[Rapid prototyping of the larynx for laryngeal frame work surgery]

A detailed understanding of the three-dimensional (3D) structure of the larynx is important for determining appropriate methods and approaches for laryngeal frame work surgery. In this study, a 3D laryngeal model was constructed based on postoperative helical CT data obtained after lateral cricoarytenoid muscle (LCA) pull surgery (Iwamura) for the treatment of unilateral vocal fold paralysis. The anatomical configurations of the arytenoid cartilages and the optimal approaches for laryngeal frame work surgery were then examined. A 3D model of the human larynx was prototyped using a selective laser sintering method. A compound powder of plastic nylon and an inorganic substance (glass beads) was used as the raw material. The cricoid cartilage and the arytenoid cartilages were prototyped, and the configurations of the arytenoid cartilages were evaluated. The results were similar to those of previous reports. The arytenoid cartilage of the unaffected side moved downward while adducting, and the vocal process moved inwards and downwards. On the other hand, the paralyzed arytenoid cartilage moved neither inward nor downward, and the vocal process was fixed at an outer and upper position. Next, the thyroid cartilage was added to the model to determine the optimal location of the window in the thyroid cartilage for the LCA pull surgery. The window after the first surgery was largened using a surgical drill. The 3D prototype model was useful for understanding the complex configurations of the laryngeal anatomy, and to determine the optimal approaches for laryngeal frame work surgery, etc.