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Bone score may predict fracture risk in postmenopausal women on bisphosphonate therapy
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Postmenopausal women with osteoporosis prescribed oral bisphosphonate therapy for at least 4 years were more likely to sustain a fracture if they had a lower bone material strength index score compared with women who did not sustain a fracture, according to findings from a Spanish study.
“Despite advantages and good adherence to therapy, some patients still experience fractures while receiving oral bisphosphonates,” Adolfo Diez-Perez, MD, PhD, of the Hospital del Mar Research Institute in Barcelona, Spain, and colleagues wrote. “Several factors may contribute to the apparent lack of full efficacy, such as low levels of vitamin D, concomitant diseases, very low bone mineral density and advanced deterioration of bone microarchitecture that induces a situation not fully compensated by the beneficial effects of drugs. Therefore, it would be interesting to explore whether bone characteristics at a tissue level can contribute to incident fractures in patients on active treatment.”
Diez-Perez and colleagues analyzed data from 39 postmenopausal women with a diagnosis of osteoporosis recruited from a specialized osteoporosis clinic in a tertiary hospital in Spain. Participants were receiving treatment with oral bisphosphonates for at least 4 years (alendronate or risedronate), had no previous fractures at baseline and demonstrated at least 80% adherence to treatment, assessed by questionnaire. Women were stratified by fracture status; those in the fracture group (n = 21) sustained a fracture at least 1 year after initiating bisphosphonate therapy. Researchers assessed serum 25-hydroxyvitamin D levels and BMD via DXA; all women underwent impact microindentation to assess bone material strength. Researchers used logistic regression analysis to compare between-group differences for bone material strength index, adjusted for age, BMI, years on bisphosphonate therapy and lumbar spine BMD.
During follow-up, 21 incident fractures occurred; most were morphometric vertebral fractures (n = 15).
Researchers found that women in the no-fracture group had a higher bone material strength index compared with women who sustained a fracture; for each standard deviation decrease in bone material strength index, women were 23% more likely to sustain a fracture (OR = 23.5; 95% CI, 2.16-255.66) after adjustment. Further adjustment for BMD of the femoral neck or total hip did not change the association.
In receiver operating characteristic analysis, area under the curve was 0.82 (95% CI, 0.68-0.95) for bone material strength index, higher than BMD at any location, which ranged from 0.64 (95% CI, 0.47-0.82) for femoral neck BMD to 0.71 (95% CI, 0.55-0.87) for lumbar spine BMD, according to researchers.
“An interesting finding from our series is that patients in the no-fracture group showed [bone material strength index] values comparable to those observed in a previous study in non-osteoporotic postmenopausal women in Spain,” the researchers wrote. “This might suggest that bone does not fracture if the patient maintains a given (not yet determined) [bone material strength index] level during a drug therapy. However, if these values are ‘low’ during the therapy, an unknown component of bone strength may determine the risk of fracture that persists in these individuals. Large, prospective studies are needed to establish the clinical value of these observations.” – by Regina Schaffer
Disclosures: The researchers report no relevant financial disclosures.
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