Department of Surgery, Western University, London, Canada.
J Bone Joint Surg Am. 2012 Nov 7;94(21):e156. doi: 10.2106/JBJS.K.00694.
Unilateral cervical spine facet injuries encompass a wide spectrum, including subluxations, dislocations, and fractures, and the instability produced varies greatly. The extent of anatomical disruption secondary to a unilateral facet injury is poorly understood, and few biomechanical studies have quantified the associated kinematics. The purpose of this study was to develop an experimental method that reliably produces an impending unilateral facet dislocation (perched facet) in cadaveric cervical spines and to identify the soft-tissue damage and resulting changes in cervical spine range of motion and neutral zone associated with this injury.
Nine fresh-frozen cadaveric human spinal motion segments (C4-C5 or C6-C7) were mounted in a spinal loading simulator to induce a perched unilateral facet injury based on a previously described mechanism of flexion and bending with increasing rotation. Loads were applied to simulate and measure flexion-extension, lateral bending, and axial rotation motions before and after achieving a perched facet. Preinjury and postinjury range of motion and neutral zone were analyzed with use of paired t tests for each movement. Systematic qualitative inspection and gross dissection were then performed to define the soft-tissue injury pattern.
Range of motion and neutral zone increased following the reduction of this injury; the largest increase (294%) occurred in contralateral axial rotation (i.e., right axial rotation after a perched left facet). Postinjury dissections revealed bilateral capsular tears, 50% disc disruption, and 50% tearing of the ligamentum flavum in most specimens. The interspinous and supraspinous ligaments were stretched in less than half of the specimens and were never completely disrupted. The longitudinal ligaments were occasionally torn as extensions of anulus fibrosus disruptions.
This study indicates that the anulus fibrosus, nucleus pulposus, and ligamentum flavum are important cervical spine stabilizers. Facet capsules were often torn bilaterally, implying a more advanced injury than a unilateral facet injury. These discoligamentous injuries result in increases in range of motion and neutral zone.
The results from this work provide further insight into the expected injury and associated instability present in a traumatic unilateral facet injury in the cervical spine.
单侧颈椎小关节损伤范围广泛，包括半脱位、脱位和骨折，所产生的不稳定性差异很大。单侧小关节损伤后解剖结构破坏的程度了解甚少，很少有生物力学研究对相关运动学进行量化。本研究的目的是开发一种可靠的实验方法，在尸体颈椎上产生即将发生的单侧小关节脱位（悬置小关节），并确定与这种损伤相关的软组织结构损伤和颈椎运动范围及中立区的变化。
将 9 个新鲜冷冻的人体颈椎运动节段（C4-C5 或 C6-C7）安装在脊柱加载模拟器上，根据先前描述的屈伸并逐渐增加旋转的机制来诱导悬置单侧小关节损伤。施加载荷以模拟并测量屈曲-伸展、侧屈和轴向旋转运动，然后在达到悬置小关节后进行测量。使用配对 t 检验分析每个运动的预损伤和损伤后的运动范围和中立区。然后进行系统的定性检查和大体解剖，以确定软组织结构损伤模式。
该损伤复位后运动范围和中立区增加；最大增加（294%）发生在对侧轴向旋转（即，悬置左侧小关节后右侧轴向旋转）。损伤后的解剖显示，大多数标本双侧囊破裂，50%椎间盘破裂，50%黄韧带撕裂。棘间和棘上韧带在不到一半的标本中被拉伸，从未完全断裂。纵韧带偶尔作为纤维环破裂的延伸而撕裂。
本研究表明纤维环、髓核和黄韧带是颈椎的重要稳定结构。小关节囊常双侧撕裂，提示损伤程度比单侧小关节损伤更严重。这些椎间盘韧带损伤导致运动范围和中立区增加。
本研究结果进一步深入了解颈椎创伤性单侧小关节损伤的预期损伤和相关不稳定。
