经皮椎体成形术后骨折椎体生物力学性能和组织形态研究

Study on the biomechanical property and histomorphological changes of fractured vertebrae after percutaneous vertebroplasty

目的:观察经皮椎体成形术后骨折椎体的生物力学性能和组织形态。方法:将105只新西兰雌兔随机分为3组,每组35只。B组和C组采用卵巢切除加地塞米松肌肉注射法进行骨质疏松造模。造模成功后,在所有实验动物L4和L5椎体上通过手术造成骨缺损,C组实验动物在形成骨缺损的椎体中模拟经皮椎体成形术注射调制好的聚甲基丙烯酸甲酯骨水泥Ⅲ。分别于模拟经皮椎体成形术完成后2周、4周、8周、12周、16周、24周、48周从各组中随机选取5只实验动物处死,取出进行过手术的2个椎体,进行生物力学强度测定。同时,C组作盐酸四环素荧光标记,经甲苯胺蓝染色后进行椎体组织形态观察。结果:①椎体轴向压缩实验结果。除48周外[(0.54±0.14)mm,(0.83±0.26)mm,(0.54±0.16)mm,F=3.744,P=0.054],3组椎体标本术后2周、4周、8周、12周、16周、24周时的轴向压缩位移比较,组间差异均有统计学意义[(0.62±0.10)mm,(0.92±0.22)mm,(0.43±0.09)mm,F=13.489,P=0.001;(0.65±0.17)mm,(1.01±0.16)mm,(0.44±0.08)mm,F=24.843,P=0.000;(0.61±0.12)mm,(1.27±0.23)mm,(0.50±0.11)mm,F=32.262,P=0.000;(0.61±0.15)mm,(1.10±0.10)mm,(0.49±0.13)mm,F=25.488,P=0.000;(0.58±0.19)mm,(1.17±0.16)mm,(0.54±0.10)mm,F=24.730,P=0.000;(0.55±0.17)mm,(1.10±0.28)mm,(0.53±0.15)mm,F=11.998,P=0.001]。进一步两两比较,A组和C组各时点轴向压缩位移均小于B组(P=0.009,P=0.001,P=0.000,P=0.000,P=0.000,P=0.001;P=0.000,P=0.000,P=0.000,P=0.000,P=0.000,P=0.001);除4周时外(P=0.038),A组各时点轴向压缩位移与C组比较,差异均无统计学意义(P=0.062,P=0.328,P=0.208,P=0.648,P=0.894)。②椎体三点弯曲实验结果。3组实验动物椎体标本术后2周、4周、8周、12周、16周、24周和48周时的最大载荷比较,组间差异均有统计学意义[(178.0±7.7)N,(130.3±6.2)N,(232.0±1.7)N,F=385.253,P=0.000;(178.3±4.4)N,(127.7±7.1)N,(226.0±5.4)N,F=371.286,P=0.000;(182.4±4.4)N,(131.8±5.2)N,(221.0±3.1)N,F=536.544,P=0.000;(184.0±0.8)N,(137.0±6.6)N,(215.0±3.2)N,F=422.579,P=0.000;(182.9±0.9)N,(140.2±1.5)N,(217.0±4.3)N,F=1 006.122,P=0.000;(189.0±3.2)N,(140.6±1.7)N,(194.0±4.9)N,F=351.372,P=0.000;(191.9±3.9)N,(142.4±2.1)N,(191.0±8.1)N,F=139.682,P=0.000]。进一步两两比较,A组和C组各时点的最大载荷均大于B组(P=0.000,P=0.000,P=0.000,P=0.000,P=0.000,P=0.000,P=0.000;P=0.000,P=0.000,P=0.000,P=0.000,P=0.000,P=0.000,P=0.000);除24周和48周外(P=0.054,P=0.724),C组各时点的最大载荷均大于A组(P=0.000,P=0.000,P=0.000,P=0.000,P=0.000)。③椎体抗扭转实验结果。3组实验动物椎体标本术后2周、4周、8周、12周、16周、24周和48周时的扭转角度比较,组间差异均有统计学意义[(3.8°±0.6°),(5.4°±0.5°),(2.4°±0.6°),F=37.977,P=0.000;(4.0°±1.3°),(5.8°±1.6°),(2.4°±0.7°),F=9.408,P=0.003;(3.7°±0.8°),(5.7°±0.4°),(2.3°±0.7°),F=32.229,P=0.000;(3.5°±0.8°),(5.8°±0.4°),(2.4°±0.5°),F=38.685,P=0.000;(3.5°±0.8°),(5.7°±0.4°),(2.4°±0.4°),F=41.931,P=0.000;(3.4°±0.8°),(5.2°±1.2°),(2.5°±0.8°),F=10.072,P=0.003;(3.0°±0.3°),(5.1°±0.4°),(2.7°±0.4°),F=53.166,P=0.000]。进一步两两比较,A组和C组各时点的扭转角度均小于B组(P=0.001,P=0.045,P=0.000,P=0.000,P=0.000,P=0.012,P=0.000;P=0.000,P=0.001,P=0.000,P=0.000,P=0.000,P=0.001,P=0.000);除4周、24周和48周外(P=0.057,P=0.171,P=0.347),C组各时点的扭转角度均小于A组(P=0.001,P=0.008,P=0.014,P=0.017)。④椎体组织学观察结果。经皮椎体成形术后2周和4周时,聚甲基丙烯酸甲酯骨水泥Ⅲ与宿主骨交界处有大量软骨细胞和成骨细胞,交界处未见纤维组织;8周时骨水泥与宿主骨结合紧密,软骨组织被新生的类骨质替代,新生骨组织明显增加,交界处未见纤维组织;12周和16周时可见纤维组织,骨水泥与宿主骨结合更加紧密,界面处类骨质减少,矿化骨痂增多,编织骨被板层骨取代;24周和48周时可见少量破骨细胞和骨单位,大部分界面结合处新生骨组织与骨水泥结合紧密。结论:经皮椎体成形术后,凝固的聚甲基丙烯酸甲酯骨水泥能与骨组织形成骨性结合,为骨折椎体提供较好的近期和远期生物力学性能。

Objective ：To observe the biomechanical property and histomorphological changes of fractured vertebrae after percutaneous vertebroplasty（PVP）. Methods：One hundred and five New Zealand female rabbits were randomly divided into 3 groups ,35 cases in each group. The rabbits in group B and group C were administrated with ovariectomy and Dexamethasone muscle injection to build models of oste- oporosis. Then, bone defects were created through surgery in the vertebral body of L4 and L5 for all rabbits. The vertebral body with bone de- fects of rabbits in group C were administrated with polymethylmethacrylate Ⅲ （PMMA Ⅲ） injection to simulate PVP. At 2,4,8,12,16,24 and 48 weeks after the simulated PVP,5 rabbits were selected from each group and were executed, and their vertebrae of L4 and L5 were fetched out for determining the biomechanical strength. Meanwhile, the samples of group C were fluorescent labeled with tetracycline hydro- chloride, and the histomorphological changes of vertebrae were observed after toluidine blue staining. Results：The axial compression test showed that there were statistical differences in axial compressional displacement of vertebral specimens between the 3 groups at different post-operative time points （ 2 weeks ：0.62 ＋/- 0.10,0.92 ＋/- 0.22,0.43 ＋/- 0.09 mm, F = 13. 489, P = 0.001 ; 4 weeks ： 0.65 ＋/- 0.17, 1.01 ＋/-0.16,0.44 ＋/-0.08 mm,F =24. 843,P =0.000;8 weeks：0.61 ＋/-0.12,1.27 ＋/-0.23,0.50 ＋/-0.11 mm,F =32. 262,P = 0.000;12 weeks：0.61 ＋/-0.15,1.10 ＋/-0.10,0.49 ＋/-0.13 mm,F =25. 488,P =0. 000;16 weeks：0.58 ＋/-0.19,1.17 ＋/-0.16, 0.54 ＋/- 0.10 mm, F = 24. 730, P = 0.000 ;24 weeks ： 0.55 ＋/- 0.17,1.10 ＋/- 0.28,0.53 ＋/- 0.15 mm, F = 11. 998, P = 0.001 ）, except at 48 weeks （0.54 ＋/- 0.14,0.83 ＋/- 0.26,0.54 ＋/- 0.16 mm, F = 3. 744, P = 0.054）. Further pairwise comparison showed that the axial compressional displacement at each time point in group A and group C were all less than those of group B（ group A vs group B ：P = 0. 009, P = 0. 001, P = 0. 000,P = 0. 000, P = 0. 000, P = 0. 001 ; group C vs group B ： P = 0. 000, P = 0. 000, P = 0. 000, P = 0. 000, P = 0. 000, P = 0. 001 ） , and there were no statistical differences in axial compressional displacement at each time point between group A and group C （ P = 0. 062, P = 0. 328, P = 0. 208, P = 0. 648, P = 0. 894） except at 4 weeks （ P = 0. 038 ）. The three-point bend test showed that there were statistical differences in maximum load on vertebral specimens between the 3 groups at different post-operative time points（2 weeks：178.0 ＋/-7.7,130.3 ＋/-6.2,232.0 ＋/- 1.7 N,F =385. 253,P =0.000;4 weeks：178.3 ＋/-4.4,127.7 ＋/-7.1,226.0 ＋/-5.4 N,F= 371. 286,P =0.000;8 weeks：182.4 ＋/-4.4,131.8 ＋/-5.2,221.0 ＋/-3.1 N,F =536. 544,P =0.000;12 weeks：184.0 ＋/-0.8,137.0 ＋/-6.6,215.0＋/-3.2 N,F=422. 579,P =0.000;16 weeks：182.9 ＋/-0.9,140.2 ＋/-1.5,217.0 ＋/-4.3 N,F=1 006. 122,P = 0.000;24 weeks：189.0 ＋/-3.2,140.6 ＋/- 1.7,194.0 ＋/-4.9 N,F =351. 372,P =0. 000;48 weeks：191.9 ＋/-3.9,142.4 ＋/-2.1, 191.0 ＋/- 8.1 N, F = 139. 682,P = 0. 000）. Further pairwise comparison showed that the maximum load at each time point in group A and group C were all greater than those of group B （ group A vs group B ： P = 0. 000, P = 0. 000, P = 0. 000, P = 0. 000, P = 0. 000, P = 0. 000, P = 0. 000 ; group B vs group C ： P = 0. 000, P = 0. 000, P = 0.000, P = 0. 000, P = 0.000, P = 0. 000, P = 0. 000 ） , and the maximum load at each time point in group C were all greater than that of group A （ P = 0. 000,P = 0. 000, P = 0. 000,P = 0. 000, P = 0. 000 ） except at 24 and 48 weeks（P = 0. 054, P = 0. 724）. The resist-torsion test showed that there were statistical differences in the torsional angle of vertebral specimens between the 3 groups at different post-operative time points （2 weeks： 3.8° ＋/-0.6°, 5.4° ＋/-0.5°, 2.4° ＋/-0.6°, F = 37. 977,P =0.000;4 weeks：4.0° ＋/- 1.3°,5. 8° ＋/- 1.6°,2. 4° ＋/-0.7°,F =9. 408,P =0. 003;8 weeks：3.7° ＋/-0.8°,5. 7° ＋/- 0.4°,2.3° ＋/-0.7°,F =32. 229,P =0.000;12 weeks：3.5° ＋/-0.8°,5.8° ＋/-0.4°,2.4° ＋/-0.5°,F=38. 685,P =0.000;16 weeks： 3.5° ＋/-0.8°,5.7° ＋/-0.4°,2. 4° ＋/-0.4°,F =41. 931,P =0. 000;24 weeks：3.4° ＋/-0.8°,5. 2° ＋/- 1.2°,2. 5° ＋/-0.8°,F = 10. 072 ,P =0. 003 ;48 weeks： 3.0° ＋/- 0.3° , 5.1° ＋/- 0.4° ,2.7° ＋/- 0.4° , F = 53. 166, P = 0. 000）. Further pairwise comparison showed that the torsional angle at each time point in group A and group C were all less than those of group B （ group A vs group B ： P = 0. 001 ,P = 0. 045 ,P = 0. 000 ,P = 0. 000, P = 0. 000, P = 0. 012, P = 0. 000 ; group B vs group C ： P = 0. 000, P = 0. 001, P = 0. 000, P = 0. 000 ,P = 0. 000 ,P = 0. 001 ,P = 0. 000） , and the torsional angle at each time point in group C were all less than those of group A（ P = 0. 001 ,P =0. 008,P =0. 014,P =0.017）except at 4,24 and 48 weeks（P =0. 057,P =0. 171,P =0. 347）. A great number of chondro- cytes and osteoblasts were found at the junction of PMMA m and host bone at 2 and 4 weeks after PVP, while no fibrous tissues were found. PMMA Ⅲ were integrated tightly with the host bones 8 weeks after the surgery, and the cartilage tissues were replaced by the neogenetic oste- oid. Meanwhile, the neogenetie bone tissues increased significantly and no fibrous tissues were found at the conjunctive area. At 12 and 16 weeks after the surgery, the fibrous tissues appeared and the PMMA m were integrated more tightly with the host bones. Meanwhile the oste- oid decreased and the mineralization bony callus increased, and the woven bone was replaced by the lamellar bone. At 24 and 48 weeks after the surgery, a small number of osteoclasts and bone units appeared and the neogenetic bone tissues were integrated tightly with the PMMA Ⅲ at most of the interfaces. Conclusion ： After PVP, the solidified PMMA m can be osseo-integrated with bone tissues, as a result, it can provide good short-term and long-term biomechanical property for the fractured vertebrae.