What congenital disorder occurs when the spinal column fails to close completely around the spinal cord?

Spina bifida is the correct answer because it specifically refers to a condition where there is an incomplete closure of the spinal column around the spinal cord. This results in various levels of vulnerability, potentially leading to physical and neurological impairments. The defect occurs during the early stages of fetal development when the neural tube—an embryonic structure that eventually forms the spinal cord and surrounding structures—does not fully close.

In contrast, cleft palate is characterized by an opening or gap in the roof of the mouth, and it does not involve the spinal column. Down syndrome, a genetic disorder caused by the presence of an extra chromosome 21, affects cognitive and physical development, but it is unrelated to structural anomalies of the spinal column. Clubfoot is a condition that affects the position of the foot and is not related to spinal development. Hence, spina bifida is the only option that fits the description of a congenital disorder involving the spinal column.