“Man vs. Machine: 3D Milling of Auricular Frameworks”

Objective Autologous rib harvest with manual framework production is the current gold standard for microtia reconstruction. Recent clinical success with implantation of cadaveric costal cartilage grafts opens the possibility of point of care auricular framework production. This paper assesses the feasibility and efficiency of 3D milling of cadaveric costal cartilage for auricular framework production. Design A Nagata/Firmin style auricular framework was manually carved en bloc out of soap and 3D scanned to design a milling toolpath on a desktop 3-axis computer numerical control (CNC) machine. An en bloc framework was then milled from cadaveric costal cartilage. Time to mill a complete framework was recorded. The dimensional/volumetric analyses were performed. Main Outcome Measure(s) The main outcome measures were total time to mill a complete auricular framework out of cadaveric cartilage and dimensional/volumetric comparisons to the model ear. Results Total milling time for the cartilage framework was approximately 7 min. Finalizing steps took an extra 20 min. Total time to produce a final framework ready for implantation was approximately 27 min, compared to the traditional 1-2 h by manual carving. All dimensional comparisons were within 2 mm to the manually carved model. Volumetric analysis showed 71% similarity. Conclusions En bloc cadaveric costal cartilage framework milling is both feasible and efficient. 3D milling significantly reduces framework production time and allows for accurate reconstruction of the complex ear geometry, which can translate to cost savings, optimized patient safety, and potential for patient-specific reconstruction. The next step toward achieving clinical application is ensuring framework sterility.