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02.05.2018 14:00:00
Strontium ranelate may prove to be an alternative to knee arthrosis surgery. The substance has been used to treat osteoporosis and, in a large-scale international study involving more than 1,600 patients with osteoarthritis of the knee (gonarthrosis, GA), has also compromised bone structure damage. Daily doses of 1 or 2 g strontium ranelate had positive effects compared to placebo. The results of the so-called SEKOIA study (Strontium Ranelate in Knee Osteoarthritis) were presented at this year's meeting of the American College of Rheumatology (ACR) [1, 2, 3].
The researchers reported that these positive effects on bone structure also resulted in fewer knee operations becoming necessary during the course of the disease. 2g doses per day also helped relieve pain and significantly improved symptoms.
"Our study suggests that the use of strontium ranelate could reduce the number of knee operations that would otherwise be required, clinical improvements occurred at 18 months, and as treatment lengthened, drug therapy was increasingly successful compared to placebo," said lead author. Jean-Yves Reginster from the Université de Liège in Belgium.
Strontium ranelate stimulates bone formation and reduces the absorption of bone. The substance contains two stable strontium atoms that are non-radioactive and are incorporated into the bone rather than calcium atoms. This is intended to inhibit the bone-degrading osteoclasts. The drug is licensed in more than 100 countries and is approved for the treatment of postmenopausal osteoporosis in women as well as for osteoporosis in men. In the US, however, it is not approved, but is used off-label against osteoporosis.
The joint space is reduced in a radiologically detectable manner
SEKOIA was a double-blind, placebo-controlled study that was conducted over 3 years at 98 centers in 18 countries. A total of 1,683 patients with one - according to the criteria of the American College of Rheumatology - mild to moderate GA were randomized to take 1 or 2 g of strontium ranelate per day or placebo.
The primary endpoint of the treatment was defined as the radiologically detectable reduction of the medial joint space in the target joint. The joint space reduction had to be evaluated by two independent investigators on the basis of X-ray images.
Subjects in the various groups had comparable demographic composition and disease characteristics. According to Reginster, the patients matched the typically enrolled participants in GA clinical trials: they were predominantly female with an average body mass index of 30 kg / m2. Two-thirds of them had a mild GA and a third a moderate. The dropout rate, at 42%, was similar to that of other placebo-controlled GA studies.
Regarding the primary endpoint, a significant reduction in joint space was observed in both intervention groups compared with the placebo group, with very little difference between the 1 g daily or 2 g daily groups (p = 0.0018 for both comparisons with placebo ).
Radiographically detectable cartilage loss of 5 mm or more could be reduced with both dosages of the active drug in 3 years compared to placebo; this limit was reduced by 34% in the 1 g group compared to placebo (p = 0.049) and by 44% in the 2 g group (P = 0.008).
"Patients with radiographically proven cartilage loss of 5 mm or more are 5-fold more likely to be operated on within 10 years," explained Reginster.
Higher dosage also has a pain-relieving effect
According to the WOMAC (Western Ontario and McMaster Universities Osteoarthritis) Index and WOMAC Pain Score, significant improvements could only be achieved with a daily dose of 2 g of strontium ranelate. The lead author noted that this was also the approved dosage for the treatment of osteoporosis and stated: "Taking 2 g of strontium ranelate per day showed significant benefit on all subscales of WOMAC." After more than 10 years of treatment experience in osteoporosis, the safety profile of strontium ranelate is well known. The only contraindication is the deep venous thrombosis, it said.
Dr. Kathryn Dao, Director of Clinical Rheumatology at the Baylor Research Institute of Dallas, Texas, highlighted the importance of these results by saying "we have very limited treatment options for knee osteoarthritis." Before strontium ranelate is introduced as a treatment option for knee osteoarthritis, further studies are needed in its view.
"Strontium ranelate appears to have a good side effect profile that is different from that of the analgesics and nonsteroidal anti-inflammatory drugs commonly used in the treatment of knee osteoarthritis," she noted for the benefit of the drug.
She said the drug was not approved for the treatment of osteoporosis in the US due to a lack of bone fracture data, but was off-label in some centers. In Europe, strontium ranelate is approved for the "treatment of osteoporosis in postmenopausal women to reduce the risk of spinal and hip fractures" as well as "the treatment of osteoporosis in adult men with increased fracture risk".
