New Perspectives on ACL Injury

摘要 这一建议挑战了目前的教条，即“非接触性”前交叉韧带（ACL）断裂是 由于突然的笨拙着陆或过载事件。在过去的融资周期中，我们开发了第一个证据 ACL也可能在重复的次最大载荷下失效（Lipps 2013），这有助于解释为什么ACL 在常规的运动动作中会失败。试点数据表明，这种疲劳失效与 股骨近端附着点附近的微损伤累积。我们要求提供资金来检验这一假设。 在AIM 1中，将对来自性别和尺寸匹配的年轻尸体（30名男性，30名女性）的60对膝关节进行 通过预张紧的膝关节肌肉-肌腱等效物以15 °的初始屈曲角定位， 膝关节在远端冲击测试载荷下弯曲。ACL疲劳寿命将通过重复的次最大 4倍体重脉冲三维复合负荷（压缩+跨膝肌肉负荷+屈曲 力矩+膝关节外展力矩+内部胫骨轴向扭矩）。考克斯回归模型 将用于对性别、股骨内轴向旋转运动范围（ROM）和 限制ACL疲劳寿命的胫骨外侧斜率。 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疲劳测试，在股骨止点处或其附近出现微损伤， 在32个未测试的配对对照膝关节中发现+3*SD面积。同样，在AIM 2b中，我们将保留ACL股骨 在60例接受常规重建的14-25岁健康年轻成人（30例女性）中植入附着点外植体 并确定显示微损伤面积超过+3*SD的外植体百分比 在30个未经测试的年龄和性别匹配的尸体对照中测量的值。 如果在体外疲劳测试膝关节（AIM 2a）和ACL损伤膝关节中发现ACL微损伤大于正常， 患者体内（AIM 2b），这表明ACL可能由于疲劳损伤的累积而失效。这将 这意味着可能有时间修改运动员工作-休息周期，以通过阻止损伤来降低ACL损伤风险 循环（Olsen 2006）并允许ACL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).