Klippel-Feil syndrome (KFS) was first described in 1912 by Klippel and Feil as a classic triad are comprised of a short neck, a low posterior hairline and restricted motion of the neck. This disease is considered as one of the congenital causes of difficult airway with the incidence of 1:42,000 live births.

The current research findings suggested that the difficulties of airway management for KFS increases with age. In pediatric patients, the airway of those patients can be managed without difficulties. For adults, the fiberoptic-assisted intubation is also suggested.

The purpose of this study is to review the airway management of pediatric patients with KFS to provide recommendation of airway management for these patients. A retrospective electronic chart review will be conducted by using Boston Children's Hospital (BCH) database, which identified patients with KFS who had undergone general anesthesia from June 2012 to June 2018.

Klippel-Feil syndrome (KFS) was first described in 1912 by Klippel and Feil as a classic triad are comprised of a short neck, a low posterior hairline and restricted motion of the neck due to fused cervical vertebrae with the incidence of 1:42,000 live births1,2. The etiology is presumed to involve in PAX gene family mutation defect and Notch signaling pathway. KFS patients are classified into 3 types based on the location of fusion; Type 1 patients have a single congenitally fused cervical segment; Type 2 patients show multiple non-contiguous, congenitally fused cervical segments; and Type 3 patients show multiple contiguous, congenitally fused cervical segments. In 1974, Hensinger et al studied 50 KFS patients aged 4 to 34 years and their associated anomalies. The findings revealed less than half had the classic triad of findings, more than half had scoliosis and a third had renal anomalies. All patients were at risk of having other serious anomalies such as Sprengel's deformity, hearing impairment, synkinesia and congenital heart disease.

The current literature focused on isolated case reports suggested an awake fiberoptic intubation as a safest option to secure airway in adult patient with KFS. For pediatric patients with KFS, their airway management could be challenging, there is no literature report describing unsuccessful or difficult mask ventilation or LMA insertion. Bakan et al reported an overview of direct laryngoscopy for tracheal intubation in KFS patients aged 26 days to 16 years old, 18 of 25 cases were successfully intubated by direct laryngoscope (DL). From 13 literatures reviewed by Bakan et al, there is no report of an unsuccessful DL in children with KFS younger than 4 years. Despite the formidable appearance for airway management, recent pediatric data encourage the anesthesia providers to perform DL instead of fiberoptic intubation. However, a successful DL event in anesthesia history record does not guarantee an ease of next DL event because the airway of KFS patients are progressively worse over time.

The investigators propose a retrospective electronic chart review of patients with KFS who had undergone general anesthesia in Boston Children's Hospital from June 2012 to June 2018. The purpose of this study is to review the airway management techniques of pediatric patients with KFS and provide recommendation of airway management for these patients. A retrospective electronic chart review will be conducted by using Boston Children's Hospital (BCH) database, which identified patients with KFS who had undergone general anesthesia from June 2012 to June 2018.

The investigators hope to provide specific anatomical abnormalities and age of pediatric patients with KFS to suggest they are at risk of difficult airway. Finally, the investigators hope this information can be used to suggest a proper choice of airway management for specific type and age group of KFS patients.

Inclusion Criteria:

• All KFS patients who scheduled for surgery at BCH from June 2012 to June 2018.

Exclusion Criteria:

• Patients with incomplete or absent of medical records on AIMS such as ventilation and intubation technique are not clearly document.

All KFS patients who scheduled for surgery at BCH from June 2012 to June 2018.

We might share individual participant data if it allows maximum use of the data.