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Scoliosis Research: Determining the Risk of Progression

Can the Likelihood of Your Child’s Scoliosis Progressing be Predicted?

A new study (ahead of publication) looks at determining the risk of progression for adolescents with idiopathic scoliosis during the peak of their growth. Researchers did this by evaluating curve size in relationship to stages of skeletal maturity to identify predictable changes.

Skeletal maturity has been typically determined by the Risser Sign. This study used a new technique which evaluates the bone development at the elbow.

What is the Risser Sign?

In 1958 Joseph C. Risser observed that the degree of formation of the bone at the top of the pelvis corresponded to a patient’s spinal skeletal maturity. Since it can be difficult to determine bone age by assessing the spinal bones, Risser discovered that when the outer top edge of the pelvis had fully developed generally coincided with full development of the vertebral growth plates (spinal bones), and so he concluded, “the attachment of the iliac apophysis has proved to be an excellent physiologic sign to indicate the completion of the vertebral growth”. This is now referred to as the Risser sign.


The Risser sign is used to indirectly measure skeletal maturity by determining the stage of ossification (bone formation) of the iliac apophysis and using this information to gauge the approximate ossification of the spinal bones. It is a scale of 0 to 5 measuring the progression of bone formation (5 means that skeletal maturity is reached).


Olecranon (Elbow) Stagesolecranon-assessment-for-scoliosis-risk-progression

Research suggests that the main progression of idiopathic scoliosis occurs during peak height growth velocity. Peak height growth velocity is the time when adolescents experience the maximum rate of growth and corresponds with the rapid phase of pubertal growth. This typically occurs between the ages of 11 and 13 for girls and 13 and 15 years in boys. During this time the Risser sign remains at grade 0.

To assess skeletal maturity prior to Risser grade 1, the researchers used a method in which changes in formation of the olecranon (the bony prominence of the elbow) are assessed. Assessment of this bony bump allows skeletal age to be evaluated easily and accurately at intervals of six months during Risser grade 0.

The present study used this method to assess skeletal maturity with relationship to curve size. They found that at the start of the pubertal growth spurt:

  • Curves greater than 30° have a 100% risk of progressing over 45°
  • Curves around 21-30° have a progression risk of 72.5%
  • Curve progression rate of 6-10° per year represents a risk of 71.8% for increasing to the level which has been historically considered a candidate for spine surgery
  • Curve progression rate greater than 10° per year represents a risk of 100% for increasing to the level which has been historically considered a candidate for spine surgery

They suggest that comparing curve sizes with height measurements and the stages of skeletal maturity offers a reliable prediction of curve progression risk in idiopathic scoliosis during Risser 0”.

NB:  Many conservative scoliosis professionals now consider surgery an “elective” procedure and only medically necessary for the largest curves, those above 70 degrees, where there is definite evidence of lung compromise.