Histologic studies of the posterior stapediovestibular joint in otosclerosis

Objective: To determine the prevalence of ankylosis or otosclerosis at the posterior stapediovestibular joint (SVJ) in temporal bones with otosclerosi s, with special reference to stapes surgery. Background: Long-term success of the laser stapedotomy minus prosthesis (ST AMP) procedure, anterior crurotomy, and similar partial stapedectomy proced ures depends on lack of ankylosis and lack of otosclerosis involving the po sterior SVJ. Previous work has shown that the air-bone gap in otosclerosis correlates with narrowing and loss of the SVJ space. However, the prevalenc e and histologic features of otosclerotic involvement of the posterior SVJ space have not been well characterized. Methods: Histologic assessment of serial sections through the oval window n iche in 140 temporal bones with otosclerosis that had been sectioned in the axial plane (age range 20-95 years, mean 68). Bones with stapes mobilizati on or stapedectomy were excluded. Results and Conclusions: Two of 140 bones had otosclerosis exclusively at t he 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 bo ny ankylosis of the posterior joint in 3 bones. Thus, 53 bones (38%) had ne ither ankylosis nor otosclerosis involving the posterior joint, and they wo uld 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 join t in one ear was significantly associated with its presence at the posterio r 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 degre e of footplate pathologic changes, such as ankylosis.