不同椎弓根钉道强化部位对绵羊骨质疏松模型胸腰椎内固定稳定性的影响

Effects of Different Pedicle Reinforcement Sites on the Stability of Thoracolumbar Internal Fixation in Sheep Osteoporosis Model

目的探讨不同椎弓根钉道强化部位对绵羊骨质疏松模型胸腰椎内固定稳定性的影响。方法选取30只生长3~5年常规牧场饲养雌性绵羊,行双侧卵巢切除术联合糖皮质激素注射建立骨质疏松模型,造模成功后(骨密度T值在-2.5以下)处死取脊柱标本,分别对腰4椎体椎弓根钉道进行强化。根据强化部位的不同分为3组,每组10具标本。A组强化钉道前1/3,B组强化钉道中1/3,C组强化钉道后1/3。3组常规固定后行疲劳实验,测量脊柱标本最大活动范围(前屈、后伸、左侧弯、右侧弯4个方向)、轴向压缩刚度及腰4左侧椎弓根螺钉的轴向最大拔出力和对侧椎弓根螺钉的最大扭力。结果3组轴向压缩刚度、螺钉最大拔出力及最大扭力比较差异均有统计学意义(P<0.01);B组和C组轴向压缩刚度低于A组,且C组低于B组(P<0.01);B组和C组螺钉最大拔出力及最大扭力均大于A组,且C组大于B组(P<0.01)。3组各方向最大活动范围比较差异有统计学意义(P<0.01);B组和C组前屈、后伸、左侧弯、右侧弯最大活动范围均小于A组,且C组小于B组(P<0.01)。结论椎弓根钉道强化时,强化部位越接近椎体后方,椎弓根螺钉的把持力越大,内固定稳定性越好。故在保证骨水泥不进入椎管的情况下,应尽量强化椎弓根钉道的根部。

Objective To investigate the effects of different pedicle reinforcement sites on the stability of thoracolumbar internal fixation in sheep osteoporosis model.Methods Thirty female sheep bred in conventional pasture for 3-5 years were selected and underwent bilateral oophorectomy combined with Glucocorticoid injection to establish osteoporosis model.After successful modeling(bone mineral density T-value below-2.5),sheep were sacrificed to collect spinal specimens and pedicle screw channels were strengthened in the four lumbar vertebrae.They were divided into 3 groups according to different reinforcement sites,with 10 specimens in each group.Group A strengthened the front 1/3 of the screw channels,group B strengthened the middle 1/3 of the screw channels,and group C strengthened the back 1/3 of the screw channels.Fatigue tests were performed after conventional fixation in the 3 groups,and the maximum range of motion(ROM)(anterior flexion,posterior extension,left flexion and right flexion),axial compression stiffness,and the maximum axial pulling force of the left pedicle screw and the maximum torque of the contralateral pedicle screw of the lumbar 4 spinal specimens were measured.Results There were significant differences in axial compression stiffness,maximum pulling force of the screw and maximum torque among the three groups(P<0.01).The axial compression stiffness of groups B and C was lower than that of group A,and lower in group C than in group B(P<0.01).The maximum pulling force of the screw and maximal torque of group B and group C were greater than those of group A,and greater in group C than in group B(P<0.01).There were significant differences in the maximum ROM in each direction among the three groups(P<0.01).The maximum ROM of anterior flexion,posterior extension,left flexion and right flexion in group B and group C was smaller than that in group A,and smaller in group C than in group B(P<0.01).Conclusion During pedicle reinforcement,the closer the reinforcement site was to the rear of the vertebral body,the stronger the holding force of the pedicle screw was,and the better the stability of internal fixation was.Therefore,in order to ensure that bone cement does not enter the spinal canal,the root of the pedicle screw channels should be strengthened.