颈椎植入性融合器PDLLA Cage的制备及置入山羊颈椎后的体外生物力学分析

背景:经典的颈椎前路减压植骨融合方法存在许多弊端.颈椎椎间融合器应用虽然取得满意的效果,但仍有许多潜在问题有待解决.目的:设计制备适合于山羊颈椎前路减压融合的颈椎间融合器PDLLA Cage,观察PDLLA Cage对山羊颈椎C_(3-4)融合后的即刻稳定作用.设计、时间及地点:随机分组设计,对比观察,于2005-06/2006 01在四川大学生物力学实验室完成.材料:15只成年(2岁)雌性山羊尸体颈椎C_(3-4)节段,另选27只成年(2岁)雌性山羊体质量(31.56±2.50)kg]的颈椎C_(3-4)用于生物力学测试.标本由四川大学华西临床医学院动物实验中心提供,用于解剖参数的测量及生物力学测试.方法:取山羊尸体颈椎C_(3-4)节段,行X射线正侧位检查,根据C_(3-4)平均椎间高度、C_3椎体下缘与前缘夹角、C_3椎体下缘前后距离及椎体中部前后缘距离设计制各PDLLA Cage,并进行力学检测,27只山羊颈椎标本进行生物力学测试后(正常对照组),标本未破坏,再随机分为3组,PDLLA Cage组(n=9),钛合金Cage组(n=9),自体髂骨组(n=9).在脊柱功能单位的椎间隙处将前纵韧带切开,摘除髓核后,去除附着肌肉,保留所有韧带,保留骨性终板和软骨下骨.PDLLA Cage组和钛合金Cage组分别置入PDLLA Cage和钛合金Cage,Cage主体空腔内植骨,并通过前方的翼板上下2个固定板以3.5mm螺钉固定于上下椎体:自体髂骨组取自体三面皮质髂骨植入.主要观察指标:采用1,2,3,4 N·m逐级加载纯力矩的方法进行前屈、后伸、侧弯和旋转的生物力学测定,由此计算出各组平均刚度及活动范围,并行比较.结果:①在1～4N·m逐级加载时,运动节段在前屈、后伸、侧屈和旋转各向量的角位移变化PDLLA Cage组和钛金属Cage组与正常对照组相比,差异均有显著性意义(P<0.05).除侧弯4 N·m加载时PDLLA Cage组与自体髂骨组差异无显著性意义(P>0.05)外,Cage组与自体髂骨组相比,各向量的角位移均减小(P<0.05),PDLLA Cage组和钛金属Cage组有前方翼板与椎体固定,其后伸稳定性明显优于自体髂骨组.与正常对照组相比,自体髂骨组后伸和侧弯两种向量的角位移均减小(P<0.05).②置入Cage后颈椎刚度显著增大,后伸和旋转加载时PDLLA Cage与钛合金Cage组间差异无显著性意义(P>0.05);钛合金Cage存其余各方向上的刚度均最大(P<0.05).PDLLA Cage比自体髂骨组的刚度大(P<0.05).结论:PDL.LA Cage置入山羊颈椎能提供足够的初始稳定性.

Preparation and in vitro biomechanical analysis of PDLLA Cage following implantation into a goat cervical spine model

BACKGROUND:Typical anterior cervical decompression and fusion method has many disadvantages.Cervical fusion cage has obtained satisfactory outcomes,but many problems should be solved.OBJECTIVE:To design a type of PDLLA Cage and to investigate the immediate stability of different fusion methods in a goat cervical spine model following C_(3-4) fusion.DESIGN,TIME AND SETTING:Randomized controlled study was performed at the Laboratory of Biomechanics,Sichuan University from June 2005 to January 2006.MATERIALS:C_(3-4) segment was obtained from a total of 15 adult female 2-year goat corpses.Additional C_(3-4) from 27 adult female 2-year goats was used in biomechanics test.Samples were supplied by the Animal Experimental Center,West China Clinical Medical College,Sichuan University to use in measurement of anatomy parameter and biomechanica test.METHODS:C_(3-4) segment obtained from goat corpse was subjected to X-ray test in an anterior lateral position.In accordance with C_(3-4) mean vertebral height,the angle of C_3 vertebral inferior border and anterior border,the anterior and posterior distance of C_3 vertebral inferior border,as well as the distance of anterior and posterior borders of the middle vertebral body,a type of PDLLA Cage was designed and made,and the biomechanical behavior analysis about the materials was performed.The 27 goat samples were not destroyed following biomechanics test (normal control group),and were assigned to 3 groups,PDLLA Cage group (n=9),titanium alloy Cage group (n=9) and autologous iliac bone group (n=9).Anterior longitudinal ligament was incised at FSU intervertebral space.Following excising the nucleus pulposus,adherent muscle was removed and the whole ligament was remained,as well as the bony terminal plate and cartilage subchondral bone were reserved.PDLLA Cage and titanium alloy Cage were respectively implanted in the cavity of the Cage main body in the PDLLA Cage group and titanium alloy Cage group.The Cage was fixed in the vertebral body using two fixing plates of anterior alar plate with 3.5-mm screw.Autologous cortical iliac bone from three surfaces was implanted in the autologous iliac bone group.MAIN OUTCOME MEASURES:Biomechanics was tested in flexion,extension,axial rotation,and lateral bending using 1,2,3,4 N·m moment of force method.The mean stiffness values and the range of motion were calculated in each group. RESULTS:In every loading mode,the displacement values were statistically significant difference between cage groups (PDLLA Cage group and titanium Cage group) compared with the normal control group (P<0.05);and the displacement of cage groups were lower than that of the autologous tricortical iliac crest bone graft group except for 4 N·m bending loading mode (P<0.05).Posterior extension was significant better in the PDLLA Cage group and titanium alloy Cage group compared with the autologous iliac bone group.Compared with the normal control group,the displacement of posterior extension and lateral bending was lower in the autologous iliac bone group (P<0.05).The stiffness of PDLLA Cage and the titanium Cage group in the flexion loading had no significant difference (P>0.05).In the others loading condition,the titanium Cage group was statistically greatest in all directions (P<0.05).The stiffness of PDLLA Cage was comparable with that of the titanium Cage and was statistically higher than that of the autologous tricortical iliac crest bone graft and intact (P<0.05).CONCLUSION:This type of PDLLA Cage can provide enough primary stability for cervical intervertebral fusion.