天鹅记忆接骨器对长骨干骨折愈合的影响

目的 探讨天鹅记忆接骨器（swan-like memory compressive connector，SMC）对实验性长骨干骨折愈合过程中骨力学性能、形态结构和微循环的影响。方法 56只新西兰大白兔行双侧肱骨干截骨后，随机选取一侧用SMC固定，取侧用四孔加压接骨板（dynamic compressive plate,DCP）固定。分别于术后2、4、8、12、16、20周取材，行应力遮挡试验、CT扫描和水平扭转力学测定，观察两组内固定对骨结构和力学性能的影响。另外于骨膜愈合情况。结果 各时相SMC时间延长而加重；SMC组皮质骨厚度和密度保持正常。术后4周开始，SMC组的扭转刚度大于DCP组。SMC组对骨血供的损伤较DCP组轻，从术后3d至术后4周，两组同骨外板血流量的差异均有显著性。SMC组骨外板血供术后4周即恢复正常，而DCP组8周才恢复正常。从内固定后即刻开始，SMC组髓内血流量始终大于DCP组。SMC组骨愈合速度比DCP组快，且骨折愈合局部无骨痂，也无骨质疏松。结论 SMC与DCP相比，具有材料和几何构型上的优势，对固定段骨干几乎不产生应力遮挡；且对骨折局部血供的损伤轻，有利于骨血供恢复。何构型上的优势，对固定段骨干几乎不产生应力遮挡；且对骨折局部血供的损伤轻，有利于骨血供恢复。

Effects of swan-like memory compressive connector on experimental humerus fracture healing

Objective To explore the effects of swan-like memory compressive connector(SMC) made of Ni-Ti shape memory alloy on stress shielding rate, struct ure and mechanical properties as well as the blood flow of cortical bone of expe rimental fracture healing. Methods Mid-shaft osteotomies of bilateral humerus we re performed in 56 rabbits. One side was randomly fixed with SMC, and the other side was plated with a 4-holes dynamic compressive plate (DCP). At 2, 4, 8, 12, 16,and 20 weeks after operations, the humeri in 8 rabbits were harvested. The st ress-shielding rate was measured using axial compressive test in situ samples. T he geometrical structure and bone density were examined by CT scans, and the mec hanical property was assessed by torsion tests. Blood flow was measured in real time using Laser-Doppler flowmetry. The cortical bone perfusion of 16 rabbits wa s measured at 10 time intervals (after periosteotomy, after fracture, instant af ter fixation, at 1, 3, and 7 days, and 2, 4, 8, and 12 weeks postoperatively). B lood flow was measured at outer and inner cortical bone beneath the fixation. Si multaneously, anteroposterior radiograph of the humerus was taken. Results The s tress-shielding rate in SMC group was significantly lower than that of DCP group (P <0.01). The cortical bone plated by DCP gradually became thinner since 8 wee ks after operation, the CT value of DCP group decreased accordingly (P<0.05 or P <0.01). Nevertheless, CT value of SMC group remained normal at all the time. Aft er 4 weeks, the torsional stiffness in SMC group was higher than DCP group (P< 0 .05 or P<0.01). SMC compromised blood supply of cortical bone significantly less than that of DCP. From 3 d to 4 weeks postoperatively, the outer cortical blood supply in SMC group was higher than that in DCP group (P<0.05 or P<0.01). Corti cal revascularization occurred 4 weeks after operation in the SMC group but not until 8 weeks in the DCP group. Up to 12 weeks postoperatively, the inner cortic al blood supply in the SMC group was higher than that in the DCP group (P<0.05 o r P<0.01). Radiographic fracture healing treated by SMC showed primary healing a nd had no cortical osteoporosis underneath the fixation material. Conclusion SM C has many advantages of material and geometrical conformation. Furthermore, it is not only beneficial to fracture healing and mechanical property of the fixed bone, but also on recovery of blood supply of cortical bones.