Preoperative radiological indicators for prediction of difficult laryngoscopy in patients with atlantoaxial dislocation

Description

We hypothesis preoperative radiological parameters are valuable in predicting difficult laryngoscopy in patients with Atlantoaxial Dislocation. Four radiological parameters showed significant difference between the difficult laryngoscopy group and non-difficult laryngoscopy group. Among which, ∆C1C2D (the difference of the distance between atlas and axis in the neutral and extension position), owned the largest AUC. A retrospective nested case-control study was conducted to investigate the radiological indicators for prediction of difficult laryngoscopy in patients with AAD. Patients without difficult laryngoscopy were randomly selected as the non-difficult laryngoscopy group by individually matching with the same gender, same surgery year, and similar age ( ± 5 years) at a ratio of 6:1. Group 1 was the difficult laryngoscopy group, and Group 2 was the non-difficult laryngoscopy group. The indicators measured in neutral position were as follows (Fig. 1): perpendicular distance from hard palate to the tip of upper incisor (HPUID), distance from mandibular body to hyoid bone (MHD), horizontal distance from the border of the nearest cervical vertebra to the highest point of hyoid bone (CHD), distance from the upper edge of C1 to the lower edge of C4 (C1C4D), distance between the occipital bone and the atlas (C0C1D), distance between the atlas and the axis (C1C2Dn) and horizontal distance between the anterior arch of the atlas and the dens of the axis (the atlantodental interval, ADIn). The indicators we measured in extension position were distance between the atlas and the axis (C1C2De) and ADIe, shown in Fig. 2. The difference between C1C2Dn and C1C2De were calculated and recorded as ∆C1C2D. The difference between ADIn and ADIe were calculated and recorded as ∆ADI. Angles measured on preoperative lateral X-ray images in the neutral position were shown in Fig. 3. Angle A is the angle between the line parallel to the hard palate (line1) and the line connecting the anterior edge of C1 and C2 (line2); angle B is the angle between line1 and the line connecting the cricoid cartilage and the midpoint of the airway (line3); angle C is the angle between the McGregor’s line (line4, connecting the posterior edge the hard palate and most caudal point of the occipital curve) and the inferior end plate of C2 (line5); angle D is the angle between line5 and the inferior end plate of C6 (line6). These angles were also measured in extension position, and the difference between these positions were recorded as ∆Angle A, B, C, D(°). The number of fixed segments (NOFS) from craniovertebral junction (C0-C1) to C6-C7 was evaluated with preoperative cervical computed tomography (CT) and X-ray images by the same experienced orthopedist, who was also blinded to group allocation and not involved in the airway management. The file format wasMicrosoft Excel (.xlsx), and the figure format was JPEG (.jpg).

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A retrospective nested case-control study within a single center longitudinal AAD cohort was conducted to investigate the radiological indicators. Patients without difficult laryngoscopy were randomly selected as the non-difficult laryngoscopy group by individually matching with the same gender, same surgery year, and similar age ( ± 5 years) at a ratio of 6:1. Group 1 was the difficult laryngoscopy group, and Group 2 was the non-difficult laryngoscopy group. All X-ray data were evaluated using radiography information system (Centricity RIS-IC CE V3.0; GE Healthcare, Little Chalfont, UK). Distance and angle indicators were measured in neutral and extension position. All imaging measurements were completed by the same radiologist. Radiological data on preoperative lateral X-ray images between the two groups were compared. Bivariate logistic regression model was applied to screen out the independent predictive indicators and calculate the odds ratios of indicators associated with difficult laryngoscopy. Receiver operating characteristic curve and area under the curve (AUC) were used to describe the discrimination ability of indicators.

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