ObjectiveTo determine the prevalence of ankylosis or otosclerosis at the posterior stapediovestibular joint (SVJ) in temporal bones with otosclerosis, with special reference to stapes surgery.BackgroundLong-term success of the laser stapedotomy minus prosthesis (STAMP) procedure, anterior crurotomy, and similar partial stapedectomy procedures depends on lack of ankylosis and lack of otosclerosis involving the posterior SVJ. Previous work has shown that the air-bone gap in otosclerosis correlates with narrowing and loss of the SVJ space. However, the prevalence and histologic features of otoscle-rotic involvement of the posterior SVJ space have not been well characterized.MethodsHistologic assessment of serial sections through the oval window niche in 140 temporal bones with otosclerosis that had been sectioned in the axial plane (age range 20–95 years, mean 68). Bones with stapes mobilization or stapedectomy were excluded.Results and ConclusionsTwo of 140 bones had otosclerosis exclusively at the posterior SVJ. Of the remaining 138 bones, all of which had otosclerosis at the anterior SVJ, 82 bones also had otosclerosis at the posterior joint. Of the 56 bones without otosclerosis of the posterior joint, there was bony ankylosis of the posterior joint in 3 bones. Thus, 53 bones (38%) had neither ankylosis nor otosclerosis involving the posterior joint, and they would be potentially suitable for a laser STAMP or a similar procedure. There was no correlation between otosclerosis at the posterior SVJ and age, sex, or duration of conductive hearing loss. Otosclerosis at the posterior joint in one ear was significantly associated with its presence at the posterior joint in the opposite ear (p = 0.01). The audiogram could not be used to reliably predict otosclerotic involvement of the posterior SVJ or the degree of footplate pathologic changes, such as ankylosis.