The influence of continuous sliding and subsequent surface wear on the friction of articular cartilage
The influence of continuous sliding and subsequent surface wear on the friction of articular cartilage
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DOI：
10.1243/0954411991535167
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发表时间：
1999-01-01
期刊：
影响因子：
1.8
通讯作者：
Fisher, J
中科院分区：
文献类型：
--
作者：
Forster, H;Fisher, J
往复运动摩擦测试进行后，软骨对金属接触，同时受到恒定的负载。将初始摩擦系数与充分载荷移除期后的重复摩擦系数进行比较。重复摩擦系数略高于初始值，两者主要取决于加载时间。得出的结论是，虽然磨损组件已被确定，适度增加摩擦系数，最重要的参数影响摩擦加载时间。作者假设，关节软骨内的流体相载荷承载（取决于加载时间）在很大程度上是混合润滑和边界润滑状态下摩擦系数低的原因。这种机制被称为双相润滑。滑液和林格氏溶液均用作润滑剂。在评估的120分钟加载时间内，滑液和林格氏溶液的摩擦系数在5秒后分别从0.005（两种润滑剂）上升至0.50和0.57。发现滑液与林格氏溶液相比在评估的加载时间的宽范围内显著降低摩擦系数（p < 0.05）。针式和非接触式激光轮廓测量成功地提供了可靠的，定量的和准确的测量表面粗糙度。连续滑动摩擦试验前后的激光轮廓测量显示表面粗糙度从R-a = 0.8（+/-0.2）μ m显著增加至R-a = 2.1（+/-0.2）μ m（p < 0.0005）;证实发生了表面磨损。扫描电子显微镜（SEM）显示了典型的高度取向的胶原纤维的浅表切线区。环境扫描电镜（ESEM）的完全水合软骨标本提供了很大程度上无特征的图像的表面，这表明，传统的扫描电镜样品制备的软骨表面外观使用SEM的真实性是有害的。使用环境扫描电镜和透射电子显微镜（TEM）鉴定了两个不同的无细胞非胶原表面层;分别称为边界层和表面层。基于磷脂/糖蛋白的边界层将在相对软骨表面的紧密接触期间提供边界润滑。表面层是蛋白聚糖原纤维间基质的连续体，其存在是为了防止下层胶原纤维的原纤化。这两层都可能有助于关节软骨的时间依赖性摩擦反应。虽然激光轮廓测量确实显示了表面磨损，这与摩擦的小幅增加一致，但控制摩擦系数的主要变量是加载时间。
Reciprocating motion friction tests were conducted upon cartilage-on-metal contacts while subjected to a constant load. Initial friction coefficients were compared with repeat friction coefficients following a sufficient load removal period. The repeat friction coefficients were marginally higher than the initial values and both were primarily dependent on the loading time. It was concluded that while a wear component had been identified, which modestly increased friction coefficients, the overriding parameter influencing friction was loading time. The authors postulate that fluid phase load carriage (being dependent on loading time) within the articular cartilage is largely responsible for low friction coefficients in the mixed and boundary lubrication regimes. This mechanism has been referred to as biphasic lubrication. Both synovial fluid and Ringer's solution were used as lubricants. Over the assessed 120 min loading time friction coefficients rose from 0.005 (for both lubricants) after 5 s to 0.50 and 0.57 for synovial fluid and Ringer's solution respectively. Synovial fluid was found to significantly reduce friction coefficients compared to Ringer's solution over broad ranges of the assessed loading times (p < 0.05). Stylus and non-contacting laser profilometry were successfully employed to provide reliable, quantitative and accurate measures of surface roughness. Laser profilometry before and after a continuous sliding friction test revealed a significant increase in surface roughness from R-a = 0.8(+/- 0.2) mu m to R-a = 2.1(+/- 0.2) mu m, (p < 0.0005); confirming that surface wear was occurring. Scanning electron microscopy (SEM) revealed the typical highly orientated collagen fibres of the superficial tangential zone. Environmental SEM (ESEM) of fully hydrated cartilage specimens provided largely featureless images of the surface which suggested that sample preparation for conventional SEM was detrimental to the authenticity of the cartilage surface appearance using SEM. Two distinct acellular, non-collagenous surface layers were identified using ESEM and transmission electron microscopy (TEM); respectively referred to as the boundary layer and surface lamina. The phospholipid/glycoprotein based boundary layer will provide boundary lubrication during intimate contact of opposing cartilage surfaces. The surface lamina, being a continuum of the proteoglycan interfibrillar matrix, is present to prevent fibrillation of the underlying collagen fibres. Both layers may contribute to the time dependent frictional response of articular cartilage. Although laser profilometry did reveal surface wear which was consistent with a small increase in friction, the primary variable controlling the friction coefficient was the period of loading.