction or upper anterior segmental osteotomy when (1) there is no orthodontic reason for extracting anterior teeth; and (2) LeFort I osteotomy with clockwise rotation of the occlusal plane is sufficient,
and/or more favorable than upper anterior segmental osteotomy to correct proclined upper incisors (see Fig. 5). The feasibility of large setback should also be carefully considered from a dental hygienic point-of-view; especially in the case of concomitant setback and intrusion, this can interfere with the patient’s ability to clean the maxillary second molars. Internal plate-and-screw fixation is achieved either first at the lateral buttresses of the maxilla (if a LeFort I osteotomy was done) and then from the medial buttress to the setback anterior segment, or vice versa. When the maxilla is split into three or more segments, extra intersegmental fixation can be performed also if sufficient bony buttresses remain and there is no risk of injury to the dental root (Fig. 8I). After maxillary fixation, internal fixation is placed in the lower jaw, and intermaxillary fixation always is released to ensure that there is no discrepancy between centric relation and centric occlusion. This technique also improves patient comfort in the immediate postoperative period. When the maxilla is either split into two pieces or only the maxillary anterior segmental osteotomy is done and both fit precisely into the splint and are rigidly fixated, the splint often is removed at the end of the operation. When the maxilla is split into three or more pieces the splint also may be removed if extra intersegmental fixation has been accomplished safely and rigidly (see Fig. 8I). If there is any question about the fit into the splint or the rigidity of fixation, the splint is left in place at the conclusion of the operation.
Complications Complications in treating the patient who has bimaxillary protrusion may result from errors in surgical planning or from errors in technical execution of the procedure.
Errors in planning Although both upper anterior segmental osteotomy and LeFort I osteotomy with setback are very powerful procedures in treating the patient who has bimaxillary protrusion, they also can have the deleterious effect of creating an aged appearance. As the skeletal support of the midfacial soft tissues moves posteriorly the soft tissues relax, causing more apparent nasolabial folds, a more obtuse nasolabial angle, and lowering of the lip vermillion, decreasing gingival display during smile and dental display at rest. All patients should be warned preoperatively of the possibility of this aged appearance, and particular care should be taken in planning such setback procedures in patients who exhibit
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any of these findings preoperatively. Care should also be taken when considering such procedures in relatively older patients (ie, age 30 years or older). Finally, at the authors’ centers patients are recommended to be seen both pre- and postoperatively by clinical psychologists to help patients and their families both anticipate and adjust postoperatively to changes in appearance.
Errors in surgical technique Osteotomy positioning In performing anterior segmental osteotomies, particular attention must be paid to design osteotomies to avoid injury to adjacent structures. In the maxilla, resection of the interdental segments must not expose the dental roots. The horizontal component also must lie superior to all dental roots. The same holds true in the mandible; in addition the horizontal osteotomy must be below the lowest dental roots but remain high enough to allow for an intervening segment of intact bone if genioplasty is to be performed. This intervening segment must be thick enough to accommodate screws for fixation without fracturing. All osteotomies should be marked carefully with a pencil before cutting, and fine burrs should be used. Segmental necrosis To avoid devascularization of osteotomized segments, subperiosteal soft tissue elevation should be performed only so far as required for performing osteotomies. Particular care should be taken to leave all posterior soft tissue attachments of the mandibular segments intact and to leave adequate palatal attachment for each maxillary segment. In the authors experience, full detachment of the pterygomasseteric muscle sling has not created any problem related to the viability of the proximal mandibular segment after BSSO; here the soft tissue attachments of the coronoid and condylar processes and the surrounding environment provide adequate circulation. Postoperative malocclusion Prevention of postoperative malocclusion of course begins with careful planning and construction of the operative splint preoperatively. Intraoperatively, however, the surgeon must be vigilant in making sure that all segments fit precisely into the splint without inappropriate rotation. The surgeon must burr any areas of bony interference between segments that prevent them from properly falling into the splint.
Summary Successful treatment of the patient who has bimaxillary protrusion relies on close collaboration between the orthodontist and surgeon and starts with a thorough understanding of the patient’s concerns. Premolar extraction with anterior segmental osteotomy and retraction is a powerful approach for treating the patient who has a predominantly horizontal maxillary excess. LeFort I osteotomy with maxillary anterior segmental osteotomy is effective in treating patients who also have significant vertical maxillary excess, or in whom posterior maxillary intrusion would be favorable for the smile arc. Isolated LeFort I osteotomy with setback is a useful alternative to, and sometimes more desirable than, maxillary anterior segmental osteotomy for correction of maxillary excess. Careful planning of osteotomies and meticulous removal of all intervening bone are essential aspects of surgery necessary to achieve an aesthetic and functional result.
References [1] Sarver DM. The importance of incisor positioning in the esthetic smile: the smile arc. Am J Orthod Dentofacial Orthop 2001;120(2):98–111. [2] Bell WH. Le Forte I osteotomy for correction of maxillary deformities. J Oral Surg 1975;33(6): 412–26. [3] Bell WH, Proffit WP. Maxillary excess. In: Bell WH, Proffit WP, White RP, editors, Surgical correction of dentofacial deformities, vol. 1. Philadelphia: WB Saunders; 1980. p. 234–441. [4] Hunsuck EE. A modified intraoral sagittal splitting technique for correction of mandibular prognathism. J Oral Surg 1968;26(4):250–3. [5] Yu C-C, Lin C-H, Huang DCS, et al. Sagittal splitting of ascending ramus revisited for large amount mandibular setback. Presented at the Program of the XIth Congress of the International Society of Craniofacial Surgery. Coolum, Queensland, Australia, September 11–14, 2005. [6] Kim CH, Lee JH, Cho JY, et al. Skeletal stability after simultaneous mandibular angle resection and sagittal split ramus osteotomy for correction of mandible prognathism. J Oral Maxillofac Surg 2007;65(2):192–7. [7] Baek SM, Kim SS, Bindiger A. The prominent mandibular angle: preoperative management, operative technique, and results in 42 patients. Plast Reconstr Surg 1989;83(2):272–80. [8] Yang DB, Park CG. Mandibular contouring surgery for purely aesthetic reasons. Aesthetic Plast Surg 1991;15:53. [9] Honda T, Lin C-H, Yu C-C, et al. The medial surface of the mandible as an alternative source of bone grafts in orthognathic surgery. J Craniofac Surg 2005;16(1):123–8.
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[10] Bendor-Samuel R, Chen YR, Chen PKT. Unusual complications of the LeFort I osteotomy. Plast Reconstr Surg 1995;96(6):1289–96. [11] Carr RJ, Gilbert P. Isolated partial third nerve palsy following LeFort I maxillary osteotomy in a patient with cleft lip and palate. Br J Oral Maxillofac Surg 1986;24(3):206–11. [12] Girotto JA, Davidson J, Wheatly M, et al. Blindness as a complication of LeFort osteotomies: role of atypical fracture patterns and distortion of the optic canal. Plast Reconstr Surg 1998; 102(5):1409–21. [13] Habal MB. A carotid cavernous sinus fistula after maxillary osteotomy. Plast Reconstr Surg 1986; 77(6):981–7.
[14] Lo LJ, Hung KF, Chen YR. Blindness as a complication of the LeFort I osteotomy for maxillary distraction. Plast Reconstr Surg 2002;109(2): 688–98. [15] Iverson RE, Lynch DJ. ASPS Committee on Patient Safety. Practice advisory on pain management and prevention of postoperative nausea and vomiting [practice guideline]. Plast Reconstr Surg 2006;118(4):1060–9. [16] Siebert JW, Angrigiani C, McCarthy JG, et al. Blood supply of the Le Fort I maxillary segment: an anatomic study. Plast Reconstr Surg 1997; 100(4):843–51.
CLINICS IN PLASTIC SURGERY Clin Plastic Surg 34 (2007) 535–546
Surgical Approach to the Patient with Bimaxillary Protrusion Yong-Ming Chu, MDa, Roger Po-Hsun Chen, DDSb, David E. Morris, MDc,d, Ellen Wen-Ching Ko, DDS, MSb, Yu-Ray Chen, MDa,* -
Discussion Patient evaluation and treatment planning Surgical technique Lower anterior segmental osteotomy (Kole procedure) Upper anterior segmental osteotomy (Wassmund procedure)
The patient who has bimaxillary protrusion often is treated using a combination of orthodontics and orthognathic surgery, and the general approach is dental extraction with retraction of the incisors and/or anterior segmental osteotomies. In certain cases, maxillary excess may be corrected solely with LeFort I osteotomy and setback and without dental extraction or anterior segmental osteotomies. This article discusses (1) treatment evaluation and planning and (2) the specific surgical techniques, primarily anterior segmental osteotomies and the technical details for setback of the LeFort I osteotomized segment (more than 5 mm), as they relate to the surgical approach of the patient who has bimaxillary protrusion.
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LeFort I osteotomy with setback Complications Errors in planning Errors in surgical technique Summary References
Discussion Patient evaluation and treatment planning Bimaxillary protrusion is a common dentofacial pattern in the Asian population. It is characterized by protrusive dentoalveolar position of the maxillary and mandibular dental arches. The perioral soft tissues demonstrate protrusive upper and lower lips, lip incompetence, excessive exposure of frontal teeth, a gummy smile, and mentalis strain. Improvement in facial aesthetics is the primary reason adult patients who have bimaxillary protrusion seek treatment. The treatment consists of orthodontic correction with extraction of four premolars and orthognathic surgery if skeletal
a
Craniofacial Center, Department of Plastic and Reconstructive Surgery, Chang Gung Memorial Hospital, Chang Gung Medical College and Chang Gung University, 5 Fu-Shin Street, Kweishan, Taoyuan 333, Taiwan b Department of Craniofacial Orthodontics, Chang Gung Memorial Hospital, Chang Gung Medical College and Chang Gung University, 6F, 199 Dung Hwa North Road, Taipei 105, Taiwan c Division of Plastic, Reconstructive, and Cosmetic Surgery, The Craniofacial Center, University of Illinois at Chicago, 811 S. Paulina, Chicago, IL 60612, USA d Shriners Hospital for Children, 2211 N. Oak Park Avenue, Chicago, IL 60707, USA * Corresponding author. E-mail address: [email protected] (Y-R Chen). 0094-1298/07/$ – see front matter ª 2007 Elsevier Inc. All rights reserved.
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problems are significant. To determine which cases are suitable for surgical correction, pretreatment skeletal, dental, and soft tissue evaluation is essential for diagnosis and treatment planning. The skeletal assessment evaluates facial symmetry, the sagittal position of maxillary and mandibular skeletal base, and the vertical proportion of lower facial height. Dental assessment includes occlusion type, alignment of dentition, and incisor inclination. Soft tissue evaluation should include both static and dynamic assessment, whether the incisors show at rest and during smiling, interlabial gap, nasolabial angle, and mentolabial fold. Cephalometric and panoramic radiographs are useful for identifying the skeletal and dental relations, demonstrating the condition of the temporomandibular joint, and identifying any pathologic lesions. The patient’s main concern and aesthetic considerations should be the first priorities in decision making and formation of a treatment plan; understanding the importance of these considerations is the key factor in treatment success and patient satisfaction. If the skeletal problems of bimaxillary protrusion involve only sagittal excess and protrusion of both jaws, the condition can be corrected by anterior segmental osteotomies and extraction of premolars of the affected jawbones (Fig. 1). The anterior segment can be set back by segmental movement or by palatal tipping of the incisors; depending on the original sagittal incisor inclination. If the anterior segment
is retracted and tipped palatally, there will be vertical discrepancy between the canines and premolars. This vertical discrepancy can be corrected orthodontically if it is less than 3 mm. A distance exceeding 4 mm predisposes the patient to potential periodontal problems during subsequent orthodontic correction. Aside from anterior segmental osteotomy of the jawbones, simultaneous genioplasty (vertical elongation or advancement) is usually required to further improve facial profile and proportion. For the patient who has bimaxillary protrusion combined with maxillary vertical hyperplasia (excess), the concomitant problems of long lower facial height, lip incompetence, and unaesthetic gummy smile should be addressed. Maxillary LeFort I osteotomy with superior impaction may be considered in the surgical plan (Fig. 2). The smiling arc can also be improved by proper maxillary posterior impaction [1]. Overimpaction of the anterior maxilla, however, widens the alar base and leads to insufficient show of the upper front teeth during smile or resting lip posture. It is important that patients have realistic expectations before surgical correction of bimaxillary protrusion. All patients should be informed of the anticipated subtle soft tissue changes such as upper lip lengthening, deepening of the nasolabial fold, and widening of the nasal base that will result from surgery. It is essential to avoid overcorrection of the anterior segment and to preserve some lip fullness, especially in older patients. It is an art for the
Fig. 1. 29 year-old woman with bimaxillary protrusion. (A, B) Preoperative views. (C, D) Fourteen months after Wassmund and Kole procedures and genioplasty.
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Fig. 2. 30 year-old man with bimaxillary protrusion. (A, B) Preoperative views. (C, D) One year after three-piece LeFort I osteotomy, Kole procedure, bilateral sagittal split-ramus osteotomy, and genioplasty.
surgeon and orthodontist to achieve the very fine balance between optimal anterior dentoalveolar retraction and preservation of a youthful appearance that is associated with a certain degree of bimaxillary fullness.
Surgical technique A number of factors, as discussed previously, determine the surgical treatment plan for the patient who has bimaxillary protrusion. More specifically, the decision as to which procedure(s) are to be used is based on clinical examination of the patient, patient desires, radiographic analysis and prediction tracing, and pretreatment and preoperative model studies. At our centers, the orthodontists perform the tracing and model tasks and then proceed to preoperative model surgery to construct the surgical splint(s). Thus the plan may include some combination of LeFort I osteotomy, bilateral sagittal split-ramus osteotomy (BSSO) of the mandible, and upper and lower anterior segmental osteotomies (Wassmund and Kole procedures, respectively). The surgical techniques for LeFort I osteotomy and BSSO are well described elsewhere for the former, the authors prefer the method described by Bell and colleagues [2,3] and for the latter they prefer that described by Hunsuck [4] with modifications that they have developed. Several points related to these procedures warrant further discussion. For BSSO, the authors routinely perform full detachment of the pterygomasseteric muscle sling and ostectomy of the pterygoid
protuberance (Fig. 3). They believe that this modified technique allows a greater amount of mandibular advancement or setback with probable better long-term stability [5,6]. In addition, it allows concomitant contouring to reduce the mandibular angle, with results that are aesthetically quite pleasing for some Asian women who desire a softer, gentler contour of the mandibular angle [7,8]. Finally, this approach provides a useful source of bone graft if needed [9]. For the LeFort I osteotomy, the authors prefer to use a 90 oscillating saw to cut the pterygomaxillary junctions initially and then complete the disjunction using a curved thin-blade osteotome (Fig. 4). In this manner, the maxilla is downfractured with relatively little effort and minimal risk [10–14]. The authors believe that this technique has the advantage of being less traumatic and requires no special instrumentation. The following discussion focuses on the authors’ surgical approach to performing upper and lower anterior segmental osteotomies and the details of their approach to setback of a LeFort I osteotomized segment greater than 5 mm. For patients who have bimaxillary protrusion, anterior segmental osteotomies are sometimes performed in isolation; in other cases these are combined with a LeFort I osteotomy or BSSO. In the latter scenario, specific points should be noted regarding both intraoperative osteotomy sequence and osteotomy design. Finally, an isolated LeFort I osteotomy with setback can be a useful alternative for correcting maxillary excess (eg, in patients
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Fig. 3. Bilateral sagittal split-ramus osteotomy. The drawing demonstrates the technique described by Hunsuck with the authors’ modifications. (A) Configuration of osteotomy lines. (B) Full detachment of the pterygomasseteric muscle sling. (C, D) Ostectomy of the pterygoid protuberance facilitates concomitant angle contouring and is a good source of bone grafts if needed. (From Honda T, Lin CH, Yu CC, et al. The medial surface of the mandible as an alternative source of bone grafts in orthognathic surgery. J Craniofac Surg 2005;16(1):123–8; with permission.)
previously compromised by extraction orthodontic treatments) (Fig. 5). When upper and/or lower anterior segmental osteotomies are to be performed, the surgeon usually extracts the bilateral first premolars at the time of the surgical procedure; alternatively, this extraction may be done early in treatment. If extractions are not necessary or feasible (eg, when teeth have been extracted previously), interdental osteotomies can be performed safely between parallel roots of the canines and premolars or the canines and lateral incisors. The authors rarely find it necessary to extract teeth just for the purpose of the surgery if there is no specific orthodontic reason for extraction. Before surgery the orthodontist removes the brackets from teeth to be extracted and segments the upper and lower arch wire that spans them so that there is discontinuity across these
teeth. This procedure makes extraction easier and also prevents extraction of the wrong teeth.
Lower anterior segmental osteotomy (Kole procedure) The upper and lower anterior gingivobuccal sulci are infiltrated with 2% xylocaine with 1:100,000 epinephrine for hemostasis. The authors use ropivacaine (Naropin), a long-acting local anesthetic, for probable better-controlled hypotensive anesthesia and less postoperative pain [15]. In general, they prefer to use only a final splint and to perform the mandibular osteotomy first. Turning first to the lower arch, the lower first premolars are extracted (Fig. 6). A gingivobuccal incision is made extending from the region of the first molar across to the contralateral first molar, and the soft tissues are elevated caudally in the
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Fig. 4. Useful pearls in performing the LeFort I osteotomy. (A) Essential instruments are a 90 right-angle saw and a curved thin-blade osteotome. (B) Placement of oscillating saw for the initial cut of the pterygomaxillary junction. (C) Completion of the pterygomaxillary disjunction with a curved thin-blade osteotome.
subperiosteal plane. Care is taken to identify and preserve the bilateral mental nerves during the subperiosteal dissection both in the symphyseal region and posterior to the nerves along the mandibular body. A small elevator is used to lift a gingival bridge buccally where the first premolars have been extracted and where the interdental osteotomy will be performed. The authors prefer to preserve continuity of this gingival bridge to maintain one additional source of vascularity to the segment and to avoid a vertical scar and recession along the gingiva that may be apparent when the patient smiles. Gingival dissection is also performed adjacent to the first premolar on the lingual side (Fig. 6A & 6C). The planned osteotomy lines are marked with a pencil. The roots of the canines are identified, and the horizontal osteotomy line is drawn at least 5 mm inferior to this level, usually at about at the level of the mental foramina (Fig. 6B). At this point it must be decided whether a genioplasty will be performed; if so, care must be taken not to draw this line too low, because an adequate intervening segment of bone must be maintained to provide stable points of fixation for both the anterior segment and the genioplasty segment and to avoid an unplanned fracture. The blood supply enters the canine root about 2 mm inferior to the tip of the root, so the horizontal osteotomy must, at the very least, be below this point. Two lines relatively perpendicular to this horizontal osteotomy line are drawn on each side that delineate the segment of bone to be removed in setting back the segment (Fig. 6A & 6C). This line is designed to not
encroach within 5 mm of the mental nerve, and care also must be taken to preserve adequate bone to support the roots of the adjacent canine and second premolars (usually at least 1 mm). Using a 3mm round burr, the vertical segments of bone where the premolars had been extracted are excised in a buccal-to-lingual fashion. In doing so the burr is maintained perpendicular to the curve of the mandibular surface, and a Ragnel retractor is used to lift the intervening gingival bridge gently. The segment can be set back about 5 to 6 mm, so the 3-mm–wide burr serves as a guide in determining how wide of a segment to resect. For an interdental osteotomy, a 1-mm round burr or even a reciprocating saw with a thin blade should be used. A reciprocating saw then is used to make the horizontal osteotomy. The blood supply to the osteotomized segment is derived primarily from the remaining lingual attachments (genioglossus muscle and gingival attachments); the maintained bridges of gingiva on the buccal side may supply a minor contribution. After the segment has been mobilized completely, reference is made to the models and splint(s) to position the segment optimally. The final position of the segment in relation to the second premolars should be noted. Typically a few areas of bony contact remain that must be identified and burred further to allow setback of the osteotomized segment into its final position. Initially attention is paid to positioning the segment appropriately horizontally with respect to the position of the bilateral second molars and to achieving inclination identical to that in the model.
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Fig. 5. A 28-year-old woman who had bimaxillary protrusion after compromised extraction orthodontic treatment performed at an outside institution. (A, B) Preoperative views. (C, D) Seven months after a LeFort I osteotomy with 5-mm setback, 3-mm intrusion, and 2.5-mm advancement genioplasty.
Additional burring of bone on one or both sides may be needed, and here care should be taken not to expose the dental roots. The surgeon also must be aware of the degree of preoperative pro/ inclination of the incisors and the desired postoperative inclination. This precaution is necessary because in cases that require a true horizontal setback (ie, no change in pro/inclination) the surgeon must avoid torquing the segment into the splint, which will result in a change in inclination. Once the ideal horizontal position is achieved, any vertical discrepancy is corrected to level the teeth of the segment in relation to those of the
adjacent stable arch (Fig. 6D). To accomplish this leveling, additional bone may be burred from the inferior edge of the segment, from the adjacent upper mandibular border, or from both. The lower teeth are placed into the splint to estimate whether the position is adequate. With the splint in place, a horizontal interdental wire is placed around the canine and second premolar bilaterally to secure the segment in place temporarily, preventing avulsion while attention is turned to the upper arch. If BSSO is necessary, the authors prefer to perform the BSSO initially but without complete splitting.
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Fig. 6. Lower anterior segmental osteotomy (Kole procedure). Markings for (A) the right vertical, (B) horizontal, and (C) left vertical components of the osteotomy. Arrows designate the canine roots. Note that the gingival bridges remain intact and are retracted. (D) The osteotomized segment is mobilized, and any bony interference preventing proper seating of the segment into the splint is burred. (E) Configuration of the fixation hardware.
The split is completed after the Kole procedure, providing better control of the segment.
Upper anterior segmental osteotomy (Wassmund procedure) As in the lower arch, upper teeth (generally the first premolars) are extracted first (Figs. 7 and 8). The authors prefer the technique relying on the use of the palatal pedicle (Fig. 7D & 8E). The palatal mucosa is elevated in the subperiosteal plane to form a tunnel between the site of each extracted tooth, converging at the midline. This tunnel should be about twice the width of the 6-mm diameter of the extracted tooth so that the palatal mucosa does not kink with setback. Anterior segmental osteotomies may be performed without concomitant LeFort I osteotomy; however if a LeFort I osteotomy is part of the surgical plan, it is completed at this time (ie, after exposure of the anterior segmental osteotomy, but before it is cut). It is much easier to perform the LeFort I osteotomy before the segmental osteotomy than the reverse. The tip of the canine root lies at about the same horizontal level as the nasal floor, and the anterior component of the
LeFort I osteotomy should be kept at least 5 mm above this. After the LeFort I osteotomy has been completed and the segment has been mobilized completely, the osteotomy lines for the anterior segmental osteotomy are drawn. The width of the bone that will be excised with burrs should be planned meticulously. Patients who have bimaxillary protrusion usually have proclined upper incisors, which should be corrected. For this correction, more bone should be removed from around the tooth level than from the upper edge of the segment (ie, the marked ‘‘ostectomy’’ segment should look roughly trapezoidal or wedge-shaped) (Fig. 8F). Parallel excision of the bone probably will result in poor bony contact along the upper edge, which may affect long-term stability. On the other hand, too much clockwise rotation of the segment into the splint secondary to inadequate bone removal must be avoided also. Hence, the surgeon must be flexible in performing the complete osteotomies and select carefully the burrs or thin-bladed reciprocating saws that are most appropriate for a given case. Again, the burr should be maintained perpendicular to
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Fig. 7. General surgical approach to a maxillary anterior segmental osteotomy (Wassmund procedure) and mandibular anterior segmental osteotomy (Kole procedure) in a patient who has bimaxillary protrusion. (A) Patient demonstrates typical skeletal and soft tissue features. (B) Extraction of the bilateral upper and lower first premolars. (C) Vertical bony segments (light blue) to be resected and site of concomitant LeFort I osteotomy (dotted line) if indicated. (D) A subperiosteal tunnel along the palate is raised to allow the osteotomy. (E) Initial LeFort I osteotomy facilitates completion of anterior segmental osteotomy. (F) The osteotomized segment has been posteriorly repositioned and set upright. (G) Resultant change in skeletal and soft tissue appearance.
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Fig. 8. Intraoperative steps in a maxillary anterior segmental osteotomy. (A–C) Preoperative radiographs of the patient in this figure. (D) Right first premolar has been extracted. (E) Subperiosteal tunnel is dissected across the hard palate between the bilateral extraction sites. (F) The gingivoperiosteal flap is left intact and retracted inferiorly while the right vertical maxillary osteotomy lines are marked. Note the trapezoidal or wedge-shaped ostectomy area. (G) Both LeFort I and anterior segmental osteotomies are completed. (H) The LeFort I posterior segment is split bilaterally in the paramedian fashion. (I) Final fixation of both segments.
the maxillary arch at all times to avoid injury to the dental roots. Both the intervening gingival bridge and the palatal mucosa are retracted away from the bone to avoid soft tissue injury. The osteotomy proceeds from laterally to the midline on one side and then laterally to the midline on the contralateral side. When a three-piece LeFort I osteotomy is indicated, unilateral paramedian split of the LeFort I posterior segment is performed if the patient does not require significant expansion or torque of the posterior arch. Bilateral paramedian split is not performed routinely if the segments fit into the splint very well after only a unilateral split (Fig. 8H). Once all segments are mobilized fully, reference is made to the surgical models and splint(s), and tooth positions are compared. Additional bone is burred from the anterior segment or from the adjacent maxilla to eliminate any bony interference that prevents the anterior segment from coming into its desired position. Each segment of the upper
dentition is placed and wired into the splint. Next, each segment of the lower arch is wired into the splint. Temporary wire fixation of the maxilla is applied first, to judge the sagittal, transverse, and vertical dimensions of the facial appearance including the profile, dental, and facial midlines and gingival and dental display. The superior aspects of the anterior and/or posterior segments may need to be burred if the maxillary excess in the vertical dimension should be corrected also (ie, too much gingival show during smile and excess dental display at rest). For correction of sagittal maxillary excess, additional LeFort I en bloc setback sometimes is necessary even after the intervening portions between the anterior and posterior segments have been removed entirely and the spaces have been closed. This situation is encountered more frequently when LeFort I osteotomy with impaction is undertaken and the sagitally longer portion of the segment has been raised, introducing additional bony interference between
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the maxillary tuberosity and pterygoid process. Clockwise rotation of the occlusal plane will worsen this situation further if it has not been included in the surgical design, because this maneuver might not be predicted precisely during preoperative surgical planning. For this reason the authors prefer to use only a final splint, with both surgeon and orthodontist taking equal responsibility for the fine adjustment of patients’ facial appearances. They do not argue against the value of two-splint designs or discount the orthodontic effort in planning two-splint cases, realizing that there is no other surgical option in these circumstances if no concomitant BSSO is performed. The coordinated effort of the orthodontist and surgeon is of utmost importance.
LeFort I osteotomy with setback For setback of LeFort I osteotomized segments, the authors would like to share their experience with several helpful nuances that facilitate this somewhat difficult procedure. First, although the authors usually prefer not to fracture or even penetrate the pterygoid process because of the associated increase in intraoperative bleeding, reducing the pterygoid process remains an alternative. When left intact, they feel that the pterygoid process provides some support while posteriorly repositioning the maxilla. Second, posterior segments of the maxillary tuberosity can be resected. Third, extraction of the third molars facilitates greater setbacks (especially > 5 mm). This procedure requires resecting more maxillary tuberosity and even the posterior palatine plates of the maxilla. An oscillating saw can be used in this scenario for controlled partial fracture laterally, quite similar to the technique the authors use in pterygomaxillary disjunction. Then the same curved thin-blade osteotome used during pterygomaxillary separation and a small curved elevator are used to take out the excess. Although limited visibility makes this procedure difficult, it can be performed meticulously and safely without tearing the palatal mucosa. For large setbacks, the descending palatine neurovascular bundles are not routinely cauterized or ligated. They can be dissected carefully from the canal and well protected. If injured, however, they are cauterized or ligated because of the risk of significant postoperative bleeding. With proper design and technique, the palatal mucosa can provide adequate blood supply even after multiple segmental osteotomies [16]. Based on this technique, the authors believe that solitary LeFort I osteotomy with setback is an alternative for treating maxillary excess without any extraction or upper anterior segmental osteotomy when (1) there is no orthodontic reason for extracting anterior teeth; and (2) LeFort I osteotomy with clockwise rotation of the occlusal plane is sufficient,
and/or more favorable than upper anterior segmental osteotomy to correct proclined upper incisors (see Fig. 5). The feasibility of large setback should also be carefully considered from a dental hygienic point-of-view; especially in the case of concomitant setback and intrusion, this can interfere with the patient’s ability to clean the maxillary second molars. Internal plate-and-screw fixation is achieved either first at the lateral buttresses of the maxilla (if a LeFort I osteotomy was done) and then from the medial buttress to the setback anterior segment, or vice versa. When the maxilla is split into three or more segments, extra intersegmental fixation can be performed also if sufficient bony buttresses remain and there is no risk of injury to the dental root (Fig. 8I). After maxillary fixation, internal fixation is placed in the lower jaw, and intermaxillary fixation always is released to ensure that there is no discrepancy between centric relation and centric occlusion. This technique also improves patient comfort in the immediate postoperative period. When the maxilla is either split into two pieces or only the maxillary anterior segmental osteotomy is done and both fit precisely into the splint and are rigidly fixated, the splint often is removed at the end of the operation. When the maxilla is split into three or more pieces the splint also may be removed if extra intersegmental fixation has been accomplished safely and rigidly (see Fig. 8I). If there is any question about the fit into the splint or the rigidity of fixation, the splint is left in place at the conclusion of the operation.
Complications Complications in treating the patient who has bimaxillary protrusion may result from errors in surgical planning or from errors in technical execution of the procedure.
Errors in planning Although both upper anterior segmental osteotomy and LeFort I osteotomy with setback are very powerful procedures in treating the patient who has bimaxillary protrusion, they also can have the deleterious effect of creating an aged appearance. As the skeletal support of the midfacial soft tissues moves posteriorly the soft tissues relax, causing more apparent nasolabial folds, a more obtuse nasolabial angle, and lowering of the lip vermillion, decreasing gingival display during smile and dental display at rest. All patients should be warned preoperatively of the possibility of this aged appearance, and particular care should be taken in planning such setback procedures in patients who exhibit
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any of these findings preoperatively. Care should also be taken when considering such procedures in relatively older patients (ie, age 30 years or older). Finally, at the authors’ centers patients are recommended to be seen both pre- and postoperatively by clinical psychologists to help patients and their families both anticipate and adjust postoperatively to changes in appearance.
Errors in surgical technique Osteotomy positioning In performing anterior segmental osteotomies, particular attention must be paid to design osteotomies to avoid injury to adjacent structures. In the maxilla, resection of the interdental segments must not expose the dental roots. The horizontal component also must lie superior to all dental roots. The same holds true in the mandible; in addition the horizontal osteotomy must be below the lowest dental roots but remain high enough to allow for an intervening segment of intact bone if genioplasty is to be performed. This intervening segment must be thick enough to accommodate screws for fixation without fracturing. All osteotomies should be marked carefully with a pencil before cutting, and fine burrs should be used. Segmental necrosis To avoid devascularization of osteotomized segments, subperiosteal soft tissue elevation should be performed only so far as required for performing osteotomies. Particular care should be taken to leave all posterior soft tissue attachments of the mandibular segments intact and to leave adequate palatal attachment for each maxillary segment. In the authors experience, full detachment of the pterygomasseteric muscle sling has not created any problem related to the viability of the proximal mandibular segment after BSSO; here the soft tissue attachments of the coronoid and condylar processes and the surrounding environment provide adequate circulation. Postoperative malocclusion Prevention of postoperative malocclusion of course begins with careful planning and construction of the operative splint preoperatively. Intraoperatively, however, the surgeon must be vigilant in making sure that all segments fit precisely into the splint without inappropriate rotation. The surgeon must burr any areas of bony interference between segments that prevent them from properly falling into the splint.
Summary Successful treatment of the patient who has bimaxillary protrusion relies on close collaboration between the orthodontist and surgeon and starts with a thorough understanding of the patient’s concerns. Premolar extraction with anterior segmental osteotomy and retraction is a powerful approach for treating the patient who has a predominantly horizontal maxillary excess. LeFort I osteotomy with maxillary anterior segmental osteotomy is effective in treating patients who also have significant vertical maxillary excess, or in whom posterior maxillary intrusion would be favorable for the smile arc. Isolated LeFort I osteotomy with setback is a useful alternative to, and sometimes more desirable than, maxillary anterior segmental osteotomy for correction of maxillary excess. Careful planning of osteotomies and meticulous removal of all intervening bone are essential aspects of surgery necessary to achieve an aesthetic and functional result.
References [1] Sarver DM. The importance of incisor positioning in the esthetic smile: the smile arc. Am J Orthod Dentofacial Orthop 2001;120(2):98–111. [2] Bell WH. Le Forte I osteotomy for correction of maxillary deformities. J Oral Surg 1975;33(6): 412–26. [3] Bell WH, Proffit WP. Maxillary excess. In: Bell WH, Proffit WP, White RP, editors, Surgical correction of dentofacial deformities, vol. 1. Philadelphia: WB Saunders; 1980. p. 234–441. [4] Hunsuck EE. A modified intraoral sagittal splitting technique for correction of mandibular prognathism. J Oral Surg 1968;26(4):250–3. [5] Yu C-C, Lin C-H, Huang DCS, et al. Sagittal splitting of ascending ramus revisited for large amount mandibular setback. Presented at the Program of the XIth Congress of the International Society of Craniofacial Surgery. Coolum, Queensland, Australia, September 11–14, 2005. [6] Kim CH, Lee JH, Cho JY, et al. Skeletal stability after simultaneous mandibular angle resection and sagittal split ramus osteotomy for correction of mandible prognathism. J Oral Maxillofac Surg 2007;65(2):192–7. [7] Baek SM, Kim SS, Bindiger A. The prominent mandibular angle: preoperative management, operative technique, and results in 42 patients. Plast Reconstr Surg 1989;83(2):272–80. [8] Yang DB, Park CG. Mandibular contouring surgery for purely aesthetic reasons. Aesthetic Plast Surg 1991;15:53. [9] Honda T, Lin C-H, Yu C-C, et al. The medial surface of the mandible as an alternative source of bone grafts in orthognathic surgery. J Craniofac Surg 2005;16(1):123–8.
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[10] Bendor-Samuel R, Chen YR, Chen PKT. Unusual complications of the LeFort I osteotomy. Plast Reconstr Surg 1995;96(6):1289–96. [11] Carr RJ, Gilbert P. Isolated partial third nerve palsy following LeFort I maxillary osteotomy in a patient with cleft lip and palate. Br J Oral Maxillofac Surg 1986;24(3):206–11. [12] Girotto JA, Davidson J, Wheatly M, et al. Blindness as a complication of LeFort osteotomies: role of atypical fracture patterns and distortion of the optic canal. Plast Reconstr Surg 1998; 102(5):1409–21. [13] Habal MB. A carotid cavernous sinus fistula after maxillary osteotomy. Plast Reconstr Surg 1986; 77(6):981–7.
[14] Lo LJ, Hung KF, Chen YR. Blindness as a complication of the LeFort I osteotomy for maxillary distraction. Plast Reconstr Surg 2002;109(2): 688–98. [15] Iverson RE, Lynch DJ. ASPS Committee on Patient Safety. Practice advisory on pain management and prevention of postoperative nausea and vomiting [practice guideline]. Plast Reconstr Surg 2006;118(4):1060–9. [16] Siebert JW, Angrigiani C, McCarthy JG, et al. Blood supply of the Le Fort I maxillary segment: an anatomic study. Plast Reconstr Surg 1997; 100(4):843–51.