腰椎解離之生物力學分析

Abstract

根據統計約有6%的成年人患有腰椎解離的疾病，常見於年輕的運動員身上，因在運動的過程中，腰椎需反覆地承受高負荷的彎曲與扭轉動作，在關節間部持續受到壓力而造成的壓迫性骨折。由於腰椎解離之後的力學行為若遭受到太大的外力，則會造成脊椎呈現不穩定而導致腰椎滑脫。 本研究以有限元素法應用於六節脊椎模型(L1-S1)來分析在解離初期之生物力學特性，探討在腰椎解離時對脊椎的影響。本研究亦加入了Follower load進行模擬，將更接近人體內真實情形。主要探討腰椎解離初期的穩定性、小面關節之受力變化、端板剪應力以及對椎間盤應力的影響。 本研究建立了L1-S1脊椎模型，並加入Follower load與文獻驗證的到合理的結果，研究結果發現在腰椎解離之後的力學行為發生變化，在後彎與扭轉動作下發生不穩定現象，而小面關節的受力會由端板與椎間盤承受，因此端板與椎間盤會有較高的應力，端板有較高的可能性發生破損，而椎間盤也有可能因受力趨勢改變發生退化，引發腰椎滑脫。

Spondylolysis occurs in 6% of the general population. Although the etiology of this continuum of conditions is uncertain, genetic predisposition and repetitive trauma have been strongly implicated. Sports in which participants are subjected to repetitive hyperextension across the lumbar spine pose a risk for such injuries. If the lumber spine was imposed to a large force after the occurrence of spondylolysis, the lumber spine might become listhesis and result in spinal instability. A verified finite element model of L1-S1 was used in this research to investigate the biomechanics of spondylolysis in the early stage. The lumbar spine can support a compressive load of physiologic magnitude without collapsing if the load is applied along a follower load path. The numerical simulation will analyze the stability of spondylolysis, forces of the facet joints, shear forces of the endplate and stresses of the disc. This study established lumbar spine model (L1-S1) using the follower load. This study found the loading pathway in the lumbar spine with double pars defect was transmitted form the disc, not from the facet joint. The fracture would be initiated at the endplate in the lumbar spine with pars defect. So the endplate shear stress and the discal stress near the fracture site remarkably increased. The lumber spine might become listhesis.