Bone Abstracts

Chronic obstructive pulmonary disease (COPD) has been found associated with low areal bone mineral density and an increase in fracture rate. Previous histomorphometric findings revealed abnormally low cancellous bone volume and thin cortices. In the present work, we studied the same transiliac bone biopsy samples from n=19 COPD patients for cancellous (Cn.) and cortical (Ct.) bone mineralization density distribution (BMDD) based on quantitative backscatter electron imaging (qBEI). The patients were postmenopausal women with an average age of 62.1±7.3 years (mean±S.D.). Eight of the patients had sustained at least one fragility fracture, 13 received treatment with inhaled glucocorticoids. The BMDD outcomes from the patients were compared to reference BMDD data and were correlated with clinical and histomorphometric findings.

Comparison of Cn.BMDD findings to reference data revealed no significant difference, in particular the average degree of cancellous bone matrix mineralization Cn.CaMean was 22.10 (21.76; 22.51) wt%Ca, median (25th, 75th percentiles) which is in the normal range of 22.23 (21.84; 22.50) wt%Ca. There were no differences in Cn. or Ct.BMDD with respect to the occurrence of fragility fractures or to treatment with inhaled glucocorticoids. Correlation analyses with histomorphometric findings revealed highly significant negative correlations of Cn. and Ct.CaMean (both R=−0.71, P<0.001), of typical degree of mineralization Cn. and Ct.CaPeak (both R=−0.65, P<0.01), and of the percentage of highly mineralized bone areas Cn.CaHigh and Ct.CaHigh (R=−0.65 and R=−0.69 respectively, both P<0.01) with endocortical bone formation rate.

The lack of deviations in BMDD from the patients is consistent with the normal histomorphometric bone formation rates reported previously. Although within the normal range, bone mineralization indices were sensitive to variations in bone turnover rates as observed by strong negative correlations. Further, our findings suggest that the occurrence of fragility fractures was not associated with differences in bone matrix mineralization in this cohort with COPD.