Application Of Digital Technique In The Three-dimensional Reconstruction Of Nasal Alar Cartilage

BackgroundCleft lip is the most common congenital maxillofacial deformity,aggravated with the widening of fissure,which can affect the growth and development of local skin,muscle,mucosa,bone and cartilage to some certain.Secondary nasal deformities follows one-stage repair of cleft lip.The deformity of nasal alar was the most obvious.In patients with unilateral cleft lip,the nasal deformity is more prominent because of the obvious comparison of nasal alar morphology between the normal side and the cleft side.The nasal deformities after unilateral cleft lip surgery are often characterized by the collapse and abduction of alar,the collapse of the nasal floor and sill,the wide and flat nostril,and the short and small deviation of the nasal columella in cleft side.Unbalanced distribution of muscle and the dysplasia of cartilage are the most important causes of nasal deformity of lip cleft^[1-2].Professor Yin Ningbei created a three-dimensional directional stereoscopic model of nasolabial muscle^[3],and proposed the reconstruction of nasolabial muscle tension band to repair the shape of nasolabial.However,if the nasolabial muscle tension band is reconstructed without the cartilage,it is difficult to gain ideal result for patients with chondrodysplasia,so it is very necessary making auto-cartilage transplant-tation to correct nasal deformity in this case population.Auto-cartilage transplantation has the advantages of easy survival,low rejection and low exposure rate.It is often used as the main transplantation material in the operation of nasal deformity of lip cleft.The three commonly used cartilage grafts are nasal septum cartilage,auricular cavity cartilage and costal cartilage.All of them have good structural support function^[4],the difficulty of operation lies in the carving and shaping of cartilage grafts,and standards of the shaping of cartilage grafts have not been reported at home and abroad.Therefore,this study focused on the three-dimensional reconstruction and measurement of nasal alar cartilage,to find a feasible way to establish a standard database of nasal alar cartilage,to guidethe engraving and shaping of the alar cartilage graft scientifically,and toassist the clinical application of autologous cartilage transplantation to repair the cleft lip nasal deformiseicienfically.Aim:1.In order to establish a standardized three-dimensional model of nasal alar cartilage,computer digital three-dimensional reconstruction technology was used to process the sectional anatomic images of normal human cadavers.2.The computer digital three-dimensional measurement technology was used to measure the specific parameters of the three-dimensional model of nasal alar cartilage,which provided relatively accurate reference data for the repair of cleft lip nasal deformity.Method:1.Normal cadaveric speciwomen was selected for scanning by CT and MRI,with embedded,embedded,frozen and milled to obtain continuous tomographic anatomical tissue images.The nasal alar cartilage was segmented by PHOTOSHOP software and marked by color filling,which was stored as a new layer.All the coating volume data were merged,the volume was drawn by computer rendering technology,and the three-dimensi-onal structure of nasal alar cartilage was reconstructed by using data processing technology and three-dimensional reconstruction software.2.The CT and MRI tomographic images obtained before cadaveric speciwomen frozen,that were imported into Radi Ant DICOM Viewer 4.6.9 software for three-dimensional nasal reconstruction.3.By observing the imaging effects of three kinds of digital three-dimensional techniques,the feasibility of CT,MRI and sectional anatomical digital three-dimensional reconstruction in three-dimensional reconstruction of nasal alar cartilage was analyzed.4.The reconstructed three-dimensional nasal alar cartilage was divided into three parts:lateral crus,middle crus and medial crus.A,B,C,D,E,F,G,H,I and J were the midpoints of the side length of each part.The pixel size of the fault image is set to 0.0425mm,and the number of pixels on the reconstructed image is measured to calculate the distance between the two points.The nasal alar cartilage（Long,）.L),width（Widthth,W）,thickness（Thickness,Th）,the angle between the medial crus and lateral crus（Included Angle,IA）and the volume of nasal alar cartilage（Volume,V）of medial crus,middle crus and lateral angle were measured by computer digitization technique objectively.Result:1.The computer digital three-dimensional reconstruction technology was used to process the images of continuous sectional anatomic specimens of normal adult nasal alar cartilage,and the three-dimensional model of nasal alar cartilage was successfully reconstructed.2.The three-dimensional model of nasal alar cartilage was measured by computer digital three-dimensional measurement technology,and 11 related measurement data were obtained in total.The medial crus has a length of 13.54 mm,the width of 4.45 mm,and the thickness of 0.37 mm.The length of the middle crus is 2.64 mm,the width is 2.52 mm,and the thickness is 0.48 mm.The length of the lateral crus is 17.76 mm.,the width is 6.79mm,and the thickness is 0.33 mm;The angle of the medial and lateral crus of the alar cartilage was 68.00°;the volume of the alar cartilage was 37.31 mm³.The measurement data of 11nasal alar cartilage obtained by computer digital three-dimensional reconstruction&measurement of three-dimensional model of nasal alar cartilage were all distributed in the range of data obtained by anatomic direct measurement method reported.Conclusion:1.With the computer digital three-dimensional reconstruction technology,the images of normal adult cadaveric specimens can be reconstructed into an objective three-dimensional model of nasal alar cartilage;2.The existing three-dimensional reconstruction techniques of CT and MRI can not reconstruct the three-dimensional model of nasal alar cartilage;3.The combination of computer digital three-dimensional reconstruction&measur-ement technology and sectional anatomy technology is beneficial to the establishment of three-dimensional database of nasal alar cartilage.