Microstructure, Micromechanical Properties Of Trabecular Bone And Regional Distribution Of Osteoblast And Osteoclast Activity In The Femoral Head With Osteonecrosis

ObjectiveTo compare the trabecular microstructure, micromechanics andosteoblast and osteoclast activity in different regions of the femoralhead with osteonecrosis.Materials and MethodsThe10femoral heads were collected from patients withosteonecrosis (Ficat IV) who had undergone total hip arthroplasty fromMarch2011to May2013. The samples were divided into subchondral boneregion, necrotic region, sclerosis region and healthy region accordingto radiographic results, then the bone microstructure, micromechanicsand osteoblasts/osteoclasts activity were analyzed by Micro-CT,RT-PCR, Nanoindentation, immunohistochemistry, Trap and ALPstaining.ResultsAccording to the micro-CT results, the continuity of trabecularbone in necrotic region was interrupted. The number of trabecula wasincreased and the gap was narrowed in sclerosis region. The shape andnumber of trabecular bone were normal in the healthy region. Theelasticity modulus were (13.808±4.22) GPa in subchondral bone regiond,(13.999±3.816) GPa in necrotic region,(17.266±3.533) GPa insclerosis region and (11.927±1.743) GPa in healthy region. Thehardness were (0.425±0.173) GPa in subchondral bone region,(0.331±0.173) GPa in necrotic region,(0.661±0.208) Gpa in sclerosis region, and (0.423±0.088) GPa in healthy region. The trap stainingof subchondral bone in healthy region and necrotic region were positivewhile other regions were negative. The ALP staining of subchondral bonein healthy region and necrotic region were negative while other regionswere positive. The RANK and RANKL staining level increasedsignificantly in subchondral bone and necrotic region compared withthat of healthy region, while Runx2, BMP2, BMP7, OPG staining levelincreased significantly in sclerosis region. The RT-PCR result showedthat the RANK and RANKL staining level increased significantly insubchondral bone and necrotic region compared with healthy region,while Runx2and BMP2staining level increased significantly insclerosis region. The Western Blot result showed that compared withhealthy region, the RANK and RANKL staining level increasedsignificantly in subchondral bone and necrotic region, while Runx2,BMP2, BMP7, OPG staining level increased significantly in sclerosisregion.ConclusionThe mechanical properties of trabecula have no significant differencebetween necrotic region and healthy region in the progress of theosteonecrosis, while the bone structure has obvious changes. An activebone resorption is observed in subchondral bone and necrotic region,while a higher bone formation activity is found in sclerosis region.