Background/Purpose: Joint space width (JSW) is suggested as an indirect measure of arthritis disease activity and could be used as a measure of radiographic progression with consequent narrowing and cartilage loss. The current gold standard for assessing rheumatoid arthritis (RA) radiographic damage is a semi-quantitative analysis by trained physicians where JSW is calculated from radiographs [Sharp, 2005].  Alternative methods include ultrasound [Möller, 2009] and magnetic resonance imaging [Peterfy, 2013] for radiation-free visualisation, and high resolution peripheral quantitative computed tomography (HR-pQCT) for three-dimensional (3D) quantification [Barnabe, 2013; Burghardt, 2013]. HR-pQCT is a novel imaging instrument for bony damage in RA, and is undergoing validation as an outcome measurement tool. In this work, three published techniques for high-throughput, robust, and reproducible measurement of JSW from HR-pQCT derived data are compared and contrasted, in order to reach consensus on a new standard in arthritis damage assessment.

Methods: The second and third metacarpophalangeal joints (MCP) of 30 RA and control subjects (n=60 joints) were imaged at three sites – 10 from the University of Lyon (LYN), 9 from the University of California San Francisco (SFR), and 11 from the University of Calgary (CLG) – using an XtremeCT I (Scanco Medical AG, Switzerland) and the agreed Study grouP for xtrEme Computed Tomography in Rheumatoid Arthritis (SPECTRA) protocol [Barnabe, 2012]. The data was then segmented to remove bone from background, and 3D JSW was calculated using each of three in-house methods [Barnabe, 2013; Burghardt, 2013; Boutroy, 2013].  The minimum, maximum and mean JSW were compared, and the intraclass correlation coefficients (ICC) calculated.

Results: The results demonstrate a high ICC (upper 95%CI, lower 95%CI) for minimum JSW of 0.986 (0.978, 0.991) between the three methods, with the ICC for mean JSW at 0.981 (0.971, 0.988), and for maximum JSW at 0.910 (0.861, 0.944).

Conclusion: The high correlation between the 3D methods suggest that they all calculate a minimum JSW from approximately the same volume of interest, while variation increases for mean and maximum JSW values which is directly related to the volume of interest and segmentation methods used in the individual methods. The goal in developing these methods is to detect arthritis change through longitudinal monitoring of patients.  In this work three methods for assessing JSW are compared in order to reach consensus on a high-throughput, robust, and reproducible measurement of JSW from HR-pQCT.

References: Sharp et al, J. Rheumatol, 32: 2456-61, 2005. Möller et al, Arthritis Care Res, 61: 435-41, 2009. Peterfy et al. Arthritis Res Ther 15: R44, 2013 Barnabe et al. Med Eng Phys 35: 1540-4, 2013. Barnabe et al, J Rheumatol, 39 : 1494-5, 2012. Burghardt et al. Ann Biomed Eng 41: 2553-64, 2013. Boutroy et al. Arthr Rheum 65(10):S840, 2013.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/reaching-consensus-volumetric-joint-space-width-calculations-in-finger-joints-of-arthritis-patients/