Clinical Analysis Of Expanded Skin Flap Damage And Studies Of Costal Cartilage Defect After Auricular Reconstruction

Background:Congenital microtia is a kind of disease with the abnormal shape of the auricle,ranging from partial structural abnormalities to the total absence of the pinna,which seriously affects the psychology and daily life of patients.The incidence of microtia in China is about 3.06/10,000,and the large number of patients need auricular reconstruction every year.Auricular reconstruction is one of the most difficult plastic surgery,requiring 2-3 surgical procedures.Currently,the most commonly used materials for auricular reconstruction are autologous costal cartilage,which is taken from the unilateral chest wall and designed as the shape of the auricle.The reconstructed auricle is transplanted to the postauricular mastoid area and the surface is covered with skin flap or fascial flap.Nagata,Brent,and Badachu methods are widely used in the world to reconstruct auricles.Jiang conducted the world's largest clinical study of auricular reconstruction using the Badachu method.The expanded skin flap and optimizing scaffold design enable the reconstructed auricle to have stable and aesthetic shape.The expanded postauricular skin flap has sufficient area,adequate blood supply,and moderate flap thickness.The auricular scaffold covered by expanded skin flap has more natural auricular shape without fascial flap coverage.The autologous costal cartilage several merits,such as sufficient volume,durable morphology,strong resistance to infection,and without tissue rejection.Although the skin flap and costal cartilage are the crucial materials to obtain satisfactory reconstructed auricles,attentions should be paid to the risks associated with the skin flap and costal cartilage.Expanded skin flap damage and abnormal thoracic morphology caused by costal cartilage defect are the two most important problems.which deserve further study in both clinical and basic research.In this study,we summarize the information about the expanded skin flap damage and relative repairment,analyze the abnormal morphology of the thorax after costal cartilage harvesting,and evaluate the feasibility of applying decellularized cartilage in the repairment of costal cartilage defects.Objectives:1.Summarize the sites,time,incentives,and corresponding repairment of expanded skin flap damage.2.Analyze the abnormal shape of the chest after costal cartilage harvesting,and study the influence of recovery times on the morphology of the chest.3.Investigate the physicochemical properties,biocompatibility,polarization response of macrophage,and tissue regeneration of decellularized auricular cartilage and decellularized costal cartilage.Methods:1.From January 2017 to September 2019,patients who accept auricular reconstruction using expanded skin flap without fascial flap transplantation were recorded in the Plastic Surgery Hospital,Chinese Academy of Medical Sciences.The cases of expanded skin flap damage were collected,the information about the time,site,incentives and corresponding repairment were analyzed.2.From January 2019 to June 2020,thoracic CT with three-dimensional reconstruction after harvesting the 6th-8th costal cartilage was collected.The costochondral junction midpoint(CJM),Haller index,thoracic height,and area was compared between the operated and unoperated sides using Mimics software.The relationship between the thoracic height,area with different recovery times took further analysis.3.The decellularized costal cartilage and decellularized ear cartilage were prepared and analyzed DNA,collagen,porosity,microstructure and other physicochemical properties using Elisa,scanning electron microscopy,histological staining,and other methods.To assess the biocompatibility of the decellularized cartilage materials,cell proliferation and cytotoxicity were performed using CCK-8,live-dead staining,and other methods.The influence of decellularized cartilage on macrophage polarization towards M1/M2 was analyzed by flow cytometry.After filling the costal cartilage defects in rabbits with decellularized cartilage,the morphology and composition of local regenerated tissues were analyzed by thoracic CT and PCR.Results:1.19 patients were found to have skin damage during the follow-up period.Most of the skin damage occurred within 4-9 months after auricular reconstruction.The lower 1/3 of the expanded skin flap during the expansion period,the middle and lower 1/3 of the reconstructed auricle were the most frequent damage sites.The causes are mainly trauma,oppression,and natural occurrence.The reduced tension suture,postauricular flap,or postauricular fascial flap were applied to repair the skin flap damage.Satisfactory results were obtained in long-term follow-up.2.28 cases of postoperative thoracic CT were collected.Three-dimensional images showed calcified tissues with different densities,which scattered along the costal cartilage area.The locations of bilateral CJM showed that the costal cartilage and ribs in the defect area were less expand in the forward,lateral,and downward direction of the thoracic cage,which creating a relatively inward,upward,and concave image.In the CJM plane of the unaffected rib,the height(7th-9th)and area(6th-8th)of the unaffected thorax exceeded that of the contralateral side due to the local depressions of the chest wall.The cases were divided into two groups according to the recovery time.In the mid-term group,the thoracic height and area of the unaffected 6th-9th rib significantly exceeded those of the contralateral side,while the average difference in height and area was decreased in the long-term group,with significant differences in the thoracic height of 7th rib and the thoracic area of 8th rib.3.After decellularization,the DNA and ?-Gal was removed effectively while most collagen and glycosaminoglycan of the extracellular matrix were retained in both decellularized cartilage materials.The structure of the extracellular matrix was loose and porous without obvious structural damage.The decellularized auricular cartilage had higher porosity and larger pore size than decellularized costal cartilage.Two types of decellularized cartilage promoted chondrocyte proliferation without obvious cell cytotoxic.Both decellularized cartilage exhibited inhibition of M1/M2 polarization,especially in the decellularized auricular cartilage.The decellularized cartilage promoted local tissue regeneration and decreased chest wall depression in the rabbit's model.The component of regenerated tissue included chondrocytes,cartilage matrix,fibrous tissue,and calcified structures.The regenerated tissues in the decellularized auricular cartilage group showed increased expression of cartilage-related genes,while the decellularized costal cartilage group had more calcified nodules,trabecular structures,and higher expression of osteogenic-related genes.Conclusion:1.The auricular reconstruction with Badachu method is flexible,in which the cartilage scaffold could be covered by expanded skin flap without fascial flap or skin graft.It provides simple,less scar,and natural shape of the reconstructed auricle.While additional attention should be paid to the risk of skin flap damage.Familiarity with the site,incentives,and other information relative to the skin flap damage is important for the selection of surgical approach,preventive measures,and efficient repairment.2.Localized abnormalities of thoracic morphology were found after costal cartilage harvesting by thoracic CT.The abnormal thoracic morphology gradually improved after long-term recovery.Optimizing surgical techniques to use the costal cartilage efficiently and finding alternative materials to repair the cartilage defects are promising solutions.3.The two types of decellularized cartilage retained the intact structure and function of the extracellular matrix,which provide suitable environment for cell proliferation and tissue regeneration.The decellularized auricular cartilage may have better application in cartilage repair and tissue regeneration in clinical surgeries.