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. Hresko

March 2019, Volume 28, Issue 3, pp 559 - 566 Original Article Read Full Article

First Online: 16 November 2018

Purpose

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.

Methods

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.

Results

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.

Conclusions

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.[Figure not available: see fulltext.]

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