前后路重建治疗II型Hangman骨折对颈椎稳定性的影响

目的评价颈前路C3椎体大部分切除、植骨融合钢板系统内固定术重建上颈椎稳定性的生物力学性能,并与临床常用的C2～3开槽植骨融合钢板内固定术、后路椎弓根螺钉内固定术作对比。方法 6例新鲜尸体上颈椎标本(含C2～4),在标本完整(完整组)、C2双侧椎弓峡部切断加C2～3前纵韧带切断加C2～3椎间盘切除(Hang-man骨折组)、后路C2双侧椎弓根螺钉内固定(后路固定组)、前路C2～3植骨融合内固定术(前路内固定组)以及前路C3椎体大部分切除、植骨融合钢板系统内固定术组(前路椎体切除+内固定组)状态下,依次用脊柱三维运动测量系统测试其C2～3、C3～4节段分别在0.5、1.5、2.5 N.m力矩下的运动范围(rage of motion,ROM),并行统计学分析。结果 (1)C2～3节段:前路内固定组和前路椎体切除+内固定组在0.5、1.5、2.5 N.m力矩载荷下的6个方向上,ROM值较完整,Hangman骨折组、后路固定组均明显减小(P<0.05),前路内固定组与前路椎体切除+内固定组间比较无显著性差异。后路固定组在各种载荷条件下6个方向ROM均较完整组大(P<0.05)。后路固定组在各种载荷条件下前屈和后伸时与骨折组无显著性差异,在所有载荷条件下左右旋转及2.5 N.m力矩载荷下左右侧屈时与骨折组间存在显著性差异(P<0.05)。(2)C3～4节段:除前路椎体切除+内固定组外,其余各组在各种载荷条件下6个方向ROM各组间无显著性差异。在各种载荷下前路椎体切除+内固定组6个方向ROM明显较其余各组小(P<0.05)。Hangman骨折组、后路固定组、前路内固定组中,虽然前路内固定组在各个方向上ROM较其他组略大,但无统计学意义。结论从生物力学观点来看,前路C3椎体大部分切除、植骨融合钢板系统内固定术固定伴有C2～3节段前纵韧带、椎间盘损伤的II型Hangman骨折较C2后路椎弓根螺钉固定更为适当和稳定,是治疗伴有C2～3椎间盘损伤的Ⅱ型Hangman骨折的一个合适选择。

Effects of anterior fusion and posterior internal fixation on stability of upper cervical vertebra in type II Hangman fracture

Objective To evaluate biomechanical properties of internal fixation after C3 corpectomy and C2-4 anterior fusion with Zephir plate in reconstructing stability of the upper cervical vertebra, and compare them with conventionally used anterior internal fixation after C2-3 intervertebral fusion and posterior internal fixation by C2 transpedicle screws. MethodsSix fresh human upper cervical vertebra specimens (including C2-4) were divided into five groups: the intact specimen group(control group), the incision of the C2-3 group (Hangman group), the posterior internal fixation by C2 transpedicle screw group (posterior fixation group), the anterior internal fixation after C2-3 intervertebral fusion with Zephir plate group (anterior fixation group), and the internal fixation after C3 corpectomy and C2-4 anterior fusion with Zephir plate group (C2-4 incision +internal fixation group). Range of motion (ROM) of the C2-3 and C3-4 segments was tested respectively under 0.5, 1.5 and 2.5 N?m moment by measurement system for three-dimensional spinal movement, and the statistical analysis was also conducted. Results(1) C2-3 segment: ROM of anterior fixation group and C2-4 incision +internal fixation group was significantly smaller than that of Hangman group and posterior fixation group in all six directions under various loading conditions (P<0.05); there was no significant difference between anterior fixation group and C2-4 incision +internal fixation group. ROM of posterior fixation group was larger than that of intact group in all six directions under various loading conditions (P<0.05); There was no significant difference in flexion and extension direction under all loading conditions between posterior fixation group and Hangman group, but significant difference was found in left/right and right/left axial rotation and under 2.5 N?m moment between posterior fixation group and Hangman group (P<0.05). (2) C3-4 segment: there was no significant difference in ROM in six directions under various loading conditions among all groups except for C2-4 incision +internal fixation group. ROM of C2-4 incision +internal fixation group was significantly smaller than that of other groups in all six direction (P<0.05). Although ROM of anterior fixation group was slightly larger than that of Hangman group and posterior fixation group, the difference was not statistically significant. Conclusions From the view of biomechanics, internal fixation after C3 corpectomy and C2-4 anterior fusion with Zephir plate is a better surgical option for stabilizing the fracture than that of posterior internal fixation by C2 transpedicle screws to treat type II Hangman fracture with C2-3 intervertebral disc injury.