MECHANICS OF THE MIDDLE-EAR IN OTOSCLEROSIS AND STAPEDOPLASTY

Seventy-three otosclerotic patients, 138 subjects who had undergone st apes surgery (50 total stapedectomies, 43 stapedotomies with stapedius tendon section and 45 stapedotomies with stapedius tendon preservatio n) and 70 normal controls were investigated by susceptance multiple fr equency tympanometry. The aims were to evaluate the efficiency of this procedure in diagnosing otosclerosis and to assess the resonance prop erties of middle ears undergoing different types of stapedectomy. Tymp anometry was performed using sweep frequencies ranging from 226 to 2,0 00 Hz for each pressure step of 12.5 daPa (pressure range from -500 to 400 daPa). The resonance frequency of the system was evaluated by ide ntifying the ''W'' morphology of susceptance tympanograms. The results of the present investigation indicate that stapes surgery abnormally reduces the stiffness of the tympano-ossicular system. This phenomenon is limited by preservation of the stapedius tendon, which confers a s ignificant degree of stiffness on the conductive system.