Three-dimensional reconstruction and measurement of the human membranous semicircular canal

The planar relationship of the human semicircular canals was determined by Blanks et al. at a series of points measured from the dissected bony labyrinth of the human skull. The relationship of membranous canal planes have not, however, been measured from the human temporal bone. We reconstructed 3 semicircular canals by computer-aided 3-dimensional analysis and measured the angles formed between pairs of 3 osseous and membranous canal planes of temporal bones. Five temporal bones in adults were used for this study. Results indicated angles formed between pairs of ipsi-lateral canal planes of both the bony and membranous labyrinth. Angles formed between the horizontal-anterior, anterior-posterior, and posterior-horizontal canal planes of the bony labyrinth were 89.64 +/- 1.82 (mean +/- SD), 90.95 +/- 1.25, and 94.02 +/- 3.77 degrees. The same angles measured from the membranous labyrinth were 90.12 +/- 2.64, 90.18 +/- 2.75, and 91.48 +/- 6.32 degrees. Differences between the angles formed between bony and membranous canal planes were 2.11, 6.05, and 3.26 degrees in the anterior, horizontal, and posterior canal. Pairs of membranous canal planes were nearly perpendicular without exception, but pairs of osseous canal planes had a larger deviation from 90 degrees. This suggested that membranous canals could successfully be constructed in adequate alignment for canal function in the large perilymphatic space within osseous semicircular canals.