Fig. 31

A single main thoracic curve with a more or less rectilinear lumbar spine (or minimal functional lumbar curve) is the N3N4 compatible curve pattern called C1 type. The transitional point (TP) is more or less balanced on the central sacral line. In this revisited version of the classification, we are not looking so much at T1 as an essential criterion. Many factors are associated to a non-relevant imbalance of T1, which is not against diagnosing a C1 type