Department of Kinesiology, University of Waterloo, Waterloo, Ontario, Canada.
Department of Kinesiology, University of Waterloo, Waterloo, Ontario, Canada.
Spine J. 2020 Mar;20(3):475-487. doi: 10.1016/j.spinee.2019.09.022. Epub 2019 Sep 26.
Prior data about the modulating effects of lumbar spine posture on facet capsule strains are limited to small joint deviations. Knowledge of facet capsule strain during rotational and translational intervertebral joint motion (ie, large joint deviations) under physiological loading could be useful as it may help explain why visually normal lumbar spinal joints become painful.
This study quantified the strain tensor of the facet capsule during rotation and translation range-of-motion tests.
STUDY DESIGN/SETTING: Strain was calculated in isolated porcine functional spinal units. Following a preload, each specimen underwent a flexion/extension rotation (F/E) followed by an anterior/posterior translation (A/P) range-of-motion test while under a 300 N compression load.
Twenty porcine spinal units (10 C3-C4, 10 C5-C6) were tested. Joint flexion/extension was imposed by applying a ±8 Nm moment at a rate of 0.5°/s, and translation was facilitated by loading the caudal vertebra with a ±400 N shear force at a rate of 0.2 mm/s. Points were drawn on the exposed capsule surface and their coordinates were optically tracked throughout each test. Strain was calculated as the displacement of the point configuration with respect to the configuration in a neutral joint position.
Compared to a neutral posture, superior-inferior strain increased and decreased systematically during flexion and extension, respectively. Posterior displacement of the caudal vertebra by more than 1.3 mm was associated with negative strains, which was significantly lower than the +4.6% strain observed during anterior displacement (p≥.199). The shear strain associated with anterior translation was, on average, -1.1% compared to a neutral joint posture.
These results demonstrate that there is a combination of strain types within the facet capsule when spinal units are rotated and translated. The strains documented in this study did not reach the thresholds associated with nociception.
The magnitude of flexion-extension rotation and anterior-translation may glean insight into the facet capsule deformation response under low compression (300 N) loading scenarios. Further, intervertebral joint motion alone, even under low compression loading, does not appear to initiate a clinically relevant pain response in the lumbar facet capsule of a nondegenerated spinal joint.
关于腰椎姿势对小关节面囊应变的调节作用的先前数据仅限于小关节偏差。了解生理负荷下旋转和平移椎间关节运动时小关节面囊的应变（即大关节偏差）可能会有所帮助，因为它可能有助于解释为什么视觉正常的腰椎关节会变得疼痛。
本研究量化了旋转和平移运动范围测试中小关节囊的应变张量。
研究设计/设置：在分离的猪功能性脊柱单元中计算应变。在预加载后，每个标本在 300 N 压缩载荷下进行屈曲/伸展旋转（F/E），然后进行前/后平移（A/P）运动范围测试。
测试了 20 个猪脊柱单元（10 个 C3-C4，10 个 C5-C6）。关节的屈伸通过以 0.5°/s 的速度施加±8 Nm 的力矩来实现，而平移则通过以 0.2mm/s 的速度向尾端椎体施加±400N 的剪切力来实现。在暴露的囊表面上绘制点，并在每次测试中通过光学跟踪其坐标。应变是通过相对于关节中立位置的点配置的位移来计算的。
与中立姿势相比，屈曲时上-下应变呈系统增加，伸展时则呈系统减小。尾端椎体向后位移超过 1.3mm 与负应变相关，明显低于前向位移时观察到的+4.6%应变（p≥.199）。与中立关节姿势相比，前向平移的剪切应变平均为-1.1%。
这些结果表明，当脊柱单元旋转和平移时，小关节囊内存在多种类型的应变。本研究记录的应变没有达到与痛觉相关的阈值。
屈伸旋转和前-后平移的幅度可以深入了解低压缩（300 N）加载情况下小关节囊的变形反应。此外，即使在低压缩加载下，单独的椎间关节运动似乎也不会在非退变的腰椎小关节中引起临床相关的小关节囊疼痛反应。
