Risk factors of myelopathy at the atlantoaxial level in spondyloepiphyseal dysplasia congenita.

Spondyloepiphyseal dysplasia congenita (SEDC) can be accompanied by hypoplasia of the odontoid and/or lax ligaments which may lead to spinal cord compression. Since an early diagnosis of myelopathy is essential for rational treatment, identification of the high-risk factors is imperative. Sixteen patients were retrospectively reviewed, 10 male and 6 female, and their average age at the time of examination was 18 (range 3-37) years. Myelopathy was seen in 6 individuals. Five were associated with atlantoaxial subluxation, and the critical value of space available for the spinal cord at the level of the atlas was 10 mm or less. Their height was less than -7SD of average Japanese of the same age, and all were associated with severe coxa vara. Although SEDC itself is a risk factor, marked short stature of less than -7SD and severe coxa vara are particularly high-risk factors for cord compression at the level of the atlas.