Development Of New 3D Printing Cervical Intervertebral Fusion Cages And Preliminary Study On Animal Experiments

BackgroundEvery year,a large number of patients in China need surgery for spinal degenerative diseases and spinal trauma.Cervical spinal surgery is one of the common types.During the operation,people often need to use an internal plant to place the cervical intervertebral space after the disc is removed,which can restore the height of the intervertebral space and promote the fusion of the upper and lower vertebral bodies.At the earliest time,the way was to take the autologous bone as a graft,but the autograft bone is prone to complications such as collapse and pseudoarticular formation.Therefore,the cervical Intervertebral fusion cage was invented to replace autologous bone graft.The Intervertebral cage can act to support the height of the intervertebral space,and a bone graft window is often placed inside the cage to fill the epiphysis.The initial Intervertebral cages were made of metal,which showed good bone fusion rates and improved patient symptoms after surgery.However,the disadvantage of the metal cage is that the modulus of elasticity is quite different from that of the bone,and the occurrence of plant sedimentation after surgery is still relatively common.In addition,metals such as titanium alloys are radiopaque,which makes it difficult to determine the effect of fusion by fluoroscopic imaging after implantation of the Intervertebral cage.With the development of materials science,high molecular weight polyetheretherketone(PEEK)has been gradually applied to the production of Intervertebral fusion cages.PEEK materials have the advantages of radiation permeability and elastic modulus close to human bones.But PEEK materials also have shortcomings such as poor osseointegration ability.The application of 3D printing technology in the medical field makes it possible to individualize the Intervertebral cage and construct the internal fine structure.Titanium alloy and PEEK materials are currently common materials for 3D printing of Intervertebral fusion cages.The surface modification of orthopedic plants can overcome some of the shortcomings of the original materials and is therefore widely studied.Surface modification of PEEK materials includes surface coating,physical modification and chemical modification.ObjectiveA new type of titanium alloy cervical Intervertebral fusion cage and two new types of PEEK material Intervertebral fusion cage were designed and rapidly formed by 3D printing technology.Surface modification technology was used to improve the performance of the new PEEK cages.By implanting these new Intervertebral fusion cages and control cages into the cervical vertebrae of goats and measuring relevant data for a period of time after surgery,it is verified whether the new Intervertebral fusion cage has an advantage in promoting bone fusion.Methods1.Obtain relevant anatomical data of the experimental goat cervical vertebra by CT scanning to design the size of the personalized Intervertebral fusion cage;2.Designing and manufacturing a new type of titanium alloy cervical Intervertebral fusion cage with gradient porous structure;3.Two kinds of new cervical Intervertebral fusion cages of PEEK with rectangular porous structure and honeycomb porous structure were designed and fabricated,and their surface modification was carried out;4.Three kinds of new cervical vertebrae Intervertebral fusion cages and the control cervical Intervertebral fusion cage were implanted into the cervical vertebrae of 8 goats by operation;5.Three months after operation,the goat cervical vertebrae were examined by imaging and biomechanical tests,and the differences in bone fusion effects were compared.Subsequently,the corresponding sections of the cervical vertebrae were further examined.Result1.CT scan results show that the cervical intervertebral space of the goat is close to the height of the human cervical intervertebral space,but the curvature of the upper and lower endplates is different from that of the human,and the height of the cervical vertebra of the goat is significantly larger than that of the human;2.X-ray and spiral CT examinations at 3 months after operation showed that there was obvious bone bridge formation in the central region of the PEEK material fusion device in the control group.The upper and lower layers and internal spaces of the new porous titanium alloy cages in the experimental group 1 have a higher density than the other surrounding palces.The experimental group 2 and the experimental group 3 have a relatively uniform density increase inside the new porous PEEK material fusion device;3.The biomechanical test and Micro-CT examination at 3 months after operation showed that the bone fusion effect of the new porous titanium alloy cage of the experimental group 1 was better than that of the control group.The bone fusion of the new porous PEEK material cage of the experimental group 2 and the experimental group 3 are worse than the control group.ConclusionThe cervical vertebrae of the goat have certain similarities with humans and can be used as an animal model for plant experiments in the spine.However,the anatomical structure must be familiar before surgery and carefully operated during surgery.Titanium alloy cervical Intervertebral fusion cage combined with gradient porous structure can effectively imitate the density gradient of natural bone.The area with higher porosity provides sufficient space for the migration,proliferation and differentiation of bone cells,while the area with lower porosity guarantees sufficient mechanical properties required for carrying.Preliminary results from animal experiments also showed that it has a better bone fusion ability relative to the control group.The PEEK material cervical interbody fusion cage combined with porous structure and surface modification did not show good bone fusion effect in this experiment,and its biomechanical and Micro-CT test results were worse than the control group.The research design of these cages needs to be improved and further experimental verification.