rhBMP-2/CPC强化骨质疏松椎体力学强度的实验研究

The experimental study of the effect of rhBMP-2/CPC on biomechanical intensity for osteoporotic vertebrae

目的观察人重组骨形态发生蛋白-2复合磷酸钙骨水泥(recombinant human bonemorphogenetic protein-2/calcium phosphate cement,rhBMP-2/CPC)强化骨质疏松绵羊腰椎生物力学强度的动态效果。方法成年雌性绵羊12只行去势手术后饲养1年,测量去势前后腰椎骨密度。取L1-L6为实验对象,空白组不给予任何处理;CPC组中,经椎弓根向椎体内注射CPC(2.0 ml);rhBMP-2/CPC组中,经椎弓根向椎体内注射rhBMP-2/CPC(2.0 ml)。于术后1天、6周、12周和24周四个时间点各随机处死3只绵羊,对椎体行压缩实验,分别测量各组中椎体的最大压缩应力(σult)和能量吸收值(EAV),对比分析同一时间点不同方法之间和同一方法的不同时间点之间的力学指标。结果去势1年后绵羊腰椎骨密度显著下降,差异有显著性(P<0.05),骨质疏松绵羊模型建立成功。在术后各时间点,CPC组和rhBMP-2/CPC组的σult和EAV均显著高于空白组(P<0.05);术后1天、6周和12周,rhBMP-2/CPC组和CPC组之间的差异无统计学意义(P>0.05),而rhBMP-2/CPC组中24周的σult显著高于CPC组(P<0.05)。空白组和CPC组中σult各时间点之间的差异均无显著性(P>0.05),而rhBMP-2/CPC组中24周的σult显著高于该组其他三个时间点(P<0.05)。结论 rhBMP-2/CPC不仅能提高骨质疏松椎体的即时强度,还能很好的维持椎体的动态力学强度和进一步提高椎体的远期强度,为脊柱达到坚强骨性融合提供了良好的力学环境。

Objective To observe the dynamic efficacy of recombinant human bone morphogenetic protein- 2/calcium phosphate cement （rhBMP-2/CPC） on the augment of biomechanical intensity of the lumbar vertebrae in ovariectomized sheep. Methods Twelve adult female sheep were ovariectomized and raised for 1 year after the surgery. Bone mineral densities （BMD） of the lumbar vertebrae were measured before and after the surgery-. L1-L6 were the experimental objects. The sheep in control group were offered no treatment. The sheep in CPC group were injected with CPC （2. 0ml） via the transpedicular of the vertebra. The sheep in rhBMP-2/CPC group were injected with rhBMP-2/CPC （2. Oral） via the transpedicular of the vertebra. Every 3 sheep were randomly killed on day 1, week 6, week 12, and week 24 after the surgery. The vertebra compression test was performed. The ultimate compressive stress （δult） and energy absorption value （EAV） of the vertebrae in every group were measured. The biomechanieal indexes were compared and analyzed among different methods at the same time and among different time points using same method. Results BMD of the sheep vertebrae significantly decreased at 1 year after the surgery （P 〈 0.05）. The osteoporotie sheep model was established successfully. The results of tru, and EAV of the CPC group and rhBMP-2/CPC group at any time points after the surgery were significantly higher than those of the control group （P 〈 0.05）. The differences between the CPC group and rhBMP-2/CPC group were not statistically significant on day 1, week 6, and week 12 （P 〉 0.05）. However, ~u~, in rhBMP-2/CPC group was significantly higher than that in CPC group on week 24 （P 〈 0. 05）. The differences of δult, between control and CPC group on each time point were not statistically significant （ P ~ 0.05 ）. However, δult in rhBMP-2/ CPC group on week 24 was significantly higher than that on other three time points in the same group （P 〈 O. 05）. Conclusion rhBMP-2/CPC not only improved the immediate mechanical strength of osteoporotic vertebrae, but also maintained the dynamic mechanical strength and further enhanced the lone-term mechanical strength of osteoporotic vertebrae, which could provide an ideal mechanical condition for firm bone fusion of the spine.