椎間核壓力量測

Abstract

近年來利用人工椎間盤來重建了椎間盤的生理功能，即恢復椎間高度、應力分佈，以及維持脊椎的運動功能與穩定性。已成為脊椎生物力學研究的重要方向之一。然而要達成這目的，則必須先了解椎間盤的力學性質。 本研究的首要目標，就是量測在不同的負載條件下椎間核的壓力。為完成這次的研究，在實驗前預先製作了針式壓力感測器，以量測椎間核的壓力。同時為了確定量測的方式是否對椎間核壓力會造成影響，所以我們在這裡採用兩種感測器的置入方向。 在本次的實驗中所使用的材料為18個新鮮豬胸椎功能性單元，並將其分為兩組，利用衝擊測試機進行衝擊負載測試，同時量測椎間核的壓力，其中9個試樣針式壓力感測器由椎間盤前方插入；另外9個試樣則由椎間盤側面插入。 實驗完成後得到了胸椎受到衝擊負載的位置改變，對胸椎功能性單元所承受力、力矩，及椎間核壓力之間的關係。同時並且發現，不同的感測器置入方向，對實驗結果確實會造成影響。 而感測器對實驗的影響可能有三：一為對椎間環造成的傷害，這對脊椎在作前彎及後仰的動作時，其能承受的力矩造成影響。二為轉動中心的移動，侵入式的感測器的可能對脊椎的運動功能造成干擾。三為間核體積的變化，當感測器放入椎間核內部後核間核液體向外流動，使得核間核膨脹。

Summery of Background Data. In recent years, it is a mainstream to replace injured intervertebral discs with artificial ones to maintain the function of disc, such as remain distance between two vertebral bodies, transmit compressive force and keep stability of spine. Before achieving these goals, it is important to understand biomechanics of disc. Objectives. The objectives of current study are to measure intradiscal pressure with thoracic one-motion segments under different loading condition. Prior to the study, a needle pressure sensor was developed. Two orientation of sensor insertion were employed to investigate how the invasion of instrument influenced the measurements of disc pressure. Methods. 18 porcine thoracic one-motion segments were subjected to 1.2J of impact loading acting on different location of top of specimens, simulating forwards flexion, neutral erect position and backward extension. Intradiscal pressures were measured in each loading condition by inserting the needle pressure sensor into intervertebral disc with anterior and lateral approach, respectively. Results. In motion segments with pressure sensor approached anteriorly, the average intradiscal pressures were 1.5 MPa (loading on vertebra body) and 0.6 MPa (loading on posterior process), respectively. With pressure sensor approached laterally, intradiscal pressures in average were 1.1 MPa (loading on vertebra body) and 1.4 MPa (loading on posterior process), respectively. Results showed that orientation of sensor insertion influenced outcome of pressure measurement significantly. Conclusions. Three possible reasons might explain the results of current study. First, insertion of needle pressure sensor could make damage to annular fiber, and then decrease the ability of disc to sustain bending moment. Second, sensor invasion might change location of center of spine rotation. Third, sensor insertion causes the fluid of nucleus to flow out and to expand volume of nucleus.