Effects of two alar base suture techniques suture techniques on nasolabial changes after bimaxillary orthognathic surgery in Taiwanese patients with class III malocclusions

Abstract

A randomized controlled trial was designed to assess the effectiveness of two alar base cinch techniques on the changes in nasolabial morphology after bimaxillary orthognathic surgery. Sixty patients requiring a Le Fort I osteotomy to correct skeletal discrepancies were selected randomly to receive either conventional or modified alar base cinching during the intraoral wound closure procedure. Conventional cinching passed through nasalis muscle and anterior nasal spine. Modified cinching also passed through dermis tissue to increase the anchorage. Postoperative hard and soft tissue changes were evaluated using cone beam computed tomography and three-dimensional stereophotogrammetry at predefined time points. Forty-eight patients with a skeletal class III malocclusion were included. In the conventional group, there was an increase of 0.31 ± 1.31 mm in nasal width and an increase of 0.97 ± 1.60 mm in columellar length. In the modified group, there was an increase of 0.81 ± 1.87 mm in the cutaneous height of the upper lip and a decrease of 0.76 ± 1.56 mm in lower prolabial width. Patients with an initial narrow nasal width, alar base width, and less vertical nostril show were more susceptible to a greater degree of change after surgery. Both alar base suture techniques are effective at controlling nasolabial form changes resulting from class III dual-jaw orthognathic surgery.

Surgical orthodontic treatment is commonly used to correct skeletal class III malocclusion. Although, in the past, skeletal class III malocclusion was treated mainly by mandibular setback, bimaxillary procedures have become more prevalent in recent years. Bimaxillary surgery not only achieves a well-proportioned facial profile and symmetry, but also provides the same skeletal stability as that of single-jaw osteotomies.

However, the maxillary Le Fort I osteotomy can alter the soft tissue in the nasolabial region. The most significant changes include an increase in the width of the alar base of the nose, anterosuperior movement of the nasal tip, and upper lip flattening. This finding is crucial for Asian populations, who tend to have wider noses, a shorter columellar height, and a flatter appearance than Caucasians do. Numerous studies have suggested that applying an alar base cinch suture could minimize alar base flaring. However, three-dimensional (3D) studies have found that the alar base width after surgery is still increased 2–3 mm with or without cinch suture placement. A modified alar base cinch suture has been suggested to mitigate the detrimental effects of the maxillary Le Fort I osteotomy on nasolabial aesthetics.

A new technique has been proposed for improving the effectiveness of the alar cinch suture technique by increasing the anchorage of the alar cinch suture to the muscle and dermis tissue over the bilateral alar base. In contrast to extraoral approaches, this technique could prevent temporary postoperative dimpling of the alar base and sensitive nasal alar skin. The aim of this study was to assess the effectiveness and resulting postoperative changes in the nasolabial region of two alar base cinch suture techniques after orthognathic surgery.

Patients and methods

Protocol

This prospective randomized controlled trial was conducted between September 2011 and February 2013. The study was approved by the Medical Ethics Committee. The trial was registered at ClinicalTrials.gov. The study was conducted according to the Consolidated Standards of Reporting Trials standards for reporting randomized controlled trials ( Fig. 1 ).

Fig. 1
Diagram illustrating the flow of participants through the randomized controlled trial, including patients withdrawn and the number of participants completing the trial in each arm.

Sample collection

All non-growing Taiwanese patients over 18 years of age who underwent a Le Fort I maxillary osteotomy were considered eligible for inclusion in the study. Patients with an associated syndromic diagnosis, cleft of the lip or palate, dentofacial trauma, or previous nasal septum or nasal tip operations were excluded.

Informed consent was obtained from all of the patients prior to surgery. The patients were assigned randomly to either the conventional group (group C) or modified group (group M). All of the cinch suture operations were performed by a single surgeon (CHL), who was informed of the assigned grouping of the patient just before orthognathic surgery by the research assistant; assignment was done according to a randomized table. All of the patients and the sole investigator (YHC) were blinded to the grouping.

Interventions

All of the patients underwent a standard Le Fort I osteotomy. Surgery was performed under general anaesthesia with nasotracheal intubation. The midface degloving procedure was begun with an incision along the bilateral upper buccal sulcus, by cutting through mucosa and muscles to the anterior wall of the maxilla. Nasalis muscles, originating from the maxilla and connected to the nasal bridge and alar cartilage, were severed and detached from the maxillary surface. After satisfactory repositioning of the maxillomandibular complex, rigid fixation involving plates and screws was applied to the medial and lateral buttresses of the maxilla. No trimming of the anterior nasal spine (ANS), bony structures around the pyriform ring, or nasal septum was done during the surgery.

Before closure of the maxillary wound, an alar base cinch suture without V–Y advancement was performed with 3–0 nylon. For group C, the suture began from the bilateral alar part of the nasalis muscle and passed through a hole drilled in the ANS. For group M, the suture began from the bilateral alar part of the nasalis muscle and dermis tissue over the alar base, and then passed through a hole drilled in the ANS. The major difference between these two methods was whether the additional anchorage sutures went through the dermis tissue over the alar base or not ( Fig. 2 ). During surgery, the surgeon repeatedly measured the alar width with the use of callipers, both before incision and during nasal cinch suturing. The surgeon attempted to maintain a consistent alar width by adjusting the tightness of the sutures. Two-hand ties with four knots were used to ensure appropriate tightness.

Fig. 2
Diagrams illustrating (a) the conventional alar base cinch technique, and (b) the modified alar base cinch technique. The conventional alar base cinch suture began from the bilateral alar part of the nasalis muscle and passed through a hole drilled in the anterior nasal spine. The modified alar base cinch suture began from the bilateral alar part of the nasalis muscle and dermis tissue over the alar base, and then passed through a hole drilled in the anterior nasal spine. m: alar part of the nasalis muscle; ANS: anterior nasal spine; D: dermis tissue over the alar base.

Outcome measures

Two types of 3D stereophotogrammetry were conducted. Cone beam computed tomography (CBCT) data were obtained both before surgery and at 4–6 weeks after surgery, and 3D digital photographs were taken before surgery (T1) and at 6 months after surgery (T2). Fifteen anthropometric parameters were measured, including baseline, nasal, and nasolabial parameters ( Table 1 and Fig. 3 ). The sagittal and vertical movement of hard tissue landmarks (the ANS, the midline point at the innermost curvature point from the maxillary ANS to the crest of the maxillary alveolar process (A point), and the midpoint of the upper incisor edge (UI level)) and soft tissue landmarks (pronasale (prn), subnasale (sn), and labiale superioris (ls)) were also measured.

Table 1
Definitions of landmarks and measurements in the assessment of 3D nasolabial changes a .
Parameter Anthropometric landmarks Abbreviation
Baseline parameter
(1) Inter-canthal distance Endocanthion R en–L en
Nasal parameters
(2) Nasal height Nasion, subnasale n–sn
(3) Nasal length Nasion, pronasale n–prn
(4) Nasal tip protrusion Subnasale, pronasale sn–prn
(5) Alar width The most lateral point on the curved base line of each ala, alar points R al–L al
(6) Alar base width Alar base points R alB–L alB
(7) Right vertical nostril show dimension Right vertical nostril show points q–r
(8) Left vertical nostril show dimension Left vertical nostril show points s–t
(9) Columellar length Labiale superioris, stomium ls–sto
Lip parameters
(10) Cutaneous height of upper lip Subnasale, highest point of columella sn–c
(11) Overall upper lip height Subnasale, labiale superioris sn–ls
(12) Vermilion height of upper lip Subnasale, stomium sn–sto
(13) Lower prolabial width Right and left crista philtrum R cphi–L cphi
(14) Upper lip protrusion Tragus, labiale superioris tr–ls
(15) Nasolabial angle (at MSR plane) Nasion, subnasale, labiale superioris NLA

3D, three-dimensional; MSR plane, mid-sagittal reference plane.

a Anthropometric landmarks and measurements were defined according to Farkas (Farkas LG. Anthropometry of the head and face. New York: Raven Press, 1994: 103–108, 112, 850).

Fig. 3
Outcome measures for 15 anthropometric parameters: (1) inter-canthal distance, (2) nasal height, (3) nasal length, (4) nasal tip protrusion, (5) nasal width, (6) alar base width, (7) right and (8) left nostril show vertical dimension, (9) columellar length, (10) cutaneous height of the upper lip, (11) overall upper lip height, (12) vermilion height of the upper lip, (13) lower prolabial width, (14) upper lip protrusion, and (15) nasolabial angle (on midsagittal plane).

CBCT capture and image processing

CBCT was performed using an i-CAT scanner (Imaging Sciences International, Hatfield, PA, USA) with 14-bit grey-scale resolution and a voxel size of 0.4 mm 3 . The CBCT data were constructed into 3D CBCT models. The head position was then oriented to the reference planes ( Fig. 4 ). Bone tissue and skin tissue surface images were segmented according to different thresholds of Hounsfield units and then superimposed. After the superimposition of the bone tissue surface images before and after orthognathic surgery, directional movements of the maxilla were measured in the x , y , and z planes. 3D CBCT image rendering, registration, superimposition, and skeletal measurements were conducted using Vultus software (3dMD, Atlanta, GA, USA).

Jan 17, 2018 | Posted by in Oral and Maxillofacial Surgery | Comments Off on Effects of two alar base suture techniques suture techniques on nasolabial changes after bimaxillary orthognathic surgery in Taiwanese patients with class III malocclusions
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