Division of Orthopaedics, Department of Surgery, The University of Western Ontario, London, Ontario, Canada.
Spine (Phila Pa 1976). 2012 May 20;37(12):1030-5. doi: 10.1097/BRS.0b013e31823b4ed0.
A biomechanical analysis of soft-tissue restraints to passive motion in odontoid fractures.
To quantify the role of the C1-C2 facet joint capsules and anterior longitudinal ligaments (ALLs) in the setting of a type II odontoid fracture in the elderly.
The odontoid process itself is the primary stabilizer at the C1-C2 level; however, little is known about the role of the soft-tissue structures that remain intact in the setting of an odontoid fracture after a low-energy mechanism.
Ten cadaveric C0-C2 spinal segments were studied. Specimens were tested under simulated axial rotation with an applied moment of ±1 Nm and with an application of a 10 N anteriorly directed force to the body of C2 to induce sagittal translation. Optical motion data were initially collected for the intact state and after a simulated dens fracture. The specimens were then divided into 2 groups, where 1 group underwent unilateral and then bilateral C1-C2 facet capsular injuries followed by an ALL injury. The second group underwent the ALL injury before the same capsular injuries. Changes in axial range of motion and C1-C2 translation were analyzed using 2-way repeated measures analyses of variance and post hoc Student-Newman-Keuls tests (α = 0.05).
In axial rotation, there was an increase in range of motion by approximately 13%, with the fracture of the dens compared with the intact state (P < 0.05). An increase was also present for each subsequent soft-tissue injury state compared with the previous (P < 0.05); however, there was no difference found between the 2 sectioning protocols. For sagittal translation testing, it was found that the odontoid fracture alone showed an increase of 3 mm of C1-C2 translation compared with intact (P < 0.05). Further soft-tissue injuries did not show an increase until the complete injury state.
This study identifies that type II odontoid fractures without associated soft-tissue injury may be stable under certain loading modes.
寰椎骨折时软组织对被动活动的约束的生物力学分析。
定量评估 C1-C2 关节突关节囊和前纵韧带（ALL）在老年 II 型齿状突骨折中的作用。
齿状突本身是 C1-C2 水平的主要稳定器；然而，对于低能量机制导致的齿状突骨折后，仍保持完整的软组织结构的作用知之甚少。
研究了 10 个颈椎 C0-C2 节段的尸体标本。标本在模拟轴向旋转下进行测试，施加 ±1 Nm 的力矩，并在 C2 体部施加 10 N 的向前力以诱导矢状平移。首先收集完整状态和模拟齿突骨折后的光运动数据。然后将标本分为 2 组，一组先进行单侧然后双侧 C1-C2 关节突关节囊损伤，然后进行 ALL 损伤；第二组先进行 ALL 损伤，然后进行相同的关节囊损伤。使用 2 因素重复测量方差分析和事后 Student-Newman-Keuls 检验（α = 0.05）分析轴向活动范围和 C1-C2 平移的变化。
在轴向旋转中，与完整状态相比，骨折后活动范围增加约 13%（P < 0.05）。与前一个状态相比，每个后续的软组织损伤状态也都有增加（P < 0.05）；然而，2 种节段化方案之间没有差异。在矢状平移测试中，发现单独的齿状突骨折与完整状态相比，C1-C2 平移增加了 3 毫米（P < 0.05）。直到完全损伤状态，进一步的软组织损伤才会导致增加。
本研究表明，无相关软组织损伤的 II 型齿状突骨折在某些加载模式下可能是稳定的。
