Fig. 43

This figure shows the principle of correction for a true double structural curve. Most but not all the double structural curves are classified as “four-curve pattern” (4C) or “B type” (B1 and B2). The objective criteria to classify 4C (or B types) can be seen later in the main text and some more figures. This current figure is about a classical B1 type, with the apical vertebrae of the right main thoracic curve at T8 and the left lumbar curve at L2. “Regional derotation” is applied here at these two regions. The main thoracic region is over-derotated to the left (yellow line A) like in previous cases. The lumbar region is over-derotated to the right with the combination of a couple of forces formed by a real left lumbar pad and a right low abdominal pad (green line D). The lumbar pad is dissociated or uncoupled from the pelvic region (it is not just a lumbar support coupled to the pelvis section) and approaches the lumbar convexity, reaching the maximum pressure at the apical level, leaving room down. Pelvis region has to be translated to the left, bringing also the lower lumbar vertebrae to the left, to the provided room caudal to the lumbar pad. Pelvis is not only translated but also derotated to the left (not over-derotated but just derotated to 0°, fixing the pelvis region in the frontal plane of reference—red line B). Two main “three-point systems” are formed with the lateral component of all the pads. The right pelvic pad, the left lumbar pad, and the right thoracic pad form the lower “three-point system”