强化骨质疏松椎弓根螺钉对脊柱稳定性影响的生物力学研究

目的探讨聚甲基丙烯酸甲酯(polymethylmethacrylate,PMMA)骨水泥,强化骨质疏松椎弓根螺钉在脊柱内固定术中,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 6具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MTS 858试验机上进行屈/伸疲劳试验.比较○a正常脊柱(正常对照组);○b损伤模型钢板固定疲劳前(强化前);○c钢板固定疲劳后(强化前);○d钢板固定疲劳前(强化后);○e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○b、○d、○e三种状态下,前屈和后伸时的运动角度分别为6.23±1.56和4.49±1.00、 4.46±1.83和6.60±1.80、 4.41±0.82和4.46±1.83,运动范围的差异无统计学意义(P＞0.05),但均小于○a、○c状态下的运动角度8.75±1.88和1.47±2.25、8.92±2.97和12.24±3.08,有统计学意义(P＜0.01).结论 PMMA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.

AN IN VITRO BIOMECHANICAL EVALUATION OF EFFECT OF AUGMENTATION PEDICLE SCREW FIXATION WITH POLYMETHYLMETHACRYLATE ON OSTEOPOROTIC SPINE STABILITY

OBJECTIVE: To ascertain whether augmentation pedicle screw fixation with polymethylmethacrylate (PMMA) can enhance the stability of unstable thoracolumbar burst fractures of osteoporotic spine. METHODS: Six fresh frozen female osteoporotic spines (T10-L5) were harvested and an anterior and posterior column unstable model of L1 was made. Each specimen was fixated with plate and the stability test were performed by flexion, extension, axial rotation and lateral bending. The test of fatigue was done with MTS 858. The tests were repeated after screws were augmented with PMMA. To compare the biomechanical stability of 6 different conditions: a. normal specimens (control), b. defect model fixed with plate, not augmented and not fatigued, c. after fatigued, not augmented, d. screws augmented with PMMA, not fatigued, e. after augmented and fatigued. RESULTS: In b., d. and e. conditions, the ranges of motion (ROM) were 6.23 +/- 1.56, 4.49 +/- 1.00, 4.46 +/- 1.83 in flexion and 6.60 +/- 1.80, 4.41 +/- 0.82, 4.46 +/- 1.83 in extension. There was no significant difference (P > 0.05), they were significantly smaller than those in a. and c. conditions (8.75 +/- 1.88, 1.47 +/- 2.25 and 8.92 +/- 2.97, 12.24 +/- 3.08) (P < 0.01). CONCLUSION: The results demonstrated that augmentation pedicle screws fixation with PMMA can increase the stability of osteoporotic spine.