- 學位論文
薦椎骨質疏鬆骨折之生物力學探討
Biomechanical Investigation of Sacrovertebral Fracture in Osteoporosis
摘要
高齡化的臺灣，薦椎骨折的比例逐年升高，骨折造成患者產生嚴重的疼痛以及行動受限。不同型態的薦椎骨折需要不同的固定方式，目前對於薦椎骨折的固定方式以及生物力學的影響，尚未完整的進行探討。因此本研究透過有限元素分析建構出多種薦椎骨折模型，進一步比較各種薦椎骨折模型在未固定與固定後的生物力學影響，並探討骨釘固定與骨板固定的差異，以提供臨床手術治療參考。 本研究利用逆向工程之雷射掃描裝置截取薦椎、尾骨、髂骨及L5腰椎的幾何型態資料，進一步匯入Avizo7.0中進行實體模型的建構。各部位的實體模型匯入Solidworks2010中進行解剖對位，以形成一組標準化的薦椎實體模型。再進一步利用電腦輔助繪圖的功能建構出具有皮質骨與海綿骨結構的實體模型，以便後續可以進行骨質疏鬆的材料設定。標準化薦椎模型透過設定骨質疏鬆的材料性質與分布區域，在施力後可以產生出五種薦椎骨折的基本模型，作為後續的骨釘與骨板形式的固定探討與比較。五種型態的薦椎骨折模型將分別進行固定與無固定的施力探討，其中的骨釘模型參考臨床使用的尺寸進行繪製，至於骨板模型則是客製化的特殊設計，此研究將提供比較骨釘與骨板固定後的生物力學影響，探討指標包括整體穩定度與蒙麥司應力值(von-Mises stress)的差異。薦椎有限元素模型的邊界條件固定在兩側的髖臼窩上；至於施力有兩種形式，第一是雙腳站立姿勢，在腰椎上施加垂直力600N的體重負荷，第二種是腰椎屈曲運動，在第五腰椎上給於10N-m的彎矩，以模擬人體進行屈曲運動。 分析結果顯示U-1L固定模型在薦椎上產生較高的應力值，但薦椎在位移方面的穩定度在站立負荷與前屈運動的情況下都具有最小的位移量，因此U-1L固定方式在整體穩定度是較佳的。薦椎T型骨折使用T-1L-2S的固定方式，也就是長型螺釘加短螺釘的組合，其位移量相較於T-1L與T-2S的固定方式明顯是較少的。YI型薦椎骨折中在使用螺釘的YI-1L-1S固定方式，其薦椎應力與螺釘應力都比其他組低，而整體穩定度也呈現出最低的位移量；在YI型薦椎骨折之骨板固定中，雖然YI-3mp的螺釘應力較其他兩者骨板固定方式高，但骨折斷面處的位移量，卻是比其他兩組小。至於YII型薦椎骨折中，YII-1L-2S型固定方式，其模型在薦椎與螺釘都具有較小的應力值，此外骨折斷面處位移量也是三種固定方式中最少的。在H型薦椎骨折之固定分析中，發現其H-1L-2Sx的固定方式穩定度較高而位移量也相對較低；在使用骨板固定評估上，發現H-MIAP-2mp的固定方式具有最小的位移量，顯示其整體骨折固定的穩定度最佳。
並列摘要
Aging society in Taiwan, the proportion of sacrovertebral fractures increased year by year for resulting in severe pain and limited movement. Different types of sacrovertebral fractures need different fixation methods. However, the effects on the fixed applications and biomechanics of sacrovertebral fractures have not been fully discussed at present. Therefore, this study constructed five varieties of the sacrovertebral fracture models with finite element analysis to further compare biomechanical effects of the sacrovertebral fractures in the non-fixation and fixation treatments, and to investigate the different between screw-type and plate-type fixations in order to provide clinical surgical reference. This study obtained geometric data of sacrum, coccyx, pelvic, and L5 lumbar from sawbones with laser scanning device by reverse engineering technique to converge into the Avizo 7.0 to construct the solid models for reflecting sawbones. Each isolated solid model were further registered in the CAD software of Solidworks 2010 to build a stander solid model of the sacrovertebra. In addition, the solid sacrovertebral model was built the structures of cortical and cancellous bone using volume-substracted operation of computer aided design to provide material setting of osteoporotic condition. The stander sacrovertebral model could generate five basic models of the different sacrovertebral fractures through setting the material properties and distribution area of bone fracture to provide investigation and comparison of fixation between screw and plate techniques. The five basic models of the sacrovertebral fractures were investigated the effects with and without fixations, moreover, screw model was constructed following the size of clinical usage, and plate model was created according to special design of customization. This study will compare the biomechanical fixed effects under screw and plate fixations including indexes of overall stability and von Mises stress. The boundary conditions of the finite element analysis in the sacrovertebral fracture models were fixed on the bilateral acetabulum of the pelvic. The force condition was considered as two types of loadings, first type was that a two-leg standing posture with a body weight of 600 N vertical force was applied on the L5 lumbar vertebrae, second type was applied a bending on the sagittal axis to simulate the lumbar flexion movement. The results showed that the U-1L fixation model produced a higher stress on the sacral body, but the stability of the sacral-fractured body had the minimum displacement in the case of standing load and forward flexion movement, therefore, U-1L fixation is better than others in stability. The T-1L-2S fixation method of T type fracture, such as the combination of long screws and short screws, was detected obviously less than that of T-1L and T-2S in the displacement. The YI-1L-1S fixation of YI type fracture with screw fixation showed that the peak stresses in the sacrum and screws were lower than that of other fixations, and the overall stability for sacral-fractured models also showed significantly the lowest displacement. In the fixed models of the YI type fracture, the results indicated that the screw stress of the YI-3mp model was higher than that of the others, but the peak displacement at the region of the fracture line was smaller than that of the others. In the YII type of the sacral fracture, the model of the YII-1L-2S was noticed a trend of decreasing stress in both sacrum and screw, moreover, the displacement in the region of the fracture line was also detected the least value in the three types of the fixations. The fixation of the H type fracture showed that the H-1L-2Sx fixation was more stable comparing with different methods and the displacement was also relatively low in the overall models. In the evaluation of bone plate fixation, the results revealed that the H-MIAP-2mp fixation could provide the minimum displacement and showed the best stability in the sacral fixation of the H fracture.