椎体后凸成形术中灌注不同凝固状态骨水泥对骨质疏松性椎体压缩性骨折绵羊椎体生物力学的影响

Biomechanical effects of different coagulated bone cements on osteoporotic vertebral compression fractures during kyphoplasty in sheep

目的探讨椎体后凸成形术中灌注不同凝固状态骨水泥对骨质疏松性椎体压缩性骨折(OVCF)绵羊椎体强度和刚度的影响。方法选取成年绵羊8只,获得L_(1~5)椎体40个,随机分为4组,每组10个。采用3%稀盐酸浸泡和双侧椎弓根微泵灌注法制作骨质疏松椎体模型,再将骨质疏松椎体置于衡翼生物力学机上并压缩其高度的1/4制作压缩骨折椎体模型。制备骨水泥灌注通道后,用球囊经双侧椎弓根复位骨折椎体,在C形臂X线机透视下,对照组(A组)不灌注骨水泥,其余各组分别在聚甲基丙烯酸甲酯(PMMA)骨水泥粉液混合后2 min(骨水泥稀薄期,B组)、4 min(骨水泥黏稠期,C组)、6 min(骨水泥凝固期,D组)灌注骨水泥。室温放置24 h待骨水泥凝固。分别于术前和术后测量各组椎体的强度和刚度。结果术前4组椎体强度和刚度组间比较,差异均无统计学意义(P>0.05)。A组术后椎体强度低于术前,B、C、D组术后椎体强度均高于术前,差异有统计学意义(P<0.05)。4组术后椎体刚度均低于术前,差异有统计学意义(P<0.05)。B、C、D组术后椎体强度和刚度均高于A组,差异有统计学意义(P<0.05);B、C组术后椎体强度和刚度均高于D组,差异有统计学意义(P<0.05);B组和C组术后椎体强度和刚度差异无统计学意义(P>0.05)。结论OVCF绵羊采用椎体后凸成形术治疗,注入稀薄期和黏稠期骨水泥的椎体强度和刚度均高于注入凝固期骨水泥的椎体。注入不同凝固状态骨水泥均可增强椎体强度,但椎体刚度均恢复不到未骨折时期状态。

Objective To investigate the effect of bone cement in different coagulation states on the vertebral strength and stiffness of sheep with osteoporotic vertebral compression fracture(OVCF)during kyphoplasty.Methods Eight adult sheep were selected to obtain L1-5 vertebral bodies.The 40 vertebral bodies were randomly and equally divided into 4 groups.The osteoporotic vertebral body model was made by 3%dilute hydrochloric acid immersion and bilateral pedicle micro-pump perfusion.Then the vertebral bodies were placed on a balanced wing biomechanical machine to compress 1/4 of their height,so as to make a compression fracture vertebral body model.After preparing the bone cement perfusion channel,the fractured vertebral body was reduced by bilateral pedicles with a balloon.Under C-arm roentgenography,the control group(group A)was not infused with bone cement,and the other groups were infused with bone cement 2 min(bone cement in thinning stage,group B),4 min(bone cement in viscous stage,group C)and 6 min(bone cement in solidification stage,group D)after PMMA bone cement powder and liquid was mixed.The bone cement was set at room temperature for 24 h.The strength and rigidity of the vertebral bodies in the 4 groups were measured before and after operation.Results There were no significant differences in the preoperative strength and rigidity of the vertebral bodies between the 4 groups(P>0.05).The postoperative vertebral strength of group A was lower than those before operation,and those of groups B,C and D were all higher than that before operation,and the postoperative vertebral stiffness of the 4 groups were all lower than that before operation,all with a statistical significance(P<0.05).The postoperative vertebral strength and stiffness of groups B,C and D were higher than those of group A,all with a statistical significance(P<0.05).The postoperative vertebral strength and stiffness of groups B and C were higher than those of group D,all with a statistical significance(P<0.05).There was no significant difference in vertebral strength and stiffness between group B and group C(P>0.05).Conclusions OVCF sheep are treated with kyphoplasty,the vertebral body strength and stiffness of bone cement injected in thinning and viscous stages are higher than those injected in solidification stage.Bone cement injected in different stage could enhance the strength of compressive vertebral body,but the stiffness of vertebral body could not restored to the unfractured state.