Obstruction of the pharyngeal airway space after correction surgery in the cervical spine for dropped head syndrome

Postoperative dysphagia has been reported to occur as the result of narrowing of the pharyngeal airway space (PAS) due to a change in the alignment of the cervical spine. This study aimed to investigate potential risk factors for postoperative PAS obstruction following corrective surgery for dropped head syndrome (DHS) by analyzing clinical and radiographic parameters. This retrospective design included 42 patients (7 men, 35 women; mean age, 71.5 years) who underwent corrective surgery for DHS. The following measurements were obtained: narrowest PAS (nPAS), cervical vertebra 2 (C2)–7 angle, occipito (O)–C1 angle, C1–2 angle, and swallowing line (S-line). The correlations between the postoperative nPAS and clinical and radiographic factors were assessed. Logistic regression analysis was used to analyze the specific factors for the occurrence of postoperative dysphagia. ROC analysis was also used to determine the cut-off values. P-values < 0.05 were considered statistically significant. The mean preoperative nPAS was 15.0 ± 4.1 mm, which significantly decreased to 11.4 ± 3.6 mm postoperatively. The mean preoperative O-C1 angle was 7.8 ± 7.1°, which decreased to −7.2 ± 6.6° postoperatively. The mean pre- and postoperative C1–2 angles were 38.9 ± 5.8° and 34.8 ± 5.8°, respectively. Among this cohort, the mean nPAS of patients with S-line(-) was significantly smaller (8.5 ± 2.5 mm) than that of those with S-line(+) (11.7 ± 3.6 mm). Postoperative nPAS was correlated with O–C1 angle (r = 0.55, P < 0.015). Forward stepwise multivariate logistic regression showed that C0-1 angle (odds ratio (OR: 5.774) was the most impactable factor for the occurrence of postoperative dysphagia. ROC analysis revealed that the cut-off value for the occurrence of postoperative dysphagia was nPAS of 10.78 mm. The reduction of the O–C1 angle as a reciprocal change after the surgical correction of mid/lower cervical spine kyphosis for DHS may be a key factor in the occurrence of postoperative dysphagia due to airway obstruction.