![]() ![]() The aim of the present study was to elucidate the validity of O-EAa as an indicator of oropharyngeal airway space in RA patients with AAS. The authors previously proposed the occipital and external acoustic meatus to axis angle (O-EAa i.e., the angle made by McGregor’s line and a line joining the external auditory canal and the middle point of the endplate of the axis ) as a novel, useful, and powerful predictor of the anterior-posterior narrowest oropharyngeal airway space (nPAS) distance in healthy subjects. However, O-C2a is unreliable in atlantoaxial subluxation (AAS) because it does not reflect the translational motion of the cranium to C2, another factor affecting oropharyngeal area in patients with rheumatoid arthritis (RA) who have reducible AAS. The occiput-C2 angle (O-C2a) is useful for preventing dyspnea and/or dysphagia because O-C2a affects the oropharyngeal space. Foreign bodies impacted at this point could be removed by use of aural hook, using the potential space at the superior portion of the isthmus.Dyspnea and/or dysphagia is a life-threatening complication after occipitocervical fusion. This is mainly an anteroposterior narrowing and is oval or inverted pear shaped. Conclusions: The isthmus is a bony-cartilaginous junction, and the narrowest point of the EAM is situated at the junction of the outer one third of the inner two thirds of the canal length. The cross-section of this area was either an inverted pear or oval shape. This narrowing was 5.7 (range 3–7) mm wide in the anteroposterior plane, but 8.2 mm (range 6.5–10) mm wide in the vertical plane. The isthmus corresponds to the bony and cartilaginous junction, which is traditionally thought to be narrowed by the canal angulation. It is approximately 3 cm long and is lined by skin containing hair follicles (tragi), sebaceous glands, and ceruminous glands (which produce cerumen ). The mean canal length was 27.7 (range 20–34.8) mm. The external auditory meatus is a short S-shaped canal within the tympanic temporal bone leading from the external acoustic pore of the auricle to the tympanic membrane. ![]() Results: The narrowest point of the EAM, i.e., the isthmus, was located at the junction of the medial two thirds (mean 17.9 mm) to the lateral one third (mean 9.8 mm) of the canal. ![]() ![]() in length if measured from the tragus from the bottom of the concha its length is about 2.5 cm. The measurements of the impressions were done by using a micrometer (Vernier caliper), calibrated to 0.1 mm. The External Acoustic Meatus ( meatus acusticus externus external auditory canal or meatus) extends from the bottom of the concha to the tympanic membrane : It is about 4 cm. All abnormal ears were excluded from the study. It contains canals and receptors (inner ear) for the hearing and equilibrium systems. The petrous part is a medial extension that forms the base of the skull between the sphenoid and occipital bones. Materials and Methods: Twelve impressions were taken from 8 adults. It contains the external auditory meatus, a canal that leads to the tympanic membrane ( eardrum) and bones of the middle ear. This study was designed to determine the location and cross-sectional shape of the narrowest point of the EAM, i.e., the isthmus, by using silicone casting material in human cadaver ears. A foreign body is more likely to be stuck at the narrowest point of the EAM. Objective: Foreign bodies are commonly impacted in the external auditory meatus (EAM), and removal is sometimes difficult due to the tortuous anatomy. While the muscle modifies the auricular shape only minimally in the majority of individuals, this action could increase the opening of the external acoustic. ![]()
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