3D Stereophotogrammetric assessment of pre- and postoperative volumetric changes in the cleft lip and palate nose

Abstract

In cleft lip and palate patients the shape of the nose invariably changes in three dimensions (3D) due to rhinoplastic surgery. The purpose of this study was to evaluate stereophotogrammetry as a 3D method to document volumetric changes of the nose in patients with a cleft lip (CL) or cleft lip and palate (CLP) after secondary open rhinoplasty. 12 patients with unilateral CL or CLP were enrolled in the study prospectively. 3D facial images were acquired using 3D stereophotogrammetry preoperatively and 3 months postoperatively. A 3D cephalometric analysis of the nose was performed and volumetric data were acquired. The reliability of the method was tested by performing an intra- and inter-observer analysis. Left, right and total nasal volumes and symmetry were compared. No statistically significant differences ( p < 0.05) were found within and between observers for the measured volumes and symmetry. Postoperatively, the total volume of the nose increased significantly, especially the volume at the cleft side. No significant volume difference pre- and postoperatively was found for the non-cleft side. The symmetry of the nose improved significantly. 3D stereophotogrammetry is a sensitive, quick, non-invasive method for evaluating volumetric changes of the nose in patients with cleft lip or cleft lip and palate.

The nose is known to be aberrant in appearance and function in patients with a cleft lip (CL) or a cleft lip and palate (CLP) . Distortions of the nose can vary from almost invisible to catastrophic, mostly dependent on the severity and type of cleft . To correct the nasal deformity in CL or CLP patients is a challenge. In the Netherlands, for the last 25 years, a primary rhinoplasty correction has been performed at the time of primary lip closure in unilateral CL or CLP patients. This usually involves reducing the asymmetry by undermining and rotating the nose without altering bony tissue. Nevertheless, as the children grow older, the nasal shape remains deformed. There is usually an underprojection of the dome at the cleft side and surgery mainly focuses on correcting this asymmetry by increasing the projection (which enhances the volume of the nasal pyramid) on the cleft side.

Various studies have been undertaken to evaluate the result of different rhinoplastic procedures , but quantification of surgical changes remains difficult. Besides direct anthropometric measurements , two-dimensional (2D) photographs and radiographs are used to document and calculate the changes after surgery . Until now, studies comparing pre- and postoperative nasal changes in patients with clefts have been limited to these techniques . The human body however, is a three-dimensional (3D) entity and any change, whether from movement during facial expression or from surgery, occurs in three dimensions. Various 3D imaging techniques have been developed to overcome the shortcomings of conventional 2D imaging. These include 3D cephalometry , Moiré topography , 3D laser scanning , 3D optoelectronic digitizers and 3D stereophotogrammetry . The latter method has gained popularity over the last years as digital 3D data sets of the face can be acquired rapidly and non-invasively, while simultaneously being archived for future analysis . Recent studies have shown 3D cephalometric measurements acquired with a 3D stereophotogrammetrical camera setup to be valid and reproducible .

To the best of the authors’ knowledge, no stereophotogrammetry studies have been performed on the volumetric 3D changes of the nose after secondary rhinoplasty in CL and CLP patients. The purpose of this study was to evaluate the value of 3D stereophotogrammetry for volumetric documentation of the nose in CL and CLP patients who underwent secondary rhinoplastic surgery.

Materials and methods

The study sample comprised of CL and CLP patients from the Cleft Palate Craniofacial Unit of the Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands, operated on between June 2007 and December 2007. Inclusion criteria were: unilateral CL or unilateral CLP; age above 12 years; and signed informed consent. Exclusion criteria were: associated cranio-facial deformities; syndromes; and earlier secondary rhinoplastic surgery.

Operative procedure

All operative procedures were performed by one surgeon (PS). An open rhinoplasty (Rethi incision: rim incision traversing the columella) was performed in all patients. Depending on the deformity, the following nasal surgery components were employed: a septal deviation was corrected by remodelling the deviating septum and trimming the base. The lower lateral cartilages were reduced and sutured together in order to narrow the dome. A columellar strut was placed for nasal tip support. For this purpose part of the septal cartilage was used or cartilage was acquired from the auricular concha. Dome sutures, shield, tip or dorsal grafts were implemented if required. When correction of the nasal bone was mandatory a medial and lateral osteotomy including efracture and infracture was performed.

Pre- and postoperative 3D documentation

A 3D stereophotogrammetrical camera setup with an integrated software program modular system V 1.0 (3dMDface™ 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. These 3D photographs were automatically saved as ‘three-dimensional surface binary’ files (.tsb file) and were visualized and analyzed using 3D editing software (3dMDpatient V3.0.1. 3dMDpatient™ Software Platform, 3dMD LLC). With this system it was possible to capture 180 degrees of the subject’s face, which concurred with an ear-to-ear 3D photograph.

The 3D photographs were taken in natural head position and habitual occlusion. Patients were asked to relax their facial musculature, swallow and keep their molars in occlusion after swallowing . 3D photographs were acquired preoperatively as well as at the clinical control visit 3 months postoperatively. The preoperative surgical deformities of the nose were recorded using criteria proposed by N akamura et al.

3D measurements

To isolate the region of interest on the 3D photographs, the neck and parts of the hair were trimmed using 3dMDpatient V3.0.1 software. The 3D photograph was exported as a wavefront object file (.obj) and imported into Maxilim ® version 2.2.2.1 (Medicim NV, Mechelen, Belgium). A surface based matching procedure for the pre- and postoperative 3D photographs was performed in five steps as described previously . On the matched 3D photographs a distance map was created giving an indication of the soft-tissue changes ( Fig. 1 ). A modified 3D cephalometric analysis, based on 3D cephalometric soft tissue analysis on CT data ( Table 1 ), was performed to outline the region of interest for the volumetric measurements. This resulted in the matched 3D photographs on a Cartesian coordinate system with the nose lined by various planes ( Fig. 2 ). These planes defined the borders of the volume of the nose and were used for further circumscription of the 3D photograph.

Fig. 1
3D distance map of the pre- and postoperative soft tissue changes in patient 6. (a) Decrease (red) of volume on the non-cleft side; (b) patient 6 frontal view; (c) increase (green) in volume on the cleft side.

Table 1
Definitions of landmarks and planes used based on the 3D cephalometric soft-tissue analysis according to Swennen .
Landmark Abbreviation Description View
Landmarks and planes
Alare (left) al(l) Left alare, most lateral point on the left alar contour. Base view
Alare (right) al(r) Right alare, most lateral point on the right alar contour. Base view
Cheilion (left) ch(l) Left cheilion, point located at the left labial commissure. Frontal
Cheilion (right) ch(r) Right cheilion, point located at the right labial commissure. Frontal
Cheilion (middle) ch(m) Soft tissue point automatically computed as the midpoint of the right cheilion and left cheilion.
Endocanthion (left) en(l) Left endocanthion, soft tissue point located at the inner commissure of the left eye fissure. Frontal
Endocanthion (right) en(r) Right endocanthion, soft tissue point located at the inner commissure of the right eye fissure. Frontal
Exocanthion (left) ex(l) Left exocanthion, soft tissue point located at the outer commissure of the left eye fissure. Frontal
Exocanthion (right) ex(r) Right exocanthion, soft tissue point located at the outer commissure of the right eye fissure. Frontal
Exocanthion (middle) ex(m) Soft tissue point automatically computed as the midpoint of the right exocanthion and left exocanthion.
Pupil reconstructed p″ Pupil reconstructed point, midpoint between the endocanthi and pupils, located on the level of the exocanthi. Frontal
Subnasale sn Subnasale, midpoint on the nasolabial soft tissue contour between the columella crest and the upper lip. Lateral right
Plane Description
Posterior nasal plane A plane through landmarks ex(l), ex(r) and ch(m).
Lateral left nasal plane A plane through landmarks en(l) and al(l) and perpendicular to the vertical plane.
Lateral right nasal plane A plane through landmarks en(r) and al(r) and perpendicular to the vertical plane.
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.
Upper nasal plane A plane through landmark ex(m) and parallel to the horizontal plane.
Lower nasal plane A plane through landmark sn and parallel to the horizontal plane.
Horizontal plane The horizontal ( x ) 3D Reference Plane is automatically computed as a plane 6.6 degrees below the Cantion – 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.

Fig. 2
3D stereophotogrammetric photograph of the face. (a) Untextured 3D photograph with landmarks identified (red dots); (b) planes derived from the landmarks to outline the nasal area; (c) and (d) untextured cropped nose; (e) and (f) right and left halves of the untextured cropped nose.

Finally, only the nose was left and a virtual volume could be computed. To compare left and right volumes, the nose was divided into a left and right part using the cephalometric-based median plane ( Table 1 ). The left and right volumes of the pre- and postoperative nose were then measured (mm 3 ).

To determine intra- and inter-observer reliability, all measurements were performed twice by two observers (BL and TM), independently of each other, with a time interval (8 weeks for BL and 2 weeks for TM), so preventing memory effects.

Statistical analysis

Means and standard deviations were calculated and comparisons were made between: the pre- and postoperative total volumes of the nose; the pre- and postoperative cleft side nasal volumes; the pre- and postoperative non-cleft side nasal volumes; the pre- and postoperative volumetric symmetry calculated by dividing the volume of the cleft side and the non-cleft side. A ratio of 1.00 means perfect symmetry.

Pre- and postoperative differences were analyzed using paired Student’s t -tests with a p -value of 0.05 indicating statistically significant differences. Paired Student’s t -tests were used to calculate the intra- and inter-observer reproducibility of the volumes for repeated measurements (mean difference) and to test for statistically significant differences. The measurement error was calculated as the standard deviation (SD) of the mean difference divided by √2. Reliability coefficients between first and second measurement were calculated as Pearson correlation coefficients. Statistical data analysis was performed with the SPSS software program, version 16.0 (SPSS Inc., Chicago, USA).

Results

Eight male and four female patients aged 13–40 years (median, 18 years) met the inclusion criteria and had various deformities of the nose ( Table 2 ). Two patients had an isolated CL and 10 had a CLP. There were 8 left- and 4 right-sided clefts.

Table 2
Surgical characteristics for the 12 patients.
Patient CL/CLP side Deformity of the nose Columellar strut Alar graft Tip graft Nasal bone osteotomy
1 Right * A, B, C, D No Yes No No
2 Left A, D No Yes No No
3 Left B, C, D Yes No No No
4 Right A, B, C, D No No No No
5 Left A, D Yes Yes No No
6 Left A, B, C, D Yes No No Yes
7 Right A, B, C, D Yes No No No
8 Left A, B, C, D Yes No No No
9 Left A, B, C, D Yes No No No
10 Right B, C, D Yes No Yes No
11 Left * A, B, C No No No Yes
12 Left A, B, C, D No No No No
(A) Deviated columella; (B) depressed and deviated nasal tip; (C) wide nasal ala on the cleft side; (D) flat and v-shaped nostril.

* CL only.

Nose septal cartilage.

Auricular cartilage.

12 secondary open rhinoplasty procedures were performed ( Table 2 ). Interdomal sutures were used in all patients. In two patients no further surgical procedures were performed. In the remaining 10 patients, one or two of the following surgical procedures were used in order to achieve more symmetry and increase the volume of the tip on the cleft side: a columellar strut was used in seven patients (five using septal cartilage and two using auricular cartilage), three patients underwent an alar wing graft (two using auricular cartilage, one using septal cartilage), a tip graft was performed in one patient (using septal cartilage) and a transcutaneous nasal bone osteotomy was performed in two patients.

No statistically significant differences ( p < 0.05) were found within and between observers for the measured volumes and symmetry ( Table 3 ). The reliability coefficients for all volumes ranged from 0.96 to 1.00; duplicate measurement errors ranged from 55.68 to 147.40 mm.

Table 3
Mean volume differences (mm 3 ) with 95% confidence intervals and p -value, reliability coefficients (Pearson’s correlation coefficient), and measurement error (mm 3 ) within and between observers.
95% Confidence interval of the difference
Mean difference (mm3) Lower Upper Sig. (2-tailed) Reliability coefficient Measurement error (mm3)
Cleft side volume
Intra 1 14.72 −101.97 131.41 0.79 0.98 129.86
Intra 2 5.47 −44.56 55.51 0.81 1.00 55.68
Inter 1 −30.74 −81.35 19.86 0.21 1.00 56.32
Inter 2 −39.99 −172.44 92.46 0.52 0.97 147.40
Non-cleft side volume
Intra 1 40.26 −17.20 97.72 0.15 0.98 63.95
Intra 2 −47.33 −125.33 30.67 0.21 0.97 86.81
Inter 1 42.04 −16.86 100.95 0.14 0.98 65.56
Inter 2 −45.55 −126.87 35.77 0.24 0.96 90.50
Mean volume ratio
Intra 1 0.00 −0.01 0.00 0.38 0.98 0.01
Intra 2 0.00 0.00 0.01 0.17 0.98 0.01
Inter 1 0.00 −0.01 0.00 0.16 0.97 0.01
Inter 2 0.00 0.00 0.01 0.36 0.99 0.00
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Feb 8, 2018 | Posted by in Oral and Maxillofacial Surgery | Comments Off on 3D Stereophotogrammetric assessment of pre- and postoperative volumetric changes in the cleft lip and palate nose
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