膝关节原发性骨关节炎软骨和软骨下骨病理改变的定量研究

HISTOMORPHOMETRIC ANALYSIS OF ARTICULAR CARTILAGE AND SUBCHONDRAL BONE FROM PRIMARY OSTEOARTHRITIC KNEES

目的观察膝关节原发性骨关节炎(osteoarthritis,OA)胫骨平台软骨和软骨下骨病理改变特点,对比内、外侧平台软骨和软骨下骨结构参数,探讨钙化层和软骨下骨在OA发病机制中的作用。方法取2009年10月-2011年5月行人工全膝关节置换术治疗的30例30膝原发性OA患者自愿捐赠的新鲜胫骨平台标本进行实验。其中男11例,女19例;年龄55～78岁,平均65.1岁。病程10～25年,平均16.6年;患膝内翻畸形1～23°,平均9.3°。大体观察胫骨平台后在内、外侧中央负重区取材,常规制备脱钙石蜡切片,行HE和番红O/固绿染色,观察关节软骨退变特点,参照Mankin评分标准评分并分期;观察钙化层及软骨下骨病理改变。应用Image Pro Plus 6.0图像分析软件测量软骨和软骨下骨结构参数,包括软骨全层(total articular cartilage,TAC)厚度、钙化层(articular calcified cartilage,ACC)厚度、ACC/TAC比值、软骨下骨板(subchondral bone plate,SCP)厚度以及骨小梁体积分数(trabecular bone volume,BV/TV)。结果大体观察内侧平台软骨退变较外侧严重,内侧平台软骨Mankin评分为(12.4±1.1)分,显著高于外侧平台的(8.3±1.6)分(t=12.173,P=0.000)。根据Mankin评分结果在60个标本中,14个为OA早期,可见软骨浅表层裂隙、潮线复制和软骨下骨增厚;19个为OA中期,可见软骨深层裂隙、多发软骨下骨吸收陷窝和明显增厚的软骨下骨;27个为OA晚期,可见软骨全层缺失、软骨内化骨和"象牙化"软骨下骨。软骨和软骨下骨结构参数测定示:内侧平台TAC厚度显著低于外侧平台,ACC/TAC比值、BV/TV及SCP厚度显著高于外侧平台,差异均有统计学意义(P<0.05)。内、外侧平台ACC厚度比较,差异无统计学意义(P>0.05)。结论钙化层和软骨下骨可能在OA发生与进展中发挥了重要作用。

Objective To investigate the pathologic characteristics of the articular cartilage and subchondral bone from osteoarthritic knees,and to compare the structural parameters of articular cartilage and subchondral bone between the medial and lateral tibial plateau,so as to determine the role of calcified zone and subchondral bone in the pathogenesis of osteoarthritis（OA）.Methods The tibial plateaus were taken from 30 patients undergoing total knee arthroplasty between October 2009 and May 2011.The subjects included 11 males and 19 females with an average age of 65.1 years（range,55-78 years）.The mean disease duration was 16.6 years（range,10-25 years）;the mean varus angle of the diseased knee was 9.3°（range,1-23°）.After gross observation,the cartilage-bone samples were taken out from the most weight-bearing regions in the internal areas of the medial and lateral plateaus.The decalcified paraffin-embedded sections were prepared and stained with HE and Safranin O/fast green for cartilage assessment（Mankin score）,staging,and bone histomorphometry;the pathologic features of the cartilage and subchondral bone were also observed.The thickness of total articular cartilage（TAC）,articular calcified cartilage（ACC）,subchondral bone plate（SCP）,and the trabecular bone volume（BV/TV） were measured by Image Pro Plus 6.0 imaging system,then the ratio of ACC/TAC was calculated.Results Macroscopic results showed that articular cartilage degeneration was more severe in the medial plateau than in the lateral plateau;Mankin score of the medial plateau（12.4 ± 1.1） was significantly higher than that of the lateral plateau（8.3 ± 1.6）（t=12.173,P=0.000）.In the 60 samples,14 samples were at stage I,characterisd by fissures within the superficial zone,duplicated tidemark,and thickend subchondral bone;19 samples were at stage II,characterisd by fissures extending into the deep zone,multiple subchondral bone resorption pits,and obviously thickend subchondral bone;and 27 samples were at stage III,characterisd by full-thickness cartilage defects,endochondral ossification,and eburnated subchondral bone.The bone histomorphometric study showed that TAC thickness of the medial plateau was significantly lower than that of the lateral plateau（P 0.05）;the ratios of ACC/TAC,BV/TV,and SCP thickness of the medial plateau were significantly higher than those of the lateral plateau（P 0.05）.However,there was no significant difference in the ACC thickness between the medial and lateral plateaus（P 0.05）.Conclusion The calcified zone and subchondral bone may play an important role in the initiation and progression of OA.