| Background:Auricular reconstruction for microtia is one of the most challenging areas in plastic surgery,as the auricle presents one of the most complex threedimensional structures of the external body.Fabricating the framework is technically difficult,and considerable effort is needed to achieve good operative results.The surgeon must delicately sculpt and assemble the rib cartilage into a harmonious framework that recreates the unique and sophisticated morphology of the ear.Chest wall deformities have been reported in many patients which is caused by rib cartilage harvesting.Rib cartilage growth is closely related to age and determines the feasibilityand outcomes of auricular reconstruction.Ear reconstruction is performed as early as age 6 in efforts to treat children before school matriculation while allowing for sufficient rib growth.But there is controversy over the optimal timing of microtia reconstruction.There are different causes for acquired auricular defects,including trauma,tumor ablation and burns,which often cause different degrees of defects in different parts of auricle.Therefore,we need personalized three-dimensional model of the auricle to assist doctors in preoperative design.Methods:1.A retrospective analysis was performed on 6-year-old microtia patients between January 2016 and June 2016.A total of 37 patients underwent preoperative 3D rib-cage CT Measurements and normal auricle scanning measurement including:the length of 6,7,and 8 costal cartilage,the width of 6,and 7 costal cartilage and the length of normal auricle.Then the data of costal cartilage was comparing with the data of the auricle.2.To reconstruct a symmetrical,accurate,prominent auricle and minimise as much as possible the chest wall deformity caused by rib cartilage harvesting,we set out to use three dimensional reconstruction technique to construct the rib cartilage of patients.Negative costal cartilage model was made and Polyurethane Foam material was injected into the negative impression to create a copy of the costal cartilage.We conducted a preoperative simulation design for 10 patients.3.From March 2015 to February 2016,12 cases of post-traumatic ear defect were treated using three-dimensional model of the auricle for preoperative design.All of them were underwent postoperative auricle scanning measurement including:the length,width,height and perimeter of bilateral auricle.Then the data of reconstructed auricle was comparing with the data of the normal auricle.Results:1.The average length of the 6,7 and 8 rib cartilage on the right was 76.1±9.2 mm(range,61.1-94.9 mm),102.6±9.9 mm(range,84.5-119.1mm)and 75.4±19.3mm(range,47.3-118.5 mm)respectively.And the the average helical length was 90.5 ± 6.8 mm(range,76.9-101.5 mm).Comparing the above data,it revealed that 6 years old was an optimal time for ear reconstruction with tissue expanding technique.2.The created three-dimensional model was very close to the real costal cartilage framework,we can performed the simulation of surgery successfully.10 patients received individualized preoperative surgical plans and good surgical outcomes.3.With a follow-up duration of 6 months,using the described technique,satisfactory results were achieved,and the reconstructed ears showed high similarity in size,shape,color and location to the contralateral normal ear.The average length,width,perimeter and height of the normal ear were 62.4±4.0mm(57.8mm-68.8mm),30.7±2.3mm(28.lmm-34.0mm),108.5±7.5mm(98.7mm-119.6mm),20.0±3.7mm(14.2mmm-25.6mm),respectively.And the average length,width,perimeter and height of the reconstructed ear were 63.4±5.1m(55.6mm-71.4mm),32.5±2.6mm(28.5mm-36.Omm),110.0±7.9mm(96.lmm-121.6mm),18.6±2.4mm(13.Omm-21.6mm),respectively.Comparing the data between normal and reconstructed ears,no significant differences were shown in length,perimeter and height(p>0.05),while significant difference was demonstrated in width(p<0.05).Conclusions:1.3D rib-cage CT for preoperative measurement of costal cartilage could be a useful method for planning microtia reconstruction.According to our study,the amount of costal cartilage of almost all 6-year-old microtia patients is enough for ear reconstruction.So 6 years old is the optimal timing of auricular reconstruction with tissue expanding method.2.By using precise costal cartilage model,simulation of creating ear framework came to very realistic technique to practice.There may be benefit for the trainee and more experienced microtia surgeon from use of a patient-specific representation of costal cartilage.3.Three-dimensional digital reconstruction technique could assist to personalize treatment for traumatic ear defects,contributing to individualized cartilage framework fabrication and satisfactory outcome.Besides,it could also provide an objective analysis of the postoperative results. |
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