Contradictions of derotation in scoliosis surgery using the CD principle.

Current literature has increasingly emphasized the problem of derotation in scoliotic deformities. The Cotrel-Dubousset (CD) principle as a means of correcting rotation has been questioned by various authors. This paper aims to draw attention, using algebraic methods, to the importance of the remaining rotational deformities, and to suggest the introduction of the notion 'rotational balance'.