FRI0596 Feasibility of joint structural analysis in hemochromatosis hand arthropathy using high-resolution peripheral quantitative computed tomography – first results and clinical correlations
Authors: U.R. Heilmeier, A.J. Burghard, P. Kapoor, R.E. Voll, S. Finzel
Journal: Annals of the Rheumatic Diseases (2018)

<h3>Background</h3> Hereditary Hemochromatosis (HH) is a common inherited disorder and characterised by an excess iron accumulation in several organs with consecutive organ dysfunction.<sup>1</sup> Apart from the liver, the joints are a major site of excess iron deposition. Joint pain counts among the most frequent (&gt;50%), earliest, and most debilitating symptoms of HH.<sup>2</sup> To date, joint health status in HH patients is routinely assessed on hand radiographs.<sup>3</sup> However, plain radiography is a low-resolution, 2D-technique with limited sensitivity to detect early joint changes or to monitor subtle progression of joint damage.<sup>4</sup> With the advent of high-resolution peripheral quantitative computed tomography (HR-pQCT), a promising imaging tool has emerged allowing for <i>in vivo</i> 3D characterisation of human joint microstructure at a spatial resolution of 130 µm.<sup>5</sup> Due to its high sensitivity to detect and monitor subtle, short-term joint changes, HR-pQCT has been successfully applied to patients with RA.<sup>6</sup> However, to date, HR-pQCT has not been used to characterise joint and bone changes seen in HH arthropathy. <h3>Objectives</h3> Here, we aimed to investigate in a cohort of HH patients 1) if the usage of HR-pQCT is feasible on HH patients; 2) to quantify joint microstructure of metacarpophalangeal joints (MCP2–4) in this specific patient group; and 3) investigate the relationship between HR-pQCT-derived joint microstructural parameters and clinical outcomes. <h3>Methods</h3> 25 HH patients were enrolled and their HH history and treatment were recorded. MCP joints of all patients were imaged at a clinical HR-pQCT system (XtremeCT, Scanco Medical AG). 330 images were acquired covering MCP 2, 3 and 4. The joint space (JS) morphology of each MCP was quantified from the HR-pQCT images semi-automatically<sup>4</sup> and volume (JSV), joint space width mean (JSW), JSW variance (JSW.SD), and JSW asymmetry (JSW.AS) were calculated. <h3>Results</h3> Out of the 75 MCP joints available for analysis, 79% were successfully segmentable, and 19% required semi-manual intervention to separate the individual bones. 3 joints were excluded due to motion artefacts, and 1 joint was unsegmentable. HH patients were 32–72 years old, in 64% male, and had been diagnosed with HH 2 months to 40 years ago. 15% were pain free at the study date. HH patients with pain showed significantly lower JSV at MCP 2 and 4 (p=0.009) and exhibited a significantly higher joint asymmetry in MCP 3 (p=0.012) compared to their pain free colleagues. When looking at clinical correlations we found that time since HH diagnosis was positively correlated with the MCP4 JSW asymmetry (R<sup>2</sup>=0.451, p=0.040) and MCP 4 JSW.SD (R<sup>2</sup>=0.475, p=0.030). The number of phlebotomies since diagnosis was strongly correlated with the JSW.SD (MCP2–4: 0.4552&lt;0.581,p&lt;0.050) at all MCP sites. <h3>Conclusions</h3> Our study provides the first evidence that joint space assessment of MCPs via HR-pQCT in patients with hereditary hemochromatosis is feasible and can provide a thorough structural joint characterisation and thus support the physician in his initial HH arthropathy assessment. Our findings suggest, that regular phlebotomies since diagnosis may preserve joint space morphology leading to a more evenly maintained joint space. However, larger studies are needed to validate our results. <h3>Disclosure of Interest</h3> None declared