title: Functional MRI demonstrates pain perception in hand osteoarthritis has features of central pain processing.
abstract: BACKGROUND
  Hand osteoarthritis (HOA) is typified by pain and reduced function. We hypothesised that people with HOA have enhanced sensitivity and activation of peripheral nociceptors in the hand, thereby potentiating chronic pain. In our study we aimed to assess if central sensitisation mediates pain perception in osteoarthritis of the hand.
  
  
  METHODS
  Participants with proximal and distal interphalangeal joint (PIP/DIP) HOA and non-OA controls were recruited. Clinical pain scores using the visual analogue scale (VAS) were recorded before and after performing a painful hand task. Central pain processing was evaluated with functional brain neuroimaging (fMRI) using a finger flexion-extension (FFE) task performed over 3 minutes. Data was analysed with FMRIB software (www.fmrib.ox.ac.uk/fsl). Group mean activation of functional MRI signal between hand osteoarthritis and control non-arthritic participants was compared.
  
  
  RESULTS
  Our group of hand OA participants reported high pain levels compared with non-arthritic controls as demonstrated by the mean VAS in hand OA participants of 59.31± 8.19 mm compared to 4.00 ± 1.89 mm in controls (p< 0.0001), despite all participants reporting analgesic use. Functional MRI analysis showed increased activation in the thalamus, cingulate, frontal and somatosensory cortex in the hand OA group but not in controls (thresholded atp< 0.05). Regions of activation were mapped to Brodmann areas 3, 4, 6, 9, 13, 22, 24 and 44. Activated regions found in our study are recognised higher brain pain processing centres implicated in central sensitisation.
  
  
  CONCLUSIONS
  People with hand osteoarthritis demonstrated features of central sensitisation that was evident after a finger flexion-extension task using functional MRI. Functional MRI is a useful biomarker in detecting pain in hand osteoarthritis and could be used in future hand osteoarthritis pain studies to evaluate pain modulation strategies.
authors.affiliation: Division of Biomedical Sciences, St George's, University of London, Cranmer Terrace, London, UK.
authors.forename: Nidhi
authors.initials: N
authors.lastname: Sofat
authors.forename: Cori
authors.initials: C
authors.lastname: Smee
authors.forename: Monika
authors.initials: M
authors.lastname: Hermansson
authors.forename: Matthew
authors.initials: M
authors.lastname: Howard
authors.forename: Emma H
authors.initials: EH
authors.lastname: Baker
authors.forename: Franklyn A
authors.initials: FA
authors.lastname: Howe
authors.forename: Thomas R
authors.initials: TR
authors.lastname: Barrick
keywords: Central sensitisation; Hand osteoarthritis; Pain functional magnetic resonance imaging