Hansson T H, Keller T S, Spengler D M
Department of Orthopaedic Surgery, Sahlgren Hospital, Goteborg, Sweden.
J Orthop Res. 1987;5(4):479-87. doi: 10.1002/jor.1100050403.
Seventeen cadaveric human lumbar motion segments from eight spines were cyclically loaded in vitro under axial compression. Loading frequency and magnitude were chosen to simulate rigorous activity within an in vivo physiological level. The load magnitude was determined as a percentage of the ultimate compressive load, the latter estimated from the bone mineral content (BMC) of lumbar vertebrae determined by dual-photon absorptiometry. Following testing, the degree of macroscopic disc degeneration was assessed and the type of fracture in each specimen was determined from serial sagittal sections. Fractures were found in all but one specimen. Three types of fractures were formed: the node of Schmorl and Junghanns (type I), central endplate fracture (type II), and a crush or burst fracture (type III). The results suggested that type I fractures were predominantly associated with segments with normal discs, type II fractures were found primarily in segments with moderately degenerated discs, and type III fractures were associated with segments that failed on the first cycle. Segment stiffness and fatigue strength (cycles to failure) were correlated with disc degeneration, age, and segment BMC, the latter an in vivo measure of bone density. Fatigue strength also decreased in proportion to a power coefficient with increasing relative stress (cyclic stress range/ultimate stress).
来自八个脊柱的17个尸体人腰椎运动节段在体外进行轴向压缩循环加载。选择加载频率和幅度以模拟体内生理水平的剧烈活动。加载幅度被确定为极限压缩载荷的百分比，后者根据双能X线吸收法测定的腰椎骨矿物质含量（BMC）估算得出。测试后，评估宏观椎间盘退变程度，并从连续矢状切片确定每个标本的骨折类型。除一个标本外，所有标本均发现骨折。形成了三种类型的骨折：施莫尔结节和容汉斯结节骨折（I型）、中央终板骨折（II型）以及挤压或爆裂骨折（III型）。结果表明，I型骨折主要与椎间盘正常的节段相关，II型骨折主要见于椎间盘中度退变的节段，III型骨折与在第一个周期就失效的节段相关。节段刚度和疲劳强度（失效循环次数）与椎间盘退变、年龄和节段BMC相关，后者是体内骨密度的一种测量指标。随着相对应力（循环应力范围/极限应力）增加，疲劳强度也与幂系数成比例下降。
