Extension of the Clinical Significance of the “Cog”

Objective: To study the clinical anatomy of the epitympanum, the attic, and its medial wall, to try to discover a new clinical operation-related anatomical landmark, and to investigate the adjacent anatomical relationship with this landmark. Materials and Methods: Eight donor temporal bone specimens were dissected endoscopically. For 29 healthy persons (17 males and 12 females), CT images of the temporal bone (57 ears) were taken, 3-dimensional (3-D) reconstruction and multidimensional plane reconstruction were performed, and identification and assessment of 3-D spatial relationships between any 2 of these complex structures were done. Results: 3-D images of the temporal bone structures including the facial nerve, the cochlea, the semicircular canal, and the brain plate were reconstructed and shown in detail. We discovered a new clinical surgery-related anatomical landmark (the "cog" tangent and the trailing edge of the cog). Based on the tangent and the trailing edge of the cog, we quantified the anatomical relationship between it and its neighboring important structures. Conclusion: Based on endoscopic anatomy and the temporal bone spiral CT 3-D structure reconstruction of the epitympanum, the attic, and the adjacent structures, we found an extension of the clinical significance the cog. Quantification of the adjacent anatomical relationship of this landmark is very important for otology microsurgical operation.
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