New Perspectives on ACL Injury

摘要 这项提议挑战了当前的教条，即非接触性的前十字韧带(ACL)断裂是 由于突然笨拙的着陆或超载事件。在过去的资金周期中，我们提出了第一个证据 ACL在重复性次最大负载下也会失败(Lipps 2013)，这有助于解释为什么 在常规的运动动作中可能会失败。飞行员数据表明，这种疲劳故障与 股骨近端附近有微小损伤堆积。我们要求提供资金来验证这一假设。 在AIM 160中，性别和大小匹配的年轻身体(30男，30女)的60对膝盖将被 通过预拉伸的膝关节肌肉-肌腱等效物定位在15o的初始屈曲角，从而允许 膝关节在远端脉冲测试负荷下屈曲。前交叉韧带疲劳寿命将通过重复次最大值来确定 4倍体重冲激三维复合负荷(压缩+跨膝肌负荷+屈曲 力矩+膝关节外展力矩+胫骨内侧轴向扭矩)施加于每个膝关节。一个Cox回归模型 将被用来对性别、股骨内轴向旋转范围(ROM)和 胫骨外侧斜度限制了前交叉韧带的疲劳寿命。 在AIM 2a中，我们将使用组织学图像和二项式精确检验来确定膝关节的百分比 接受AIM-1疲劳试验，在股骨股骨头端部或其附近表现出超过 +3*在32个未经测试的配对对照膝盖中发现了SD区域。同样，在AIM 2b中，我们将挽救前交叉韧带股骨 60例14~25岁健康青壮年(女30例)常规再造术中的根尖外植体 并确定微损伤面积超过+3*SD的外植体的百分比 在30名未经测试的年龄和性别匹配的身体对照中测量的值。 如果在体外疲劳测试(AIM 2a)和前交叉韧带损伤中发现大于正常的前交叉韧带微损伤 活体患者(AIM 2b)这表明，由于疲劳损伤的累积，前交叉韧带可能会失效。这将会 暗示可能有时间修改运动员的工作-休息周期，以通过阻止受伤来降低前交叉韧带受伤的风险 周期(Olsen 2006)和允许前交叉韧带愈合(Maekawa 1996)。

Abstract This proposal challenges the current dogma that `non-contact' anterior cruciate ligament (ACL) ruptures are due to sudden awkward landing or overload event. In the past funding cycle we developed the first evidence that the ACL can also fail under repetitive sub-maximal loading (Lipps 2013), helping to explain why an ACL can fail during a routine athletic maneuver. Pilot data suggest that this fatigue failure is associated with an accumulation of microdamage near the proximal femoral enthesis. We request funds to test this hypothesis. In AIM 1 60 pairs of knees from sex- and size-matched younger cadavers (30 males, 30 females) will be positioned at an initial flexion angle of 15o via pretensioned knee muscle-tendon equivalents that allow the knee to flex under a distal impulsive test load. ACL fatigue life will be determined via repetitive sub-maximal four-times bodyweight impulsive 3-D compound loading (compression + trans knee muscle loading + flexion moment + knee abduction moment + internal tibial axial torque) applied to each knee. A Cox regression model will be used to rank the relative importance of sex, internal femoral axial rotation range of motion (ROM) and lateral tibial slope in limiting ACL fatigue life. In AIM 2a we will use histological images and a binomial exact test to determine the percentage of the knees undergoing AIM 1 fatigue testing that exhibit microdamage at or near the femoral enthesis exceeding the +3*SD area found in the 32 untested, paired, control knees. Similarly, in AIM 2b we will salvage ACL femoral enthesis explants in 60 healthy young adults (30 females) aged 14-25 years undergoing routine reconstruction of their ACL and determine the percentage of explants exhibiting microdamage area exceeding the +3*SD value measured in 30 untested age- and sex-matched cadaveric controls. If greater-than-normal ACL microdamage is found in fatigue-tested knees in vitro (AIM 2a) and in ACL-injured patients in vivo (AIM 2b) this suggests the ACL can fail due to an accumulation of fatigue damage. This would imply that there may be time to modify athlete work-rest cycles to reduce ACL injury risk by arresting the injury cycle (Olsen 2006) and allowing the ACL to heal (Maekawa 1996).