New approach to diagnose arytenoid dislocation and subluxation using three-dimensional computed tomography.

Understanding the complex three-dimensional (3D) arrangement of the arytenoid cartilage is necessary for diagnosing arytenoid dislocation (AD) and arytenoid subluxation (AS). We examined the 3D arrangements of AD and AS (AD/AS) cases by region and considered their new diagnoses. This retrospective study included 2 patients with AD, 10 with AS, and 23 with unilateral vocal fold paralysis (UVFP) for comparison. The etiologies were intubation-induced and idiopathic. We classified the AD/AS position into four joint regions: mediocaudal, laterocaudal, mediocranial, and laterocranial. We generated 3D computed tomography (3DCT) images during rest and phonation to analyze functional movements. We attempted to compare the endoscopic findings and 3DCT images of patients with UVFP and AD/AS. To examine the joint status, we especially focused on the position and movements of the muscular process (MP) on the joint because the arytenoid facet is mainly located on the back of the MP. We were able to obtain endoscopic and 3DCT findings characteristic of each AD/AS region. The dislocated MPs were localized to the mediocaudal, mediocranial, and laterocranial regions. Two AD cases were diagnosed due to complete separation of the joint surfaces during rest and phonation. The finding of MPs displacing partially outside the cricoid facet is common to both severe UVFP and AS. The most important differentiation point was that the MP in UVFP cases was located on both the medial and lateral side regions of the joint, but that of AS was on one side region only. Furthermore, no cases of passive gliding movements characteristic of UVFP that have been described previously by us were observed in AD/AS cases. AD can be diagnosed by findings of complete joint separation. AS can be diagnosed based on positions and movements distinct from those of UVFP.