A Comparative Finite Element Analysis of Two Surgical Methods for Cryptotia

Cryptotia is an auricular muscle abnormality that causes the superior and posterior auricular area to be buried under the temporal skin. Surgical treatment approaches can be divided into skin grafts and local flaps. Complex cases also require cartilage/muscle modification. In this study, we treated one case each with the Square flap method and the Cat’s Ear flap method. The aim was to help surgeons select the most appropriate surgical procedure on a case-by-case basis. METHODS: Two typical cryptotia cases were treated with the Square or Cat’s Ear flap method. Finite element analysis was performed with ADINA v8.9 software, a PC (Windows 7, CPU: Core i7, Memory: 8 GB), and a hyperelastic skin model (skin diameter 20 cm; thickness 2 mm). The model scales were about 500 nodes and 500 elements (tetrahedron). RESULTS: The Square flap method involved advancing the square flap between the two triangular flaps. Switching then generated dog-ears that created a big valley. In the Cat’s Ear flap method, the two triangular flaps were rotated in the same direction, whereas a square flap was advanced slightly on the opposite side. This created a large dog-ear. CONCLUSIONS: This study suggested that the Cat’s Ear flap method may be particularly useful for cryptotia patients whose posterior auricular groove is shallow when the buried helix is pulled out. The Square flap method may be suitable for other cases because it effectively extrudes the buried helix with comparatively small excision.