The fracture risk assessment tool (FRAX) may help identify more appropriate candidates for pharmacologic intervention for osteoporosis among patients with knee osteoarthritis, according to study results published in the Journal of Clinical Medicine.

Previous studies have suggested that osteoarthritis might have a protective effect on osteoporosis, while others have concluded that increased bone mineral density (BMD) in these patients does not reduce fracture risk. As such, the association between osteoporosis and osteoarthritis is complex and controversial.

FRAX is the most commonly used tool for fracture risk assessment and can aid in the decision to treat osteoporosis. The goal of this study was to assess the frequency of high-risk osteoporotic fracture in patients with knee osteoarthritis comparing the FRAX and the World Health Organization (WHO) criteria based on BMD measured by dual-energy x-ray absorptiometry.

The retrospective study included 239 Korean patients aged ≥50 years (231 women, 8 men) with knee osteoarthritis who visited 5 medical centers between November 2012 and November 2017. A control group included 239 patients matched for age, sex, and body mass index.

Using WHO criteria, there was no statistically significant difference in the frequency of osteoporosis based on BMD values in patients with knee osteoarthritis (96 of 239 patients, 40.2%) compared with healthy controls (87 of 239 patients, 36.4%).

The mean FRAX major osteoporotic fracture probabilities calculated with and without femur neck BMD were 6.9±3.8% and 8±3.6%, respectively, for patients with osteoarthritis and 6.1±2.8% and 6.8±2.3%, respectively, for healthy controls. These FRAX calculations, regardless of femur neck BMD, showed higher probabilities of major osteoporotic fracture in patients with knee osteoarthritis vs healthy controls (P =.000 with femur BMD; P <.001 without femur BMD).

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For hip fractures specifically, mean FRAX probabilities calculated with and without femur neck BMD were 2.1±2.4% and 3±2.3%, respectively, for patients with osteoarthritis and 1.7±1.8% and 2.4±1.6%, respectively, for healthy controls. These FRAX calculations indicated higher probabilities of hip fracture in patients with knee osteoarthritis vs healthy controls, regardless of femur neck BMD (P =.006 with femur BMD; P <.001 without femur BMD).

For patients who were classified as being at high risk for fracture based on FRAX, prevalence of osteoporosis was higher compared with those not classified as having a high fracture risk.

The study had several limitations, including the relatively small number of patients with knee osteoarthritis. The assessment was also limited to knee osteoarthritis and did not consider other joints. In addition, the cross-sectional design of the study precludes determining causality.

“FRAX may have a clinical impact on treatment decisions aimed at reducing the development of osteoporotic fractures in patients with knee [osteoarthritis],” wrote the researchers.

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Reference

Kim BY, Kim HA, Jung JY, et al. Clinical impact of the Fracture Risk Assessment Tool on the treatment decision for osteoporosis in patients with knee osteoarthritis: A multicenter comparative study of the Fracture Risk Assessment Tool and World Health Organization criteria [published online June 26, 2019]. J Clin Med. doi:10.3390/jcm8070918