[Microarchitecture features and pathology of necrotic region in patients with steroid-induced and alcohol-induced osteonecrosis of femoral head]

Objective: To investigate the pathological and microstructural features of the osteonecrosis samples from subjects with steroid-induced or alcohol-induced osteonecrosis of the femoral head (ONFH).

Methods: Thirty femoral head bone samples were collected from ONFH patients who underwent total hip arthroplasty between August 2015 and April 2016. There were 22 males and 8 females. The etiology of ONFH was alcohol-induced in 15 patients and steroid-induced in 15 patients. No significant difference of Association Research Circulation Osseous (ARCO) stage was found between alcohol-induced and steroid-induced ONFH ( Z=2.143, P=0.143). The femoral head bone samples in different areas (necrosis, sclerosis, and normal) from involved subjects was taken, and gross observation, HE staining were carried out (the rate of empty lacunaes was calculated). The intact femoral head was scanned by Micro-CT and the parameters of bone microstructure were analyzed quantitatively. The parameters included bone volume to total volume (BV/TV), bone surface area to bone volume ratio (BS/BV), bone mineral density (BMD), bone mineral content (BMC), structural model index (SMI), trabecular plate number (Tb. N), trabecular plate thickness (Tb. Th), and trabecular spacing (Tb. Sp).

Results: As observed in hard tissue slicing of both groups, the integrity of trabecular bone was destructed and cystic lesions left by the bone resorption was replaced by granulation tissues. Significant revascularization was found in granulation tissues of steroid-induced ONFH, but not in the alcohol-induced one. HE staining showed that the bone marrow structure was disordered in both group, as well as bone marrow necrosis and empty bone lacunaes noticed. The structure and integrity of trabecular bone of steroid-induced ONFH was far more severe whereas that of alcohol-induced one were thicker and better. The rate of empty bone lacunae in necrosis area of steroid-induced group was significantly higher than that of alcohol-induced one ( P<0.05), but no significant difference was found in sclerotic and normal areas between 2 groups ( P>0.05). Micro-CT showed that necrotic and sclerotic areas of both groups were low bone density. Bone structure in the former area was mostly heterogeneous. Further blood-rich granulation tissues formation was observed in the same places of hard tissue slicing, while the sclerotic one wasn't. The results of quantitative bone structure analysis showed that BV/TV, BMD, BMC, Tb.N, and Tb.Th of the necrotic and sclerotic areas of steroid-induced ONFH were significantly lower than those of alcohol-induced one ( P<0.01), BS/BV, SMI, and Tb.Sp of steroid-induced ONFH were significantly higher than those of alcohol-induced one ( P<0.01). No significant difference among the indexes above was found in the normal areas of both groups ( P>0.05).

Conclusion: The integrity of trabecular bone was destroyed in necrotic area of steroid-induced or alcohol-induced ONFH. However, they performed different features of osteonecrosis and contrasted with each other. The steroid-induced ONFH was characterized by multiple "osteolytic bone destruction", while the alcohol-induced one was manifested by some kinds of "coagulative destruction".