Wilke Hans-Joachim, Herkommer Andrea, Werner Karin, Liebsch Christian
Institute of Orthopaedic Research and Biomechanics, Trauma Research Centre Ulm, Ulm University, Ulm, Germany.
Front Bioeng Biotechnol. 2020 Jun 17;8:614. doi: 10.3389/fbioe.2020.00614. eCollection 2020.
The hydrostatic pressure of the nucleus pulposus represents an important parameter in the characterization of spinal biomechanics, affecting the segmental stability as well as the stress distribution across the anulus fibrosus and the endplates. For the development of experimental setups and the validation of numerical models of the spine, intradiscal pressure (IDP) values under defined boundary conditions are therefore essential. Due to the lack of data regarding the thoracic spine, the purpose of this study was to quantify the IDP of human thoracic spinal motion segments under pure moment loading. Thirty fresh-frozen functional spinal units from 19 donors, aged between 43 and 75 years, including all segmental levels from T1-T2 to T11-T12, were loaded up to 7.5 Nm in flexion/extension, lateral bending, and axial rotation. During loading, the IDP was measured using a flexible sensor tube, which was inserted into the nucleus pulposus under x-ray control. Pressure values were evaluated from third full loading cycles at 0.0, 2.5, 5.0, and 7.5 Nm in each motion direction. Highest IDP increase was found in flexion, being significantly ( < 0.05) increased compared to extension IDP. Median pressure values were lowest in lateral bending while exhibiting a large variation range. Flexion IDP was significantly increased in the upper compared to the mid- and lower thoracic spine, whereas extension IDP was significantly higher in the lower compared to the upper thoracic spine, both showing significant ( < 0.01) linear correlation with the segmental level at 7.5 Nm (flexion: = -0.629, extension: = 0.500). No significant effects of sex or age were detected, however trends toward higher IDP in specimens from female donors and decreasing IDP with increasing age, potentially caused by fibrotic degenerative changes in the nucleus pulposus tissue. Sagittal and transversal cuttings after testing revealed possible relationships between nucleus pulposus quality and pressure moment characteristics, overall leading to low or negative intrinsic IDP and non-linear pressure-moment behavior in case of fibrotic tissue alterations. In conclusion, this study provides insights into thoracic spinal IDP and offers a large dataset for the validation of numerical models of the thoracic spine.
髓核的静水压力是脊柱生物力学特征的一个重要参数，影响节段稳定性以及纤维环和终板上的应力分布。因此，对于实验装置的开发和脊柱数值模型的验证，确定边界条件下的椎间盘内压力（IDP）值至关重要。由于缺乏关于胸椎的数据，本研究的目的是量化在纯力矩加载下人体胸椎运动节段的IDP。来自19名年龄在43至75岁之间捐赠者的30个新鲜冷冻功能性脊柱单元，包括从T1-T2到T11-T12的所有节段水平，在屈伸、侧弯和轴向旋转中加载至7.5 Nm。在加载过程中，使用柔性传感管测量IDP，该传感管在X射线控制下插入髓核。在每个运动方向上，从第三次全加载循环在0.0、2.5、5.0和7.5 Nm时的压力值进行评估。发现IDP在屈曲时增加最高，与伸展IDP相比显著（<0.05）增加。侧弯时的中位压力值最低，同时显示出较大的变化范围。与胸段中部和下部相比，胸段上部的屈曲IDP显著增加，而与胸段上部相比，胸段下部的伸展IDP显著更高，两者在7.5 Nm时均与节段水平呈显著（<0.01）线性相关（屈曲：=-0.629，伸展：=0.500）。未检测到性别或年龄的显著影响，然而女性捐赠者的标本中IDP有升高趋势，且随着年龄增长IDP降低，这可能是由髓核组织的纤维化退行性改变引起的。测试后的矢状面和横断面切割揭示了髓核质量与压力力矩特征之间的可能关系，总体而言，在纤维化组织改变的情况下会导致低或负的固有IDP以及非线性压力-力矩行为。总之，本研究提供了关于胸椎IDP的见解，并为胸椎数值模型的验证提供了一个大型数据集。
