| BackgroundThe pharynx is one muscular duct structure affected by its own tension and surrounding tissues,which plays an important physiological role in the process of respiration and swallowing.It is widely accepted that the craniofacial abnormalities such as micrognathia,mandibular dysplasia or mid-facial dysplasia could change the volume and morphology of pharynx.Thus,clinicians not only assess the upper respiratory airway function of patients in maxillofacial examination but also pay attention to the influence of craniofacial morphology on the pharyngeal structures.Hemifacial microsomia(HFM)is a kind of craniofacial malformation with hypoplasia of the mandible.The clinical features are unilateral or bilateral hypoplasia of the mandible and the undeveloped soft tissue in the suffering side.According to the morphology of undeveloped mandible,there are four types of HFM based on the Pruzansky-Kaban classification including ?,?a,?b and ? type.Also,it is believed that the HFM patients are more likely to suffering from the apnea syndrome comparing with normal individuals.As the basis of three-dimension reconstruction,computed tomography(CT)can provide more effective anatomical information than two-dimensional imaging technologies.After reconstruction with CT scan,the relationship between pharyngeal cavity structure and surrounding tissues can be clearly displayed in the software.At the same time,the comparison of preoperative and postoperative CT scans can effectively show the changes of pharyngeal morphology after mandibular distraction osteogenesis(MDO).Polysomnography(PSG)is one of basic examination technology of sleep medicine and was seen as the gold standard of sleep respiratory function evaluation.With the sleep monitoring and ECG technology,the PSG can describe the relationship between respiration and different sleep stages within the effective sleep ranges.Although previous studies have described the pharyngeal characters of patients with hemifacial microsomia,there were few reports on the pharyngeal characters between different types of HFM.Also,there were few reports about the influence of mandibular distraction osteogenesis on pharyngeal morphology and the functional examinations.Pourtaheri N et al analyzed the morphology and structure of pharynx with 5 HFM cases treated with MDO.The results showed that MDO increased the volume and surface area of the pharynx in HFM patients,but the number of cases in this study was small and there was no statistical analysis in the report.Baugh AD et al has analyzed the results of PSG in 9 HFM cases.The results showed that HFM combined with OSA has the characteristics of high carbon dioxide partial pressure and low oxygen saturation.However,the study did not analyze the structure of pharynx and the changes after MDO.Therefore,if the study makes a detailed analysis of the pharyngeal morphology and functional evaluation between different types,it may be obtained better clinical outcomes after treatment.ObjectiveThrough the study of imaging data and PSG of HFM patients aged from 3 to 15,the pharyngeal morphology of HFM patients with different types were calculated and analyzed.In addition,with the comparative research of preoperative and postoperative imaging data,we analyzed the influence of MDO on pharyngeal morphology and hyoid bone position of HFM patients.Finally,by analyzing the functional parameters of HFM patients who accepted the PSG,the effect of MDO on the upper airway function of HFM was evaluated.The purpose of this study is to evaluate the influence of MDO on HFM pharynx and help plastic surgeons to make reasonable treatment plan to HFM patients.MethodThis study selected HFM patients with unilateral subgroup who seek the consulation to the department of maxillofacial plastic surgery,plastic surgery hospital of Chinese Academy of Medical Sciences from 2009 to 2020.The first part of the study involved 66 cases,the second part involved 32 cases,and the third part involved 8 cases.The first section:Selected 66 CT scans of unilateral HFM patients who have not received treatment were imported the software.Pharyngeal model of HFM patients was established in Mimics 19.0 software.The volume(V),length(L),surface area(SA),minimum cross-sectional area(Min-CSA),mean cross-sectional area(Mean-CSA),anterior posterior width(AP)and lateral width(LAT)of the pharynx of HFM patients with different types were measured and analyzed in Mimics 19.0.The second section:Retrospective study was undertaken by analyzing 32 cases of HFM patients accepted MDO treatment.The morphological parameters of the pharynx were measured and the effect of MDO on the pharyngeal structure of HFM was analyzed.The height of hyoid bone in the vertical direction was measured.The third section:8 patients with HFM who received PSG were analyzed retrospectively.According to the PSG reports,the apnea hypopnea index(AHI),oxygen desaturation index(ODI),lowest oxygen saturation(LSO2),mean oxygen saturation(MSO2),longest apnea event time(LAT)and mean apnea event time(MAT)were statistically analyzed before and after MDO treatment.Pearson correlation coefficient,Fisher exact test,paired sample t test,Wilcoxon signed rank sum test and other statistical methods were used to analyze the above data.Results1.In the nasopharynx,there was no significant difference in the morphological parameters between type ?,? and ?(P>0.05).The oropharyngeal measurement data showed that the average cross-sectional area(P=0.037)and narrowest cross-sectional area(P=0.017)in type I patients were larger than those parameters in type ? patients,and there was no statistical significance in oropharyngeal morphological data between ? and ? groups(P>0.05).In the measurement of cross-sectional morphology,the AP and LAT results showed the decreased trend from ? to ? groups.In the laryngopharyngeal section,the length,volume and surface area were decreased from ? to ? groups according to the data.And no statistical difference was found in laryngopharyngeal cross-sectional morphological parameters.2.After MDO,the nasopharyngeal,oropharyngeal and laryngopharyngeal parameters of HFM patients were measured.There were significant differences in area(SA),mean cross-sectional area(mean-CSA)and minimum cross-sectional area(min-CSA)compared with preoperative parameters showing the increase trend after MDO.The distance from hyoid bone to the third cervical vertebra(H-C3)had found significant increased after MDO treatment(P<0.01).At the same time,there was a significant difference in the distance between hyoid bone and Frankfort plane before and after treatment showing the longer distance after MDO(P=0.004).With the mandible and cervical vertebra were used as reference system,the hyoid bone position was found moving forward and lower after MDO.3.The lowest oxygen saturation of HFM patients was found significantly improved after treatment(P=0.038),while AHI was found weakly correlated in the study(P=0.053).There was no significant difference in oxygen desaturation index,mean apnea duration,longest apnea duration and mean oxygen saturation.ConclusionIn the measurement of parameters in pharynx of HFM patients,there was no difference between groups in nasopharyngeal section.With the measurement in different types of HFM patient pharyngeal section,the outcomes of V,SA and mean-CSA of oropharyngeal and laryngopharynx showed the decreasing trend from ? to ? groups.MDO can affect the morphology of pharyngeal and mandibular morphology in HFM patients,which was related to the spatial position of hyoid bone.MDO can improve the lowest oxygen saturation and reduce the sleep apnea index in HFM patients during sleep showing the positive effect of MDO. |
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