探討區域差異與梔子素對健康椎終板之雙向靜水壓阻的影響

Abstract

背景簡介：液體在椎間盤與椎體間的對流，是椎間盤獲取養分以及代謝廢物的方法之一。椎終板是位於椎間盤與椎體之間液體流動的界面。椎間盤的功能好壞與新陳代謝正常與否息息相關。椎間盤內部壓力的改變，驅動液體在椎間盤及椎終板之間流動。然而目前對影響椎終板液體通透性的因子，了解仍然有限。 目的：比較椎終板各區域水流阻力的差異，並探討液體流向、椎間核的存在以及交聯劑的浸泡，對椎終板水流阻力的影響。 材料與方法：使用健康豬胸椎的椎終板，依實驗需求以穴鋸從椎終板各區域取出直徑5mm，長6mm的圓柱作為試樣，試樣總數為125個。以客製化的液壓系統，將1ml食鹽水，以0.0075ml/s的速率，分別從試樣的兩端推進，以模擬液體流進、流出椎間盤的情形。在注射食鹽水的過程中，以壓力感測器量測水流阻力變化。共進行三組實驗。實驗1：比較椎終板前方、後側及中央區域水流阻力的差異。實驗2：保留椎終板中央區域上方的椎間核物質，探討椎間核的存在與否，對水流阻力的影響。實驗3：比較浸泡於梔子素、食鹽水、蒸餾水各一天的椎終板，其兩側水流阻力的差異。實驗後取得液體通過椎終板之壓力值，並進行統計分析。 結果：椎終板的前方、後側及中央區域，液體從椎間盤排出所需要的壓力，皆顯著地大於流入椎間盤所需要的壓力。椎終板中央區域的水流阻力顯著地小於周圍區域的水流阻力。當椎間核存在時，液體流進、流出椎間盤的壓力較高。與未經任何溶液浸泡的試樣比較，梔子素提高了0.98倍的液體流出椎間盤之阻力(P=0.038)，以及提高了1.02倍液體的流入椎間盤之阻力 (P=0.089)。 結論：由於椎終板的結構特性，造成液體進、出椎間盤所需要的壓力有顯著的差別。液體經椎終板排出椎間盤所需之壓力大於流入椎間盤所需之壓力。液體經椎終板中央區域進、出椎間盤的阻力較低。當椎間核存在時，液體較難排出椎間盤。梔子素會提高液體經由椎終板流進、出椎間盤所需之壓力。

Objectives. To investigate the effect of regional variation, nucleus material and genipin immersion on the bi-directional fluid flow resistance of healthy vertebral endplate. Summary of Background Data. The exchange of nutrients and wastes for metabolic process in the intervertebral disc can occur via fluid convection through the endplate. The fluid flow can be driven by pressure gradient between the vertebra and the intervertebral disc. However, the factors that influence the resistance of fluid flow of endplate have not been well studied yet. Methods. 125 plugs (diameter: 5mm, length: 6mm) were harvested form the healthy porcine thoracic endplates with a trephine drill. The customized pumping system was used to inject 1mL saline at a speed of 0.0075ml/s through two ends of each plug, simulating the fluid outflow and inflow of the intervertebral disc. During saline injection, the fluid flow resistance was measured as steady state pressure by a pressure transducer connected to the customized pumping system. Three experimental groups were performed to investigate the effect of regional variation, nucleus material and genipine on the fluid flow resistance, respectively. The plugs were harvested from the anterior (n=18), posterolateral (n=18), and central (n=18) endplate for Protocol 1, from the central endplate without removal of nucleus material (n=18) for Protocol 2, and from the central endplate with 18 plugs soaked in genipin solution, 18 plugs soaked in saline, and 17 plugs soaked in distilled water for 1 day for Protocol 3. Results. The resistance of fluid outflow was significantly greater than that of fluid inflow through every region of the endplate. The lowest resistance of fluid inflow/outflow was in the central endplate. The existence of nucleus material increased fluid flow resistance bi-directionally. In comparison with the plugs without being soaked in any solutions, the resistance of fluid outflow increased by 98% (p=0.038), and the resistance of fluid inflow increased by 102% (p=0.089) for the plugs soaked in genipin solution.

Conclusions. The resistance of fluid flow of the endplate is direction-dependent and region-dependent. Genipin can increase the resistance of fluid outflow and inflow of the endplate.