The Risser classification is used to grade skeletal maturity based on the level of ossification and fusion of the iliac crest apophyses.
- stage 0: no ossification center at the level of iliac crest apophysis
- stage 1: apophysis under 25% of the iliac crest
- stage 2: apophysis over 25-50% of the iliac crest
- stage 3: apophysis over 50-75% of the iliac crest
- stage 4: apophysis over >75% of the iliac crest
- stage 5: complete ossification and fusion of the iliac crest apophysis
As stage 0 and stage 5 can appear similarly, age and long bone growth plates may be of help in discriminating the two. A patient with stage 0 will still have open growth plates in most of the long bones and will likely be younger than age 16 (female) or 18 (male). A patient with stage 5 will have no open growth plates in the long bones.
Above mentioned is the U.S. Risser staging system. The French Risser staging system has stage 4 representing complete ossification and fusion and divides the partial fusion in three thirds, i.e. stage 1-2-3 representing 0-33%, 33-66% and >66% of fusion.