Facial Surface Changes After Cleft Alveolar Bone Grafting

J Oral Maxillofac Surg 69:80-83, 2011

Facial Surface Changes After Cleft Alveolar Bone Grafting Michael Krimmel, MD, DMD, PhD,* Nils Schuck, MD, DMD,† Margit Bacher, DMD,‡ and Siegmar Reinert, MD, DMD, PhD§ Purpose: The aim of this study was to assess the 3-dimensional facial surface changes after cleft alveolar

bone grafting with digital surface photogrammetry. Patients and Methods: In a prospective study, 22 patients with cleft lip and palate underwent alveolar bone grafting. Before the procedure and 6 weeks postoperatively and before the continuation of orthodontic treatment, 3-dimensional images were taken with digital surface photogrammetry. Seven standard craniofacial landmarks on the nose and the upper lip were identified. Their spatial change because of bone grafting was assessed. Statistical analysis was performed with analysis of variance and t test. Results: A significant increase in anterior projection on the operative side (P ⬍ .05) was found for the labial insertion points of the alar base (subalare). No significant changes were detected for the position of the labial landmarks. Conclusion: Our results show 3-dimensionally that there is a positive influence of the alveolar bone graft on the projection of the alar base on the cleft side. © 2011 American Association of Oral and Maxillofacial Surgeons J Oral Maxillofac Surg 69:80-83, 2011 and 6 months after alveolar bone grafting, an intraoral radiograph should be taken as a record. This radiograph, however, can only show the height of the reconstructed alveolar process and its relation to the teeth adjacent to the cleft. Because the cleft alveolar bone graft also gives support to the overlying soft tissue of the face, secondary changes of the facial surface can be expected. Methods used for the analysis of the face include direct anthropometry,5-7 2-dimensional photogrammetry, laser scanning,8 and computed tomography scanning.9 These methods have their specific disadvantages, such as complexity, inaccuracy, prolonged image capture time, and radiation exposition, and therefore have not gained access to routine use in the cleft pediatric population. With the advent of 3-dimensional (3D) photogrammetry, the study of the 3D surface morphology of cleft patients became easier and more accurate.10-13 By use of this noninvasive method, the aim of this longitudinal study was to analyze the changes of the facial surface overlying the cleft alveolar process. In particular, the expected increase in nasal and labial projection after cleft alveolar bone grafting with iliac cancellous bone should be quantified.

Bone grafting of the alveolus is an essential part of the surgical management of cleft lip and palate (CLP) deformities.1,2 In its contemporary form of secondary grafting, the technique provides a predictable and adequate amount of bone for tooth eruption, orthodontic tooth movement, or endosteal implant placement. The hypoplastic piriform aperture can be reconstructed, and the bone graft may support the soft tissue of the nasal base. The success rate for the grafting procedure with iliac cancellous bone is high.3 The Eurocleft project emphasized the need for minimum record taking to monitor the individual treatment and for quality improvement and research reasons.4 According to these recommendations, before

Received from the University Hospital Tübingen, Tübingen, Germany. *Surgeon, Department of Oral and Maxillofacial Surgery. †Surgeon, Department of Oral and Maxillofacial Surgery. ‡Specialist in Orthodontics, Department of Orthodontics. §Surgeon and Department Head, Department of Oral and Maxillofacial Surgery. Address correspondence and reprint requests to Dr Krimmel: Klinik und Poliklinik für Mund-, Kiefer- und Gesichtschirurgie, Osianderstrasse 2-8, D-72076 Tübingen, Germany; e-mail: Michael. [email protected]

Patients and Methods STUDY SAMPLE

© 2011 American Association of Oral and Maxillofacial Surgeons

Twenty-two patients with CLP were prospectively enrolled in the study. Their age at the time of cleft

0278-2391/11/6901-0012$36.00/0 doi:10.1016/j.joms.2010.03.009

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alveolar bone grafting ranged from 9 to 20 years (mean, 13.9 years). Of the patients, 18 had unilateral CLP and 4 had bilateral CLP. All bilateral CLP patients received bilateral alveolar bone grafts. The cleft alveolus was complete in 18 cases and incomplete in 4 cases. Cleft alveolar bone grafting was performed by use of the technique of Boyne and Sands14 with cancellous bone from the iliac crest. Healing was uneventful in all cases. DIGITAL SURFACE PHOTOGRAMMETRY

Image acquisition was performed with the 3dMDface system (3dMD, London, England) 1 day before and 6 weeks after bone grafting. Four geometry and 2 texture cameras simultaneously capture the facial surface. The attached computer generates a 3D image. The technique is based on the application of synchronized pairs of digital cameras that view the surface of interest from different angles. Corresponding points on the facial surface are identified, and by triangulation, their 3D coordinates are calculated. With the application of an infrared speckle and visible light, the simultaneous capture of geometry and texture data is possible. Capture time is reduced to only 8 milliseconds. Per image, approximately 60,000 polygons were calculated. A geometric accuracy better than 0.5 mm could be achieved.10-12 System calibration according to the manufacturer’s protocol was performed before every imaging session.

FIGURE 2. Location of examined facial landmarks. (ac/ac, alare curvature/alare laterale; ch, cheilion; ls, labiale superius; n, nasion; prn, pronasale; sbal, subalare; sn, subnasale.) Krimmel et al. Facial Surface Changes After Bone Grafting. J Oral Maxillofac Surg 2011.

SURFACE DISTANCE MEASUREMENTS

Initially, the landmark nasion was identified.15 In a second step, a circle with a diameter of 5 cm and its center in the point nasion was selected on the preoperative image. Superimposition of preoperative and postoperative images occurred in this assumedly surgically unaffected area of the face. Registration of the

Table 1. DEFINITION OF EXAMINED LANDMARKS ACCORDING TO FARKAS

Abbreviation ac al ch ls n prn FIGURE 1. Preoperative and postoperative 3D surface images superimposed in a circular area centered on landmark nasion (n). Changes are shown color coded. (RMS, root mean square; StdDev, standard deviation.) Krimmel et al. Facial Surface Changes After Bone Grafting. J Oral Maxillofac Surg 2011.

sbal sn

Landmark

Definition

Alare curvature Most lateral point in curved baseline of each ala Alare laterale Most lateral point on each alar contour Cheilion Point located at each labial commissure Labiale Midpoint of upper superius vermilion line Nasion Point in midline of both nasal root and nasofrontal suture Pronasale Most protruded point of apex nasi Subalare Labial insertion point of alar base Subnasale Midpoint of angle at columella point base

Krimmel et al. Facial Surface Changes After Bone Grafting. J Oral Maxillofac Surg 2011.

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FACIAL SURFACE CHANGES AFTER BONE GRAFTING

FIGURE 3. Box plot showing mean increase in projection of examined bilateral landmarks. All changes are significant (P ⬍ .01). (ac, alare curvature; al, alare laterale; ch, cheilion; ls, labiale superius; no, nonoperative; o, operative; sbal, subalare.) Krimmel et al. Facial Surface Changes After Bone Grafting. J Oral Maxillofac Surg 2011.

preoperative and postoperative surfaces was done with the iterative closest point method. This is an algorithm used to minimize the difference between 2 clouds of points by iteratively revising their transformation (translation and rotation). Pre- and postoperative surface changes were presented as color-coded linear distance measurements between the images (Fig 1). Evaluation of distance measurements was performed for 5 bilateral and 2 median landmarks on the lip and the nose. In detail, the following landmarks were chosen: pronasale, subnasale, subalare, alare laterale, alare curvature, labiale superius, and cheilion (Fig 2, Table 1).15 STATISTICAL ANALYSIS

The distance measurements between preoperative and postoperative surfaces were statistically analyzed with the analysis of variance test. To concentrate the observed changes exclusively on those due to the osteoplasty, the differences in distance measurements between the operative and nonoperative sides were calculated in unilateral cases. The results were then statistically analyzed with the 2-sided t test (level of significance, P ⬍ .05).

Results All examined landmarks showed a highly significant anterior displacement after alveolar bone grafting (P ⬍ .01) (Fig 3). Even on the nonoperative side, the nasal and labial landmarks were positioned significantly more anterior. The highest increase in anterior projection was measured for the landmarks subalare and alare curvature.

To determine the actual influence of bone grafting versus possible persistent swelling, a comparison between the grafted and nongrafted sides was made for the group of unilateral CLP patients. The difference between the 2 sides was calculated. By doing so, only the changes in the area of the landmark subalare were significant (Table 2). The landmark alare curvature showed a difference in the increase in anterior projection of 0.5 mm between the operative and nonoperative sides, but this did not achieve the level of significance (P ⫽ .08). There was no significant difference between the operative side and the nonoperative side in the area of the landmarks alare, labiale superius, and cheilion. The surface changes of the median landmarks pronasale and subnasale were also significant. Especially in those cases that received bilateral osteoplasty, the increase in anterior projection of the nasal tip and the subnasal area was high (Fig 4).

Discussion Cleft alveolar bone grafting aims to stabilize the maxillary segments, to render bony support to the erupting teeth adjacent to the cleft or provide adequate bone stock for placement of a dental implant, and to give skeletal support to the overlying soft tissue of the face.3,16 Supposedly, this skeletal support enhances the projection of the lip and nose on the cleft side and thus improves facial symmetry in cleft deformity. Three-dimensional surface imaging is an ideal tool to prove this hypothesis of the effect of cleft bone grafting on the facial appearance, because it is nonin-

Table 2. SURFACE DISTANCES FOR OPERATIVE VERSUS NONOPERATIVE SIDES IN UNILATERAL CLEFT LIP AND PALATE PATIENTS (n ⴝ 18)

Operative side (mm) Nonoperative side (mm) Difference (mm) P value (t test)

Subalare

Alare Curvature

Alare Laterale

Labiale Superius

Cheilion

1.87 ⫾ 1.1 1.27 ⫾ 0.7 0.60 ⫾ 1.2 .04

1.56 ⫾ 1.0 1.06 ⫾ 0.6 0.50 ⫾ 1.1 .08

0.76 ⫾ 0.6 0.76 ⫾ 0.7 0.0 ⫾ 0.8 .99

1.09 ⫾ 1.6 0.97 ⫾ 1.6 0.12 ⫾ 0.4 .19

1.24 ⫾ 1.2 1.15 ⫾ 1.3 0.09 ⫾ 0.9 .68

NOTE. Data are presented as mean ⫾ SD. Krimmel et al. Facial Surface Changes After Bone Grafting. J Oral Maxillofac Surg 2011.

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The major support of the lip is probably determined by the underlying teeth and not so much by the alveolar bone. The increase in alar base projection leads to an improvement in symmetry of the nose and the face.17 A subsequent septorhinoplasty for residual cleft nose deformity, which has to be undertaken consequently, is then carried out from a more symmetric skeletal base and probably has a better outcome.18 This study was able to quantify the increase in nasal and labial projection after cleft alveolar bone grafting. The influence of bone grafting to augment the deficient alar base was shown after 6 weeks.

References

FIGURE 4. Mean increase in projection of examined median landmarks: (A) pronasale (prn) and (B) subnasale (sn) in unilateral and bilateral clefts. Krimmel et al. Facial Surface Changes After Bone Grafting. J Oral Maxillofac Surg 2011.

vasive and objective and can be easily performed before and after the procedure. The superimposition of the images gives an accurate and quantifiable result of the surgical changes. In our study, there was a postoperative increase in anterior projection in all examined landmarks when we looked at the landmarks independently, even on the nonoperative side. It can be assumed that this phenomenon was caused by persistent swelling 6 weeks postoperatively. The time interval chosen for postoperative assessment was probably too short to eliminate the acute soft tissue swelling. At 6 weeks postsurgery, there were probably still soft tissue form differences resulting from the surgery that would be modified by 6 months after surgery or even at 1 year. However, because orthodontic treatment was continued after this time and mostly growing adolescents were studied, we chose this interval deliberately to minimize the influence of surgery, orthodontics, and growth. By calculating the difference between the changes on the operative and nonoperative sides, we eliminated the influence of swelling. We could then show that alveolar bone grafting significantly enhances the projection of the alar base, but not of the upper lip.

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