Background Synovitis is a pain generator in patients with osteoarthritis and associated with upregulation of pro-inflammatory cytokines, which have been found to lead to pain sensitivity and worse self-reported pain(1).
Objectives This study aimed to investigate the association between pre- and perioperative synovitis from imaging and histology and self-reported pain 12 months after total knee arthroplasty (TKA).
Methods Preoperative synovitis was assessed from MRI data of the knee by 11 point synovitis score a.m Guermazi (2) using contrast enhanced MRI (CE-synovitis) and heuristic time intensity curve analysis of the dynamic contrast enhanced MRI (DCE-MRI) data using the DYNAMIKA® software (Image Analysis group, London) providing Dynamic Enhanced MR Quantification (DEMRIQ) Indices (3). Perioperative synovitis was also assessed from biopsies of the synovium in 6 predefined places graded histologically a.m Krenn (4). Worst pain within the last 24-hours (visual analog scale, VAS, 0-100) was assessed before and 12 months after TKA. Patients were divided into a low-pain (VAS≤30) and a high-pain (VAS>30) group based on 12-months postoperative VAS.
Results Twenty-six patients had full pre- and postoperative data and were analysed. The high-pain group had significantly lower CE-synovitis (P=0.03), DCE-MRI inflammation indices (DEMRIQ-inflammation) (P<0.03) and a trend towards lower histologically assessed synovitis grades (P=0.077) compared to the low-pain group at baseline. Preoperative synovitis scores were also inversely correlated with pain 12-months after TKA, CE-synovitis (R = - 0.455, P = 0.022) and DCE-MRI inflammation (R = -0.528, P = 0.007), indicating that more severe preoperative synovitis is associated with less severe pain at 12-months.
Conclusion Higher preoperative synovitis scores are associated with less postoperative pain 12-months after TKA. Further, correlation analysis revealed that less severe preoperative synovitis was associated with worse pain 12-months after TKA, suggesting that CE and DCE-MRI synovitis quantification could be used as imaging markers for prediction of good surgical outcomes.
References  Schaible HG. Nociceptive neurons detect cytokines in arthritis. Arthritis Res. Ther. 2014:470.
 Guermazi A, et al. Assessment of synovitis with contrast-enhanced MRI using a whole-joint semiquantitative scoring system in people with, or at high risk of, knee osteoarthritisAnn. Rheum. Dis. 2011
 Riis RGC, et al. The association between histological, macroscopic and magnetic resonance imaging assessed synovitis in end-stage knee osteoarthritis Osteoarthr. Cartil. 2017;
 Krenn V, et al. Grading of chronic synovitis-a histopathological grading system for molecular and diagnostic pathology. Pathol. Res. Pract. 2002
Acknowledgement Image Analysis Group, for providing DYNAMIKA software and support for the DCE-MRI/DEMRIQ analysis
Disclosure of Interests Kristian Kjær Petersen: None declared, Lars Arent-Nielsen: None declared, Mikael Boesen Shareholder of: Image Analysis Group, UK, Grant/research support from: Image Analysis Group, UK, OAK Foundation, EUROSTAR, Consultant for: Esaote, Eli Lilly, Celgene, Carestream, UCB, Abbvie, Pfizer, Astra Zeneka, Roche, Siemens, Image Analysis Group, Jonathan Vela: None declared, Soeren Skou: None declared, Mikkel Eld: None declared, Nasir Musa Al-Mashkur: None declared, Robert Riis Consultant for: Image analysis Group, Ole Simonsen: None declared
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