OBJECTIVETo provide anatomical data for transoral atlantoaxial reduction plate internal fixation.

METHODMicrosurgical dissecting was performed on 10 fresh craniocervical specimens layer by layer according to transoral approach. Stratification of posterior pharyngeal wall, course of vertebral artery, adjacent relationships of atlas and axis and correlative anatomical parameters of internal fixation to atlantoaxial joint were observed.

RESULT(1) Posterior pharyngeal wall consisted of 2 layers and 2 interspace: mucosa, anterior fascia of vertebrae, posterior interspace of pharynx and anterior interspace of vertebrae. (2) The range from anterior rim of foramen magnum to C3 could be exposed by this approach. (3) The distance between the vertebral artery at atlas and midline was (25.2 +/- 2.3) mm and that between the vertebral artery at axis and midline was (18.4 +/- 2.6) mm. (4) The width of atlas and that of axis could be exposed respectively to (39.4 +/- 2.2) mm and (39.0 +/- 2.1) mm. The distance (a) between 2 atlas screw inserting points (center of anterior aspect of C-1 lateral mass) was (31.4 +/- 3.3) mm. The vertical distance (b) between the connecting line of 2 atlas screw inserting points and that of 2 axis screw inserting points (at the central part of the vertebrae which was 3 - 4 mm lateral to the midline of C-2 vertebrae) was (18.7 +/- 2.7) mm. The odds of a/b was 1.5 approximately 1.7.

CONCLUSIONSAnterior atlantoaxial plate internal fixation through transoral approach is suitable and feasible. The design of the plate should be based on the above data.