J Oral Maxillofac Surg 69:352-355, 2011

Medial Canthal Region as an External Reference Point in Orthognathic Surgery José Nazareno Gil, DDS, PhD,* Felipe Eduardo Baires Campos, DDS,† Jonathas Daniel Paggi Claus,‡ Luiz Fernando Gil, DDS,§ Charles Marin, DDS,储 and Sérgio Fernando Torres de Freitas, PhD¶ Purpose: The aim of this investigation was to evaluate the effectiveness of using the medial canthal

region (MCR) as an external reference point to determine the vertical dimension during maxillary repositioning as planned in model surgery and predictive tracing. Materials and Methods: The analyzed group consisted of 43 consecutive patients who underwent maxillary or bimaxillary orthognathic surgery. Before downfracture, the vertical height was established from the distance of the MCR to the incisal edge of the right upper central incisor (UCI). The vertical dimension was obtained with frequent measurements by use of calipers as desired during cephalometric tracing and model surgery. After rigid fixation, the vertical height was verified again. The UCI was traced from the postoperative cephalogram and predictive tracing onto a preoperative tracing. Repositioning of the maxilla and postsurgical movements of the UCI were registered at the horizontal and vertical planes. Comparison was made between the predicted maxillary position on the cephalometric tracing and the actual position, as well as between the planned maxillary position in model surgery and the actual position. Results: The mean difference between the planned UCI position on predictive tracing and postsurgical position was 0.30 mm (SD, 0.21 mm; P ⬎ .05) in the vertical plane. The variation between the planned maxillary position in model surgery and the actual position was 0.37 mm (SD, 0.31 mm; P ⬎ .05) in the vertical plane. Conclusions: Good surgical accuracy in positioning the mobilized maxilla can be achieved by use of the MCR as an external reference point. © 2011 American Association of Oral and Maxillofacial Surgeons J Oral Maxillofac Surg 69:352-355, 2011 reference points (IRPs)3-5 and external reference points (ERPs).1,2,6-8 Both techniques (IRP and ERP) use a mobile reference mark in the maxilla, which is in the upper central incisor (UCI), that will be moved and another immovable mark above the Le Fort I osteotomy. This mark is located directly above the bone cut in the IRP technique, and the mark is typically a Kirschner wire

A major challenge for oral maxillofacial surgeons is locating the maxilla in maxillary orthognathic surgery. The ability to predict the outcome of surgery is related to the ability of the surgeon to reproduce the planned model surgery and to use predictive tracing in the surgery room.1,2 Several techniques have been published for accurate intraoperative positioning of the maxilla. The most cited are the use of internal *Chairman, Oral and Maxillofacial Surgery Department, College of Dentistry, Santa Catarina Federal University, Florianópolis, Brazil. †Resident, Oral and Maxillofacial Surgery Department, College of Dentistry, Santa Catarina Federal University, Florianópolis, Brazil. ‡Surgeon, Oral and Maxillofacial Surgery Department, Santa Catarina Federal University, Florianópolis, Brazil. §Resident, Oral and Maxillofacial Surgery Department, College of Dentistry, Santa Catarina Federal University, Florianópolis, Brazil. 储Surgeon, Oral and Maxillofacial Surgery Department, Santa Catarina Federal University, Florianópolis, Brazil.

¶Professor, Public and Health Department, College of Dentistry, Santa Catarina Federal University, Florianópolis, Brazil. Address correspondence and reprint requests to Dr Gil: Department of Oral Maxillofacial Surgery, University Hospital, College of Dentistry, Santa Catarina Federal University, Rua Tenente Silveira, 293 Sala 1001, Edifício Reflex, Centro, Florianópolis, SC-Brazil, CEP 88010-301; e-mail: [email protected] © 2011 American Association of Oral and Maxillofacial Surgeons

0278-2391/11/6902-0007$36.00/0 doi:10.1016/j.joms.2010.07.023

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FIGURE 1. Anterior view of right eye and specific MCR used as ERP (asterisk). Gil et al. Medial Canthal Region as Reference Point. J Oral Maxillofac Surg 2011.

Maxillary surgery was performed in 9 patients, Le Fort I osteotomy and mentoplasty were performed in 2 patients, and 32 patients underwent bimaxillary surgery. The maxilla was first mobilized in all patients during bimaxillary surgery. The intact mandible with the intermediate splint provided the anteroposterior and transverse maxilla position. Plates and screws were applied to maxillae in all patients to provide rigid internal fixation (2 plates, n ⫽ 18; 4 plates, n ⫽ 25). Allogeneic bone grafts were used in 6 patients who underwent maxillary advancement and inferior repositioning. The mandible was mobilized by use of the following methods: vertico-sagittal ramus osteotomy in 14 patients, intraoral vertical ramus osteotomy in 7 patients, and bilateral sagittal split osteotomy in 11 patients. SURGICAL PROCEDURES

(K-wire) fixed at the nasal bone in the ERP technique. An alternative marker for a fixed reference point would be the medial canthal region (MCR) instead of the K-wire. An intermediate splint makes maxillary repositioning relatively simple and provides the proper 3-dimensional position. With this technique, the surgeon only has to ensure that the condyles are properly seated and determine the desired vertical dimension. The purpose of this study was to evaluate the effectiveness of use of MCR as an ERP during maxillary repositioning as planned in model surgery and predictive tracing.

All procedures were performed by the same surgeon (J.N.G.). The oral and facial area was draped to expose the perioral region and the right MCR (Fig 1). Vertical height was obtained preoperatively by use of calipers and by measuring the distance from the right MCR to the incisal edge of the right UCI (Fig 2). After downfracture, the maxillomandibular complex was manipulated with the condyles seated in the fossae. The intermediate (2-jaw surgery) or final splint was applied at this time. The surgeon could control the vertical dimension with frequent measurements using calipers as desired during cephalometric tracing and model surgery. After rigid fixation, the vertical height was verified again.

Materials and Methods For this retrospective study, 43 consecutive patients were selected (22 female and 21 male patients), ranging in age from 13 to 58 years (mean age, 29 years), and were submitted to maxillary or bimaxillary orthognathic surgery during the period from December 2006 to April 2009. The inclusion criteria were patients with complete preoperative and postoperative (7-10 days after surgery) radiographic documentation, predictive tracings, model surgery casts, and records with planned movements of maxillary surgery. This study was submitted to and approved by the Ethical Committee for Research in Human Beings of Santa Catarina Federal University, Florianópolis, Brazil. The casts for all patients were mounted on a semiadjustable articulator with face-bow transfer and centric relation interocclusal registration.9 Cast measures were made on the Erickson Model Surgery Platform (Florianópolis, Santa Catarina/Brasil).

FIGURE 2. Preoperative measurement of distance between MCR and maxillary central incisor edge. Gil et al. Medial Canthal Region as Reference Point. J Oral Maxillofac Surg 2011.

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CEPHALOMETRIC ANALYSIS

Tracings of all cranial structures were performed with preoperative cephalograms. These were first superimposed on the postoperative cephalogram film and then on the predictive tracings by 1 chief resident using cranial base structures. The resident was blinded to the specific movements of the maxilla. The UCI was traced from the postoperative cephalogram and predictive tracing onto the preoperative tracing. Repositioning of the maxilla and postsurgical movements of the UCI were determined for both horizontal and vertical planes. Changes in the vertical position of the UCI were assessed by measurement perpendicular to the preoperative Frankfort horizontal line. The horizontal position of the UCI was measured parallel to the Frankfort horizontal plane. To eliminate bias, half of the patients were randomly selected and retraced to confirm data obtained during the first measurement. STATISTICAL ANALYSIS

Changes in UCI movement from preoperatively to the follow-up immediately postoperatively (7-10 days) were analyzed in the horizontal and vertical directions. All measurements were converted to positive numbers for statistical analysis to remove directional differences between subjects. A paired t test was used to compare the predicted maxillary position on cephalometric tracing and the actual position, as well as the planned maxillary position in model surgery and the actual position. Statistical significance was set at P ⬍ .05. Any association between planned surgical movements and postsurgical changes was investigated with Pearson correlation.

Results The mean desired horizontal movements of the UCI in predictive tracing and model surgery were 3.24 mm (SD, 3.23 mm) and 3.16 mm (SD, 3.28 mm), respectively. In the vertical plane, the mean predicted maxillary movements in predictive tracing and model surgery were 2.49 mm (SD, 2.08 mm) and 2.36 mm (SD, 1.98 mm), respectively. There was a strong positive correlation between the maxillary position in the planned model surgery, predictive tracings, and surgical results. The mean difference between the planned UCI position in predictive tracing and postsurgical position was 0.30 mm (SD, 0.21 mm; P ⬎ .05) in the vertical plane (Fig 3A). One case presented a difference of 1.07 mm, which was relatively close to satisfactory (difference ⱕ1.0 mm). The majority (86%) of cases varied less than 0.5 mm. The variation between the planned maxillary position in model surgery and

FIGURE 3. A, Relationship between predictive tracing and actual surgical position of UCI in vertical movement. B, Relationship between model surgery and postoperative surgical position of UCI in vertical movement (correlation coefficient, R ⫽ 0.98). Gil et al. Medial Canthal Region as Reference Point. J Oral Maxillofac Surg 2011.

actual position was 0.37 mm (SD, 0.31 mm; P ⬎ .05) in the vertical plane (Fig 3B). Only 2 cases (4.6%) presented a variation greater than 1.0 mm, with differences of 1.19 and 1.32 mm.

Discussion In 1985 Johnson7 first described the use of the nasion mark as an ERP for vertical maxillary repositioning. The technique described involved the place-

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ment of a suture through the skin at the soft tissue nasion. Nishioka and Van Sickels8 considered soft tissue mobility during surgery to be a problem. A modified ERP technique was demonstrated in 1987, involving fixation of a K-wire in the nasal bone, which has become the most common method for vertical maxillary control during orthognathic surgery. Our results confirm that accurate vertical control of the UCI can be achieved while using the MCR as the ERP. This is similar to previously published data that used a K-wire fixed at the nasal bone as the ERP. This method presents horizontal accuracy within 2 mm and vertical accuracy within 1 mm of predictive tracings.3,4 Van Sickels et al3 compared the predictability of postoperative UCI positioning in patients in whom IRP or ERP had been used. In the ERP group, UCI was outside of the predicted measurement for a mean of 1.1 mm in the horizontal plane and 0.7 mm in the vertical plane. Polido et al10 compared ERP with IRP and found no difference between the 2 groups in horizontal positioning accuracy of the maxilla, but there was a significant difference in vertical repositioning. Use of an ERP proved to be a more accurate method for vertical maxillary repositioning. In contrast to these 2 previous studies, Ong et al11 achieved intraoperative control of the mobilized maxilla vertically using a combination of ERP and IRP. Repeated measurements of the distance between the nasion screw and a central incisor point were made with large calipers. Their results confirmed that accurate intraoperative movement of incisor tips could be achieved. The vertical dimension was only obtained by ERP in this study. Considering that a 1-mm variance is not likely to be detected by the patient nor is it clinically relevant,11 more than 97% of the patients evaluated showed a variation of less than 1.0 mm between the predictive tracing and actual position in the vertical plane. In the specific case that presented a difference of 1.07 mm, a 10-mm maxillary advancement was planned with 1-mm anterior upper repositioning. This result may be due to the triangulation effect or parallax error.4 There is also a strong positive correlation, with greater than 88% of the analyzed patients exhibiting variation of less than 0.5 mm between model surgery and postsurgical results. We encourage the use of MCR as an external reference mark in comparison to K-wire fixed in the nasal bone. The use of an alternative technique is desirable in light of the possible complications that may arise, such as injury to the frontal sinus or perforation of the

anterior cranial fossa.12 Disadvantages also include screw loosening or movement during surgical manipulation and hypertrophic scarring related to the skin incision. The disadvantage of the technique presented herein is the inherent effects of triangulation, especially when vertical repositioning is accomplished with large anteroposterior movements of the maxilla. This effect can be eliminated with the use of a specific gauge, as previously shown by Cope.6 Although the MCR is a soft tissue, it is a well-fixed structure that does not exhibit mobility or distortion during manipulation of the maxillomandibular skeletal complex or by the intratracheal tube. The intraoperative edema does not influence the use of this landmark, because the most superior subperiosteal dissection extends to the infraorbital foramen and nerve. Moreover, the operatory field was decreased. This is the first study found in the literature that evaluated the effectiveness of the MCR as a reference for maxillary repositioning in orthognathic surgery. Therefore this technique using the MCR is a viable option with a relatively easy clinical application in comparison to the technique involving a K-wire settled in the nasal bone.

References 1. Bryan DC, Hunt NP: Surgical accuracy in orthognathic surgery. Br J Oral Maxillofac Surg 31:343, 1993 2. Jacobson R, Sarver DM: The predictability of maxillary repositioning in Le Fort I orthognathic surgery. Am J Orthod Dentofacial Orthop 122:142, 2002 3. Van Sickels JE, Larsen AJ, Triplett RG: Predictability of maxillary surgery: A comparison of internal and external reference marks. Oral Surg Oral Med Oral Pathol 61:542, 1986 4. Stanchina R, Ellis E, Gallo WJ, et al: A comparison of two measures for repositioning the maxilla during orthognathic surgery. Int J Adult Orthodon Orthognath Surg 3:149, 1988 5. Gil JN, Claus JD, Manfro R, et al: Predictability of maxillary repositioning during bimaxillary surgery: Accuracy of a new technique. Int J Oral Maxillofac Surg 36:296, 2007 6. Cope MR: Measuring changes in maxillary height during osteotomy surgery. Br J Oral Maxillofac Surg 32:257, 1994 7. Johnson DG: Intraoperative measurement of maxillary repositioning: An ancillary technique. Oral Surg Oral Med Oral Pathol 60:266, 1985 8. Nishioka GJ, Van Sickels JE: Modified external reference measurement technique for vertical positioning of the maxilla. Oral Surg Oral Med Oral Pathol 64:22, 1987 9. Ellis E: Accuracy of model surgery: Evaluation of an old technique and introduction of a new one. J Oral Maxillofac Surg 48:1161, 1990 10. Polido WD, Ellis E, Sinn DP: An assessment of the predictability of the maxillary surgery. J Oral Maxillofac Surg 48:697, 1990 11. Ong TK, Banks RJ, Hildreth AJ: Surgical accuracy in Le Fort I maxillary osteotomies. Br J Oral Maxillofac Surg 39:96, 2001 12. Scarbrough FE, Ghali GE, Smith BR: Anatomic guidelines for the placement of external references for maxillary repositioning. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 84:465, 1997