Matyas J R, Anton M G, Shrive N G, Frank C B
Department of Surgery, McCaig Centre for Joint Injury and Arthritis Research, University of Calgary, Alberta, Canada.
J Biomech. 1995 Feb;28(2):147-57. doi: 10.1016/0021-9290(94)00058-c.
The cells in the midsubstance portion of skeletal ligaments typically have elongated shapes, but where ligaments insert into bone the cells appear very rounded and the tissue phenotype is that of fibrocartilage. Between the midsubstance and the insertions there is a gradient in cell shape and tissue phenotype that has been hypothesized to reflect a gradient of mechanical stresses. To test this hypothesis, cell shapes (an index of tissue phenotype) were quantified in the central part of the femoral insertion of the rabbit medial collateral ligament by computer-assisted histomorphometry. Morphometric measurements were correlated with the mechanical stresses and strains in the central part of the insertion as predicted by finite element analysis. Throughout the ligament the direction of the predicted principal tensile stresses coincides with the direction of the collagen fibers which curve from the midsubstance to meet the femur at nearly right angles. Principal compressive stresses also occur within the ligament: the highest are localized near the bone; the lowest in the midsubstance. The areas with the roundest cells correspond to the areas with the highest principal compressive stresses in the model; the areas with the flattest cells correspond to the areas with the lowest compressive stresses in the model. A correlation between cell shape and mechanical stresses suggests that physiological loading of the MCL is important for the maintenance of tissue phenotype throughout this insertion. We theorize that the cells in ligament insertions adapt to the prevailing local mechanical environment.
骨骼肌韧带中间部分的细胞通常呈细长形，但在韧带与骨的附着处，细胞显得非常圆，且组织表型为纤维软骨。在中间部分和附着处之间，细胞形状和组织表型存在梯度变化，据推测这反映了机械应力的梯度。为了验证这一假设，通过计算机辅助组织形态计量学对兔内侧副韧带股骨附着处中央部分的细胞形状（组织表型指标）进行了量化。形态测量结果与有限元分析预测的附着处中央部分的机械应力和应变相关。在整个韧带中，预测的主拉应力方向与胶原纤维的方向一致，胶原纤维从中部弯曲，以近乎直角的角度与股骨相交。韧带内也存在主压应力：最高值位于靠近骨的部位；最低值位于中间部分。细胞最圆的区域对应于模型中主压应力最高的区域；细胞最扁平的区域对应于模型中压应力最低的区域。细胞形状与机械应力之间的相关性表明，内侧副韧带的生理负荷对于维持整个附着处的组织表型很重要。我们推测韧带附着处的细胞会适应当地主要的机械环境。
