Differences in the risser grading systems in the United States and France

A grading system for ossification of the iliac apophysis (Risser sign) came into use in the mid1950s in the United States and was adopted sometime later with modifications in France and other European countries. Although called by the same name, these systems have important differences that could lead to different choices of how and when to treat patients with spinal deformity. In a retrospective study, two experienced examiners (FDB and KPV) independently reviewed 301 randomly selected spine radiographs from 167 patients with adolescent idiopathic scoliosis and graded them for bilateral iliac crest apophyseal excursion each using a different system. The two grading systems were compared using percent agreements and kappa statistics. There was good to excellent agreement between the two Risser systems in only 50.8% of the patients. In disagreements regarding 147 of 148 patients, the US Risser grade was higher than the French Risser grade. In 130 of these patients (88.5%) the disagreement was one grade, and in 17 patients (11.5%), it was two grades. Therefore, the French Risser grading system uniformly undervalued the ossification excursion compared with the US Risser grading system. We think that the observed discordance is a source of miscommunication and descriptive confusion in the literature and in patient treatment.