In 1958 Dr Joseph Risser made an important observation while looking at an Xrays of the pelvis of adolescents with Scoliosis.
He recognised that as the growth plate on top of the pelvis, completed growing it changed from cartilage to bone. Bone would first appear at the outer border of the growth plate and then progress inwards as growth neared completion
This takes 2 years on xray this bone appears like a cap on top of the pelvis. When a bone first appears a prediction can be made that an average growth of 2 years remains. The cap can then be followed like the hands of a clock from the outer aspect of the pelvis inward. Risser divided the appearance of this bony cap into 4 sections, when 25% of the bony cap can be seen on xray it is described as "Risser I", 50% is "Risser II", 75% is "Risser III", 100% "Risser IV". The final stage being "Risser V" when the space between the cap and the pelvis fills in completley with bone.
Most physicians agree that by the time "Risser 3" the patient has passed the peak of the "growth spurt" (a period of rapid spinal growth during which Scoliosis curves can increase rapidly).
Skeletal maturity can be assessed by the Risser sign. A radiograph is employed to see how far the patient's iliac apophysis (Orange) has progressed from the anterior superior iliac spine (Green). During development, the iliac apophysis first appears laterally and grows medially. The stages are Risser I through Risser V, where Risser V denotes that the apophysis has completely fused with the iliac crest and therefore skeletal maturity can be assumed.
Rissers Sign - evaluation of the iliac apophysis. Closure of the iliac crest apophysis occurs from anterior (zone 1) to posterior (zone 4).