Bak B, Jensen K S
Department of Connective Tissue Biology, University of Aarhus, Denmark.
Bone. 1992;13(4):289-95. doi: 10.1016/8756-3282(92)90073-6.
The influence of the fracture level on the biomechanical properties of healing rat tibial fractures has not been investigated so far, despite the widespread use of rats in fracture healing studies. Fractures were produced in four different zones in the right rat tibia and immobilized with a K-wire. A fifth group of rats was not fractured. After 40 days of healing the fractures and the non-fractured bones were tested in three-point bending. A distinct correlation was found between fracture level and mechanical parameters: maximum load, maximum stiffness, and maximum stress decreased the more distal the fracture was located. In the non-fractured bones, maximum load and maximum stress were constant in all four zones tested, whereas energy absorption increased in the distal part of the tibia. No influence of the healing fracture was found on the contralateral, non-fractured tibia, compared with the animals left undisturbed, and the mechanical properties of the right and the left tibia were found to be symmetrical in terms of mean values. Four different methods of determining the area moment of inertia were investigated, and the simple method of approximating the cross section to an elliptical annulus was found to correlate well with the area moment of inertia, determined from computer tracings of bone slices prepared from the test specimens after the bending test. The computer tracings were corrected for the compression of the specimens caused by the mechanical test.
尽管大鼠在骨折愈合研究中被广泛使用，但迄今为止尚未研究骨折部位对大鼠胫骨骨折愈合生物力学特性的影响。在右侧大鼠胫骨的四个不同区域制造骨折，并用克氏针固定。第五组大鼠未骨折。愈合40天后，对骨折和未骨折的骨头进行三点弯曲试验。发现骨折部位与力学参数之间存在明显相关性：骨折位置越靠近远端，最大载荷、最大刚度和最大应力下降得越多。在未骨折的骨头中，在所测试的所有四个区域中，最大载荷和最大应力是恒定的，而胫骨远端的能量吸收增加。与未受干扰的动物相比，未发现愈合骨折对侧未骨折的胫骨有影响，并且发现左右胫骨的力学性能在平均值方面是对称的。研究了四种不同的确定惯性矩面积的方法，发现将横截面近似为椭圆环的简单方法与通过对弯曲试验后从测试标本制备的骨切片进行计算机追踪确定的惯性矩面积有很好的相关性。对计算机追踪结果进行了校正，以消除机械测试对标本造成的压缩影响。
