• 1.) To determine the incidence of curve progression 2.) Identify factors related to curve progression 3.) Use factors related to progression to predict which curves will progress

The natural history of adolescent idiopathic scoliosis is still not entirely understood despite decades of research. This study by Lonstein and Carlson is truly one of the classic papers published on the subject of idiopathic scoliosis, looking at the prognostic factors related to curve progression.  The study population was drawn from a database of juvenile and adolescent patients seen between 1970 and 1979. The inclusion criteria was based on a curve of 29 degrees or less on initial standing AP radiographs and follow-up to a Risser sign of 5 (or progression of the curve).  Definition of progression was clearly defined by the authors.

Based on the analysis, 23.2% of the 727 patients had curve progression. This is nearly identical to a recent study by Zhang et al (Eur Spine Journal 2015) where 23.6% of 89 female patients showed evidence of curve progression during the course of the study.  In many cases, comparing curve progression across studies is challenging as there are differences in the criteria for progression.

The major findings from Lonstein et al have shown that the initial curve magnitude, age of the patient at initial presentation, menarchal status, and Risser sign were all associated with curve progression. The authors did utilize the factors that appeared to have the highest correlation with curve progression, in a model to predict curve progression. Utility of the model is questionable as accuracy varied for some cases, but this has provided a solid basis for future model development.

Multiple current studies looking at factors relating to curve progression has validated the work of Lonstein and Carlson. Tan et al (Spine 2009), Lee et al (Spine 2012), Zhang et al (Eur Spine Journal 2015), and Wong and Tan (Indian Journal Ortho 2010) all agree that curve magnitude at initial presentation may be one of the strongest risk factors for future progression. Patient age and menarchal status also appear to be prognostic in most, but not all studies.

While a model to predict curve progression with great accuracy has yet to be developed, this well designed and conducted study by Lonstein et al has provided a solid contribution to the literature that newer investigations continue to draw off of.