The Prevalence of Klippel-Feil Syndrome: A Computed Tomography-Based Analysis of 2,917 Patients.

STUDY DESIGN: Cross-sectional study.

OBJECTIVE: To determine the prevalence of KFS in asymptomatic patients in New York State.

SUMMARY OF BACKGROUND DATA: Klippel-Feil syndrome (KFS) is characterized by congenitally fused cervical vertebrae and may not be diagnosed clinically because most patients do not have the classic triad of short neck, low posterior hairline, and decreased neck range of motion. KFS may be associated with abnormalities such as congenital scoliosis and deafness, and patients are at higher risk for neurologic injury following cervical spine trauma. The prevalence of KFS has not been evaluated in a large series but is estimated to occur every 40,000 births.

METHODS: A total of 3,534 cervical computed tomography (CT) scans at the emergency department of a level I trauma center were obtained during a one-year period. Duplicate scans and outside hospital imaging were excluded, resulting in 2,917 cervical CT scans for review. Demographic information was collected, and if KFS was present, level(s) fused, Samartzis classification type, and presence of cervical scoliosis and cervical spine fractures were recorded.

RESULTS: The prevalence of KFS was 0.0058% (1 in 172). Of the 17 subjects with KFS, 8 were female and 9 were male. The most commonly fused levels were C5-C6 and C2-C3. All 17 subjects were classified as Samartzis type I, with a single congenitally fused cervical segment. None of the subjects had cervical scoliosis or cervical spine fractures.

CONCLUSIONS: The prevalence of KFS in our series is much higher than previously described. Because clinical diagnosis may not be reliable, it is likely that this condition is underreported and may only be found incidentally on imaging.

LEVEL OF EVIDENCE: Level III.