Clinical Research On Symmetric Analysis And Surgical Treatment Of Progressive Hemifacial Atrophy

Objective1?This study aims to establish a three-dimensional(3D)coordinate system for patient with progressive hemifacial atrophy(PHA)based on computed tomography(CT)data.The Asymmetry Index(AI),the Asymmetry Rate(AR),the Volume Deficiency Rate(VDR)and the Midline Deformation Rate(MDR)are calculated and analyzed respectively through the measurements of 3D bony and soft tissue models,which further providing quantitative references for the symmetric classification of PHA and the surgical design.2?To develope a sequential treatment combines the autologous mandibular outer cortex(MOC)grafting with fat grafting in PRS patients,and apply computer-aided design(CAD)and computer-aided manufacture(CAM)techniques to improve the surgical accuracy,reduce perioperative risks and assess the efficacy.3?To introduce and evaluate a novel method of "Sandwich" style mandibular augmentation with contralateral MOC in the treatment of lower face asymmetry in PHA patient and study the basis of this method in clinical application.This method has not been reported at home and abroad.Methods:1?37 patients with PHA received preoperative CT scan were enrolled in our study from July 2012 to July 2015.The 3D models were reconstructed and the 3D coordinate system was established to mark the symmetric anatomical landmarks and calculate different symmetric values.Further,the morphological characteristics of facial asymmetry of PHA would be analyzed and discussed to provide quantitative references for the classification,design and treatment for PHA.2?15 patients with PHA were randomly enrolled in our study.Based on the CT data and the classification reference from the previous study,the deficiency of bone and soft tissue were assessed.By using CAD and CAM techniques,the surgical simulation was performed preoperatively and the surgical templates for malarplasty,genioplasty,gonioplasty,MOC harvesting and grafting were designed and printed out to guide the surgeries.All 15 patients received sequential surgical procedure combined the autologous MOC grafting with fat grafting simultaneously or 6 months later.The topographic map of fat grafting was generated.The accuracy of surgery was assessed by registration of CAD and immediately postoperative CT data.The accuracy of MOC bone grafting was evaluated by the MOC thickness(MOC-T)relative error,the MOC-T accuracy at the preop most severe bone atrophy point(preop MSBAP),and the MOC volume(MOC-V)accuracy.The absorption rate of MOC bone grafting was evaluated by the MOC-T absorption at the preop MSBAP and MOC-V absorption rate.The percentage volume maintenance(PVM)of the fat grafting surgery was assessed.Surgeons'attitude towards the practicability of the surgical templates and patients'satisfaction were evaluated with Likert scale.3?14 patients with lower facial asymmetry of PHA were received surgery of "Sandwich" style mandibular augmentation with contralateral MOC.The bony survival rate was assessed by CT data at preop-,immediately postop-,6 months postop-,and long term follow up(1-6 years),the registration to show the discrepancy were made by comparing mandibles at different time.Results:1?Based on the proportion values of soft tissue and bone from AI,AR,VDR,MDR,we classified PHA into 2 types:type I,all 4 proportion values were greater than 1,the soft tissue deficiency primarily lead to the facial asymmetry,the treatment should focus on soft tissue reconstruction;type Ila,4 proportion values were either greater than 1 or less than 1,the deficiency involved both soft tissue and bone atrophy,the treatment combined osseous reconstruction with soft tissue restoration was recommended;type IIb,all 4 proportion values were less than 1,the deficiency involved both soft tissue and bone atrophy,the bony deficiency should firstly be repaired;2?All patients achieved significant outcomes and high satisfaction without complications.The registration showed minimal differences.The MOC-T relative error was 5.91±2.91%,the MOC-T accuracy at the MSBAP was 3.1 ±1.17%,and the MOC-V accuracy was 2.59?1.49%.The MOC-T absorption at the preop MSBAP was 3.44±1.09%and MOC-V absorption rate was 19.09±3.61%at 6 months follow up.The first and second PVM of the fat grafting surgery was 55.82±9.7%and 58.58±5.86%respectively.The good symmetry and high stabilization can be seen at long term follow ups;3?All 14 patients achieved significant surgical results and high satisfaction without complications.The surgery of "sandwich" style mandibular augmentation with contralateral MOC can be a reliable choice for lower facial asymmetry in PHA patients.The survival rate of the grafting side was 76.62111.77%at 6 months follow up,while the survival rate of the grafting side was 73.63± 12.27%at 1 to 6 years follow up.Conclusion:1?The proportion of soft tissue and bone from AI,AR,VDR,MDR with relationship with "1" to classify PHA symmetry can guide the treatment principle and can also be a supplement of other classifications.2?The sequential PHA treatment combined MOC with fat grafting to restore facial symmetry can achieve significant surgical results with the help of the symmetric classification and computer-assisted techniques.3?The "Sandwich" style mandibular augmentation with contralateral MOC is an effective way to improve lower facial asymmetry and highly recommended in the treatment of PHA.