The Design Of Absorbable Dense/Porous β-Tricalcium Phosphate Bioceramic Cervical Intervertebral Fusion Cage And Initial Animal Experiment

[Objective]:In recent years,[3-tricalcium phosphate(β-TCP) bioceramic was more and more popular and became the neotype of biomaterial in clinical medicine. Because of its good capability of biocompatibility,degradation and bone conduction,β-TCP bioceramic was extensively utilized in clinical orthopedics as materials for bone repair,repairing the bone defect caused by trauma,tumor,inflammation and osteopathia.But since its poor mechanical property,the application was restricted to replace non-weight loading part.The absorbable dense/porousβ-TCP bioceramic was designed with the help of Bio-Lu company,combining the dense ceramic which had good mechanical property but poor biocompatibility and the porous ceramic which had good biocompatibility but poor mechanical property.Then the absorbable dense/porousβ-TCP cervical intervertebral fusion cage was invented via the above technique,on the morphological basis of three-dimensional images and large sample anatomic data of Chinese cervical intervertebral space.Besides,we measured the mechanical intensity of the cage,established anterior cervical discectomy goat model, and carried out initial experiments on observation and evaluation of clinical effects, which provided the evidence for clinical application.[Methods]:ⅠSix young male fresh cadavers were chosen which had no cervical vertebrae deformation,trauma,tumor and obviously degeneration.After defrosting, their head and neck were separated from the body and then 64 row thin sheet CT scan and MRI scan were undertaken on the head neutral position and the natural neck curve.Afterwards,the cervical spine specimens were fixed on the same position by the external fixation.All the anulus fibrosus,nucleus and cartilaginous endplate of cervical intervertebral spaces were removed and replaced by injecting silica gel to get the three-dimensional model of cervical intervertebral spaces.The models were measured and scanned so as to get three-dimensional images of Chinese cervical intervertebral spaces.Compared the data from those three methods of CT scan,MRI scan and silica gel model,CT scan was considered as a more suitable method of cervical intervertebral space measurement especially for large samples.Ⅱ.97 qualified young volunteers were chosen randomly,including 63 male(21～29 years old,average age 25.2 years) and 34 female(20～29 years old,average age 24.3 years). They took cervical spine CT scan grouped by gender.By this means,the anatomic data of Chinese cervical intervertebral spaces were gained.Based on the morphological data of the above experiments,the absorbable dense/porousβ-TCP bioceramic cervical intervertebral fusion cage was produced,its physical chemistry property and mechanical property was measured as well.Ⅳ.10 two years old adult goats,20～25kg,male or female,were divided into two groups:5 goats in group A wereβ-TCP bioceramic cervical intervertebral fusion cage group,and the other 5 in group B were autogenic iliac bone group as control.Anterior cervical decompression and fusion goat model was established.After anterior cervical discectomy at single level,cartilaginous end-plate was removed,thenβ-TCP bioceramic cervical intervertebral fusion cage and autogenic iliac bone was implanted separately.At last anterior plate was fixed.Lateral cervical X-ray photo was taken after operation.The goats were raised 8 weeks.Ⅴ.The goats were sacrificed to take lateral cervical X-ray and CT scan.The sagittal reconstruction was established afterwards.X-ray was used to evaluate the change of the operated cervical intervertebral space height.CT scan and reconstruction was to compare intervertebral fusion.[Results]:Ⅰ.The three-dimensional images of Chinese cervical intervertebral space are gained by silica gel moulding which is used to get the three-dimensional model of cervical intervertebral space.The accuracy of CT scan and MRI scan is proven.Ⅱ. The anterioposterior length of Chinese cervical intervertebral space is 16.35～19.81mm in male,14.98～17.43mm in female.It is 18.55～22.50mm in male and 16.55～20.69mm in female from left to right.On midsagittal plane,the height of anterior cervical intervertebral space is 7.26～9.03mm in male and 5.36～5.98mm in female.The height of middle point is 8.01～9.24mm in male,7.65～8.12mm in female.Posterior border is 5.01～5.22mm in male,4.76～5.03mm in female.The intervertebral space is larger and larger from above down and male has larger space than the same level of female.Ⅲ.The absorbable dense/porousβ-TCP bioceramic cervical intervertebral fusion cage's shape is like a box,has a ladder-shaped cross section,porous in center and dense surrounding.It is about 12mm in width,9mm in depth and 8mm in height.The mechanical intensity of the dense/porous one is significantly augmented than the simply porous so that it is able to perform supportive role and bone conduction better.Ⅳ.The anterior cervical intervertebral fusion model of goat is a good animal model for human cervical spine research.So results from this model is accurate and creditable.Ⅴ.The absorbable dense/porousβ-TCP bioceramic cervical intervertebral fusion cages are able to maintained the height of cervical intervertebral space.And there is no statistical difference of intervertebral fusion rate between these two groups.[Conelusions]:The absorbable dense/porousβ-TCP bioceramic cervical intervertebral fusion cage we designed is absorbable.Its elastic modulus is similar to human bone.It provides enough support for cervical intervertevral fusion,and produces fusion not less than auto-iliac bone at least.In conclusion,the absorbable dense/porousβ-TCP bioceramic cervical intervertebral fusion cage has good supporting ability,biocompatibility,mechanical property and intervertebral fusion effect,which indicates its perspective clinical application in cervical intervertebral fusion.