T1倾斜角对Zero-P固定力学影响的有限元分析

A finite element analysis of biomechanical effect of T1-slope on C5~6 fixation with zero profile intervertebral fusion system

摘要:

[目的] 研究 T1倾斜角 (T₁-slope, T₁S) 对 Zero-P 术后椎间活动度及椎间盘应力的影响。[方法] 选择 2 例 C_5/6椎间盘突出患者为研究对象。术前进行 C₁~T₂椎体螺旋 CT 薄层扫描，在 Mimics 14.0、Geomagic Studio 10.0、Cero 3.0 分别建立 T₁S≤ 18°及 T₁S＞18°的颈椎 C_5/6节段 Zero-P 固定及正常对照颈椎的有限元模型，测量椎间活动度及椎间盘应力。[结果] T₁S≤18°组与 T₁S＞18°组各节段的活动度均显著大于对照组 (P＜0.05)。屈伸载荷下，T₁S≤18°组活动度显著＞T₁S＞18°组 (P＜0.05)。而单侧弯和单侧旋转载荷下，T₁S≤18°组与 T₁S＞18°组中各节段的活动度比较差异均无统计学意义 (P＞0.05)。在前屈、后伸、侧弯及旋转载荷作用下，Zero-P 模型邻近节段椎间盘的应力均显著大于对照模型组 (P＜0.05)。而前屈、后伸载荷下，T₁S≤18°组中 C_4/5、C_5/6融合器、C_6/7应力均显著＞T₁S＞18°组(P＜0.05)。侧弯及旋转载荷下，两模型之间应力差异无统计学意义(P＞0.05)。[结论]T₁S 减小可能是导致颈椎前路单节段 Zero-P 融合术后邻近节段椎间盘活动度及椎间融合器应力增加的主要因素。

Abstract:

[Objective] To explore the biomechanical effect of T₁-slope (T1S) on intervertebral mobility and disc stress secondary to C5/6 fixation with zero profile intervertebral fusion system (Zero-P) . [Methods] Two patients with C_5/6 disc herniation and T₁S≤18° and T₁S＞18° were selected, and had preoperative spiral CT scanning performed from C₁ to T₂. Three dimensional finite models of cervical vertebrae, in- cluding T₁S≤18 °and T₁S＞18° with Zero-P fixation, as well as the normel cervical vertebrae were established by using mimics 14.0, Geo- magic studio 10.0 and Cero 3.0. The range of motion (ROM) of C_3/4 to C_6/7 intervertebral space, and Von Mises stress on disc endplate or im- plant were measured under the flexion, extension, lateral bending, rotation loading. [Results] Both T₁S≤18 °and T₁S＞18° groups had signifi- cantly higher ROMs on each segment than the control group (P＜0.05) . Under flexion and extension loadings, the T₁S≤18 ° group had signif- icantly higher ROMs on each segment than T₁S＞18° group (P＜0.05) . However, there was no significant difference in the ROMs of each seg- ment between T₁S≤18 °and T1S＞18° groups under unilateral bending and unilateral rotation loadings (P＞0.05) . In addition, the Von Mises stresses on the adjacent intervertebral disc in T₁S≤18° and T₁S＞18° groups were significantly higher than that in control group (P＜0.05) . The Von Mises stresses of C_4/5, C_5/6 fusion cage and C_6/7 under flexion and extension loadings in the T₁S≤18° group were significantly higher than those in the T1S＞18° group (P＜0.05) , whereas they became not significant different between the two groups under lateral bending and rotating loadings (P＞0.05) . [Conclusion] The decrease of T₁S might be the main factors leading to the increase of adjacent segment disc mo- tion and cage stress after Zero-P fusion.