Customed Implants Made By Additive Manufacturing Technology For The Treatment Of Spinal Tumors

Chapter 1: Evaluation of Mechanical Properties and Osteogenic Ability of Composited Porous Titanium Alloy Scaffolds Manufactured by Selective Laser Melting TechnologyOBJECTIVE: To evaluate the mechanical properties and osteogenic ability of composited porous titanium alloy(Ti6Al4V)scaffolds prepared by selective laser melting technology(SLM).METHODS: Computer-assisted design(CAD)software was used to combine two different porous structures into a new composited one by a Boolean union operation.Based on this idea,four kinds of porous titanium alloy scaffolds were manufactured by selective laser melting technology,named A,B,C,and D,respectively.Structure A and B were uniform pore groups,C and D are composited groups,and traditional forging samples were used as a control group.The mechanical properties,in vitro cell compatibility,in vivo osseointegration ability,and pull-out tests were evaluated.RESULTS: Compared with the traditional samples,the elastic modulus of the four sets of porous titanium alloy scaffolds was closer to the normal bone tissue of the human body,and the elastic modulus of the composited group was higher than the others,and the difference was statistically significant(P<0.05).In terms of cytocompatibility,the number of mesenchymal stem cells increased over time in each group of porous scaffolds,but the number of cells on each set of porous titanium scaffolds differed at 5 Days.At 10 Days,the number of cells in the D group was the highest(P<0.05).And this group also had higher ALP activity(P<0.05)in the 14 Days of the osteogenic differentiation experiment.According to the results of the in vitro cell test,We selected the B and D groups of structures to make in vivo implants for comparison.According to the in vitro test results of the two in vivo implantation experiments,the bone volume fractions between the B and D groups were observed at 3 months.There was no statistically significant difference(P>0.05).The pull-out force test showed that D was better than B,and the difference was statistically significant(P<0.05).CONCLUSION: This study shows that the composite porous titanium alloy stent prepared by SLM has suitable elastic modulus and satisfactory osseointegration ability,which provides a new choice for the preparation of personalized implants.Chapter 2: Accuracy Evaluation of 3D Model Based on Magnetic Resonance Data and Clinical ApplicationsSection OneOBJECTIVE: This study was designed to investigate whether magnetic resonance image data is suitable for reconstruction of 3D printed models.METHODS: Using CAD software to design a model consisting of three mutually perpendicular hollow cylinders,four different specifications were made by additive manufacturing techniques,and a diluted contrast agent was poured into the models.CT and different types of MRI sequences were scanned for the same model and reconstructed to obtain corresponding 3D models.The selected MRI sequences are conventional T1 WI sequence,conventional T2 WI sequence,3D-Vibe isotropic sequence,3D-Vibe anisotropic sequence,3D-Dess isotropic sequence,3D-Dess anisotropic sequence,3D-Space Isotropic sequence,3D-Space anisotropy sequence.The model reconstructed by CT data was selected as the control group,and it was placed in the same coordinate system as the model reconstructed by MRI.After mutual registration,the matching degree between the two models was calculated and statistical analysis was performed.RESULTS: Compared with the conventional sequence,the 3D sequence was more suitable for the reconstruction of the three-dimensional models,and the difference between the matching degrees was significant(P<0.01).When comparing the matching degree of 3D isotropic sequences with the anisotropic sequences,it can be found that when the model is small,there is a significant difference between the matching degrees(P<0.01).As the model volume increases,too.The difference in matching degree was gradually reduced.The consistency test indicates that there is a good agreement between the model obtained by the 3D magnetic resonance isotropic sequence and the model obtained by CT.CONCLUSION: 3D magnetic resonance isogenic sequences are suitable for reconstruction of 3D models.Section TwoOBJECTIVE: We used the magnetic resonance sequence selected in the first section for the actual model reconstruction process,and summarized the general flow of composite modeling using CT and MRI data and finally preparing medical models by 3D printing.METHODS: VX2 cells were used to construct a tumor-bearing rabbit model.CT and MRI scans were performed at 2 and 4 weeks postoperatively for 3D reconstruction.The femoral model obtained by CT was registered with the femoral model obtained by MRI and the degree of matching was calculated.After the registration is completed,the femoral model obtained by CT and the tumor model obtained by MRI is Boolean operations to obtain a composite model.RESULTS: The correctness of the conclusions obtained in the first section was demonstrated in this section by reconstruction of the animal model.Based on the 3D isotropic magnetic resonance sequence image data or the model reflects the actual shape of the femur,and combined with the CT data,the contour and details of the lesion can be reconstructed more realistically.CONCLUSION: The possibility of accurate reconstruction of bone and joint models using MRI data was again demonstrated by actual modeling operations.Chapter 3: Customed Implants for Thoracolumbar Reconstruction After Spinal Tumors ResectionOBJECTIVE: To introduce the preliminary results of anterior column reconstruction using customed vertebral implants made by additive manufacturing technology after primary thoracolumbar tumor resection.METHODS: After fully informed and signed informed consent,from January 2018 to March 2019,a total of eight patients volunteered to receive operation.The patients were followed up at 3 months,6 months,and 9 months,and the corresponding imaging data were obtained.The results were compared with the preoperative data.RESULTS: After up to 10 months of clinical follow-up,no sinking,movement,and rupture of the implant occurred in all patients,and the average time(4.5 ± 0.9)minutes for implanting a single-segment personalized implant was observed.The required number of X-ray exposures was(3.5 ± 0.7)times.The multi-segment time(7.5 ± 0.5)minutes,the required number of X-ray exposures was(4.5 ± 0.5)times.CONCLUSION: Additive manufacturing artificial vertebral implants meet the needs of spinal reconstruction and they are new choices for reconstruction after spinal tumor resection.