European Spine Journal

, Volume 28, Issue 3, pp 559–566 | Cite as

The “Risser+” grade: a new grading system to classify skeletal maturity in idiopathic scoliosis

  • M. J. Troy
  • P. E. Miller
  • N. Price
  • V. Talwalkar
  • F. Zaina
  • S. Donzelli
  • S. Negrini
  • M. T. HreskoEmail author
Original Article



This study aims to propose and validate a new unified “Risser+” grade that combines the North American (NA) and European (EU) variants of the classic Risser score. The “Risser+ ” grade can effectively combine the North American and European Risser Classifications for skeletal maturity with adequate intra-rater/inter-rater reliability and agreement.


Agreement and reliability were evaluated for 6 raters (3-NA, 3-EU) who assessed 120 pelvic radiographs from the BrAIST trial, all female, average age 13.4 (range 10.1–16.5 years). Blinded raters reviewed x-rays at two time-points. Intra- and inter-rater agreement (RA) were established with Krippendorff’s alpha (k-alpha), while intra- and inter-rater reliability (RR) were established with intraclass correlation coefficients (ICC). Acceptable agreement and reliability were set a priori at 0.80.


Inter-RA for the second reading met study requirements (k-alpha = 0.86 [0.81–0.90]) compared to the first reading (0.72 [0.63–0.79]) while combined readings was close to target agreement (0.79 [0.74–0.84]). Removal of 20 readings demonstrating outlier tendencies increased agreement for the first, second, and combined reads (k-alpha = 0.85, 0.89, 0.87, respectively). Intra-RA was sufficient for 4 out of 6 raters (k-alpha > 0.80) and one rater from EU and NA presented subpar intra-RA (k-alpha = 0.64 and 0.74, respectively). Inter-RR met study requirements overall reads (ICC = 0.96 [0.95–0.97]) including the first (0.94 [0.92–0.95]) and second (0.97 [0.97–0.98]) reads, independently.


The Risser+ system showed excellent reliability across multiple reads and raters and demonstrated 79% agreement overall reads and ratings. Agreement increased to over 85% when raters could distinguish Risser 0 + from Risser 5.

Graphical abstract

These slides can be retrieved from electronic supplementary material.


Risser Scoliosis Idiopathic scoliosis Skeletal age 


Compliance with ethical standards

Conflict of interest

The authors declare that they have no conflict of interest.

Supplementary material

586_2018_5821_MOESM1_ESM.pptx (9.1 mb)
Supplementary material 1 (PPTX 9268 kb)


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Copyright information

© Springer-Verlag GmbH Germany, part of Springer Nature 2018
corrected publication 2019

Authors and Affiliations

  • M. J. Troy
    • 1
  • P. E. Miller
    • 1
  • N. Price
    • 2
  • V. Talwalkar
    • 3
  • F. Zaina
    • 4
  • S. Donzelli
    • 4
  • S. Negrini
    • 5
    • 6
  • M. T. Hresko
    • 1
    Email author
  1. 1.Boston Children HospitalHarvard Medical SchoolBostonUSA
  2. 2.Children’s Mercy HospitalKansas CityUSA
  3. 3.Shriners HospitalLexingtonUSA
  4. 4.ISICO - L’Istituto Scientifico Italiano Colonna VertebraleMilanItaly
  5. 5.University of BresciaBresciaItaly
  6. 6.IRCCS Fondazione Don Carlo GnocchiMilanItaly

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