SAN DIEGO, CA—Using a new definition of radiological progression, patients with osteoarthritis of the knee treated with strontium ranelate had a significant reduction in such progression, “suggesting a long-term beneficial effect on knee osteoarthritis-related surgery,” according to a study presented at the 2013 ACR/ARHP Annual Meeting.

Previously, results of a randomized, placebo-controlled, double-blind Phase 3 study found strontium ranelate 2g/day demonstrated a structure-modifying activity that was associated with symptom improvement in patients with knee osteoarthritis.

In this analysis, Olivier Bruyère, PhD, associate professor in the Department of Public Health, Epidemiology and Health Economics of the University of Liège, Liège, Belgium, aimed to “describe the efficacy of strontium ranelate on radiological progression with a new definition of radiological progressing patients,” who are at higher risk of knee surgery. The definition is based on an algorithm designed to ensure robustness of changes in joint-space narrowing (JSN), including consistency over time.

A total of 1683 patients with symptomatic primary knee osteoarthritis (ACR criteria) were randomly assigned to strontium ranelate 1g, 2g, or placebo for 3 years. Radiological progression was defined as an initial JSN ≥75% of 0.6mm (eg, 0.45mm) with a JSN ≥0.20mm in at least one following visit; a JSN ≥50% of 0.60mm (eg, 0.30mm) in at least at two visits (with restrictions) or a JSN ≥0.6mm at the end.

The intent-to-treat population included 1371 patients (82% of those randomized). Mean age was 63+7 years; 69% were female; BMI was 30+5kg/m2; joint space width was 3.5+0.8mm; and 61% were Kellgren Lawrence grade II.

Significantly fewer patients in the strontium ranelate groups had radiological progression between baseline and last observation—1g, 23.8% (P<0.001) and 2g, 25.3% (P<0.001)—compared with placebo (41.7%). The relative risk reduction and number needed to treat (NNT) vs. placebo were 42.9% (NNT=6) in the strontium ranelate 1g group and 39.3% (NNT=7) in the 2g group.

These results were confirmed using the per-protocol population (n=865): relative risk reduction for strontium ranelate 1g was 26.4% (P<0.001) and for 2g, 27.6% (P<0.001), vs. 49.0% in the placebo group. Results were similar after adjusting for confounding.

Dr. Bruyère noted, “Strontium ranelate 1g and 2g/day reduced the number of knee osteoarthritis patients with a significant radiological progression.”