Quantitative magnetic resonance imaging as marker of synovial membrane regeneration and recurrence of synovitis after arthroscopic knee joint synovectomy: a one year follow up study

Objectives-By repeated magnetic resonance imaging (MRI) to study synovial m embrane regeneration and recurrence of synovitis after arthroscopic knee jo int synovectomy in patients with rheumatoid arthritis (RA) and other (non-R A) causes of persistent knee joint synovitis. Methods-Contrast enhanced MRI was performed in 15 knees (nine RA, six non-R A) before and one day, seven days, two months, and 12 months after arthrosc opic synovectomy. Synovial membrane volumes, joint effusion volumes, and ca rtilage and bone destruction were assessed on each MRI set. Baseline micros copic and macroscopic assessments of synovitis and baseline and follow up s tandard clinical and biochemical examinations were available. Results-Synovial membrane and joint fluid volumes were significantly reduce d two and 12 months after synovectomy. However, MRI signs of recurrent syno vitis were already present in most knees at two months. No significant diff erences between volumes in RA. and non-RA knees were seen. Synovial membran e volumes at two months were significantly inversely correlated with the du ration of clinical remission, for all knees considered together (Spearman's correlation r(s)=-0.67; p<0.05), for RA knees (r(s)=-0.76; p<0.05), and fo r non-RA knees (r(s)=-0.83; p<0.05). Baseline volumes were not significantl y correlated with clinical outcome, Only three knees (all RA) showed erosiv e progression. The rate of erosive progression was not correlated with MRI volumes or with clinical or biochemical parameters. Conclusion-The synovial membrane had regenerated two months after arthrosco pic knee joint synovectomy and despite significant volume reductions compar ed with baseline it often showed signs of recurrent synovitis. MRI seems to be valuable as a marker of inflammation, destruction and, perhaps, as a pr edictor of therapeutic outcome in arthritis.