BACKGROUND: Microwave treatment is a common physical therapy method that can increase the temperature and blood circulation of deep tissues, and is used for improving fracture repair. However, microwave treatment cannot be used if there is surgically implanted metal plate or screw. OBJECTIVE: To observe the dame of microwave treatment to the tissues surrounding the titanium alloy implants. METHODS: Forty-four New Zealand white rabbits were randomized into experimental and control groups. The model of the fracture at the middle of the femur was established in all rabbits, and the rabbits in the experimental group were implanted with titanium alloy internal fixation systems. A 30-day microwave treatment (2 450 MHz, 20 W or 40 W, 20 minutes daily) was applied to the fracture site in all rabbits at 3 days after operation. RESULTS AND CONCLUSION: After 20 W of wave microwave treatment, the temperature of tissues around the implants showed no significant increase or severe heat injury. While, 40 W of wave microwave treatment significantly increased the temperature of tissues around the implants and the tissue was damaged severely. Our results indicate that, the low-dosage microwave treatment may be a promising method in the rehabilitation therapy of fractures with titanium alloy internal fixation.%背景:普通接骨板内固定后容易出现"应力遮挡"效应,而组合式可变应力接骨板内固定能够减少接骨板的"应力遮挡"效应,促进骨质的正常愈合,降低普通钢板所引起并发症,缩短骨折愈合时间.目的:观察不同内固定方式对实验性羊股骨骨折愈合过程的影像学及组织学的影响.方法:选用32只健康成年山羊随机分为实验组和对照组,每组16只,通过股骨截骨方法构建骨折动物模型,实验组和对照组分别采用组合式可变应力接骨板和普通直型钢板进行固定,采用X射线、CT及组织学方法对固定后4,8,12周骨痂进行观察和比较.结果与结论:①X射线片检查结果显示,两组动物固定后4-12周骨折线从逐渐模糊到完全愈合,且骨折断端间隙明显减小,且取出内固定发现,实验组术中见骨折端周围骨痂量少且坚硬,接骨板本身无骨痂覆盖,对照组接骨板见大量骨痂覆盖,钢板周围骨痂量也较大;②CT 检查结果显示,两组动物术后4-12周 CT值和骨痂横截面积值逐渐升高,且实验组动物在术后4,8,12周CT值和骨痂横截面积值均显著高于对照组(P < 0.05),且对照组在术后8,12周骨髓腔直径显著高于实验组(P < 0.05),而骨皮质厚度值显著低于实验组(P < 0.05);③组织学检查结果显示,与对照组相比,实验组骨折线愈合,髓腔内纤维骨痂减少,骨痂更稀疏,大部分纤维骨痂被吸收,髓腔再通;④结果说明,组合式可变应力接骨板内固定能够为股骨骨折断端早期愈合提供较稳定的生物力学环境,降低钢板应力遮挡效应,促进骨痂形成,从而有利于骨折愈合.
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