骨水泥强化骨质疏松椎弓根螺钉的生物力学特征

Biomechanical characteristics of pedicle screw repaired with cement in the treatment of osteoporosis

目的:评价聚甲基丙烯酸甲酯骨水泥强化骨质疏松椎弓根螺钉脊柱内固定术对不稳定性胸腰椎损伤的即刻稳定性和反复载荷后的稳定性。方法:选用南方医科大学生物力学实验室1997-12/1999-12自愿捐赠的6具自然死亡的新鲜女性骨质疏松脊柱标本(T10～L5),制备L1椎体节段不稳定性损伤模型后椎弓根螺钉系统固定,行左/右侧弯、左/右旋转和前屈/后伸6个方向的稳定性测试,并在MTS858试验机上进行屈/伸疲劳试验。比较:①正常脊柱。②损伤模型未钢板固定疲劳前(强化前)。③未钢板固定疲劳后(强化前)。④钢板固定疲劳前(强化后)。⑤钢板固定疲劳后(强化后)5种状态下脊柱的稳定性变化。结果:①损伤模型未强化疲劳前、强化后疲劳前、强化后疲劳后3种状态下,运动范围的差异无统计学意义(前屈和后伸时的运动角度分别为6.23°±1.56°,4.49°±1.00°,4.46°±1.83°和6.60°±1.80°,4.41°±0.82°,4.46°±1.83°,P>0.05)。②损伤模型未强化疲劳前、强化后疲劳前和强化后疲劳后均小于正常脊柱、未强化疲劳后状态的运动角度(8.75°±1.88°,1.47°±2.25°和8.92°±2.97°,12.24°±3.08°,P<0.01)。结论:聚甲基丙烯酸甲酯强化骨质疏松椎弓根螺钉脊柱内固定能明显增强脊柱的稳定性和抗疲劳能力。

AIM： To evaluate the immediate stability of pedicle screw fixation with polymethyl methacrylate （PMMA） of cement in augmentation of osteoporotic spine as well as the stability after repeated load. METHOIDS： Osteeporotic spines （T10-L5） from 6 fresh female corpora of natural death in the Biomechanical Laboratory of Southern Medical University from December 1997 to December 1999 were selected. Pedicle screw fixation was performed after the establishment of L1 vetebral sectional unstable injured models, and then stabilities of left and right lateral bending, left and right rotation and anteflect/post-extension were tested. Fatigue experiments of reflexion and extention were done with MTS 858 testing machine. Comparison of changes of vertebral stabilities under the following 5 status： ①Normal vertebral column.②Injured models without steel-plate fixation before fatigue （before augmentation）.③Injured models without steel-plate fixation after fatigue （before augmentation）.④ Injured models with steel-plate fixation before fatigue （after augmentation）. ⑤Injured models with steel-plate fixation after fatigue （after augmentation）. RESULTS： ①There were no significant differences in range of motion （ROM） in injured models without augmentation before fatigue, after augmentation before fatigue and after augmentation and fatigue [angles of flexion and extension were respectively （6.23°±1.56° ）, （4.49°±1.00° ）, （4.46°±1.83°） ,and （6.60°±1.80°） ,（4.41°±0.82°） , （4.46°±1.83°） ,P 〉 0.05]. ②Motion angles of injured models before augmentation and fatigue, after augmentation before fatigue, after augulentation and fatigue were smaller than those of normal vetebral column and those before augmentation after fatigue （8.75°±1.88°, 1.47°±2.25°and 8.920°2.97°, 12.24°±3.08° ,P 〈 0.01 ）. CONCLUSION： PMMA augmentated osteoporotic pedicle screw fixation can significantly reinforce vertebral stability and anti-fatigue capability.