The impact of residual growth on deformity progression
Idiopathic scoliosis is a disease of the growing spine. Risk of progression and aggravation of disease are mainly dictated by the remaining growth and curve magnitude. Remaining growth can be estimated by repeated biometric measurements, tanner sign and bone age estimation. Puberty is the turning point in the natural history of this disease. The first two years following puberty are the turning point in the natural history of this disease since 90% of growth occurs during this period. Lateral olecranon radiograph is effective for estimating bone age during this phase. Growth acceleration is followed by a deceleration phase of three years where menarche occurs. Bone age during this phase is evaluated by hand X-rays and the Risser sign. Progression risk assessment of idiopathic scoliosis showed that a 30° curve at the beginning of puberty together with 20° to 30° curves with more than 10° of annual curve progression has a 100% risk of progression towards the 45° surgical threshold. In these patients, anticipation may be the key for effective treatment strategy. Treating these curves earlier than the surgical threshold before increased stiffness would lead to a better outcome.