Influence of maxillofacial skeletal morphology on difficult laryngoscopy

Background: Although mandibular retrognathia has been recognized as one of the predictors of difficult laryngoscopy, its definition remains vague, with no clearly established skeletal evaluation systems. The Sassouni classification system, used to categorize the maxillofacial morphology systematically (nine types), can be easily performed using preoperative radiographic findings. This study aimed to investigate the relationship between difficult laryngoscopy and Sassouni type 5, a group characterized by a small mandible and a large overbite. Methods: This retrospective study comprised patients diagnosed with jaw deformities who underwent orthognathic surgery for malocclusion under general anesthesia at our clinic. The patients were divided into two groups: Sassouni 5 and non-Sassouni 5 (types 1, 2, 3, 4, 6, 7, 8, and 9). Difficult laryngoscopy was evaluated by examining the degree of difficulty in laryngeal exposure, which was defined as grades 3 and 4 based on the Cormack-Lehane (CL) classification. Additionally, we evaluated the relationships between the Sassouni 5 group and three predictors of difficult laryngoscopy (Mallampati classification, Wilson score, and hyomental distance [HMD]). Results: Of the 187 patients included in this study, 44 belonged to the Sassouni 5 group, and the remaining 143 belonged to the non-Sassouni 5 group. The proportion of patients with CL grade 3 or higher was significantly higher in the Sassouni 5 group (n = 9; 20.5%) than in the non-Sassouni 5 group (n = 6; 4.2%). Furthermore, 10 (22.7%) patients in the Sassouni 5 group had a Mallampati score of 3 or higher, 44 (100%) had a Wilson score of 2 or higher, and 38 (96.7%) had an HMD of less than 3 fingerbreadths. The corresponding numbers in the non-Sassouni 5 group were 8 (5.6%), 48 (33.6%), and 43 (30.1%), respectively. The incidence of difficult laryngoscopy in the Sassouni 5 group was significantly higher than that in the non-Sassouni 5 group (p < 0.001). Conclusions: These findings indicate that the incidence of difficult laryngoscopy can be predicted using the Sassouni classification, which can be easily analyzed using lateral cephalograms obtained routinely before corrective surgical procedures. The Sassouni 5 group could be used as an important predictive tool in clinical practice.