| In the 1990s, it was for the first time that Dr. Robert used CR cage in the cervical diseases'operation in France. Since then , more and more vertebrae cages have been applied in the clinical treatment and most of the cases demonstrated satisfactory effects. The first and second generation cages were mainly made in Titanium alloy, which has the good biocompatibility and similar rigidity of bone tissue. But due to the small volume and the structure of the opaque metal, the evaluation of the bone graft's growth and fusion in the cages becomes harder than that in the translucent cages. Now it is still lack of the efficient non-invasive or slight invasive method to do such a job.AIM: Different imageology methods were adopted to explore the better way to evaluate the bone graft's fusion state and activity in the cages and expected to give some valuable advice to the rehabilitation of the postoperative patients.METHODS: In our study, we took the threaded fusion cage as an example. All the 51 patients who had undergone the cervical vertebrae threaded cages plus anterior plates implantation were followed up. The follow-up period ranges from 3 to 15 months postoperatively. The X-ray was taken as the anterioposterior, lateral postion just one week postoperatively and when followed up the extension and flexion position were taken as well as the above mentioned. According to the American FDA and Kandziora standards, the criterion was established as the following: 1) the angle between vertebrae to be fused varies less than 5o; 2) there is no distinguished translucent belts around the cages can be found and no migration of the cages; 3) no loosened fixation plates system and the translucent belts around the plates occupy less than 50%. Only conforming to all the sentence above could be regarded as the bone graft fusion, otherwise non-fusion. The CT reconstruction was performed only when followed up 3 to 15 months postoperatively with the Toshiba Aquilion spiral CT made in Japan. The CT tomoscans were performed with the slice thickness of 0.5 mm, and 2-dimensional reconstruction images such as the sagittal, coronary and axial positional ones were acquired reconstruction images. The fusion and activity of bone graft's in the cage were observed. 41 patients suffering from the spondylosis who had undergone the operation of cages and anterior internal fixation plate implantation were treated as observed group, another 20 patients who matched in sex, age and other associated factors were chosen as the control group. These two groups of patients both accepted the 99mTc-MDP injection through vein approach which can demonstrate radionuclide imaging through nuclide bone tomoscans, and evaluate the growth condition of the bone graft in the cages.RESULTS: All the patients got just the right position of cages as just one week postoperatively, no migrations, no subsidence and even no distinguished translucent belt could be seen around the cages, no loosened internal fixation. The number of the patients with angles between the vertebrae to be fused varying from 0 to 2 degrees adds up to 16 and the other 35 ones without any angle variation measurable. The rate of bony fusion reached 100%. By the 2-dimensional CT reconstruction images, the bone graft's growth condition could be clearly seen in the cages. By our study, we found that almost all the cases with bone structures connecting the lower and upper vertebrae to be fused. According to the shape of the graft and the extent of the bone quality fusion could be further divided as the three classes, excellent, good and poor. After comprehensive analyses we found 21 excellent ones totally occupied 41.2%, the good 52.9%, and the poor 5.9%, with the total bony fusion rate 94.1%. The results of CT reconstruction and X-ray was analyzed in matched chi-square test by SPSS13.0 statistical software and the Kappa value was 0.90, theχ~2 value 0.35, P > 0.05, which demonstrated that there was no significant difference between the methods, and both came to a high consensus. As for the bone graft's activity, two groups'results were expressed asχ±s , the t test was used to analyse the results. The radioactivity ratio respectively as 1.8804±0.293, 1.084±0.016, t value equals to 2.713, P value less than 0.05. We found that 3 to 15 months postoperatively the metabolism of the bone graft in the cage is activer than the surrounding area and the nuclide was gathering more in the bone graft, and the radioactivity counting ratio is much higher than the control group. The survival ratio of bone graft in the cages adds up to 92.7 %.CONCLUSION: Firstly, X-ray is lack of precision but more economical in evaluating the bone fusion in the cage and is suit for the rechecking, screening in the postoperative follow-up. Secondly, the CT reconstruction was more direct and exact, we could observe the bone in the cage directly, even know the exact way of bone growth, and the early non-fused bone but without any sign by X-ray evaluation could be observed. Thirdly, the nuclide tomoscans by HawkeyeSPECT/CT could evaluate the bone growth by precise location and monitoring the bone metabolism, and it is probably suitable to monitor the bone fusion in earlier time. Finally, it has been confirmed that fusion with the autograft from verterbra acquired higher rate and bone graft got high activity.
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