Institute of Orthopaedic Research and Biomechanics, Ulm University, Helmholtzstrasse 14, Ulm, Germany.
J Biomech. 2010 Sep 17;43(13):2473-9. doi: 10.1016/j.jbiomech.2010.05.028. Epub 2010 Jun 20.
The rat is of increasing importance for experimental studies on fracture healing. The healing outcome of long bone fractures is strongly influenced by mechanical factors, such as the interfragmentary movement. This movement depends on the stability of the fracture fixation and the musculoskeletal loads. However, little is known about these loads in rats. The musculoskeletal loads during gait were estimated using an inverse-dynamic musculoskeletal model of the right hindlimb of the rat. This model was based on a micro-CT scan of the lower extremities and an anatomical study using 15 rat cadavers. Kinematics were reconstructed from X-ray movies, taken simultaneously from two perpendicular directions during a gait cycle. The ground reaction forces were taken from the literature. The muscle forces were calculated using an optimization procedure. The internal forces and moments varied over the gait cycle and along the femoral axis. The greatest internal force (up to 7 times bodyweight) acted in the longitudinal direction. The greatest internal moment (up to 13.8 bodyweight times millimeter) acted in the sagittal plane of the femur. The validity of the model was corroborated by comparing the estimated strains caused by the calculated loads on the surface of the femoral mid-shaft with those from the literature. Knowledge of the internal loads in the femur of the rat allows adjustment of the biomechanical properties of fixation devices in fracture healing studies to the desired interfragmentary movement.
大鼠在骨折愈合的实验研究中越来越重要。长骨骨折的愈合结果受机械因素的强烈影响，如断端间的活动。这种活动取决于骨折固定的稳定性和肌肉骨骼的负荷。然而，对于大鼠的这些负荷知之甚少。通过大鼠右后肢的反向动力学肌肉骨骼模型来估计步态时的肌肉骨骼负荷。该模型基于下肢的微 CT 扫描和使用 15 只大鼠尸体的解剖学研究。通过 X 射线电影从两个垂直方向在步态周期中同时重建运动学。地面反作用力取自文献。肌肉力通过优化程序计算。在步态周期内和股骨轴线上，内部力和力矩发生变化。最大的内力（高达体重的 7 倍）沿纵向作用。最大的内部力矩（高达 13.8 倍体重毫米）在股骨矢状面作用。通过将计算出的负载在股骨中段表面引起的估计应变与文献中的应变进行比较，验证了模型的有效性。了解大鼠股骨内的负荷可以调整骨折愈合研究中固定装置的生物力学特性，以达到所需的断端间活动。
