Is the Rate of Responders to Hyaluronic Acid Injection for Patients with Knee Osteoarthritis Stable Over Time? Post hoc Analyses of a 6-Month Follow-Up Study

INTRODUCTION: Recently, a study showing the non-inferiority of a single injection of sodium hyaluronate plus sorbitol (Synolis VA(®)) compared to hylan G-F20 (Synvisc-One(®)) over a 24-week period in patients with knee osteoarthritis was published. The objective of the present study is to assess if a short-term response to a single injection of sodium hyaluronate plus sorbitol can be maintained over a 6 month-period and if the maintenance of the response to treatment is dependent on the functional status at baseline. METHODS: Responders to treatment at days 28, 84, and 168 were evaluated according to the responder criteria proposed by the OMERACT-OARSI. The Western Ontario and McMaster Universities Arthritis Index (WOMAC) was used to assess functional status at baseline. All analyses were adjusted for age, gender, BMI, and baseline WOMAC total score using data from the intention-to-treat (ITT) population. RESULTS: Out of the 96 patients included in the study who were receiving Synolis VA(®), 59.38% were responders at day 28 according to the OMERACT/OARSI responder criteria, 59.78% at day 84, and 64.52% at day 168. Among the responders at D28, the probability of being responder at D84 and D168 was significantly higher than among non-responders, with corresponding odds ratio (95% CI) of 2.85 (1.07–7.59) and 7.28 (2.53–20.93), respectively. Patients with a poorer physical function at baseline were more likely to respond to the treatment at all time points, compared to those with a better physical function (OR 3.74 [1.37–10.21]). CONCLUSIONS: An early response of a single injection of sodium hyaluronate plus sorbitol is predictive of long-term response, up to 24 weeks. Patients with a poorer physical function may best benefit from the treatment.