title: Metacarpal Index Estimated by Digital X-ray Radiogrammetry as a Tool for Differentiating Rheumatoid Arthritis Related Periarticular Osteopenia.
abstract: To investigate Metacarpal Index (MCI) and Bone Mineral Density (BMD) estimated by Digital X-ray Radiogrammetry (DXR) with respect to its ability to quantify severity-dependent variations of bone mineralisation in patients with early rheumatoid arthritis compared to Dual Energy X-ray Absorptiometry (DXA), 122 patients underwent a prospective analysis of BMD and MCI by DXR, whereas both DXR-parameters were estimated from plain radiographs of the non-dominant hand. In comparison DXA measured BMD on total femur and lumbar spine (L2-L4). Additionally Steinbrocker Stage was assessed to differentiate the severity of rheumatoid arthritis (RA). Disease activity of RA was estimated by C-reactive Protein (CRP; in mg/l), Erythrocyte Sedimentation Rate (ESR in mm/1st hour) and by the disease activity score with 28-joint count (DAS 28). In consequence, The DXR-parameters, in particular DXR-MCI, revealed significant associations to age, Body Mass Index, CRP, DAS 28 and Steinbrocker graduation; no significant associations could be verified between DXA-parameters and all characteristics of disease activity and severity of RA. The highest correlation was found between DXR-MCI and DXR-BMD with R=0.89 (independent from severity of RA). In all patients DXR-MCI significantly decreased (-14.3%) from 0.42 ± 0.09 (stage 1) to 0.36 ± 0.07 (stage 2) dependent on severity of RA. The comparable relative reduction of DXR-BMD was -11.1%. The group of patients with minor disease activity (DAS 28>5.1) showed a significant flattened reduction (-11.4%) for DXR-MCI from 0.44 ± 0.08 (stage 1) to 0.39 ± 0.08 (stage 2). For accentuated disease activity (DAS 28>5.1) the DXR-MCI revealed a pronounced reduction (-23.1 %). No significant declines were observed for DXA-BMD of the lumbar spine and total femur in all patients as well as dependent on disease activity.
  
  
  CONCLUSIONS
  DXR can exactly quantify cortical thinning of the metacarpal bones and can identify cortical demineralisation in patients suffering from early rheumatoid arthritis surpassing DXA-measurements at axial bone sites. In this context DXR-MCI seems to be the most sensitive parameter for differentiation of patients with minor or accentuated disease activity following severity-dependent cortical bone loss.
authors.affiliation: Institute of Diagnostic and Interventional Radiology, Friedrich Schiller University Jena Erlanger Allee, Jena, Germany;
authors.forename: Joachim
authors.initials: J
authors.lastname: Böttcher
authors.forename: Alexander
authors.initials: A
authors.lastname: Pfeil
authors.forename: Alexander
authors.initials: A
authors.lastname: Petrovitch
authors.forename: Mirco
authors.initials: M
authors.lastname: Schmidt
authors.forename: Anika
authors.initials: A
authors.lastname: Kramer
authors.forename: Max Ludwig
authors.initials: ML
authors.lastname: Schäfer
authors.forename: Mieczyslaw
authors.initials: M
authors.lastname: Gajda
authors.forename: Gert
authors.initials: G
authors.lastname: Hein
authors.forename: Gunter
authors.initials: G
authors.lastname: Wolf
authors.forename: Werner A
authors.initials: WA
authors.lastname: Kaiser
keywords: bone mineral density; digital X-ray radiogrammetry; dual energy X-ray absorptiometry; metacarpal index; rheumatoid arthritis; steinbrocker stage