One of the simplest and most rational classifications of congenital clefts of the lip and palate was suggested by Ritchie and Staige Davis in 1922. Taking the alveolar border as a fixed point, they divide the clefts into three groups: (1) prealveolar; (2) postalveolar, and (3) alveolar.
Every cleft of the alveolar border is placed in the third group, whether the lip in front or the palate behind is open or closed. It is divided into three varieties: (1) the unilateral, in which the cleft lies between the premaxilla and the maxilla of one or other side; (2) the bilateral, in which clefts are present on each side between the contiguous margins of the premaxilla and maxillae, and (3) the median, in which, owing to faulty development or absence of the premaxilla, the cleft lies between the anterior ends of the maxillae.
It is my intention to base the description
THOMPSON JE. USE OF A SEPTAL FLAP IN CLOSURE OF UNILATERAL CLEFTS OF THE PALATE. JAMA. 1926;87(17):1384–1390. doi:10.1001/jama.1926.02680170038012