颈前路椎间盘切除植骨融合术中后纵韧带的生物力学作用

摘要

目的 比较颈前路椎间盘切除减压植骨融合中后纵韧带切除前后颈椎的即刻稳定性变化.方法 14具新鲜小牛颈椎标本(C3～T1)随机平分为单节段(1)组和双节段(2)组.每组又分为正常对照组(N组)、椎间盘切除植骨组(A组)、椎间盘切除植骨内固定组(B组)、椎间盘切除植骨后纵韧带切除组(C组)和椎间盘切除植骨后纵韧带切除内固定组(D组).使用万能材料实验机分别测试各组在轴向压缩、前屈、后伸、侧屈状态下的应变、载荷-位移关系、刚度及抗扭转性能.结果 (1)应变:A1组较N组在轴向压缩、前屈、后伸、侧屈状态应变增大(P＜0.05);C1组平均应变大于A1组(P＜0.05).(2)载荷-位移关系:A1、A2组的平均位移比N组位移大(P＜0.05),C1比A1组平均位移增大11%,前屈状态增大20%(P＜0.05);C2组的平均位移比N组增大15%(P＜0.05),加用内固定后B2比C2平均位移小18%(P＜0.05).(3)刚度:在100N生理载荷作用下,N组的平均轴向刚度为(25.38±1.78)Nn,A1、A2组分别比N组下降8%、12%;平均轴向刚度B1组、B2组高于N组;D1、D2组颈椎的轴向刚度与同节段B组无差异(P＞0.05).(4)各组的扭转力学性能高低依次为B组＞D组＞N组＞A组＞C组.结论 颈椎后纵韧带的完整性对维持颈椎的稳定性起重要作用.单、双节段颈前路椎间盘切除减压操作中后纵韧带的切除将显著降低标本的即刻生物力学稳定性.植骨、内固定能有效地增强术后标本的即刻稳定性.%Objective To compare immediately biomechanical stability between reservation and resection of the cervical posterior longitudinal ligament(PLL) when performing anterior cervical decompression and fusion. Methods Fourteen fresh frozen calf cadaveric cervical spine specimens(C3-T1 ) were equally divided into two groups of l(single segment) and 2(two segments). Each group was subdivided into groups of N(normal control), A(cervical disc resection with interbody bone graft and PLL intact),B(group A combined with anterior plate fixation), C(group A with PLL resection), and D(group B with PLL resection). The load-straining, force-displacement, stiffness and torque performance were tested by Universary Testing Machine in the mode of axial compression, flexion,extension and lateral bending. Results The value of load-straining of group A1 was greater than that of group N(P＜0. 05),which of C1 was greater than that of A1(P＜0. 05). The results of two segments groups were similar to those of the single segment The force-displacement results showed that the averaged displacement in groups of A1 and A2 was larger than that in group N(P＜0. 05). Compare to group Al,the displacement in group C1 increased by 11％, and flexion condition by 20％(P＜0.05).The displacement of group C2 was 15％ greater than that of group N(P＜0. 05) ,which of group B2 was 18％ smaller than that of group C2 after internal fixation(P＜0. 05). As to the stiffness in the physiological load of 100 N, the average axial stiffness of group N was (25.38±1.78) N/mm, which of A1 and A2 was 8％ and 12％ smaller than that of group N. The values of axial stiffness of group B1 and B2 were (26. 85±1.93) N/mm and (26. 28±2. 05) N/mm, respectively,which were larger than those of group N. The values of axial stiffness in group D1 and group 12 were (26. 34 ±1.89 ) N/mm and (26. 15±1.82) N/mm, respectively, which were larger than those of group N. The torsion performance sequence was in an order of groups of B＞D＞N＞A＞C. Conclusion The study displays the pivot role of cervical posterior longitudinal ligament in the stability of cervical spine. Resection of the PLL decreases the immediately biomechanical stability both in single segment and two segments. Bone grafting or adding internal fixation can enhance the stability of cervical specimen.