Anti-resorptive therapy compromises bone’s material composition predisposing to atypical femoral fractures — ASN Events
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Anti-resorptive therapy compromises bone’s material composition predisposing to atypical femoral fractures (#44)

Roger Zebaze 1 , Cherie Y Chiang 1 , Hanh Nguyen 2 , Yu Peng 3 , Ali Ghasem-Zadeh 1 , Xiao-Fang Wang 1 , Sandra Iuliano-Burns 1 , Maria B Zanchetta 4 , Jose R Zanchetta 4 , Peter R Ebeling 2 , Ego Seeman 1 5
  1. Departments of Endocrinology and Medicine, Austin Health, University of Melbourne, West Heidelberg, VIC, Australia
  2. Department of Medicine, Monash University, Melbourne, VIC, Australia
  3. Straxcorp, Melbourne, VIC, Australia
  4. Instituto de Diagnóstico e Investigaciones Metabólicas (IDIM), Buenos Aires, Argentina
  5. Institute for Health and Ageing, Australian Catholic University, Melbourne, VIC, Australia

Background                        Antiresorptive therapies slow the deterioration of bone’s microstructure. However, the less renewed bone may accumulate microcracks and become more completely mineralized facilitating microcrack propagation. We hypothesized that treated women with atypical femoral fractures (AFFs) differ from treated women without AFFs by having less deteriorated microstructure (due to treatment) but higher matrix mineral density (MMD).

Methods                  Distal radial cortical porosity and MMD were measured using high resolution peripheral computed tomography in 342 healthy pre- and 55 postmenopausal women and 109 women treated with antiresorptives; 49 with AFFs, 29 with typical fragility fractures and 31 remaining fracture free. Deterioration in porosity and MMD was expressed as a Material Fragility Score (MFS) quantified using a StrAx Index. Results were expressed as standardized deviation scores (SD ± sem) relative to the young normal mean and odds ratios (OR, 95% confidence intervals, CI).

Results                     There was an inverse association between cortical porosity and matrix mineral density in healthy women, not women with AFFs. They had 0.88 ± 0.26 SD (p <0.0001) lower cortical porosity but 0.68 ± 0.17 SD higher matrix mineral density than treated women without AFF (p<0.0001); features captured in the MFS which distinguished them from treated women without AFF [OR = 5.7, 95%CI 2.5.1-12.9, P < 0.0001, sensitivity 77.4%, specificity 65.4%] and from untreated women [OR = 7.5, 95% CI 3.1-18.2, P < 0.0001, sensitivity 80%, specificity 65.3%].

Conclusion                 High porosity and MMD distinguish women at risk for AFF from women with higher porosity and low MMD at risk for typical fragility fractures; this may assist in targeting therapy.