骨水泥在骨质疏松性骨折椎体内分布状态与生物力学性能的关系

 目的 研究骨水泥在腰椎骨质疏松性骨折椎体内不同区域分布状态的生物力学特性，为经皮椎体后凸成形术(percutaneous kyphoplasty，PKP)临床应用提供理论依据。方法 取12具福尔马林固定的老年尸体腰椎标本(包括L1~L5)，共筛选49个椎体。对各椎体标本施加轴向压力负载，测量各椎体的原始强度和刚度，并建立椎体压缩骨折模型。按临床PKP手术操作要求根据不同的椎体分区灌注骨水泥，分为对照组和6个实验组，每组7个椎体。测量每组的最大压缩强度和刚度。结果 PKP术后各实验组最大压缩强度较初始强度均明显增强。单侧前2/3灌注组和单侧后2/3灌注组比较，单侧全灌注组、双侧前2/3灌注组和双侧后2/3灌注组比较差异均无统计学意义；椎体最大压缩强度双侧全灌注组>单侧全灌注组、双侧前2/3灌注组和双侧后2/3灌注组>单侧前2/3灌注组和单侧后2/3灌注组。PKP术后双侧全灌注组椎体刚度和初始刚度比较差异无统计学意义，其余各组度均明显小于初始刚度。单侧前2/3灌注组、单侧后2/3灌注组和单侧全灌注组比较，D和双侧后2/3灌注组比较差异无统计学意义；双侧全灌注组>双侧前2/3灌注组和双侧后2/3灌注组> 单侧前2/3灌注组、单侧后2/3灌注组和单侧全灌注组。结论 骨水泥分布在骨质疏松性骨折椎体的不同区域，其生物力学性能存在差异，骨水泥在椎体双侧分布较单侧分布可以获得更好的生物力学效应。骨水泥均匀分布于椎体前2/3区域是较为理想的分布状态，但仍需临床进一步验证。

Biomechanical effect of bone cement volume and distribution on lumbar vertebral body with osteoporotic fracture

Objective To evaluate biomechanical effect of bone cement distribution on lumbar vertebral body with osteoporotic fracture. Methods Forty nine lumbar vertebrae (L1-L5) specimens were collected from 12 old cadavers. After exerting axial pressure load on every specimen, the initial intensity and stiffness were measured, and then vertebral body crush fracture models were established. According to zones where bone cement was injected in vertebrae, the specimens were divided into one control group and six experimental groups: A, B, C, D, E, F groups, i.e. unilateral anterior 2/3 group, unilateral posterior 2/3 group, unilateral whole group, bilateral anterior 2/3 group, bilateral posterior 2/3 group, and bilateral whole group, respectively, including 7 specimens in each group. In A, B, C groups, unipedicular balloon kyphoplasty was done, while in D, E, F groups, bipedicular balloon kyphoplasty was done. Then the maximum compressive strength and stiffness were measured. Results After percutaneous kyphoplasty, the maximum strength in all experimental groups was significantly greater than that in the control group. There were no significant differences in strength between A and B groups, between C, D and E groups. For the maximum strength, the results of comparison were: F group > C group, D and C groups > A and B groups. Except for F group, the stiffness in other 5 experimental groups was significantly lower than its initial value. There were no significant differences in stiffness between A, B, and C groups, between D and E groups. However, the stiffness in F group was greater than those in D and E groups, and it was greater in bilateral groups than those in unilateral groups. Conclusion Bone cement distribution in lumbar vertebral body can affect biomechanical property of vertebral body, and the bilateral distribution can cause better biomechanical effect than unilateral distribution. The ideal distribution zone of bone cement is in the anterior 2/3 of the vertebral body.