PubMed · 10350826
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1999. Communicate with bone conduction.. https://pubmed.ncbi.nlm.nih.gov/10350826/
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OBJECTIVE: To describe the pathophysiology and treatment of the lateralized tympanic membrane that occurs after canal wall down tympanoplasty. STUDY DESIGN: Retrospective case review. SETTING: Tertiary referral hospital. PATIENTS: Four patients in whom lateralization of the tympanic membrane developed as a complication of canal wall down tympanoplasty. RESULTS: The patients had undergone middle ear surgery 20 to 34 years before their first visit to the authors. A Bondy operation with soft-wall reconstruction of the ear canal had been performed in three patients and a modified radical mastoidectomy in one patient. They all had severe conductive hearing loss. Common findings were anterior canal sulcus blunting, good tubal function, normal middle ear mucosa, and mobile stapes. At revision surgery, the lateralized tympanic membrane was removed, and the temporalis fascia was grafted medial to the malleus manubrium. The exposed bony surface in the ear canal was covered with a split-thickness skin graft, and the ear canal and the mastoid cavity were tightly packed to secure the graft. All the patients regained good hearing after the revision. Although deterioration of the anterior tympanic ring was presumed to be the primary cause of the graft lateralization, the lack of a posterior bony ear canal might have facilitated this condition. CONCLUSION: Lateralization of the tympanic membrane can occur even in an ear with a radicalized mastoid cavity, especially when the anterior tympanic ring is torn and the posterior ear canal is reconstructed with soft tissue.
We report a series of 100 stapes operations performed for otosclerosis. The problems in reporting the results of stapedectomies are discussed. The audit showed a difference in the measured results between two consultants. As a result, the consultant with the worse outcome chose to stop operating on patients with otosclerosis. The advantages and disadvantages of a single surgeon performing all the cases are discussed. We advocate a central registry of all surgeons performing stapes surgery to allow periodic national comparative audits.
Measurement of the motion of the malleus umbo and stapes footplate during bone conduction (BC) stimulation was conducted in vitro in 26 temporal bones using a laser Doppler vibrometer over the frequency range 0.1 to 10 kHz. For lower frequencies, both ossicular sites followed the motion of the temporal bone. The differential motion between the malleus and the surrounding bone was greater than the differential motion of the stapes footplate; both resonated near 1.5 kHz. Different lesions were shown to affect the response: (1) a mass attached to the umbo lowered the resonance frequency of the ossicular vibration; (2) fixation of either the malleus or stapes increased the stiffness and shifted the resonance frequency upward; and (3) dislocation of the incudo-stapedial joint did not significantly affect the ossicular vibration. The sound radiated from the tympanic membrane was approximately 85 dB SPL at an umbo differential velocity of 1 mm/s for low frequencies in an open ear canal and about 10 dB higher for an occluded one; at higher frequencies (above 2 kHz) resonances of the canal determine the response. It was also found that the motion between the footplate and promontory was within 5 dB when the specimen was stimulated orthogonal to the vibration direction of the ossicles than in line with the same. Measurement of the differential motion of the umbo in one live human skull gave similar response as the average result from the temporal bone specimens.