Department of Orthopaedic Surgery, Southern California Orthopedic Institute, Van Nuys, California, U.S.A..
Department of Orthopaedic Surgery, University of California at Davis, Sacramento, California, U.S.A.
Arthroscopy. 2021 Jul;37(7):2173-2180. doi: 10.1016/j.arthro.2021.02.042. Epub 2021 Mar 10.
The purpose of this study was to determine whether aging imparts a clinically significant effect on the (1) mechanism of graft failure and (2) structural, material, and viscoelastic properties of patellar tendon allografts by evaluating these properties in younger donors (≤30 years of age) and older donors (>50 years of age).
A total of 34 younger (≤30 years of age) and 34 older (>50 years of age) nonirradiated, whole bone-tendon-bone allografts were prepared for testing by isolating the central third of the patellar tendon using a double-bladed 10-mm width scalpel under a 10-N load to ensure uniformity of harvest. Bone blocks were potted in polymethylmethacrylate within custom molds. Tendon length and cross-sectional area were measured using an area micrometer. A mechanical loading system was used to precondition the grafts for 100 cycles with a load between 50 N and 250 N (1 Hz). A creep load (500 N) was then applied at a rate of 100 mm/min (10 minutes). Grafts were allowed to recover at 1 N (10 minutes), followed by pull-to-failure at a rate of 100% strain per second. Mechanisms of failure (midsubstance vs avulsion) were noted and the structural, material, and viscoelastic properties calculated and compared between groups.
There were 33 (97%) midsubstance tears in the younger group and 28 (82%) in the older group (P = .034). Younger grafts showed greater ultimate load to failure (1,782 N [1,533, 2,032] vs 1,319 N [1,103, 1,533]) (P = .006) and ultimate tensile stress (37.4 MPa [32.4, 42.4] vs 27.5 MPa [22.9, 32.0]) (P = .006). There were no significant differences in displacement (P = .595), stiffness (P = .950), strain (P = .783), elastic modulus (P = .114), creep displacement (P = .881), and creep strain (P = .614).
This in vitro study suggests that aging weakens the bone-tendon junction and decreases the ultimate tensile strength of patellar tendon allografts. However, aging did not affect the displacement, strain, stiffness, elastic modulus, creep displacement, or creep strain of patellar tendon allografts.
Surgeons should be aware that patellar tendon allografts from donors >50 years of age have a lower ultimate tensile stress than donors ≤30 years of age.
本研究旨在通过评估年轻供体（≤30 岁）和老年供体（>50 岁）中这些特性，确定衰老是否对（1）移植物失败的机制和（2）髌腱同种异体移植物的结构、材料和粘弹性特性产生临床显著影响。
共制备了 34 个年轻（≤30 岁）和 34 个老年（>50 岁）非辐照、全骨-腱-骨同种异体移植物，通过在 10-N 载荷下使用双刀片 10-mm 宽度手术刀从髌腱的中心第三部分分离，以确保收获的均匀性，从而进行测试。骨块在定制模具内用聚甲基丙烯酸甲酯（PMMA）盆栽。使用面积千分尺测量肌腱长度和横截面积。使用机械加载系统对移植物进行 100 个循环的预加载，载荷在 50N 至 250N 之间（1Hz）。然后以 100mm/min（10 分钟）的速度施加蠕变载荷（500N）。移植物在 1N（10 分钟）下恢复，然后以 100%应变/秒的速度拉断。记录失效机制（中间撕裂与撕脱），并在组间计算和比较结构、材料和粘弹性特性。
年轻组中有 33 例（97%）中间撕裂，老年组中有 28 例（82%）（P=0.034）。年轻移植物的最终失效载荷更大（1782N[1533，2032] vs 1319N[1103，1533]）（P=0.006）和最终拉伸应力更高（37.4MPa[32.4，42.4] vs 27.5MPa[22.9，32.0]）（P=0.006）。两组间位移（P=0.595）、刚度（P=0.950）、应变（P=0.783）、弹性模量（P=0.114）、蠕变位移（P=0.881）和蠕变应变（P=0.614）均无显著差异。
这项体外研究表明，衰老削弱了骨-腱结合处，降低了髌腱同种异体移植物的最大拉伸强度。然而，衰老并未影响髌腱同种异体移植物的位移、应变、刚度、弹性模量、蠕变位移或蠕变应变。
外科医生应该注意到，>50 岁供体的髌腱同种异体移植物的最大拉伸应力低于≤30 岁供体。
