Bone Abstracts

Objective: To assess the effect of mechanical loading in anorexia nervosa (AN) in vivo, by comparing bone geometry and microarchitecture in weight bearing versus non-weight bearing bone.

Subjects and methods: A total of 26 female patients with AN, and 26 female controls matched on age and height were included. Bone geometry, volumetric bone mineral density (vBMD) and microarchitecture were assessed using HR-pQCT (Scanco Medical, Brütisellen, Switzerland) of the distal radius and tibia. At each site, a 9.02-mm 3D axial representation comprising 110 slices with an isotropic image voxel size of 82 μm was obtained. Medical history, including history of fractures, was obtained by questionnaires. The local ethics committee approved the study.

Results: Cortical perimeter and total bone area were similar in patients and controls at both sites. Total vBMD was lower in patients with AN in tibia (P=0.0002) but not in radius (P=0.11) compared to controls. In tibia, cortical thickness (Ct.Th.) was approximately 25% decreased (P=0.0001) in the AN group, whereas in radius there was no significant difference. In terms of trabecular microarchitecture in tibia, all indices (bone volume/tissue volume (BV/TV); trabecular thickness (Tb.Th.), trabecular number (Tb.N) and trabecular spacing (Tb.Sp.) were impaired in AN compared to controls (P values range=0.0000–0.006). In radius, BV/TV and Tb.N were lower (P=0.002 and P=0.0006, respectively). Tb.Sp. was higher (P=0.0006), whereas Tb.Th. did not differ (P=0.16) compared to controls. Cortical porosity did not differ between groups at any site.

Conclusion: We found impaired bone microarchitecture in patients with AN compared to controls. The overall pattern of impairment was comparable between radius and tibia, except for Ct.th. and Tb.th. that were significantly lower in tibia, but not in radius. Thus, it is possible that these parameters are affected mainly by body weight per se, through decreased mechanical loading of the skeleton.