Objective: To provide the anatomic data for operation on the middle ear through the observation and measurement of related anatomic structure.
Method: Forty human temporal bones of 20 voluntary bone donors were dissected, relative anatomical data of operation were observed and measured under operating microscope through posterior tympanum approach entering posterior tympanum.
Result: The average distances from suprameatal spine to short crus of incus, pyramid segment of facial canal were 19.14 mm, 16.30 mm, respectively. The average distances from pyramid segment of facial canal to the surface of mastoid, crotch of chorda tympani nerve, posterior wall of auditory meatus were 20.84 mm, 11.28 mm, 4.40 mm, respectively. The average length of facial nerve in the horizontal segment, the perpendicular paragraph was about 11.60 mm, 15.30 mm, respectively. The average distance from pyramidal eminence to the anterior lip of round window niche, from oval window to round window niche, from incudostapedial joint to round window niche was 4.46 mm, 3.74 mm, 3.80 mm, respectively. The included angle of facial nerve in the horizontal segment and chorda tympani nerve with facial nerve in the perpendicular paragraph was 110.4 degrees, 24.8 degrees, respectively. Horizontal semicircular canal and facial nerve in the level paragraph was 17.5 degrees, long process of incus and incus buttress was 46.0 degrees.
Conclusion: The position of anatomic structure in middle ear was constant and the relationship including distance and angle between anatomic structures changed in limited region. The anatomical parameters provide a reference value for avoiding the injury during the operation.