The type I thyroplasty window: implications of normal thyroid cartilage thickness

This paper describes the dimensions and placement of a standardized Isshiki Type I thyroplasty window and the thickness of the thyroid cartilage at the window corners. In addition, the intraoperative optimal medialization of a series of windows is compared to these cartilage thickness measurements and these comparisons analyzed for their implications in surgical approach. Fifty-one Type I thyroplasty windows were fashioned on 42 larynges (cadaveric and surgical). Measurements were taken of the window sizes, depth of medialization (surgical cases), and thickness of the thyroid cartilage at the four corners of the rectangular window. Sexes were kept separate because of inherent size differences of male and female larynges. From these physical measurements it is found that: (1) the thyroid cartilage window is not uniform in thickness throughout; there is a gradation of thickness from anterior to posterior and from superior to inferior; (2) when comparing the average depth of medialization to the window cartilage thickness in a standardized Isshiki window, the average distance of window depression almost equals the thyroid cartilage thickness, whereas posteriorly there is slightly more distance between the external surface of the window cartilage and the internal surface of the surrounding thyroid cartilage. Implications of the varying thickness of the thyroid cartilage and its relationship to the average depth of medialization in a standardized Isshiki thyroplasty window are discussed.