C_2椎弓根螺钉置入内固定治疗Hangman骨折的生物力学评价(英文)

Biomechanical evaluation of C_2 transpedicle screw fixation for Hangman fractures

背景：C2椎弓根钉置入内固定治疗Hangman骨折因固定可靠，无生理功能的丢失而受到众多学者的青睐，根据文献报道，单节段固定治疗Hangman骨折的适应证差异较大，并且缺乏生物力学依据。目的：评价C2椎弓根螺钉置入内固定治疗Hangman骨折的生物力学性能。设计、时间和地点：2004-05/08在解放军第一军医大学全军生物力学重点实验室完成的对比观察实验。材料：材料采用AO通用的钛合金颈椎椎弓根螺钉，长度18-25mm，直径3.5mm。6具新鲜C1-C4颈椎标本依次制成Ⅰ型、ⅡA型和Ⅱ型Hangman骨折模型。方法：椎弓根螺钉固定后在非破坏方式下用脊柱三维运动实验机进行测量，通过加载盘对标本施加2.0N·m的纯力偶矩，使标本产生前屈/后伸、左/右侧弯和左/右轴向旋转6种生理运动；每次测试重复3次加载/卸载循环，在第3次循环时进行运动学测量。主要观察指标：由激光扫描仪（精度0.1%）摄取在零载荷和最大载荷时的脊柱运动图像，并用相应软件系统进行图像分析，计算出标本的三维运动范围。结果：Ⅰ型骨折C2椎弓根螺钉固定后相对稳定性在屈曲、后伸、侧弯及旋转达到了对照组的100.62%，96.91%，99.19%，97.12%（P〉0.05）。ⅡA型骨折C2椎弓根螺钉固定后旋转稳定性达到了对照组的61.86%（P〈0.05）。Ⅱ型骨折C2椎弓根螺钉固定后相对稳定性在屈曲、后伸、侧弯及旋转为对照组的47.84%，21.29%，65.98%，41.69%（P〈0.05）。结论：生物力学评估提示，HangmanⅠ型、ⅡA型骨折基本适合C2椎弓根螺钉置入治疗，置入固定后骨折可达生理性固定或稳定性较好；Ⅱ型骨折固定后稳定性较差，不适合单纯椎弓根钉内固定置入。

BACKGROUND： C2 transpedicle screw fixation for Hangman fractures has been paid more attention due to reliability and no loss of physiological function. However, there are lacks of biomechanical evidences for indication treatment because the fixation is single segmental. OBJECTIVE： To investigate the biomechanical stability of C2 transpedicle screw fixation for Hangman fractures. DESIGN, TIME and SETTING： This was a contrast study which was performed at the General Key Laboratory of Biomechanics, First Military Medical University of Chinese PLA from May to August 2004. MATERIALS： AO-universal titanium alloy transpedicle screw of 18-25 mm in length and 3.5 mm in diameter was adopted in this study. Six fresh C1-C4 cervical vetebrae samples were ordinally made into type Ⅰ, Ⅱ A, and Ⅱ Hangman fracture models. METHODS： After transpedicle screw fixation, Hangman fracture models were measured by non-destroyed style with spinal 3D motor equipment. Pure moment of couple （20 N · m） was exerted via loading disc to generate six physiological motions： anterior flexion/posterior extension, left/right lateral curvature, and left/right axial direction. Loading/unloading circulation was performed three times during each testing. Kinematics indicators were measured on the 3^rd circulation. MAIN OUTCOME MEASURES： Spinal motor images at zero load and maximal load were obtained with laser photoscanning （0.1% in precision）, and the corresponding systematic software was adopted to calculate 3D range of movement. RESULTS： The relative stability of type Ⅰ Hangman fracture models after C2 transpedicle screw fixation was 100.62% （inflexion）, 96.91% （posterior extension）, 99.19% （lateral curvature）, and 97.12% （rotation） as compared to control group （P 〉 0.05）. The relative stability of type Ⅱ Hangman fracture models after C2 transpedicle screw fixation was 47.84% （inflexion）, 21.29% （posterior extension）, 65.98% （lateral curvature）, and 41.69% （rotation） as compared to control group （P 〈 0.05）. CONCLUSION： Biochemical evaluation suggests that type Ⅰ and Ⅱ A Hangman fractures do fit for C2 transpedicle screw fixation, and the fixation may generate well physiological fixation or stability. However, stability of type Ⅱ Hangman fracture is poor, so it is not suitably adopted single transpedicle screw fixation.