Inclusion Criteria:  Patients undergoing anterior cervical surgery from 2010 to 2019; Age ≥ 18 years old.  Exclusion Criteria:  Age ≤ 18 years old; Patients with neck tumor, infection and goiter; Neck soft tissue and bone structure deformity; Ankylosing spondylitis; Oral and laryngopharyngeal diseases; Hysteria or mental illness; Postoperative anesthesia can not be normal resuscitation patients; Nervous system diseases: such as Parkinson's disease. Patients with airway obstruction due to epidural hematoma underwent reoperation.