Improved accuracy in Risser sign grading with lateral spinal radiography

Development of the ossification of the iliac crest is used to assess the remaining spinal growth. The clinical value of the Risser sign has been questioned because of its inaccuracy in grades 3 and 4. Estimation of the Risser sign based on the lateral spinal radiograph has not been reported. The aim of the study was to evaluate the course of ossification of the iliac apophysis along its full extension and to investigate relevance of the lateral spinal radiograph for more accurate Risser sign grading. Cross sectional analysis of spinal frontal and lateral long cassette standing spinal radiographs of 201 girls aged from 10.2 to 20.0 years were done. On the lateral spinal view, the ossification of the posterior part of the iliac apophysis was quantified at four grades: absent (A), partial (B), complete (C) or fused (D). The position of the posterior superior iliac spine was studied on both views as well as in pelvic specimens. The results showed that the posterior one-third portion of the iliac apophysis was sagittally oriented and obscured on the frontal radiograph by the sacroiliac junction. It could be studied on the lateral radiograph and revealed a different grading of the apophysis excursion in 58 of 201 (29%) patients, comparing to the frontal view. Both advanced or delayed ossification was observed and assessed with Lateral Risser Modifiers. Twenty-five percent of the patients at Risser 0 or 1 or 2 demonstrated a simultaneous ossification of the most anterior and the most posterior part of the iliac crest. The Risser grades of capping or fusion could be more precisely diagnosed using lateral radiograph in complement to the frontal one. The conclusions drawn from this study were: (1) Currently used Risser sign grading does not consider the actual excursion of the iliac apophysis, because one-third of the apophysis cannot be observed on the frontal radiograph. (2) Iliac apophysis full excursion or fusion can be more accurately estimated when the lateral spinal radiograph is analyzed with Lateral Risser Modifiers.