Background/Purpose:  Inflammation in osteoarthritis (OA) is the basis for the use of steroid injection therapy which has demonstrated efficacy for symptoms of hip OA in a randomized placebo-controlled trial¹. Both synovitis and bone marrow lesions (BML) have been associated with pain in OA and can be detected on MRI. Two scoring methods have been developed which assess synovitis-effusion but score BML using different approaches: 1) the Hip Inflammation MRI Scoring System (HIMRISS) assesses BML using consecutive images in the coronal plane and a dichotomous (yes/no) scoring method; 2) the Hip Osteoarthritis MRI Scoring System (HOAMS) is a whole joint scoring system which assesses BML according to volume of region affected on both coronal and sagittal scans.  We aimed to determine the reliability and responsiveness of both methods for detecting change in these MRI lesions and associations with clinical changes in patients receiving steroid injection therapy.

Methods:  Six readers (3 radiologists, 3 rheumatologists) assessed MRI scans of hip joints from 18 patients enrolled into a randomized double-blinded placebo-controlled trial of intra-articular steroid treatment for hip OA.  Scans were performed at baseline and the primary endpoint at 8 weeks.  Coronal STIR sequences of the hip joints were evaluated. For HIMRISS, the sum of femoral BML scores (0-65), acetabular BML scores (0-35), effusion score (0-30) and total score was calculated based on femoral and acetabular subregion readings. In HOAMS, BML (0-3) and synovitis (0-2), were assessed in femoral and acetabular subregions and summed scores for all subregions were calculated for BML (0-45) and synovitis (0-8). Reliability of change scores was assessed using intra-class correlation coefficient (ICC), responsiveness by standardized response mean (SRM) and Guyatt’s effect size (ES). We assessed associations with WOMAC pain subscale in the same patients and a second cohort of 27 patients with early OA by regression analysis.

Results:  Inter-observer reliability of change scores was very good to excellent for femoral BML, and good to very good for synovitis-effusion and acetabular BML despite limited training. Reliability was comparable between radiologists and rheumatologists. Responsiveness and discrimination was moderate to high for synovitis-effusion. Significant associations were noted between BML or synovitis scores and pain scores for baseline values (p ≤ 0.001 in combined N=45) but not change values (N=18). The association with pain was particularly evident in patients with early OA (N=27) with the HIMRISS synovitis-effusion (p = 0.001) and HOAMS synovitis (p = 0.005) scores.

	ICC (change)	ICC (Rheumatologist)	ICC (Radiologist)	SRM	Guyatt’s ES
Total HIMRISS Femoral BML HIMRISS Acetabular BML HIMRISS Synovitis-effusion HIMRISS	0.77 0.81 0.49 0.35	0.76 0.80 0.52 0.48	0.82 0.82 0.54 0.36	0.16 0.03 0.14 0.55	0.33 0.08 0.19 0.69
HOAMS BML HOAMS Synovitis	0.71 0.58	0.73 0.58	0.71 0.69	0.18 0.44	0.29 0.95

Conclusion: Change in BML and synovitis on MRI is reliably detected using both HOAMS and HIMRISS but only synovitis scores are responsive to treatment. Association with pain is primarily evident in early OA and with scores for synovitis-effusion.

1. Lambert et al. Arthritis Rheum 2007; 56: 2278

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/reliability-and-responsiveness-of-two-methods-for-assessment-of-magnetic-resonance-imaging-abnormalities-in-hip-osteoarthritis-in-a-placebo-controlled-trial-of-intra-articular-steroid-injection/