Objective To study the effect of bone cement dosage on the biomechanics of the extracorporal quintuplet osteoporosis vertebral model after percutaneous kyphoplasty(PKP). Methods Fresh adult pig thoracolumbar segments were applied to develop the quintuplet osteoporosis with Ⅱ degree compression fracture models,which were randomly divided into groups A,B,C,and D,with 15 models per group. All animals of model but group A underwent unilateral(right) puncture approach PKP,and the amount of bone cement was 15%,25%,35% of the volume of the injured vertebrae,and the leakage of bone cement was recorded. All the spine units were placed on the electronic mechanical testing machine,and the axial load was applied 24 h after the operation. The ultimate compressive strength and rigidityof each spinal unit were recorded. Groups B,C and D were continuously pressed until 2 new fractures of the vertebral body wasfound(except for the primary fracture of vertebral body),and the location of the new fracture was recorded. Results The rigidity of B,C and D groups after strengthened was (234±8)N/mm,(259±12)N/mm and (294±13)N/mm respectively,and all these values were better than that of group A [(204±12)N/mm]. The difference was statistically significant(P < 0.05). The ultimate compressive strength of groups B,C and D after strengthened was (3428±96)N,(3134±86)N and (2615±90)N,and all were superior to that of group A[(1758±55)N]. The difference was statistically significant(P<0.05). Groups B,C and D had 17,21,and 27 new vertebral fractures located in the adjacent position of the strengthened vertebra,and there were 1,3,and 11 spinal units of bone cement leakage. The difference was statistically significant(P<0.05). Conclusion PKP can effectively restore the mechanical properties of fractured vertebral body,and its ultimate compressive strength and rigidity are improved obviously. However, the stress of the adjacent vertebral body could increase significantly after the injection of bone cement,and the amount of bone cement is one of the factors leading to vertebral fracture.%目的 研究行单侧椎弓根穿刺椎体后凸成形术(PKP)后,骨水泥用量对中间椎体压缩骨折的骨质疏松性五联椎体模型的生物力学影响.方法 采用新鲜成年猪脊柱胸腰段五联椎体制作中间椎体骨质疏松并Ⅱ度压缩骨折模型,分为A、B、C、D 4组,每组15个标本.A组不行PKP术,B、C、D组行经单侧(右侧)穿刺PKP术,注入骨水泥量分别为伤椎体积的15%、25%、35%,记录骨水泥渗漏情况.手术24 h后应用电子力学实验机测试各脊柱单元的极限抗压强度及刚度;B、C、D组继续加压直至出现两处新发椎体骨折(伤椎除外),并记录新发骨折椎体的位置.结果 B、C、D组脊柱单元强化后的刚度分别为(234±8)N/mm、(259±12)N/mm、(294±13)N/mm,均优于A组的(204±12)N/mm,差异有统计学意义(P<0.05).B、C、D组强化后的脊柱单元极限抗压强度分别为(3428±96)N、(3134±86)N、(2615±90)N,均大于A组的(1758±55)N,差异有统计学意义(P<0.05);B、C、D组分别有17、21、27个新发椎体骨折位于强化椎相邻位置,且分别有1、3、11个脊柱单元发生骨水泥渗漏,组间差异均具有统计学意义(P<0.05).结论 PKP可有效恢复骨折椎体的力学性能,使其刚度及极限抗压强度得到明显改善;但强化椎邻近椎体的应力在PKP术后较术前有明显增加,使椎体极限抗压强度下降,骨水泥用量是导致强化椎邻近椎体骨折的因素之一.
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