Three-dimensional evaluation of the alar cinch suture after Le Fort I osteotomy

Abstract

Orthognathic surgery has an influence on the overlying soft tissues of the translated bony maxillomandibular complex. Improvements in both function and facial appearance are the goals of surgery. However, unwanted changes to the soft tissues, especially in the nose region, frequently occur. The most common secondary change in the nasolabial region is widening of the alar base. Various surgical techniques have been developed to minimize this effect. The purpose of this study was to evaluate the changes in the nasal region due to orthognathic surgery, especially the alar width and nasal volume, using combined cone beam computed tomography (CBCT) and three-dimensional (3D) stereophotogrammetry datasets. Twenty-six patients who underwent a Le Fort I advancement osteotomy between 2006 and 2013 were included. From 2006 to 2010, no alar base cinch sutures were performed. From 2010 onwards, alar base cinch sutures were used. Preoperative and postoperative documentation consisted of 3D stereophotogrammetry and CBCT scans. 3D measurements were performed on the combined datasets, and the alar base width and nose volume were analyzed. No difference in alar base width or nose volume was observed between patients who had undergone an alar cinch and those who had not. Postoperatively the nose widened and the volume increased in both groups.

Aside from skeletal changes, changes to the related soft tissues also invariably occur as a result of orthognathic surgery. Various studies have shown changes in the nasolabial morphology associated with the Le Fort I osteotomy, especially an increase in alar width. A suturing method can be applied to prevent this increase in alar width. Reorientation of the displaced peri-nasal musculature and control of the alar base width is said to be possible with the use of an alar base cinch suture before incision closure. The alar base cinch suture was originally described by Millard, who used this suture in patients with cleft lip undergoing nasal defect correction, and its use was later described in non-cleft patients. Modified alar cinch suturing techniques have been developed to improve the narrowing effect and to simplify the execution of this technique. Studies describing the outcome of the suture in relation to postoperative alar width changes have reported contradictory results.

The change in alar width has been studied anthropometrically, two-dimensionally by means of photographs, and three-dimensionally by means of cone beam computed tomography (CBCT) and computed tomography (CT). Using two-dimensional (2D) techniques, data are possibly missed. As the human body is a three-dimensional (3D) entity, any change, whether from movement during facial expression or from surgery, happens in three dimensions.

The purpose of this study was to employ 3D techniques to evaluate the changes in the nasal region (inter-alar width and nose volume) occurring as a consequence of orthognathic surgery (Le Fort I osteotomy), with and without alar cinch suturing, in three dimensions.

Materials and methods

Patients

Patients (age >16 years) with maxillary hypoplasia who underwent a Le Fort I advancement osteotomy between 2006 and 2013 in the department of oral and maxillofacial surgery of a university medical centre in the Netherlands were included in this study. From 2006 to 2010, no alar cinch sutures were performed. From 2010 onwards, alar cinch sutures were performed because of the observed widening of the alar width in the first group of patients.

The following exclusion criteria were applied: missing preoperative or postoperative 3D photographs or CBCT scans, multi-segment Le Fort I osteotomy, anterior open bite cases, rhinoplasty surgery during or within 1 year after the Le Fort I osteotomy, and patients with accompanying craniofacial syndromes.

Pre- and postoperative 3D documentation

A CBCT scan (i-CAT 3D Imaging System; Imaging Sciences International Inc., Hatfield, PA, USA) was used to acquire bony tissue information. A 3D stereophotogrammetry camera setup (3dMD System; 3dMD LLC, Atlanta, GA, USA) was used to capture 3D photographs of the face. The 3D photographs were generated from six 2D photographs taken simultaneously (four grey-scale photographs and two full-colour photographs). A polygon light pattern was projected onto the four grey-scale photographs. Based on this pattern and its deformed image, a 3D photograph was reconstructed.

A full field of view extended height CBCT scan was acquired preoperatively and at 1 year postoperative. 3D photographs were acquired directly preoperative and at 1 year postoperative.

3D measurements

The method described previously by this research group was used to evaluate the hard tissue maxillary changes and the soft tissue nasal changes. Briefly, both the CBCT and the 3D photographs were taken in natural head position and habitual occlusion. 3D models were created and aligned using voxel-based matching in Maxilim software (Maxilim version 2.2.2.1; Medicim NV, Mechelen, Belgium). A surface-based matching procedure for the preoperative and postoperative 3D photographs was performed in five steps, as described in a previous study. A distance map was created on the matched 3D photographs, indicating the soft tissue changes ( Fig. 1 ). Finally a modified 3D cephalometric analysis was performed ( Table 1 ). From this analysis, the inter-alar width and planes lining the nose were acquired ( Fig. 2 ). The planes indicated the region of interest (ROI). The volumes of the left and right sides of the nose were calculated from this ROI.

Fig. 1
Distance kit indicating the differences between the preoperative and postoperative 3D soft tissues. The range of the colour histogram is −5 mm to 5 mm.

Table 1
Definitions of the landmarks and planes used in the analysis.
Landmark Abbreviation Description
Alare (left) al(l) Left alare, most lateral point on the left alar contour
Alare (right) al(r) Right alare, most lateral point on the right alar contour
Cheilion (left) ch(l) Left cheilion, point located at the left labial commissure
Cheilion (right) ch(r) Right cheilion, point located at the right labial commissure
Nasion n Nasion, the midpoint of the frontonasal suture
Subnasale sn Subnasale, midpoint on the nasolabial soft tissue contour between the columella crest and the upper lip

Plane Description
Median plane The median ( z ) 3D reference plane is computed through the pupil reconstructed point and as a plane perpendicular to the horizontal ( x ) and the vertical ( y ) 3D reference planes
Horizontal plane The horizontal ( x ) 3D reference plane is automatically computed as a plane 6.6° below the canthion–superaurale line, along the horizontal direction of the natural head position and through the pupil reconstructed point translated 77.2 mm more posteriorly
Vertical plane The vertical ( y ) 3D reference plane is computed as a plane perpendicular to the horizontal ( x ) 3D reference plane and along the horizontal direction of the natural head position
Lateral left nasal plane A plane through landmarks ch(l) and al(l) and perpendicular to the vertical plane
Lateral right nasal plane A plane through landmarks ch(r) and al(r) and perpendicular to the vertical plane
Upper nasal plane A plane through landmark n and parallel to the horizontal plane
Lower nasal plane A plane through landmark sn and parallel to the horizontal plane

Fig. 2
Region of interest (ROI) for the volumetric measurements. (A) Planes marking the nasal area on the distance kit. (B) The nasal ROI on the preoperative 3D photograph. (C) The nasal ROI on the postoperative 3D photograph.

Operative procedure

All surgical operations were performed or supervised by one of the authors (MdK). Intraoperative antibiotics were given (1000 mg cefazolin and 500 mg metronidazole). After nasotracheal intubation, the mucobuccal fold of the maxilla was infiltrated with local anaesthetic (articaine; Ultracain DS Forte). The Le Fort I procedure started with an incision in the gingivobuccal sulcus from the canine on the one side to the canine on the other side. After elevation of the mucoperiosteum and nasal mucosa, the osteotomy line was designed with a fine burr, after which the cut was made with a reciprocal saw. The lateral nasal walls and nasal septum were osteotomized with a nasal osteotome. The piriform aperture and when necessary the nasal spine was rounded off. After mobilization of the maxilla, it was positioned in the planned position using an acrylic wafer. Fixation was performed with four 1.5-mm miniplates (KLS Martin, Tuttlingen, Germany), one paranasal and one on the buttress on each side. The mucosa was closed with a 4–0 Vicryl suture (Ethicon; Johnson and Johnson Medical, Norderstedt, Germany). No alar cinch or VY closure was performed up until 2010. In the alar cinch group, alar cinch and VY closure was performed. The alar cinch procedure was performed through the intraoral incision. A 2–0 Vicryl suture was passed through the fibromuscular tissue of the alar base from anterior to posterior on both sides. Control of the suture was performed, checking the movement of the alar base. The two free ends of the suture were tied together in the centre.

Statistical analysis

The reproducibility of the landmarks used in the soft tissue analysis was evaluated beforehand and ranged from 0.04 mm (standard deviation 0.48 mm) to 0.08 mm (standard deviation 0.65 mm). The paired Student t -test was used for the statistical analysis, with a P -value of 0.05 indicating statistical significance.

The preoperative and postoperative measurements were compared using the Student t -test. The difference between the alar cinch group and the control group was tested using the Student t -test as well as the Fisher’s exact test. The influence of sex, age, the presence or absence of a cinch suture, and maxillary translations and rotations on the change in alar base width was investigated using linear regression analysis, with statistically significant differences indicated by a P -value of <0.05.

The statistical data analysis was performed with SPSS version 16.0 software (SPSS Inc., Chicago, IL, USA).

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Dec 15, 2017 | Posted by in Oral and Maxillofacial Surgery | Comments Off on Three-dimensional evaluation of the alar cinch suture after Le Fort I osteotomy
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