Aho Olli-Matti, Finnilä Mikko, Thevenot Jerome, Saarakkala Simo, Lehenkari Petri
Department of Anatomy and Cell Biology, Institute of Biomedicine, University of Oulu, Oulu, Finland.
Research Unit of Medical Imaging, Physics and Technology, Faculty of Medicine, University of Oulu, Oulu, Finland.
PLoS One. 2017 Mar 20;12(3):e0173726. doi: 10.1371/journal.pone.0173726. eCollection 2017.
Osteoarthritis (OA) has often regarded as a disease of articular cartilage only. New evidence has shifted the paradigm towards a system biology approach, where also the surrounding tissue, especially bone is studied more vigorously. However, the histological features of subchondral bone are only poorly characterized in current histological grading scales of OA. The aim of this study is to specifically characterize histological changes occurring in subchondral bone at different stages of OA and propose a simple grading system for them.
20 patients undergoing total knee replacement surgery were randomly selected for the study and series of osteochondral samples were harvested from the tibial plateaus for histological analysis. Cartilage degeneration was assessed using the standardized OARSI grading system, while a novel four-stage grading system was developed to illustrate the changes in subchondral bone. Subchondral bone histology was further quantitatively analyzed by measuring the thickness of uncalcified and calcified cartilage as well as subchondral bone plate. Furthermore, internal structure of calcified cartilage-bone interface was characterized utilizing local binary patterns (LBP) based method.
The histological appearance of subchondral bone changed drastically in correlation with the OARSI grading of cartilage degeneration. As the cartilage layer thickness decreases the subchondral plate thickness and disorientation, as measured with LBP, increases. Calcified cartilage thickness was highest in samples with moderate OA.
The proposed grading system for subchondral bone has significant relationship with the corresponding OARSI grading for cartilage. Our results suggest that subchondral bone remodeling is a fundamental factor already in early stages of cartilage degeneration.
骨关节炎（OA）通常仅被视为一种关节软骨疾病。新证据已将范式转向系统生物学方法，其中对周围组织，尤其是骨骼的研究也更加深入。然而，在当前的OA组织学分级量表中，软骨下骨的组织学特征描述甚少。本研究的目的是具体描述OA不同阶段软骨下骨发生的组织学变化，并为其提出一个简单的分级系统。
随机选择20例行全膝关节置换手术的患者进行研究，并从胫骨平台采集一系列骨软骨样本进行组织学分析。使用标准化的OARSI分级系统评估软骨退变，同时开发了一种新的四阶段分级系统来说明软骨下骨的变化。通过测量未钙化和钙化软骨以及软骨下骨板的厚度，对软骨下骨组织学进行进一步定量分析。此外，利用基于局部二值模式（LBP）的方法对钙化软骨-骨界面的内部结构进行表征。
软骨下骨的组织学外观与软骨退变的OARSI分级密切相关，发生了显著变化。随着软骨层厚度的减小，用LBP测量的软骨下板厚度和取向紊乱增加。钙化软骨厚度在中度OA样本中最高。
所提出的软骨下骨分级系统与相应的软骨OARSI分级有显著关系。我们的结果表明，软骨下骨重塑在软骨退变的早期阶段就是一个基本因素。
