在脊椎生物力學領域中有兩項重要的主題，一為脊椎做連續性活動，二為小面關節在分攤脊椎運動元所承受的載荷大小。此兩種機制也與造成下背痛(low back pain, LBP)的因素有關。脊椎承受連續式載荷造成脊骨承受累積的壓縮力與剪力而使得椎骨的勁度性質降低，提升了下背痛的發生率以及挫屈傷害的危險。迄今也並無相關文獻探討在衝擊載荷狀態下，小面關節與椎間盤兩者之間分攤載荷能量的交互作用並無法得知，此外也並無其他文獻探討連續式載荷下脊椎運動的整體力學分析。
　　本研究旨在利用本實驗室所發展之連續式衝擊測試機構(Continuous Impact Testing Apparatus, 以下簡稱CITA)以及各種感測器的使用，研究連續式載荷下脊椎運動的整體力學反應，並發展一套量測設備系統，可以有效量測在不同的衝擊載荷條件下脊椎運動單元之小面關節分攤垂直載荷之特性。
　　使用豬腰椎模型進行體外生物力學測試。在連續性載荷方面，在均佈連續性載荷與前彎連續性載荷兩種不同載荷條件下，利用連續式衝擊測試機構提供5個小時90000次週期的連續性載荷測試。在衝擊載荷方面，將壓力感測器插入小面關節內以得到小面關節之接觸力。透過本實驗室所研發之連續式衝擊測試機構提供1.2焦耳之衝擊能量至試件上。點衝擊載荷分別施予在椎體的前端、中心以及後端等區域以模擬不同的載荷條件。分別記錄豬腰椎試件的x-y-z, 3個方向的力量與彎矩、軸向位移量以及壓力感測器所量測到的小面關節接觸力。
　　結果顯示，在連續性載荷方面，發現在兩種不同的載荷條件下，其三個方向的力量反應大致相同，但在力矩反應上則截然不同。當均佈連續性載荷時，力矩為前彎3 N-m，而當前彎連續性載荷時，力矩為前彎11N-m。連續位移潛變曲線圖中可證實經過5個小時90000次週期的連續性載荷測試後，脊椎關節運動並未達到穩定狀態。在衝擊載荷方面，提供固定600N衝擊載荷下，當點載荷施加在椎體前端時，小面關節分攤了椎體所承受的載荷約4％，此時腰椎所承受的彎矩約為前彎20N-m；而當點載荷施加在椎體後端時，小面關節分攤了椎體所承受的載荷約30％，此時腰椎所承受的彎矩約為伸展15N-m，當點衝擊載荷越往椎體後端作用，則小面關節分攤椎體所承受的載荷以及彎矩也就越增加。
　　本研究已成功發展出可以有效控制載荷力量的連續式載荷測試設備，可有效發現脊椎運動在連續性載荷下整體的力學反應以及小面關節分攤載荷的力學模式與源由。此一設備可以擷取受測試樣整體的力與力矩資訊。此外，也成功發展出一套可以有效量測在不同的衝擊載荷條件下脊椎運動單元之小面關節分攤垂直載荷之特性。

　　Finding the spinal motion segment under repetitive activities and the facet joint load sharing of spinal motion segment under compressive impact loading are an important spine biomechanics subjects. We also believed that two factors have been associated with low back pain (LBP). The cyclic loading causes a decline in the stiffness properties of the motion segments and predisposes them to more risk of buckling injury. The facet joint plays an important role in load sharing of spinal motion segment. Nevertheless, to the best of authors’ knowledge, no body up to data gives quantitative ideas of the mechanical interaction within the spine, and no body is able to detect the force history of facet joint under impact loading. The current study developed a unique apparatus using an in vitro porcine lumbar spine model to quantify the gross force and moment response of spine motion segment during cyclic loading and facet joint contact force during impact loading
　　In cyclic loading, eight fresh-frozen porcine spine joint (L3/L4) was used in the experiment. A “drop-tower type” impact testing apparatus was modified for the testing. The energy was transmitted to the specimen through the impounder. The specimen was loaded at two postures; i.e., the distributed and anterior point-load posture. The loading was set at 200 N compression and 100 N tension. The loading time is five hours; hence 90,000 cycles in total were applied. We record half second data every 5 minutes. Sixty sets of data were collect through the loading history. Signals of input force, three dimensional reaction forces and moments from the six-axial force load cell were all recorded at 10 kHz sampling frequency.
　　In impact loading, the pressure sensors were inserted into the both facet joints to find the joint contact force. The 1.2J impact energy was transmitted to the specimen through the impounder. The specimen was loaded at seven points from anterior to posterior. Signals of facet joint contact force, input force, three dimensional reaction forces and moments from the six-axial force load cell were all recorded at 10 kHz sampling frequency.
　　We found that the axial force responses between two loading conditions are similar. The anteroposterior and lateral shear force are slightly higher at point-loaded loading condition. However, the bending moment responses is very different between the two loading posture. The peak to peak magnitude of bending moment reaches 3 Nm during distributed loading, but reaches 11 Nm during anterior pointed loading. the cyclic creep deformation curve showed that the spine joint had not reached the steady state after 5 hours, i.e., 90,000 cycles of loading. In impact loading, the moment is in flexion when the load was applied at the anterior of vertebral body, and is in extension when the load is applied at central and posterior vertebral body . The facet joint force remained constant when the loading was applied anteriorly, but responed quite promptly when the loading was applied posteriorly. The facet joint shared 13% and 28% of axial loading when the load is applied anteriorly and posteriorly. The extension moment increased as the loading point moves posteriorly .
　　We successfully developed an apparatus that is able to give force controlled cyclic loading at very low price. The testing apparatus is able to detect the three dimension forces and moments responses of testing specimens and that is able to detect the force history of facet joint.

1.Wilder DG, Pope MH et al. Mechanical stress reduction during seated jolt/vibration exposure Clinical Biomechanics, 1996 20(1):54-60.
2.Wang JL, Parnianpour M, Shirazi-Adl A, Engin AE. Rate effect on sharing of passive lumbar motion segment under load-controlled sagittal flexion: viscoelastic finite element, Theoretical and Applied Fracture Mechanics, 1999,32:119-128. .
3.Wang JL, Parnianpour M, Shirazi-Adl A, Engin AE. Viscoelastic finite element analysis of a lumbar motion segment in combined compression and sagittal flexion – effect of loading rate Spine, 2000, 25(3): 310-318
4.Wang JL, Parnianpour M, Shirazi-Adl A, Engin AE. The dynamic response of L2/L3 motion segment in cyclic axial compressive loading. Clinical Biomechanics, 1998, 13 : 16-25.
5.A. Shirazi-Adl, Biomechanics of the Lumbar Spine in Sagittal / Lateral Moments. Spine, 1994. 19, 2407-2414.
6.Manoj Sharma, Noshir A. Langrana et al. Role of Ligaments and Facet in Lumbar Spinal Stability. Spine, 1994. 20, 887-900.
7.Mark Lorenz, MD, Avinash Patwardhan, PhD et al. Load – Bearing Characteristics of Lumbar Facets in Normal and Surgically Altered Spinal Segments. Spine, 1982, 8(2) 122-130.
8.K. H. Yang, A. I. King. Mechanism of Facet Load Transmission as a Hypothesis for Low-Back Pain. Spine, 1984. volume 9, 557-565
9.James P. Dickey*, Kevin A. Gillespie Representation of passive spinal element contributions to in vitro flexion-extension using a polynomial model: illustration using the porcine lumbar spine. Journal of Biomechanics 36(2003) 883-888.
10.C.M.A. Ashruf, Thin Flexible Pressure Sensors. Sensor Review 2002, 322-327
11.Martin Ferguson-Pell, Satsue Hagisaea, Evaluation of a Sensor for Low Interface Pressure Applications. Medical Engineering & Physics 2000, 22: 657-663.
12.Balakrishnan, A., Kacher, et al. Smart Retractor for Use in Lmage Guided Neurosurgery. Summer Bioengineering Conference 2003, June 25-29
13.Panjabi MM, Krag M, Summers D, et al. Biomechanical time-tolerance of fresh cadaveric human spine specimens. J Orthop Res 1985; 3:292-300.
14.Elaine N. Marieb, Jon Mallatt Human Anatomy 3rd 2001, 170-172
15.韓毅雄, 1983. 骨骼肌肉系統之生物力學, 219-240.
16.李彥霖, 2002. 豬膝關節受衝擊與連續性載荷時之動力學與運動學分析. 台台灣大學醫學工程研究所碩士論文, 1-62.
17.鍾政賢, 2003. 膝關節受到衝擊時脛骨關節之壓力變化與載荷傳遞情形. 台台灣大學醫學工程研究所碩士論文, 12-34.