Bone Abstracts

The aim of the study is to evaluate bone quantity (aBMD) and bone quality as assessed by TBS in DMD subjects.

43 boys and girls suffering from DMD with a mean age 10.5±3.7 years and height and weight z-score (Zc) medians of −0.67 and 0.25 S.D. were included in the study. Spine DXA scans were obtained using a GE Lunar iDXA with software v13.31. Lumbar spine trabecular bone texture (TBS) was determined using Med-Imaps custom software to calculate raw values that were subsequently adjusted for tissue thickness based on a normative population of healthy Spanish boys (n=1468) and girls (n=2659). Subjects were stratified based on tertile approach for TBS and aBMD.

Overall, the mean aBMD Zc of the population was moderate (−1.19±1.19 S.D.) while TBS Zc was normal for age (−0.08±1.32 S.D.). Negative associations were observed between aBMD, Height and weight Zcs and age (r=−0.56, −0.43 and −0.51, P<0.001) whereas no association was obtained with TBS Zc (r<0.1, P=0.9). aBMD explained 25% (r²) of TBS values. Considering subjects in the lowest tertile (LT), 14 subjects were in this tertile based on aBMD or TBS. No differences in terms of age, height and weight Zcs, lumbar tissue thickness or fat percent (all P>0.7) were observed between these two group of subjects. The LT cut-off values were 0.582 g/cm² for aBMD (Zc=−0.84 S.D.) and 1.188 for TBS. Subjects in the aBMD LT have a TBS value normal for age (Zc=−0.04 S.D.) while subjects in the TBS LT have a low aBMD for age (Zc=−0.95 S.D.). Interestingly, considering the minimum of TBS or aBMD LT values, 21 subjects were classified as low bone status.

As expected, low aBMD was observed in DMD subjects. Interestingly, a normal TBS for age was observed in those patients. aBMD and TBS identified similar number of subjects with low bone status. One striking finding concerns the cut-off value of TBS LT which is similar to that obtain for adults and link to a high risk for fracture (1.188 vs 1.200). In addition, it seems that the combination of aBMD and TBS allows to identify more subjects with low bone status. Further researches are needed to evaluate parameters associated with a low TBS value as well as TBS changes during growth in DMD subjects.

Disclosure: Renaud Winzenrieth is senior scientist at Med-Imaps.