The Appliance Of Finite Element Method On Orthopaedic Biomechanics

This paper aimed at the appliance of finite element method(FEM) on orthopaedic biomechanics to serve for clinic. Proper, vivid and effective models about biomechanical problems were build and studied in this paper, such as the mechanical problems correlative with the human spine, artificial joint replacement and the evaluation of orthopaedic instruments et al. Some of the results were compared with that obtained from experiments to explain the clinical phenomenon as well as to provide biomechanical proof and direction for clinical appliance. On this process, good methods on reconstruction and simulation were explored, and some good models that can reflect the biomechanical effect were accumulated for the next studies. Main studies are shown below:1. Contact is very common in the study of biomechanics. In this paper, the contact phenomenon exists on lumbar facet joints were analysed. The lumbar facet joints play a considerable part in resisting the intervertebral loads. A three-dimension FEM model of normal L4-5 was built, and the lumbar facet joints were treated as to contact with each other. Various motions of L4-5 were simulated by changing the loads: anteflexion, retroversion, right rotation, right bending and longitudinal compression. The strain and stress on both sides of the facet joints were calculated, analysed and compared with each other. As a conclusion, the lumber facet joints bear the largest loads in axial rotation among the five motions.2. Artificial joint replacement is the hotspot in biomechanics recently. In this paper, the artificial disc replacement on L4-5 was studied. The artificial disc replacement on lumbar is a new kind of operation, and the changes of mechanics aroused by it are not very clear, which restrict it's application on clinics. On the-3-basis of FEM model L4-5, three kinds of models were built to simulate the normal disc, the degraded disc and the artificial disc. Under the same conditions as specified in item 3, the strain and stress in the L4-5 and the facet joints were calculated and compared with each other. Additionally, the artificial disc was analysed to confirm its rationality and safety as well as its deficiency.3. The fracture mechanism of the atlas(Cl) were studied in this paper. Levine and Edwards divided the fracture of Cl into three types: type I :the posterior arch fracture; typell:the lateral mass fracture and type III: the Jefferson fracture. A three-dimensional FEM model of atlas was constructed and analysed to simulate each kind of fracture. From the simulations, we can see the distributions and transmission of strain and stress in model under different loadings, and the results explained the fractures very well.4. Similarly, a axis FEM model was constructed to simulate the axis fracture, emphasized on the odontoid process. Three kind of odontoid process fracture were analysed on this model, which occurred respectively on the tip, the middle and the fundus. The results gave the best angle to fracture the odontoid process of the axis. Additionally, the Hangman atlas fracture was simulated and the calculation gave the expected results.5. The biomechanical features of medical treatment instruments are concerned by clinicians, which is composed of structure stability, intensity limitation, anti-fatigue, resonance-responding and impact characters et al. These features are all related to the rationality and safety of instruments. In this paper, FEM were applied and personal techniques were bring forward to solve these problems. Examples of the analysis by finite element method were also shown in it, which includes: the modified anterior plate instrumentation(MAPI), the anterior thoracolumbar K-plate system, the short reduction-fixation(HOIST device) for lumbar spondylolisthesis and the artificial femoral head.