Vol.23 No.4

Original Article

MR-defined fat infiltration of the lumbar paravertebral muscles differs between non-radiographic axial spondyloarthritis and established ankylosing spondylitis

Authors

Ozgur Akgul1 , Arif Gulkesen2 , Gurkan Akgol2 , Salih Ozgocmen1

  • Division of Rheumatology, Department of PMR, Faculty of Medicine, Gevher Nesibe Hospital, Erciyes University, 38039 Kayseri, Turkey
  • Department of PMR, Faculty of Medicine, Firat University, Elazig, Turkey
Received:

6 July 2012

Accepted:

17 August 2012

Published online:

13 September 2012

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Abstract

Objective The aim of our study was to compare the magnetic resonance imaging (MRI)-defined cross-sectional area and semi-quantitative grading of fatty degeneration of lumbar paravertebral muscles in patients with non-radiographic axial spondyloarthritis (nr-axSpA) and established ankylosing spondylitis (AS).
Methods Cross-sectional area (CSA) of lumbar paravertebral muscles, including the right and left multifidus (MF), erector spina (ES), psoas (PS), vertebral body and muscle:vertebra ratio (MVr), was measured. Fat infiltration of the paravertebral muscles was graded semi-quantitatively.
Results The CSA of the MF, ES and PS muscles and the MVr (at the L2, L3, L4 and L5 levels) were quite similar between patients with nr-axSpA (n = 14) and AS (n = 22). However, patients with AS had higher grades of fat infiltration than those with nr-axSpA (Right L4 grading of MF ? ES muscles: 1.4 ± 0.73 vs. 0.51 ± 0.52, respectively, p = 0.001; left L4 grading: 1.36 ± 0.65 vs. 0.38 ± 0.50, respectively, p%ABST%.0001). This difference remained significant after adjusting for age and symptom duration. The inter-rater reliability was good (intraclass correlation coefficient 0.75 and 0.85).
Conclusions This is first study demonstrating that MRIdefined fatty degeneration differs between patients with nr-axSpA and established AS. Semi-quantitative grading is reliable, and fatty degeneration of paravertebral muscles seems to be related to chronicity and spinal functions in patients with nr-axSpA and AS.

Key words

Ankylosing spondylitis, Paravertebral muscle, Fat infiltration, Magnetic resonance imaging