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Skeletal Radiol. 2011 Mar;40(3):303-7. doi: 10.1007/s00256-010-1000-7. Epub 2010 Jul 25.

Grading the severity of soft tissue changes associated with metal-on-metal hip replacements: reliability of an MR grading system.

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1
Department of Radiology, Norfolk and Norwich University Hospital, Colney Lane, Norwich, Norfolk, NR4 7UY, UK.

Abstract

INTRODUCTION:

Metal-on-metal (MoM) soft tissue reactions or aseptic lymphocytic vasculitis-associated lesions (ALVAL) are being recognised using metal artefact reduction (MAR) MR with increasing frequency following the advent of second generation metal-on-metal bearings, but there is no standardised technique for reporting of MR appearances in this disease. The aim of this study was to measure the reliability of a grading system designed for scoring the severity of MoM disease on MRI.

MATERIALS AND METHODS:

MRI examinations of 73 hips in 59 patients were retrospectively selected and then anonymised, randomised and reviewed by three independent observers (musculoskeletal radiologists). Each MR examination was scored as either A: normal, B: infection, C1: mild MoM disease, C2: moderate MoM disease or C3: severe MoM disease according to pre-defined criteria. Kappa correlation statistics were used to compare the observations.

RESULTS:

There was substantial agreement among all three observers; the correlation coefficient between the two most experienced observers was κ = 0.78 [95% confidence intervals (CI): 0.68-0.88] and when compared with the least experienced observer coefficients were κ = 0.69 (95% CI: 0.57-0.80) and κ = 0.66 (95% CI: 0.54-0.78). The strongest correlation occurred for grades A, C2 and C3. The weakest correlations occurred for grades B and C1.

CONCLUSION:

The grading system described in this study is reliable for evaluating ALVAL in MoM prostheses using MR but is limited in differentiating mild disease from infection.

PMID:
20658133
DOI:
10.1007/s00256-010-1000-7
[Indexed for MEDLINE]
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