Fig. 25

The third 3C compatible curve pattern is the composite “major main thoracic”/“minor lumbar.” Both curves are structural but lumbar is a more flexible, minor, probably secondary curve. This is called A3 type and the second radiological criteria to confirm 3C is the TP offset to the convex thoracic side, like in A1 and A2 types. Due to the lumbar structural curve, it is wrongly taken like 4C by many Chêneau followers, but a structural lumbar curve is not criterion enough to decide about using a 4C brace design. It can be combined, like most of types by a primary or secondary or iatrogenic proximal thoracic curve