LAS VEGAS – Bisphosphonates may slow the onset and progression of osteoarthritis (OA), according to data from the National Institutes of Health–sponsored Osteoarthritis Initiative. “Bisphosphonates warrant further study as potential disease-modifying agents in osteoarthritis,” Tuhina Neogi, MD, declared in presenting the study findings at the World Congress on Osteoarthritis.
In addition to the promising signal of a preventive effect for bisphosphonates, her analysis of Osteoarthritis Initiative data yielded two other major findings: Changes over time in the MRI-based three-dimensional bone shape of the knee constitute a novel structural imaging biomarker that appears to be of value in monitoring patients with OA or at high risk for the joint disease, and bisphosphonate-induced suppression of bone turnover had no adverse long-term impact on osteoarthritis risk.
“While bisphosphonates may have beneficial articular cartilage effects, there are potential theoretical concerns regarding long-term effects of bone turnover. This issue hasn’t previously been addressed. Bone turnover suppression may lead to more bone deposition and bone stiffness, with adverse biomechanical consequences. But it did not appear, in this sample at least, that suppression of bone turnover had a negative impact over the long term,” said, professor of medicine at Boston University.
The Osteoarthritis Initiative is a multicenter, longitudinal, prospective, observational study of knee osteoarthritis launched by the NIH in 2002. Dr. Neogi’s analysis was limited to the 1,071 female participants free of radiographic knee OA at baseline and who had 3-Tesla MRIs of the right knee at baseline and annually thereafter for 4 years. They were at increased risk for OA on the basis of their age – a mean of 62 years – along with their mean body mass index of 28.3 kg/m2. Just under one-quarter of the women were on bisphosphonate therapy.
Prior studies of the effects of bisphosphonates in patients with knee OA have yielded conflicting results, in part because radiographic findings are a relatively crude indicator of bone and joint changes. 3D bone shape of the knee has been shown to change much more quickly than traditional radiographic measures. These changes predict the incidence of knee OA even years later, the rheumatologist explained at the congress sponsored by the Osteoarthritis Research Society International.
Using bone shape analytic software developed by England-based Imorphics, she and her coinvestigators categorized the women into three distinct groups on the basis of the trajectory of MRI changes toward a more osteoarthritic bone shape over time. Of them, 23% fell into the fast-change group, 49% were in the intermediate group, and 28% were in the slowest-changing group. The rate of MRI bone shape progression toward knee OA was 2.7-times higher in the fastest, compared with the slowest, group.
The incidence of radiographic OA during 4 years of prospective follow-up was 14% in the fastest bone shape-changing group, 8% in the intermediate-speed group, and 4% in the slowest-changing group.
In a multivariate analysis adjusted for age, BMI, education, race, quadriceps strength, and history of knee injury, bisphosphonate users were 41% less likely to be in the fastest bone shape–changing group and 32% less likely to be in the intermediate group, compared with the slowest-changing group.
As a rheumatologist with a PhD in epidemiology, Dr. Neogi was readily prepared to critique her own study. The major limitation in her view was the potential for residual confounding, which is inherent in observational studies. In this instance, the possibility of confounding by indication cannot be excluded. Also, bone mineral density data wasn’t collected in the Osteoarthritis Initiative. Future studies should evaluate the impact over time of new-onset bisphosphonate therapy as a means of altering the slope of the trajectory of MRI-based 3D bone shape of the knee, Dr. Neogi said.
She reported having no financial conflicts regarding the NIH-sponsored study.