Objective

To determine changes of subchondral bone composition, micro-structure, bone marrow adiposity and micro-vascular perfusion in end-stage osteonecrosis of the femoral head (ONFH) compared to osteoarthritis (OA) using a combined in vivo and ex vivo approach.

Design

Male patients up to 70 years old referred for total hip replacement surgery for end-stage ONFH were included (n = 14). Fifteen patients with OA were controls. Pre-operative MRI was used to assess bone perfusion (dynamic contrast-enhanced (DCE) sequences) and marrow fat content (chemical shift imaging). Three distinct zones of femoral head subchondral bone – necrotic, sclerotic, distant – were compared between groups. After surgery, plugs were sampled in these zones and Raman spectroscopy was applied to characterize bone mineral and organic components (old and newly-formed), and contrast-enhanced micro-computed tomography (CE-μCT) to determine bone micro-structural parameters and volume of bone marrow adipocytes, using conventional 2D histology as a reference.

Results

In the necrotic zone of ONFH patients compared to OA patients: 1) the subchondral plate did not exhibit significant changes in composition nor structure; 2) the volume fraction of subchondral trabecular bone was significantly lower; 3) type-B carbonate substitution was less pronounced, 4) collagen maturity was more pronounced; and 5) bone marrow adipocytes were significantly depleted. The sclerotic zone from the ONFH group showed greater trabecular thickness, and higher DCE-MRI AUC and K_trans. Volume fraction of subchondral bone, trabecular number, and K_ep were significantly lower in the distant zone of the ONFH group.

Conclusions

This study demonstrated alterations of subchondral bone microstructure, composition, perfusion and/or adipose content in all zones of the femoral head.

中文翻译：

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股骨头坏死中的软骨下受累：对局部成分、微观结构和血管形成的了解

客观的

使用体内和体外联合方法确定与骨关节炎 (OA) 相比，股骨头终末期骨坏死 (ONFH) 中软骨下骨成分、微结构、骨髓肥胖和微血管灌注的变化。

设计

纳入因终末期 ONFH 接受全髋关节置换手术的 70 岁以下男性患者（n  = 14）。15 名 OA 患者作为对照。术前 MRI 用于评估骨灌注（动态对比增强 (DCE) 序列）和骨髓脂肪含量（化学位移成像）。比较两组股骨头软骨下骨的三个不同区域——坏死、硬化、远处。手术后，在这些区域对栓塞进行取样，并应用拉曼光谱来表征骨矿物质和有机成分（旧的和新形成的），并使用对比增强微计算机断层扫描 (CE-μCT) 来确定骨微结构参数和骨髓脂肪细胞的体积，使用传统的 2D 组织学作为参考。

结果

与 OA 患者相比，ONFH 患者的坏死区：1）软骨下板的组成和结构没有显着变化；2）软骨下骨小梁的体积分数明显降低；3）B型碳酸盐取代不太明显，4）胶原成熟度更明显；5 ) 骨髓脂肪细胞显着耗竭。ONFH 组的硬化区显示出更大的小梁厚度，以及更高的 DCE-MRI AUC 和 K _trans。ONFH组远区软骨下骨体积分数、骨小梁数和K _ep显着降低。

结论

这项研究证明了股骨头所有区域的软骨下骨微结构、组成、灌注和/或脂肪含量的变化。