. 2010 Nov 3;20(5):698–705. doi: 10.1007/s00586-010-1617-1

Table 1.

The table provides detailed information regarding the Postacchini and Massobrio [7] classification and Maigne et al. [2, 8, 9] evaluation system by using dynamic X-rays

Classification introduced from Postacchini and Massobrio [7]	Type I: Coccyx curved slightly forward
	Type II: More markedly curved, with the coccyx pointing straight forward
	Type III: Sharply angled anteriorly
	Type IV: Subluxation of the sacrococcygeal or intercoccygeal joints
Maigne et al. [2, 8, 9] introduced the use of dynamic X-rays, comparing standing and sitting radiographs	Type I: Curving more than 25^o
	Type II: Displaced or sublaxated posteriorly
	Type III: Immobile with a spicule in the dorsal surface of the last coccygeal segment.