Study Of The Spatial Relationship Between The Palatopharyngeal Muscles And Surrounding Structures In Normal People And Patients With Cleft Palate Based On Micro-CT

Research background:Pronunciation is driven by coordinated movements of numerous muscles in the soft palate and pharynx.The principle of human pronunciation and swallowing could be understood by studying the normal palatopharyngeal muscles.While studying these muscles in patient with cleft palate could guide the reconstruction of muscles in palatoplasty,grasp the formation of cleft palate speech and learn the way to train speech after operation.The relationship between muscles of the palatal muscles and pharyngeal muscles is complicated.At present,there is lack of anatomical studies on the detailed relationship between muscle fibers of the palatal muscles and pharyngeal muscles,as well as the anatomy of the palatine aponeurosis and the structure around the pterygoid hamulus.Due to the lack of samples,similar studies on the muscles of the cleft palate are rare.Objective:This study used micro-computed tomography to observe the relationship between the muscle fibers,the anatomy of the palatine aponeurosis and pharyngeal muscles on six normal samples and four samples with cleft palate.Gross anatomy was performed on 2 normal samples to observe the direction of the palatopharyngeal aponeurosis.These findings may be helpful for the improvement of cleft palate repair and for better understanding of the formation of cleft palate speech.Materials and Methods:1 Sample stainingSix normal adult fresh cadavers and four cleft palate aborted fetus were included in this study.These samples were cut between the plane of the orbital floor and the plane of the mouth bottom,included the tongue,palate and the upper part of the pharynx.Soaked the tissue in 4%formaldehyde solution for 8 hours,and immersed it in solution for 14 Days(3.75%Lugol’s solution for 2 normal samples,3%phosphomolybdic acid solution for 4 normal samples,3%phosphomolybdic acid solution for cleft palate samples).2 Computed tomographic scanningTheses samples were removed and washed with 75%alcohol.The micro-CT scanner used in the present study was provided by the Institute of Laboratory Animal Science of the Chinese Academy of Medical Sciences.3 Three-dimensional(3-D)model constructionAfterward,all files were imported into Mimics to reconstruct three-dimensional model of the muscles.In MIMICS,we established different masks of various colors for different tissues.Then "mask editing" function was used and manual editing method was adopted to draw the muscle fibers in the two-dimensional slice plane according to the direction and origin of fibers(using the same color to edit the muscle fibers that have the same direction and source).The edited radiographs were gathered and stacked together by three-dimensional calculate function.Finally,the target 3-D model was obtained.4 Gross anatomyIn two cases,the oral mucosa of the soft palate was removed and the inferior head of the palatopharyngeal muscle attached to the posterior nasal spine was cut to observe the PA.Results:1 Anatomy of the palatal muscles and pharyngeal muscles(1)The levator veli palatini(LVP)moved from the base of skull to the soft palate,which occupied the middle 34-39.8%of the soft palate.The attachment of the LVP was not the posterior margin of the hard palate and palatine aponeurosis(PA),but the 21.71-44.2%of the anterior cleft edge in the cleft palate.(2)The palatopharyngeal(PP)comprised three fasciculi attaching to different areas.First,the inferior head that covered the anterior palatine aponeurosis and lateral surfaces of the LVP on the oral side;second,the superior head on the middle surface of the LVP on the nasal side;and third,the posterior head on the side and back of the LVP on both oral and nasal sides.In the cleft palate,PP was composed of two bundles:the inferior head and the superior head,which clasped the LVP between them.(3)The uvula muscle was located on both sides of the cleft edge in the cleft palate.It originated from the edge and was not evenly distributed.(4)The palatoglossus and the pharyngeal muscles were consistent with normal people in cleft palate.2 Anatomy of the structure around the pterygoid hamulusThree muscles were present around the pterygoid hamulus,namely the PP,superior constrictor(SC),and tensor veli palatini(TVP).The hamulus connects these muscles as a key pivot.The TVP extended to the palatine aponeurosis,which bypassed the pterygoid hamulus,and linked the PP with SC.Some muscle fibers of the SC originated from the hamulus,the aponeurosis of which was wrapped around the hamulus.There was a distinct gap between the aponeurosis and the palatine aponeurosis.This formed a pulley-like structure around the pterygoid hamulus.3 Anatomy of palatine aponeurosisThe PA covered the anterior(32.1-38.8%)of the soft palate,extending from the TVP and connecting to three muscles:PP,uvula muscle,and SC.The PA extended from the TVP to the midline and the posterior edge of the hard palate.The PA was not uniformly distributed,which was complementary to the attached muscles in thickness.Conclusion:With the help of the high-resolution Micro-CT technology,some new digital anatomical characteristics of the muscles,aponeurosis and pterygoid hamulus can be recognized.The muscles in the palate and the pharynx are interrelated and form a three-dimensional "velopharyngeal muscle complex".These findings provide anatomical basis for the improvement of cleft palate repair.