Author(s)
Ryan Smith
Tood Goldstein, PhD
Affiliation(s)
Northwell;
Abstract:
Background: Laryngotracheal reconstruction (LTR) is often performed with hand carved costal cartilage grafts. 3D Computer Numerical Control (CNC) milling has recently been introduced for medical use. This technology involves cutting away material to carve complex precise geometries from larger materials. In this paper we examine the feasibility of using CNC milling to fabricate grafts for LTR.
Hypothesis: 3D automated CNC milling will produce more precise LTR grafts faster than surgeons can carve by hand.
Methods: Ideal anterior and posterior grafts were designed in CAD software (Onshape). Five mock anterior and posterior grafts each were hand sculpted from soap by a student and an attending surgeon with carving time measured in seconds. Reference designs were optimized for milling and loaded onto a APSX Spyder CNC Machine. A total of five anterior and five posterior grafts were fabricated, with each milling operation timed and documented. Comprehensive 3D scanning was performed on all grafts (hand carved and CNC milled) using a 3-Shape 3D scanner and imported into Materialise 3Matic for volumetric analysis of graft accuracy.
Results: Mean carving times (+/- standard deviation) for student and attending were similar for both anterior (290+/-139s; 254+/-70s) and posterior (243+/-58s; 285+/-130s) grafts with no statistically significant difference in carving times (P>0.05). Machine carving times were significantly faster for both anterior (36+/-0s) and posterior (26+/-0s) grafts compared with both student and attending (P<0.05). CAD design volume was 686mm3 and 219mm3 for anterior and posterior grafts respectively. CNC machined anterior and posterior grafts (698+/-25mm3; 255+/-7mm3) were significantly more accurate than similar hand carved grafts for both student (2960+/-1047mm3; 704+/-305mm3) and attending (1278+/-168mm3; 430+/-127mm3) when compared with CAD designs (P<0.05). Attending anterior grafts were more accurate than student anterior grafts (P<0.05) with no difference for posterior grafts (P>0.05).
Discussion: 3D CNC milling/machining may represent a substantial improvement for fabrication of both anterior and posterior grafts with significantly shorter production time and improved accuracy. Surgeons should consider implementing this technology in the operating room.