Bone Abstracts

Beside the bone mass, structural changes are important determinants of the bone strength. Patients with osteoarthritis (OA) seem protected against femoral neck (FN) fracture. When compared to osteoporosis, FN in OA are characterized by a higher bone mass and a better trabecular microarchitecture (Blain et al., 2008, Boutroy et al., 2011). The presence of microcracks is one of the determinants of the bone strength. The aim of this study was to evaluate the microcracks density (Cr.N/BV) and length (Cr.Le) in the FN in hip OA and its relation with microarchitecture. Osteophyte being common features in OA, the presence of microcracks was separately analyzed in the osteophyte area. FN samples were obtained during arthroplasty for hip OA in 18 postmenopausal women. Bulk-staining of the specimens was performed with calceïn. 3D measurements of the bone mass and microarchitectrure were assessed by HR-pQCT (Xtreme CT, Scanco Medical). Osteophytes were present in all samples, but microcracks were observed in only four. Cr.N/BV was significantly higher in trabecular than cortical bone (0.020±0.010 vs 0.005±0.008 /mm² respectively, P < 0.001) but the mean length tended to be higher in cortical than cancellous bone (103.0±61.9 vs 60.5±28.2 μm respectively, P=0.07). Cr.N/BV was significantly lower in osteophytes than in the other part of FN (0.01±0.016 vs 0.019±0.015 respectively, P<0.04). The bone mass and microarchitecture of the osteophytes were significantly different than the other parts of FN (P< 0.001 for BV/TV, Tb.N, Tb.Sp). However, no correlation was found between Cr.N/BV and parameters of microarchitecture. In conclusion, these results showed that in FN from hip OA, the microcracks formation tended to be lower in the osteophytes but was not related to the microarchitecture. These results suggest that osteophytes may limit the microcracks formation.