![]() This approach is contingent upon careful removal of all surrounding connective tissue from the surface of ear construct. Local and global shape similarity to the pre-implantation geometry was determined by comparing the volumetric pixels with variation of less than 1 mm from the designed ear geometry. A three-dimensional laser scanning system was used to capture the surface geometry of engineered ear constructs. However, this method is subjective and provides no quantitative benchmarks. An approach, modified from Tanzer's classifications of auricular deformities, graded ear morphology based upon the shape of specific ear landmarks. We also employed more rigorous methods to analyse the fidelity of the ear geometry after in vivo implantation.įew attempts have been made to objectively quantify three-dimensional size and shape changes of engineered ear-shaped constructs. The technology is now under development for clinical trials, and thus we have scaled-up and redesigned the prominent features of the scaffold to match the size of an adult human ear and to preserve the aesthetic appearance after implantation. Additionally, the ear scaffold size (half-size of an adult human ear) was designed to fit on the back of a mouse and the master was hand carved without consideration of feature definition loss when placed under the skin. These two-dimensional measurements indicated a successful proof-of-concept prototype but offered limited information on the three-dimensional behaviour of the complex structure. A two-dimensional profile analysis, commonly used to assess basic shape changes, showed minimal shrinkage of the engineered ears containing a wire framework (2.0%) compared with those without the wire framework (16.5%). The wire framework also had sufficient flexibility to permit natural elastic bending of the ear structure. A key feature of this scaffold was the presence of an embedded titanium wire framework, which had sufficient rigidity to maintain the shape of the ear despite the compressive forces of implantation and contractile forces exerted during neocartilage formation. A proof-of-concept study in immunocompromised mice demonstrated the development of flexible neocartilage within a composite ear-shaped biodegradable collagen scaffold. Tissue-engineered ear cartilage presents a promising alternative that can overcome the drawbacks of existing methodologies. Polymer implants are capable of excellent cosmetic results, but the constructs are inflexible and can fracture, and possess a long-term risk of extrusion through the skin. Carved costal cartilage retains some compliance but lacks flexibility, and cosmetic results are somewhat unpredictable. However, neither approach truly meets the functional requirements of shape fidelity and flexibility. Current reconstruction strategies have used carved costal cartilage or rigid polymer implants. True hallmarks of a successful reconstruction include recreation of the complex three-dimensional contours of the outer ear, as well as the considerable flexibility of auricular cartilage. These quantitative shape analysis results have identified opportunities to improve shape fidelity of engineered ear constructs.Ĭomplete reconstruction of the external ear remains a surgical challenge for both congenital and acquired auricular defects. Eighty-nine per cent of local curvature measurements experienced a bending moment less than 50 µN-m owing to deformation forces during implantation. Overall curvature changes identified regions most susceptible to deformation. Length and width changed by less than 2%, whereas the depth decreased by approximately 8% and the minimum intrahelical distance changed by approximately 12%. Local curvature values were measured to gain understanding of the bending forces experienced by the framework structure in situ. Several parameters were measured including the overall length, width and depth, the minimum intrahelical distance and overall curvature values for each beam section within the framework. Computer models of the titanium framework were obtained from CT scans before and after implantation. A non-invasive method was developed to assess size and shape changes of the engineered ear in three dimensions. The ear geometry was redesigned to achieve a more accurate aesthetic result when implanted subcutaneously in a nude rat model. We have previously demonstrated that a titanium wire framework within a composite collagen ear-shaped scaffold helped to maintain the gross dimensions of the engineered ear after implantation, resisting the deformation forces encountered during neocartilage maturation and wound healing. Engineered cartilage is a promising option for auricular reconstruction.
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