When viewed from the back, the spine should be completely straight. Small curvatures and twists are part of normal variation and are very common. Only the larger deformities are of clinical importance and require good control or treatment. If a sideways curvature is present (in the frontal plane), this is called scoliosis [Figure 67]. Scolioses can be divided into structural and non-structural scolioses.
With the structural form, the scoliosis persists after cancelling out any additional findings, such as a leg length difference or a poor posture. With non-structural forms, scoliosis will have disappeared. When the patient stoops over, no twisting of the vertebrae should be visible. If some rotation prevails, it could involve structural scoliosis or simply a twisting of vertebrae around their axis, without the presence of a curvature in the frontal plane. If there is only rotation of a section of the spine without curvature in the frontal plane then it does concern a structural deformity, although it will not require any treatment.
Figure 67