title: [Applied anatomy of operation through posterior tympanum approach].
abstract: OBJECTIVE
  To provide the anatomic data for operation on the middle ear through the observation and measurement of related anatomic structure.
  
  
  METHODS
  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.
  
  
  RESULTS
  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.
  
  
  CONCLUSIONS
  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.
authors.affiliation: Department of Otolaryngology-Head and Neck Surgery, the First Affiliated Hospital of Anhui Medical University, Hefei, 230032, China.
authors.forename: Yongjun
authors.initials: Y
authors.lastname: Zhu
authors.forename: Busheng
authors.initials: B
authors.lastname: Tong
authors.forename: Shengchun
authors.initials: S
authors.lastname: Xu
authors.forename: Yehai
authors.initials: Y
authors.lastname: Liu
authors.forename: Maoli
authors.initials: M
authors.lastname: Duan
mesh_terms: D000328:Adult; D002814:Chorda Tympani Nerve / Q000033:anatomy & histology; D004432:Ear, Middle / Q000033:anatomy & histology* / Q000601:surgery*; D005154:Facial Nerve / Q000033:anatomy & histology; D005260:Female; D006801:Humans; D008297:Male; D012405:Round Window, Ear / Q000033:anatomy & histology / Q000601:surgery; D013701:Temporal Bone / Q000033:anatomy & histology / Q000294:innervation