| During the operation of the anterior cervical, decompression, interbody fusion and plate interfixation has come to be a common surgicall procedure for cervical disease. The principle of the operation is decompression completely and fusion, and the fixation by the plate is one of the method for fusion. With the advancing of the knowledge and technique, more and more instrument has come to the area. In spite of the autograft or the AO plate and TFC, some disadvantage could be found in them . The price of the imports is too high for our Chinese people. So according to the tradition method of autograft and allograft,retaining the endplates, we design the Anatomy Allograft Cortical Ring(AACR) and biomechanical properties of AACR were tested. At the same time ,we had done the animal experimentAnd we use it in the clinical practice. Biomechanical test had also been done on differ time after operation. The AACR retains the nature BMP and other alive substance, this is helpful for fusion. We suggest we can measure the disc space by MRI,and preserving the endplates during the operation. Part I. The applied anatomy for lower cervical anterior fusionObjective and methods By the scanning on 35 healthy volunteers by MRI T2WI, we measured the height(anterior,middle,posterior) ,width,depth of the disc space on C2~C7.We also measured the width and depth on dry specimen of C^~C7 by precision vernier calipers-According to the clinical request, we designed the AACR for cervical fusion.Results The anterior height of the disc space is 0.46 + 0.06-0.60 0.05cm; the middle height is 0.56 0.07-0.72 0.06cm; the posterior height is 0.40+0.07-0.50 0.07cm. The depth of the dry cervical vertebral is 1.45 0.14-1.68 0.17cm, the depth of nucleus pulpous is 0.91 0.13-1.08 0.14cm.Anterior cervical decompression and implanting the AACR,we should leave 3-4mm amortizing area to avoid the compression in spinal cord.So the best depth of the AACR is 12-14mm. And the depth of the AACR that we had designed was 13.42mm.According to measurement on the distance betweenbilateral anterior feet of uncinate increased from 15.4mm in C3 to 20.2mm in C6 byJiangfugui,so we could determine the width of the AACR by these parameters.The width is14mm.Part II .The composing of the AACR and the principle for stabilizationAccording to the measurement, we use the allograft (radius,ulna and fibulae) to design Anatomical Allograft Cortical Ring (AACR).It is comprised by the design of inverse indention on each side, depth and width of the indention is 0.45mm and l.Smm.On both lateral side, there are 3 tiny bores in it. On the anterior side of the AACR, there is a 3mm(diameter) bore in it, which is designed by mechanic thread. The AACR preserves the natural BMP and other alive substance. The type of the AACR are: a 4mm(posterior),5.6nim(niiddle),4.43(anterior);b5mm(posterior),6.6mrn(iniddle),5.43(anter ior),c 6mrn(posterior),7.6mm(middle),6.43(anterior).Its width and depth are 14mm and 13.42mm.The assistant manipulating appliance are : A: the same size just as the AACR anatomy module;B: two squareness curettes;C 6mm(diameter) trepan. Part minstant stability by biomechanical evaluation on the differ interfixation of cervical anterior approach.Objective and methods To offer science evidence for clinical appiliation,the biomechanical properties of the AACR was investigated. Sixteen fresh human cervical spines(C4~C5) were tested under the various physiologic loading condition, which were divided into three groups(A, B, C) and fixed by several methods(preserving endplate and not preserving endplate;with anterior-plate and without anterior-plate). The strength and stability of spine were investigated and compared with stress analysis ways. Results The spinal strength and stability of the several types of interbody implants were significant difference. The strength, rigidity, flexibility, extension, axial rotation movement of the AACR with anterior-plate which was fixed by preserving endplates was larger than any other methods. Conclusion The AACR with anterior... |
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