To compare the efficacy on pain relief and function of one, two or three injections of intra-articular hyaluronic acid in symptomatic osteoarthritis (OA) of the carpometacarpal joint of the thumb (CMCJ).

Among subjects with symptomatic OA of the CMCJ of the thumb referred to the Rheumatology Department of Nice, patients free of any joint injection in last 6months with pain visual analogue score (VAS) >40 and with Kellgren and Lawrence score between 2 and 4 were included. Each subject was randomly allocated to receive, at weekly intervals, 1 (group 1) or 2 (group 2) or 3 injections (group 3) of 1ml Sodium Hyaluronidate (Sinovial^®). Injections were given under imaging control. Sociodemographic characteristics, VAS and functionality (Dreiser Functional Index) were assessed at baseline, at one month and at three months. An intention to treat analysis was performed.

Forty two subjects were enrolled in the study. Their mean age was 64.8 (8.0) years, and 90.5% were women. Baseline pain VAS, and mean Dreiser functional index were respectively 57.7 (17.1) and 12.5 (5.8). A repeated measure analysis of variance (ANOVA) model was used to compare the time-course profile of the three treatment groups for VAS and Dreiser index. Due to statistically significant groups-time interaction the analyses were conducted at each evaluation time. No difference was found for VAS at 1month (p=0.075) and 3months (p=0.382). Intra group differences between baseline and three months was significant in groups 2 and 3 (p=0.012 and p=0.002).

No significant differences were found between each group over the study period for pain relief and function. But the intra groups analysis results show that intra-articular sodium hyaluronidate injections into the carpometacarpal joint of the thumb in osteoarthritis can be efficacious on pain and fuctionality. What is now needed is a controlled placebo randomised study with larger samples and longer term follow up of the achieved effects.