Table 2.

Summary of features associated with Klippel-Feil syndrome

Reference	Cervical fusion abnormalities	Thoracic fusion abnormalities	Lumbar fusion abnormalities	Other malformations	Inheritance
Klippel et al., 1912	short neck, low posterior hairline, absence of cervical vertebrae	N/A	N/A	N/A	sporadic
Feil, 1919	group I: massive fusion of many vertebrae group II: fusion of 1 or 2 cervical interspaces group III: cervical	groups I and III	group III	Sprengel deformity	N/A
Heisenger et al., 1982; MacEwen et al., 1972	type 1: C2–C3 fusion with occipitilization of the atlas type II: long cervical fusion with an abnormal occipitocervical junction type III: 2 blocked vertebral segments with a single open interspace	N/A	N/A	N/A	N/A
Clarke et al., 1995	KF1: C1 fusion is the most rostral KF2: C2–C3 fusion is dominant and most rostral KF3: C3 (C2–3 or C3–4) most rostral fusion, isolated fusions	N/A	N/A	KF1: cardiac, urogenital, hearing, craniofacial, limb, digital, and ocular defects KF2: craniofacial, hearing, otolaryngeal, skeletal, and limb defects KF3: craniofacial abnormalities syndrome, characterized by narrowed palpebral fissure, globe KF4: Wildervank syndrome (Duane retraction and failure of abduction of eye and sensorineural hearing loss)	KF1: autosomal recessive KF2: autosomal dominant KF3: autosomal recessive and autosomal dominant KF4: X linked dominant
Manaligod et al., 1999	cervical fusion	thoracic fusion	N/A	N/A	N/A
Samartzis et al., 2006	type 1: single congenital fused cervical segment type II: multiple noncontiguous congenitally fused segments type III: multiple contiguous, congenitally fused cervical segments	N/A	N/A	N/A	N/A

KF = Klippel-Feil syndrome; N/A = not applicable.