[Fates of bone defects in the mastoid cavity studied from the findings of two-stage tympanoplasty].

The incidence and prognosis of bone defects occurring in the mastoid cavity were investigated in 205 ears of 197 patients who underwent planned two-stage tympanoplasty by the intact canal wall technique. Bone defects found at the first stage had spontaneously closed by the second stage in 43 of 62 ears at the mastoid tegmen, in 13 of 15 ears at the posterior wall of the mastoid cavity and in 2 of 17 ears at the posterior wall of the external ear canal. Twenty two ears developed bone defects at the ear canal between the first and second operations, despite the canal wall having been primarily preserved. Of the 6 ears with closure of the labyrinthine fistula using temporalis fascia at the first stage, the defects were obliterated with regenerated bone in 5 ears at the second stage. Bone defects at the facial canal were recognized in 67 ears at the first stage, 21 of which were no longer seen at the second stage.