Three-dimensional Digital Research Of Skin And Soft Tissue Usage Strategies In Total Ear Reconstruction With Tissue Expansion

Objective Total ear reconstruction using tissue expansion at subcutaneous level is one of the classic surgical procedures of treating ear absence, however, obvious scars and color aberration are sometimes discovered due to adopting skin grafts. Before deciding how to encapsulate the cartilage framework, it is important to evaluate the skin size needed for encapsulating the framework and the actual size of the postauricular flap that we can utilize to encapsulate the framework. The purposes of our study are investigating the methods of measuring and calculating the skin size needed for encapsulating the framework and the effective size of the postauricular flap with three-dimensional measurement technology technology. Afterwards, we can modify the classic surgical strategy, and establish a "precision medical model" for total ear reconstruction surgery using subcutaneous tissue expansion, to provide individual surgical strategies for microtia patients with assistance of three-dimensional measurement technology.Methods1.20 patients of microtia were randomly recruited from 2013--2014 in Ear Reconstruction Center of Plastic Surgery Hospital, Chinese Academy of Medical Sciences. A 50ml kidney-shaped expander was inserted behind the remnant ear subcutaneously. After the expansion was completed, we marked an area using a standard mold in the middle of the flap. The measurement procedures were:mark the flap --shoot photos--remove the expander and shoot photos after flap retraction/ withdrawn the liquid from the expander and shoot photos of flap retraction process--measure the changes of the marked area using Image-pro Plus 6.0, a professional image analysis software. Then, we calculated the immediate retraction rate of the postauricular expanded flap, and explored the rules of postauricular expanded flap retraction with curve fitting statistical analysis using SPSS 22.0 software.2.30 patients of unilateral microtia were randomly recruited from 2013--2014 in Ear Reconstruction Center of Plastic Surgery Hospital, Chinese Academy of Medical Sciences. After the expansion procedure was finished, we scanned the patients’ normal ears and expanded postauricular flap using a handheld portable 3D structured light scanner(Artec Spider). Then we used reverse engineering software(Geomagic studio 11.0) to process the original three-dimensional image, and explore specific three-dimensional measuring method according to ear reconstruction surgery. The measurements included normal ear parameters (Se1, Se2, Se3, Sb1, S11), and expanded postauricular flap parameters (Sf, Sb2, S12). Afterwards, we calculated corrected normal ear area (Se1’, Se2’, Se3’)> and effective area of expanded postauricular flap (Sef). The overall differences between Se1’, Se2’， Se3’ and Sef was analyzed through Variance Analysis using SPSS 22.0 software. And we compared the size of Se1’, Se2’, Se3’ and Sef of each patient to understand the personal differences of the relative relationships between the skin size needed for encapsulating the framework and the effective size of the expanded postauricular flap.3.185 patients of microtia were randomly recruited from 2013--2014 in Ear reconstruction Center of Plastic Surgery Hospital, Chinese Academy of Medical Sciences. Before total ear reconstruction surgery, we measured patients’normal ear and expanded postauricular flap with 3D measurement technologies, and calculated Se1’, Se2’, Se3’and Sef. We improved the classical surgical procedures through modifying the usage of skin and fascia, and devised personalized surgical procedures for different patients:the extended and expanded postauricular flap method, the double pedicle expanded postauricular flap method, and the classical single pedicle expanded postauricular flap method. After long-term follow-up study, we evaluated the outcomes of the 3 different surgical methods.Results1. Using rapid expansion combining 4 weeks’sustained static expansion method, the immediate retraction rate (Retraction) of the expanded postauricular flap was 29.7428± 3.1482%. The retraction process of the expanded flap was an instantly fast-slow-fast process, which was coincided with cubic regression equation:Y=126.1691-1.2798V +0.0246V2+0.003 V3.2. We grasped 3D scanning and measuring methods of patients’normal ear and expanded postauricular flap, as well as the methods of calculating and analyzing. Correction normal ear area, Se1/2/3’=Se1/2/3 -Sb1; effective area of expanded postauricular flap, Sef=Sf×(1-Retraction)-Sb2-Variance analysis of Se1’, Se2，Se3’ and Sef showed a statistically significant difference (P<0.01), which disclosed an overall rule:Se3’> Se2’> Sef> Se1’. Comparing each patients’calculating results Se1’, Se2’, Se3’ and Sef, we discovered three different relative relationships:I, Sef> Se3’(6.67% of the total); Ⅱ, Se3’> Sef>Se2’(26.67% of the total); Ⅲ, Se2’> Sef> Se1’(66.67% of the total).3. Assisted by the 3D measurement technologies and calculating methods of patients’ normal ear and expanded postauricular flap, we established the "precision medical model" of total ear reconstruction procedures using subcutaneous tissue expansion techniques, which allowed us to choose individualized surgical methods according to patients’personal conditions, including the extended and expanded postauricular flap method (29 unilateral cases,7 bilateral cases), the double pedicle expanded postauricular flap method (47 unilateral cases,2 bilateral cases) and the classical single pedicle expanded postauricular flap method(100 unilateral cases).The evaluations of three different surgical procedures after long-term follow-up:(1) Among the three different surgical procedures, the position, size, shape, auriculocephalic angle of the reconstructed ears were basically the similar as the opposite ear;(2) There were no significant color aberration using the extended and expanded postauricular flap method;(3) The reconstructed ear swelling time was shorter using the extended and expanded postauricular flap method and double pedicle expanded postauricular’flap method than single pedicle expanded postauricular flap method, with statistical significance (P＜0.05);(4) The scar length of the reconstructed ear and the chest:extended and expanded postauricular flap method<double pedicle expanded postauricular flap method< single pedicle expanded postauricular flap method, with statistical significance (P <0.05);(5) Complications:Risks of helix skin necrosis and cartilage exposure using extended and expanded postauricular flap method was greater than the latter two.Conclusions1. Using the 3D measurement technologies and calculating methods, we can evaluate skin size needed for encapsulating the framework and the effective size of the expanded postauricular flap precisely, which can effectively assisted the skin and soft tissue utilization in total selection auricular reconstruction surgery.2. The extended and expanded postauricular flap method and the double pedicle expanded postauricular flap method are modified surgery based on the classical single pedicle expanded postauricular flap method, which supplement the ear reconstruction system. The two novel methods can diminish or significantly improve the scar behind the ear and chest, and color aberration.3. The "precision medical model" of total ear reconstruction procedures using subcutaneous tissue expansion techniques, assisted by 3D measurement techniques and computational methods, is a successfully investigation of organic combination of clinical surgery with advanced measurement technology, which might have profound influences on the development of modern total ear reconstruction surgery.