J Oral Maxillofac

Surg

49904-907. 1991

Fixation for the Modified Le Fort Osteotomy I

DAVID J. DARAB DDS, MS,* AND WILLIAM

Stabilizing the Le Fort I osteotomy following maxillary advancement may be difficult and challenging. To improve stability of maxillary advancement surgery, the Le Fort I osteotomy has undergone numerous modifications in design and stabilization. Bennett and Wolford’ described a maxillary step osteotomy to improve the predictability and accuracy of maxillary advancement. In this technique, the lateral maxillary osteotomy is made parallel to Frankfort Horizontal. This places the osteotomy higher into the zygomatic buttress where a vertical step is made. Fixation is then achieved with Steinmann pins and maxillomandibular fixation. An advantage of this technique is elimination of the ramping effects associated with the traditional Le Fort I osteotomy. Additionally, the vertical step at the zygomatic buttress provides a well-visualized site for bone graft placement. The occasional lack of bone density in this area, however, may make the use of plate fixation difficult. Keller and Sathe? described a modification designed to treat midface deficiency, which they termed the quadrangular Le Fort I osteotomy. In this design, the horizontal osteotomy is made at the level of the infraorbital nerve, with a vertical step at the zygomatic buttress. Inlay-onlay iliac crest corticocancellous bone grafts are placed along the osteotomy sites to stabilize the advanced maxilla. Fixation is achieved through the use of transosseous suspension wires combined with maxillomandibular fixation. The high level of the osseous cut, combined with the thin bone along the anterior maxil-

lary wall, may preclude the application of miniplate fixation. With the use of small screw and plate fixation systems, the advanced maxilla can now be stabilized without maxillomandibular fixation or skeletal suspension. Paramount to the success of these techniques is adequate thickness of bone for the application of such screws and plates. The difficulties encountered in placing screw and plate fixation along the thin lateral maxillary wall have been circumvented by modifing the design of the Le Fort I osteotomy, and extending the lateral maxillary osteotomy into the zygomatic root.3-5 Such a modification provides the necessary bone for the application of bone screw osteosynthesis. Potential advantages of the modified Le Fort I osteotomy include 1) enhanced stability from screw and plate osteosynthesis, 2) versatility of osteotomy design enabling both vertical and anteroposterior maxillary skeletal deformities to be corrected, 3) extension of the lateral maxillary osteotomy high into the zygomatic root allowing for augmentation of the zygomatic, infraorbital, and paranasal regions, 4) reduction of telescoping of posterior segments following maxillary repositioning, 5) reduction of injury to tooth root apices following screw placement, and 6) avoidance of possible damage to developing tooth buds enabling maxillary surgery to be performed at an early age. Experience by the authors has led to a modification of the conventional technique where miniplates are placed at both the piriform aperture and zygomatic roots. In this technique, positional screws in the zygomatic roots, combined with either miniplates or positional screws and interpositional bone grafts along the piriform rims and anterior maxilla, are used to provide fixation of the repositioned maxilla.

Received from the Division of Oral and Maxillofacial Surgery, University of Texas Southwestern Medical Center, Dallas. * Resident. t Professor. Address correspondence and reprint requests to Dr Bell: Division of Oral and Maxillofacial Surgery, The University of Texas at Dallas, Southwestern Medical Center, 5323 Harry Hines BIvd, Dallas, TX 752354031. 01991 American

Association

of Oral and Maxillofacial

H. BELL, DDSt

Technique A horizontal incision is made in the maxillary vestibule extending from first molar to first molar. The inferior mucoperiosteal flap is elevated to allow

Sur-

geons 0276-2391/91/4906-0020$3.00/O

904

DARAB AND BELL

visualization of the bone encasing the apices of the teeth. The superior flap is elevated to expose the infraorbital nerve and maxilla. Posteriorly, the reflection is extended over the inferior aspect of the zygoma. The tendonious origin of the masseter is sharply incised in the region of the zygomaticmaxillary buttress, and reflection is continued to gain access to the inferior aspect of the zygoma. To ensure accurate vertical repositioning an external reference point is established by placing a K-wire into the nasofrontal region. The preoperative vertical relationship is then recorded by measuring the distance from the K-wire to the superior aspect of the maxillary incisor orthodontic bracket with a Boley gauge. The position and angulation of the osteotomy is based upon a correlated clinical examination, the esthetic treatment objectives, cephalometric planning studies, and mode! surgery. Based on measurements made from cephalometric prediction tracings, the proposed osteotomies are inscribed into the lateral maxilla. The lateral maxillary osteotomy extends from the piriform aperture at a level just beneath the infraorbital foramen posteriorly into the dense root of the zygoma, 6 mm or more above the inferior aspect of the zygoma (Fig IA). The degree of penetration of the zygoma and posterior extension of the lateral maxillary osteotomy is dependent upon the pneumatization of the maxillary antrum, position of the posterior maxillary wall, and the planned surgical movement. Using a reciprocating saw blade, the lateral maxillary osteotomy is extended anteriorly to the lateral piriform rim. The cut is then carefully continued medially at a level just beneath the junction of the lateral nasal wall with the inferior turbinate (Fig IA). Osteotomies are carefully performed in this region to avoid injuring the nasolacrimal ostium and duct located superior to this level.6q7 By reflecting the mucoperiosteum off the lateral nasal wall in the inferior meatus, and directing osteotomes inferiorly towards the nasal floor, injury to nasolacrimal structures is avoided. Posteriorly, the lateral maxillary osteotomy is extended into the dense root of the zygoma 5 to 6 mm above the inferior aspect of the body of the zygoma, and 4 to 6 mm posterior to the zygomaticomaxillary suture line. A vertical osteotomy is then made to the inferior and deep aspect of the zygoma with an oscillating saw blade. The vertical osteotomy through the posterior maxilla to the pterygomaxillary junction is then completed. Finally, separation of the maxilla from the pterygoid processes, the lateral nasal wall,and the bony nasal septum is completed with osteotomes. Downfracturing is initiated by hinging the maxilla inferiorly and posteriorly while stabilizing the mid-

FIGURE I. A, Diagram of modified osteotomy. A horizontal osteotomy extends from the piriform aperture, immediately below the anterior, inferior aspect of the inferior turbinate, into the dense bone of the zygoma at a level just beneath the infraorbital foramen. B, Following Le Fort I downfracture and mobilization, the advanced maxiha is temporarily stabilized with the aid of the interocclusal splint and intraosseous suspension wires at the zygomatic-maxillary extensions. These suspension wires can be removed following positional screw placement at the zygomatic roots. C. Fixation for the modified Le Fort I. Following maxillary advancement vertical interpositional corticocancellous bone grafts can be positioned along the anterior maxilla and stabilized with 2-mm self-tapping positional screws. Miniplates may also be used at the piriform aperture depending on hone thickness and the bony interface along the osteotomy (inset). Lateral view demonstrating bone graft fixation with positional screw.

face structures. Following this the maxilla is throughly mobilized in all directions to assure passive repositioning. With the maxilla in the downfractured position, bony interferences are removed under direct visualization. Submucous resection of the cartilagenous nasal septum is performed if the maxilla is to be repositioned superiorly. After the maxilla is completely mobilized the interocclusal splint is ligated to the maxillary dentition. The mandibular teeth are indexed into the splint, and maxillomandibular fixation accomplished with wire ligatures. The maxillomandibular complex is then rotated as a unit through the mandibular arc of rotation so that areas of bone contact can be visualized. Bone is removed from the posterior margins until the maxilla can be passively seated in the desired vertical position and the margins of the lateral maxillary osteotomies are approximated. Prior to fixation, the correct vertical position of the maxilla is established with the aid of the external reference K-wire. Due to the position and angulation of the

FIXATION FOR THE MODIFIED LE FORT I OSTEOTOMY

horizontal osteotomy, changes in vertical dimension can result secondary to the ramping effect following maxillary advancement. The maxilla is stabilized in the planned position by screw and plate osteosynthesis. Intermediate stabilization of the repositioned maxilla is accomplished with 24-gauge intraosseous wires suspending the zygomatic-maxillary extensions (Fig 1B). Additional help in stabilizing the skeletal segments is provided by the surgical assistant. Positional screws are then placed through the zygomatic extensions of the maxilla and into the dense bone of the zygomatic root. Screw placement in this region must be done judiciously to prevent fracture of the small portion of bone lateral to the zygomaticomaxillary suture. Position and angulation of the zygomatic screws are dependent upon the bony interfaces following maxillary repositioning, as well as the thickness of the buttress. Ideally, screw position and angulation should enable the dense bone of the zygomatic root to be engaged on both the proximal and distal segments (Fig 2). The bone is predrilled with a 1S-mm diameter drill bit under copious saline irrigation. A depth gauge is then inserted to determine the appropriate screw length (typically 12 to 14 mm). A 2-mm diameter, self-tapping screw is inserted with a screw-holding clamp and tightened securely. A similar procedure is accomplished on the opposite side. Following this, bony interfaces along the anterior maxilla are carefully inspected to confirm correct position prior to plate osteosynthesis. With the maxilla now secured at the zygomatic root, miniplates are adapted across the osteotomy site at the piriform rim. Selection of the appropriate length and contour of the plate is facilitated by the use of thin, malleable tin templates. The appropriate size and shape of plate is chosen to insure that at least two screws are placed in both the proximal and distal segments. The template is first adapted to the contour of the maxilla across the osteotomy site. A similar type and size bone plate is then formed with bending forceps so that it duplicates the shape of the template. Small adjustments are made to ensure that the plate lies passively across the osteotomy site and is flat against bone surfaces. The plate is then held in position and secured to both distal and proximal segments with 2.0-mm selftapping screws. Alternatively, when insufficient bone thickness or a poor bony interface along the osteotomy makes the placement of piriform miniplates difficult, the advanced maxilla can be stabilized with interpositional corticocancellous bone grafts secured with positional screws (Fig 1C). In our experience, however, the lateral portion of the anterior maxilla provides sufficient bone thick-

ness for positional screw placement. Bone thickness along the medial portion of the anterior maxilla is more variable, being insufficient at times to provide secure screw fixation. It should be emphasized that following placement of bilateral zygomatic positional screws, secure fixation of the single piece maxilla can be obtained, making the method of fixation for the anterior maxilla less critical. Potentially, such an osteotomy design can provide additional stability in large advancements. Finally, maxillomandibular fixation is released and the stability of the repositioned maxilla is confirmed. The mandible is then passively rotated into the occlusal splint, maintaining the proper condylefossa relationship with superior and anterior digital pressure in the angles of the mandible. It is important to insure that the mandible indexes passively and precisely into the splint without interferences or condylar shifts. In selected patients, when the maxilla has not been segmented and a stable occlusion has been achieved, the occlusal splint can be removed and the patient allowed to function immediately, maintaining proper occlusal relationships with light elastics. Discussion Modifying the Le Fort I osteotomy by extending the lateral maxillary osteotomy high into the thick bone of the zygomatic root provides excellent bony interfaces following maxillary repositioning. Using positional screws in the zygomatic root combined with miniplates or screw osteosynthesis and interpositional bone grafts at the piriform aperture provides excellent stability for the anteriorly repositioned maxilla. Experience with this technique in

FIGURE 2. Cephalometric radiograph demonstrating and medial angulation of zygomatic positional screws.

superior

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DARAB AND BELL

seven cases has demonstrated the following disadvantages: 1) increased operating time, 2) technically more difficult, 3) potential for fracture of the zygoma, 4) undesirable changes in vertical dimension can result if position and angulation of the lateral maxillary osteotomy is not carefully determined from cephalometric prediction tracings, and 5) asymmetric maxillary movements can produce undesirable soft-tissue changes. In summary, the modified Le Fort I osteotomy is a useful technique for treating anteroposterior maxillary hypoplasia in combination with vertical skeletal deformities. In those instances where large maxillary advancements are combined with simultaneous vertical changes, stabilization of the repositioned maxilla with zygomatic screws combined with miniplates or positional screws and bonegrafts along the piriform aperture provides excellent clinical stability.

References I. Bennett MA, Wolford LM: The maxillary step osteotomy and Steinmann pin stabilization. J Oral Maxillofac Surg 43:307, 1985 2. Keller EE, Sather AH: Quadrangular LeFort I osteotomy: Surgical technique and review of 54 patients. J Oral Maxillofac Surg 48:2, 1990 3. Bell WH. Mannai C, Luhr HG: Art and science of the LeFort I downfracture. Int J Adult Orthod Orthognath Surg 1:23, 1988 4. VanSickles JE, Jeter TD, Aragon SB: Rigid fixation of maxillary osteotomies: A preliminary report and technique article. Oral Surg 60:262, 1985 5. Kaminishi RM. Davis WH, Hochwald DA, et al: Improved maxillary stability with modified LeFort I technique. J Oral Maxillofac Surg 41:203, 1983 6. Demas PN, Sotereanos GC: Incidence of nasolacrimal injury and turbinectomy associated atrophic rhinitis with LeFort I osteotomies. J Cranio-Maxillofac Surg 17: 116, 1989 7. Calhoun KH, Rotzler WH. Stiemberg CM: Surgical anatomy of the lateral nasal wall. Otolaryngol Head Neck Surg 102:156, 1990