A Preliminary Study On The Blood Supply Of Velopharyngeal Muscles And The Vascular Protection Strategy In Cleft Palate Repair

Background:Velopharyngeal muscles are the key part of human pronunciation and swallowing function.Cleft palate is a common congenital malformation in oral and maxillofacial region.Poor speech improvement after levator veli palatini reconstruction may be related to intraoperative neurovascular injury.The research on the blood supply of velopharyngeal muscles and the strategy of vascular protection play an important role in the functional recovery after muscle reconstruction in the repair of cleft palate and velopharyngeal insufficiency.Velopharyngeal muscles have fine and complex anatomical structure,and their blood supply come from the branches of small blood vessels.At present,it is generally accepted that the ascending palatine artery,the ascending pharyngeal artery and the maxillary artery are the main arteries supplying the velopharyngeal region.However,there are still many disputes about the blood supply of velopharyngeal muscles due to ethnic differences and anatomical variations,and the current anatomical research methods have limited understanding of velopharyngeal microvessels.Objectives:1.This study intended to combine microvascular perfusion technology,muscle fiber staining technology,microCT scanning and three-dimensional reconstruction technology to realize the simultaneous three-dimensional visualization of velopharyngeal microvessels and muscle fibers.The origin,course,location and distribution of blood supply to velopharyngeal muscles were observed.The three-dimensional reconstruction model of velopharyngeal blood supply was constructed.2.The blood supply of the soft palate(SP)was located and divided into safe and dangerous regions.This study aimed to examine the vascular anatomy of velopharyngeal muscles to provide a guide for artery protection in cleft palate repair.Methods:1.21 adult cadaveric heads were perfused with gelatin lead oxide.Velopharyngeal tissue samples were taken and stained with 3.75%potassium iodide solution for 4 weeks.The specimens were scanned with mcroCT,the image data were transformed into DICOM format and imported into MIMICS MEDICAL 21.0(Materialise NV,Leuven,Belgium)software.The clear vascular images were obtained by adjusting the threshold,and the three-dimensional model of velopharyngeal blood supply was reconstructed.2.Observe the distribution area of velopharyngeal muscles and arteries on VGSTUDIO Max 3.4(volume graphics,Heidelberg,Germany)workstation,and analyze their spatial relationship through measurement of two-dimensional images.3.According to the arterial distribution of the SP,the vascular safety zone and danger zone of the SP were defined,and the vascular protection strategy of the SP in cleft palate repair was preliminarily established.Results:1.The arterial supply of velopharyngeal muscles mainly come from the ascending palatine artery,the ascending pharyngeal artery and the maxillary artery.The ascending palatine artery(APaA),especially the posterior branch,is the main artery supplying the velopharyngeal muscles.The APaA were asymmetrically distributed both anteroposteriorly and bilaterally.Extensive anteroposterior vascular anastomosis can be seen under the oral mucosa.However,there are few vascular anastomosis at the palatal midline.2.The posterior branch of the APaA reaches the pars dorsalis of uvularis in the posterior 1/3 SP and lies 1.75 mm(standard deviation,0.06)under the nasal mucosa;the anterior branch penetrates the anterolateral side of levator veli palatini(LVP)to reach the anterior 1/3 SP and lies 7.09 mm(0.03)under the oral mucosa.The posterior APaA had a mean diameter of 0.41 mm(0.04)at 0.5 cm distance from the palatal midline,whereas the anterior APaA had a mean diameter of 0.46 mm(0.06)at 1 cm distance.At 1.5 cm distance from the palatal midline,the mean diameter of the APaA trunk was 0.65 mm(0.04).3.When performing muscle dissection in SP,APaA may not be damaged within the range of 0.5 cm from the palatal midline,which belongs to the safety zone.However,the posterior branch of APaA may be damaged within a distance of 0.5-1 cm,which belongs to the relative safety zone,mainly interfering with the blood supply of musculus uvulae(MU).Moreover,the anterior branch of APaA would also be damaged within a distance of 1-1.5 cm,which belongs to the relative danger zone,resulting in disturbance of blood supply to the intrapalatal LVP.Additionally,dissection exceeding the distance of 1.5 cm would damage the APaA trunk(0.65 ± 0.04 mm),which belongs to the danger zone,resulting in disruption of blood supply to almost all velopharyngeal muscles.Conclusion:Mobilization of muscles during intravelar veloplasty should be performed within a distance of 1 cm from the palatal midline,avoiding over dissection of the LVP.Dissection of the oral submucosa should be reduced in the anterior 1/3 soft palate while wide dissection of the nasal submucosal should be avoided in the posterior 1/3 soft palate.Performing the minimum mobilization required to allow reconstruction of the levator sling and repair of the mucosal surface of the palate may reduce the incidence of fistulae and increase the likelihood of normal speech after cleft palate repair.