A Micro-Computed Tomographic Study

OBJECTIVES: To examine the anatomical relationship of the angles between tympanic membrane and stapes footplate and the variation of these angles among different temporal bones in order to characterize the optimal shape of total ossicular reconstruction prostheses (TORPs). METHODS: Ten specimens of human temporal bones were prepared for examination with micro-computed tomography. Five of the 10 temporal bones were implanted with 3 types of TORPs before subjecting them to micro-computed tomography. The angles between tympanic membrane and stapes footplate were determined. The contact of the TORPs to these structures was assessed. RESULTS: The angle between the stapes footplate and the tympanic membrane was, on average, 25.9 degrees in a plane along the transverse axis of the stapes footplate and 24.6 degrees in a plane along the longitudinal axis of the stapes footplate. Consideration of these angles in TORPs resulted in an optimal contact with the tympanic membrane and stapes footplate, especially for prostheses with a large foot. CONCLUSION: TORPs should be adjusted in shape before insertion into the middle ear. Further developments should consider prostheses with preadjusted angles or appliances for the exact modification of the prostheses during surgery.