Non traumatic osteonecrosis of the femoral head is associated with low bone mass.

OBJECTIVE: Osteoporosis (OP) and osteonecrosis of the femoral head (ONFH) share common clinical and pathophysiological features we sought to determine whether ONFH was associated with an increased prevalence of OP and whether the increased prevalence of OP was related to the stage of ONFH at diagnosis. METHODS: We included 243 patients with ONFH and 399 age and sex-matched healthy controls. Data was gathered including demography, risk factors, ARCO staging of ONFH and bone mineral density (BMD). RESULTS: Overall, BMD (defined by the T-score) was significantly lower in the ONFH group at both the femoral head (-0.96±1.11) and the lumbar spine (-1.22±1.47) compared to the control group (-0.55±0.97 and -0.73±1.31) (p<0.01). The ONFH group depicted a significantly higher proportion of osteopenia (50.39% vs 40.87%, p=0.027) and of OP (18.78% vs 7.33%, p<0.001) relative to the control group. Stage 1 and 2 ONFH patients (53.86%, p=0.0203; OR=1.54 (95% CI: [1.04; 2.29])) were at a higher risk of osteopenia than the control group (40.88%), but not stages 3 or 4 (48.47%, p=0.2569; OR=1.27 (95% CI: [0.78; 2.06]). Patients with stage 3 or 4 ONFH (25.31%, p<0.001; OR=3.93 (95% CI: [1.63; 10.96])) were at a higher risk of osteoporosis than patients in the stage 1 and 2 ONFH (7.24%), and compared to the control group (7.33%, adj. p-value<0.001; OR=4.89 (95% CI: [2.77; 8.76]). CONCLUSIONS: Non-traumatic osteonecrosis of the femoral heads is associated with low bone mineral density. This study showed that fractural stages ONFH were associated with a 5-fold risk of osteoporosis.

Osteonecrosis of the Femoral Head: Lipotoxicity Exacerbation in MSC and Modifications of the Bone Marrow Fluid.

Osteonecrosis of the femoral head (ON) is a multifactorial bone disease that can evolve to a progressive destruction of the hip joint. Different pathogenic processes have been proposed, among them, an increase of bone marrow (BM) fat resulting from adipocyte accumulation. Marrow adipocytes are active BM residents that influence the microenvironment by releasing cytokines, adipokines, and free fatty acids (FA). We explored the impact of palmitate (Palm) and oleate on function and survival of BM-derived mesenchymal stromal cells (MSC) of osteonecrotic patients (ONMSC) and healthy volunteers. Moreover, we analyzed the FA profile of the serum and the BM supernatant fluid (BMSF). We demonstrated that exposure to the saturated FA Palm favored MSC differentiation through the adipogenic lineage at the expense of the osteoblastic phenotype. Moreover, adipogenesis was intensified in ONMSC. The susceptibility to Palm toxicity was aggravated in ONMSC concomitantly with a greater activation of the proapoptotic extracellular signal-regulated kinase pathway. Moreover, cellular mechanisms implicated in the protection against lipotoxicity, such as stearoyl-coenzyme A desaturase 1 and carnitine palmitoyl transferase 1 expression, were dysregulated in ONMSC. Palm-induced interleukin (IL)-6 and IL-8 secretion was also exacerbated in ONMSC. Our results established that, in the serum, the FA profiles were comparable in ON and healthy subjects. However, both the concentrations and the FA composition were modified in the BMSF of ON patients, highlighting a drastic change of the BM microenvironment in ON patients. Altogether, our work suggests that marrow adipocyte enlargement could affect the process of bone remodeling and, therefore, play a role in the pathogenesis of ON.