The Probert Encyclopaedia of Medicine

COCCYX

The coccyx (or 'tailbone') is composed of three to five rudimentary vertebrae. Often, the first of these coccygeal vertebrae is separate, while the remainder are fused together. The articulation between the coccygeal vertebrae and the sacrum allow some flexibility in the coccyx, which is particularly beneficial in taking the stresses of sitting and falling. The coccyx is extremely susceptible to shock fracture, as might be induced from a fall. Furthermore, since a number of nerve pathways pass near this area, damage to the coccyx threatens damage to the nerves of the lower body. The juncture of the first coccygeal vertebra with the sacrum occurs at the lower facet of the sacrum.
Research Coccyx