人體老化脊椎終板之靜水壓抗壓強度與破壞模式分析

Abstract

目的：分析椎終板的靜水壓抗壓強度與破壞模式。 背景簡介：將椎間核替代物或可刺激細胞再生的物質以注射的方式注入椎間核，是新一代治療椎間盤退化的方法之一。在注射液狀物體時，需了解椎終板的靜水壓抗壓強度與液體在椎間盤內的擴散模式，才可決定此治療方式的有效性及適合此方法的病人篩選準則。 材料與方法：由五副人體脊椎取得15個胸椎(T11-T12)與腰椎(L1-L5)，平均年齡為86(5)歲。利用「椎間盤體積-壓力關係量測」儀器將顯影劑注射入椎間盤，得到椎終板靜水壓抗壓強度，並以電腦斷層掃描儀拍攝注射過程。以影像分析程式，將電腦斷層切片重建成3D影像後，分析顯影劑在試樣的擴散模式，以線性回歸分析椎終板靜水壓抗壓強度與骨質密度關係。將試樣沿著冠狀切面，做厚度為1mm的切片，觀察顯影劑洩漏位置與椎終板退化程度的關聯性。 結果：由電腦斷層掃描影像量測椎終板厚度，得到中間最薄(1.03±0.14mm)，周圍逐漸增厚(1.26±0.06mm)，兩者有顯著性差異，並可觀察到顯影劑主要從椎間核或椎間環裂縫往外擴散。之後再由椎終板流入椎骨或由椎間環洩漏。其中椎終板(0.18±0.17MPa)比椎間環(0.27±0.21MPa)靜水壓抗壓強度低。椎終板與椎間環的靜水壓抗壓強度與骨質密度呈正相關。從電腦斷層掃描影像與切片圖像，發現顯影劑易穿透椎終板破裂處或鈣化處而流入椎骨。從電腦斷層掃描可觀察到椎終板與椎間盤界面為不連續的鋸齒狀線，該不連續線可能表示椎終板的退化。 結論：椎終板與椎間環的靜水壓抗壓強度與骨質密度呈正相關。在退化的椎間盤內，顯影劑不會均勻擴散，會以裂縫擴散模式擴散，並由椎終板破裂處或鈣化處流入椎骨。

Objective： To evaluate the strength of hydrostatic pressure of endplate and the spreading pattern of contrast agent in the disc. Summary of Background Data： One of the disc degeneration therapies is to inject the biomaterials, which replace or promote regeneration of nucleus into the nucleus pulposus. To determine the efficacy of this therapy and the criteria of patient selection, it is important to evaluate the hydrostatic pressure strength of endplate and the injection pattern of contrast agent in the disc. Methods：Fifteen discs from 5 cadaver thoracic and lumbar spines (aged 77-92 years, mean age: 86 years) were injected with contrast agent using the quantitative discomanometry (QD) apparatus. The injection process was scanned with cine-CT. The endplate leakage pressure, spreading pattern of contrast agent in the disc, and the correlation between leakage pressure and bone mineral density (BMD) were analyzed. To observe the grade of endplate degeneration and the leakage site of the contrast agent, the discs were sectioned along the coronal plane, and macroscopic photographed. Result：The center region of endplate (1.03±0.14mm) was the thinner than the one of periphery region (1.26±0.06mm). Spreading patterns of contrast agent in the disc included “nucleus space expansion” and “anular fissure formation”. The contrast agent was found to leak through the endplate and the anulus fibrosis. The endplate leakage pressure (0.18±0.17MPa) was lower than the anular leakage pressure (0.27±0.21MPa). The endplate and anular leakage pressure were found positively correlated with BMD. Comparing CT images to macroscopic photographies, the contrast agent leaked through the fissure and the sclerosis site of endplate. The discontinuous lines between endplate and disc in CT images may be the indication of endplate degeneration. Conclusion：Both of the endplate leakage pressure and the anular leakage pressure were correlated positively with BMD. The contrast agent spread through the anular fissure of disc, and leaked through the fissures and the sclerosis site of endplate.