Mølster A O, Gjerdet N R, Langeland N, Lekven J, Alho A
J Orthop Res. 1987;5(1):29-35. doi: 10.1002/jor.1100050106.
Ninety-six rats underwent a midshaft transverse osteotomy followed by osteosynthesis with an intramedullary nail, so that the effect of bending instability on time to union and on the mechanical properties of experimental diaphyseal fracture could be evaluated. Rotation was reduced by cementing both nail ends to the bone. Rigid nails made of stainless steel were used on one group and flexible nails made of polyacetal resin were used on another group. Serial radiographs were evaluated at 4-6-week intervals. Twelve animals with either nail type were killed at 4, 8, 16, and 24 weeks. Both femora were mechanically tested and the callus diameters were measured. There was no significant difference in time to union between the two groups. The cross-sectional area of callus was significantly higher at 8 and 16 weeks in femora with flexible nails. The strength, toughness, and resilience of the bone increased in this group until 24 weeks. Between 16 and 24 weeks, these parameters did not improve in femora with rigid nails. Poorer mechanical properties in femora with steel nails are interpreted as an effect of stress protection of the bone. This study, therefore, indicates that flexible nails prevent stress protection effects without delaying union.
96只大鼠接受了骨干中段横向截骨术，随后用髓内钉进行骨固定，以便评估弯曲不稳定性对骨折愈合时间和实验性骨干骨折力学性能的影响。通过将髓内钉两端与骨固定来减少旋转。一组使用由不锈钢制成的刚性髓内钉，另一组使用由聚甲醛树脂制成的柔性髓内钉。每隔4至6周对连续的X线片进行评估。每组中有12只动物在4周、8周、16周和24周时处死。对双侧股骨进行力学测试并测量骨痂直径。两组之间在骨折愈合时间上没有显著差异。在使用柔性髓内钉的股骨中，骨痂横截面积在8周和16周时显著更高。该组中骨的强度、韧性和弹性在24周前均有所增加。在16周至24周之间，使用刚性髓内钉的股骨中这些参数没有改善。使用钢钉的股骨力学性能较差被解释为骨应力保护的结果。因此，本研究表明，柔性髓内钉可防止应力保护效应且不延迟骨折愈合。
