The relationship between quantitative measures of disc height and disc signal intensity with Pfirrmann score of disc degeneration.

Sara Salamat,John Hutchings,Mark J Hancock,Clemens Kwong,John Magnussen

doi:10.1186/s40064-016-2542-5

Sara Salamat, John Hutchings + Show 3 more

Open Access

https://doi.org/10.1186/s40064-016-2542-5

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Abstract

PurposeTo assess the relationship between quantitative measures of disc height and signal intensity with the Pfirrmann disc degeneration scoring system and to test the inter-rater reliability of the quantitative measures.MethodsParticipants were 76 people who had recently recovered from their last episode of acute low back pain and underwent MRI scan on a single 3T machine. At all 380 lumbar discs, quantitative measures of disc height and signal intensity were made by 2 independent raters and compared to Pfirrmann scores from a single radiologist. For quantitative measures of disc height and signal intensity a “raw” score and 2 adjusted ratios were calculated and the relationship with Pfirrmann scores was assessed. The inter-tester reliability of quantitative measures was also investigated.ResultsThere was a strong linear relationship between quantitative disc signal intensity and Pfirrmann scores for grades 1–4, but not for grades 4 and 5. For disc height only, Pfirrmann grade 5 had significantly reduced disc height compared to all other grades. Results were similar regardless of whether raw or adjusted scores were used. Inter-rater reliability for the quantitative measures was excellent (ICC > 0.97).ConclusionsQuantitative measures of disc signal intensity were strongly related to Pfirrmann scores from grade 1 to 4; however disc height only differentiated between grade 4 and 5 Pfirrmann scores. Using adjusted ratios for quantitative measures of disc height or signal intensity did not significantly alter the relationship with Pfirrmann scores.

Highlights

The clinical importance of lumbar disc degeneration as measured on MRI remains controversial and uncertain
Reliability of quantitative measures The reliability values were excellent for both disc height and signal intensity measures, regardless of whether the raw scores were used or either of the 2 ratios
Relationship between quantitative measures of disc height and Pfirrmann score The relationship between the 3 quantitative measures of disc height can be seen in Table 3 and Fig. 2

Summary

Introduction

The clinical importance of lumbar disc degeneration as measured on MRI remains controversial and uncertain. The most widely used assessment of disc degeneration is the 5-grade classification system of disc degeneration proposed by Pfirrmann et al (2001) This grading system is primarily based on changes in signal. To overcome some of these limitations quantitative measures of disc degeneration on MRI have been developed and used. These quantitative measures most commonly include measurement of the signal intensity of nucleus pulposus and the disc height (Videman et al 2008; Tunset et al 2013; Watanabe et al 2007; Niemeläinen et al 2008). Quantitative measurements are generally reported to have excellent reliability (Videman et al 2008; Teichtahl et al 2015) and are more sensitive to change than traditional subjective scales

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