Risser Sign
Original Editor - Naomi O'Reilly
Top Contributors - Naomi O'Reilly and Khloud Shreif
Introduction
The Risser Sign is a critical radiographic indicator used in orthopedic medicine to assess skeletal maturity and predict the progression of spinal deformities, such as scoliosis.[1] Named after Dr. Joseph C. Risser[2], this sign evaluates both the ossification and fusion of the iliac apophysis, a growth plate on the pelvis.
Anatomy and Physiology
The iliac crest is the uppermost part of the pelvis, and its growth plate (the iliac apophysis) ossifies in a predictable manner during adolescence. This ossification begins laterally, near the anterior superior iliac spine, and progresses medially toward the posterior iliac spine. The Risser Sign grades this process, correlating it with the overall skeletal maturity of the individual.
The Grading Systems
The Risser Sign, traditionally graded from 0 to 5, has differentiated into North American and European versions as shown below; [3]
North American Risser Grades
In North America the Risser Grade divides the ossifcation of the iliac wing into quarters with complete apophysis fusion to the iliac wing occurring at Risser Grade 5.
Grade 0: No ossification of the iliac apophysis (indicates early skeletal growth).
Grade 1: Ossification begins, covering 0-25% of the iliac crest.
Grade 2: Ossification progresses to 26-50% of the crest.
Grade 3: Ossification extends to 51-75% of the crest.
Grade 4: Ossification completes (76-100%), but the growth plate has not yet fused.
Grade 5: The iliac apophysis is fully fused with the ilium, indicating the end of skeletal growth.
European Risser Grades
In the European version, the ossifcation is broken into thirds, where Risser Grade 4 denotes the apophysis beginning to fuse to the iliac wing, and Grade 5 represents the conclusion of the fusion to the iliac wing.
Grade 0: No ossification center at the level of iliac crest apophysis (indicates early skeletal growth).
Grade 1: Apophysis under 33% of the iliac crest
Grade 2: Apophysis over 33-66% of the iliac crest
Grade 3: Apophysis over >66% of the iliac crest
Grade 4: Complete ossification of the iliac crest
Grade 5: Complete fusion of the iliac crest apophysis
Risser+
A new unified “Risser+” is an 8-point scale that combines the above North American and European variants of the Risser Sign and incorporate triradiate acetabular cartilage development in order to weigh non-operative and operative treatment options for idiopathic scoliosis. [3]
Grade 0-: Tri-radiate Cartilage not ossified.
Grade 0+: Tri-radiate Cartilage closed.
Grade 1: 0 - 25% coverage
Grade 2: 25 - 50% coverage
Grade 3: 50 - 75% coverage
Grade 3/4: 75 - 100% coverage
Grade 4: Start of fusion
Grade 5: Complete fusion [3]
Clinical Importance
Scoliosis Monitoring
- The Risser sign is most commonly used in the management of adolescent idiopathic scoliosis (AIS). The risk of scoliosis progression is highest during rapid skeletal growth. A lower Risser Grade (0–2) indicates ongoing growth and a higher likelihood of curve progression, whereas a higher Risser Grade (3-5) signals reduced growth potential and less risk of progression.
Growth and Maturity Assessment
- Besides scoliosis, the Risser Sign aids in evaluating skeletal maturity in conditions requiring a precise understanding of growth, such as limb length discrepancies or certain endocrine disorders.
Treatment Decisions
- Orthopedic interventions, such as bracing for scoliosis, are influenced by the Risser Grade. For instance, bracing is typically more effective in individuals with open growth plates (lower Risser Grades).
Variability in Interpretation
While the Risser Sign is a valuable tool, its interpretation may vary due to differences in ossification patterns across populations. Notably, the differences in the North American Risser Grading System and European Risser System as highlighted above, has led to confusion in the medical literature. [3][4]
Physicians must also consider other indicators, such as the Tanner Stages of Sexual Maturity, chronological age, and puberty history for a comprehensive assessment.
Imaging and Technique
The Risser Sign is typically evaluated on an anteroposterior (AP) pelvic X-ray. Accurate positioning and visualisation of the iliac crest are crucial for reliable grading. Advances in imaging techniques, such as digital radiography, have improved the clarity of apophyseal visualization, aiding precise grading.
Limitations
While the Risser Sign provides valuable insights, it has limitations.
- It can be subject to interobserver variability.
- It is not a direct measure of vertebral growth or curve progression but an indirect estimate of skeletal maturity.
- Some conditions, such as endocrine or metabolic disorders, may alter ossification patterns, making the Risser Sign less reliable.[1]
Conclusion
The Risser Sign remains a cornerstone in assessing skeletal maturity and guiding treatment decisions in scoliosis and other growth-related conditions. Understanding its grading system, clinical applications, and limitations allows healthcare professionals to make informed decisions and provide optimal care for adolescent patients.
References
- ↑ 1.0 1.1 Risser J. The Classic: The Iliac Apophysis: An Invaluable Sign in the Management of Scoliosis. Clinical Orthopaedics & Related Research. 2010;468(3):646-53. doi:10.1007/s11999-009-1096-z
- ↑ Hacquebord JH, Leopold SS. In brief: the Risser classification: a classic tool for the clinician treating adolescent idiopathic scoliosis.
- ↑ 3.0 3.1 3.2 3.3 Troy MJ, Miller PE, Price N, Talwalkar V, Zaina F, Donzelli S, Negrini S, Hresko MT. The “Risser+” grade: a new grading system to classify skeletal maturity in idiopathic scoliosis. European Spine Journal. 2019 Mar 5;28:559-66.
- ↑ Bitan FD, Veliskakis KP, Campbell BC (2005) Diferences in the Risser grading systems in the United States and France. Clin Orthop Relat Res 436:190–195