The Realization Of Non-Fusion Technology Of Artificial Vertebral Body And Finite Element Analysis

Objective:(1) The improvement structure of frame type artificial vertebral body which based on basic theory of frame type artificial vertebral body, can achieve the shock absorption and universal movement of the spine motor unit. The new structure can realize the non-fusion technology of artificial vertebral body.(2) The three-dimensional finite element model of non-fusion technology of artificial vertebral body was established by the application of computer software using reverse engineering technology. And the finite element mechanics analysis was performed to test the biomechanical rationality of the artificial vertebral body with non-fusion technology.Methods:(1) The X-rays of healthy adult volunteers' lumbar under weight and nonweight bearing condition were collected. The height of the disc, and anteroposterior diameter and height of vertebra segment from lateral view were measured. The transverse diameter from anteroposterior view was measured. The improvements which involving space structure of frame type artificial vertebral body were made according to the collected data. The hardness of final silica gel for substitution was 60 ~ 80 shore according to plenty testaments. This kind of hardness can help to achieve shock absorption and universal movement of the spine motor unit. Another advantage of this silica gel can perfectly match up with top and bottom plate and column in inlay manner. The disc, top and bottom plate and column were designed into different sizes according to the size of vertebral body.(2) Healthy adult volunteers' thoracic and lumbar CT data was collected. The data of CT images of DICOM format were imported into Mimics. The primary three-dimensional models of T11, T12 and L1 were created in Mimics and saved as "*.txt" format after they were optimized. The "*.txt" format data was imported into Geomagic Studio for final moulding. For those irrelevant points do not go through point cloud shall be excluded and the noise as well. Then the uniform sampling and encapsulation were carried out. The point cloud was connected using triangular. Grid Doctors was applied to remove the high refraction, intersecting edge and non-streamline edge etc. Then filled model and simplify it using loosening and abrasive paper function. The model was spherized and ended up with NURBS curve face. The model got further optimizing using loosening curve face to edit. The three-dimensional entity model of vertebral body with simulated operation, then export and save it in IGES format. The 3 d model of vertebral body and non-fusion artificial vertebral body were assembled in Pro E and three-dimensional finite element model was achieved. The 3 d model of vertebral body and non-fusion artificial vertebral body which was imported into Ansys Workbench as "*.stp" was transversed into the finite element 3 d model. 500 N and 800 N vertical load were laid at the bottom of L1 and on top of the T11 as well in the constraint model.Results:(1) The non-fusion artificial vertebral body is composed of two plates, silica gel disc, and the column between them. The plates have an arc-shape sunken at canalis vertebralis which coordinate with endplates. The central part of the plate is elliptic protrusions and has lateral mass on the side. The size of lateral mass was 2×2cm which has two locking holes for early or temporary fixation. The diameter of the plate from non-fusion artificial vertebral body was designed as size 1~5 according to parameter of different human vertebral bodies. The thickness of the silica gel disc is 5mm and has inlaying structure on both ends. And the disc also has 5 different sizes. The two ends of the column were connected to the plates and the central diameter of the column was 12 mm. The column also has 5 sizes to work with the plates from 20~40mm.(2) The solid model of T11, T12 and L1 were established using reverse engineering technology. The T12 replaced 3d model was created in Proe/Engineer. The Ansys Workbench was applied to fix the finite element 3 d model. The maximum stress concentration area were at the medium and posterior parts of the silica disc when the load was 500 N and 800 N respectively. the maximum stress concentration area was in the posterior of the plate and the deformation was found at the edge of posterior side from the replaced model.Conclusion:(1) The whole package of non-fusion artificial vertebral body which using 60~80 shore silica gel disc in mosaic fixation combined with titanium end plates and column was achieved. It has the function of filling up and bearing from space structure aspect and shock absorption and universal movement of the spine motor unit form movement aspect.(2) The non-fusion artificial vertebral body model can be established by applying the theory of engineering technology. And the foundation was laid for future finite element mechanics analysis. The deformation and the load differences of the silica disc and the prosthesis were close to that of normal disc and vertebral body.