Donahue T L, Gregersen C, Hull M L, Howell S M
Biomedical Engineering Program, University of California at Davis, Davis, CA 95616, USA.
J Biomech Eng. 2001 Apr;123(2):162-9. doi: 10.1115/1.1351889.
Due to ready availability, decreased cost, and freedom from transmissible diseases in humans such as hepatitis and AIDS, it would be advantageous to use tendon grafts from farm animals as a substitute for human tendon grafts in in vitro experiments aimed at improving the outcome of anterior cruciate ligament (ACL) reconstructive surgery. Thus the objective of this study was to determine whether an anterior cruciate ligament (ACL) graft composed of two loops of bovine common digital extensor tendon has the same viscoelastic, structural, and material properties as a graft composed of a double loop of semitendinosus and gracilis tendons from humans. To satisfy this objective, grafts were constructed from each tissue source. The cross-sectional area was measured using an area micrometer, and each graft was then pulled using a materials testing system while submerged in a saline bath. Using two groups of tendon grafts (n = 10), viscoelastic tests were conducted over a three-day period during which a constant displacement load relaxation test was followed by a constant amplitude, cyclic load creep test (first day), a constant load creep test (second day), and an incremental cyclic load creep test (third day). Load-to-failure tests were performed on two different groups of grafts (n = 8). When the viscoelastic behavior was compared, there were no significant differences in the rate of load decay or the final load (relaxation test) and rates of displacement increase or final displacements (creep tests) (p > 0.115). To compare both the structural and material properties in the toe region (i.e., < 250 N) of the load-elongation curve, the tangent stiffness and modulus functions were computed from parameters used in an exponential model fit to the load (stress)-elongation (strain) data. Although one of the two parameters in the functions was different statistically, this difference translated into a difference of only 0.03 mm in displacement at 250 N of load. In the linear region (i.e., 50-75 percent of ultimate load) of the load-elongation curve, the linear stiffness of the two graft types compared closely (444 N/mm for bovine and 418 N/mm for human) (p = 0.341). At failure, the ultimate loads (2901 N and 2914 N for bovine and human, respectively) and the ultimate stresses (71.8 MPa and 65.6 MPa for bovine and human, respectively) were not significantly different (p > 0.261). The theoretical effect of any differences in properties between these two grafts on the results of two types of in vitro experiments (i.e., effect of surgical variables on knee laxity and structural properties of fixation devices) are discussed. Despite some statistical differences in the properties evaluated, these differences do not translate into important effects on the dependent variables of interest in the experiments. Thus the bovine tendon graft can be substituted for the human tendon graft in both types of experiments.
由于容易获取、成本降低，且不存在诸如肝炎和艾滋病等人类可传播疾病，在旨在改善前交叉韧带（ACL）重建手术效果的体外实验中，使用农场动物的肌腱移植物替代人类肌腱移植物将具有优势。因此，本研究的目的是确定由两圈牛指总伸肌腱组成的前交叉韧带（ACL）移植物是否具有与由人类半腱肌和股薄肌腱双圈组成的移植物相同的粘弹性、结构和材料特性。为实现这一目标，从每种组织来源构建移植物。使用面积测微计测量横截面积，然后将每个移植物置于盐浴中，使用材料测试系统进行拉伸。使用两组肌腱移植物（n = 10），在三天时间内进行粘弹性测试，在此期间，先进行恒定位移载荷松弛测试，接着进行恒幅循环载荷蠕变测试（第一天）、恒载蠕变测试（第二天）和增量循环载荷蠕变测试（第三天）。对两组不同的移植物（n = 8）进行破坏载荷测试。比较粘弹性行为时，载荷衰减率或最终载荷（松弛测试）以及位移增加率或最终位移（蠕变测试）均无显著差异（p > 0.115）。为比较载荷 - 伸长曲线趾部区域（即<250 N）的结构和材料特性，根据拟合载荷（应力） - 伸长（应变）数据的指数模型中使用的参数计算切线刚度和模量函数。尽管函数中的两个参数之一在统计学上存在差异，但这种差异在250 N载荷下仅转化为0.03 mm的位移差异。在载荷 - 伸长曲线的线性区域（即极限载荷的50 - 75%），两种移植物类型的线性刚度相近（牛肌腱为444 N/mm，人肌腱为418 N/mm）（p = 0.341）。在破坏时，极限载荷（牛肌腱和人肌腱分别为2901 N和2914 N）和极限应力（牛肌腱和人肌腱分别为71.8 MPa和65.6 MPa）无显著差异（p > 0.261）。讨论了这两种移植物之间特性的任何差异对两种体外实验结果（即手术变量对膝关节松弛度和固定装置结构特性的影响）的理论作用。尽管在评估的特性方面存在一些统计学差异，但这些差异并未转化为对实验中感兴趣的因变量的重要影响。因此，在这两种类型的实验中，牛肌腱移植物均可替代人肌腱移植物。
