[Experimental study on screw insertion in lower cervical pedicle assisted by multi-spiral computerized tomography three dimensional reconstruction techniques].

OBJECTIVE

To assess the clinical significance of transpedicular screw insertion in lower cervical vertebra assisted by multi-spiral CT (MSCT) three dimensional (3D) image reconstruction techniques.

METHODS

Eight cervical vertebra specimens were examined by MSCT, and the messages were sent to SGI02 Workstation; according to the parameter requirements of lower cervical pedicle fixation, by using post-process of volume rendering (VR) the condition was judged and multi-planar reformation (MPR) was used to do individual analysis; and the ideal path of screw insertion was obtained and the related parameters were measured. After preoperative plan being finished, referring to these measured parameters, 3.5 mm screws were inserted into C37 pedicles of these 8 specimens. After insertion of screws, MSCT scanning and 3D reconstruction were performed again to evaluate the accuracy of lower cervical pedicle screw inserting. From May 2007 to November 2009, 28 patients who received screw insertion in lower cervical spines were given MSCT scanning and 3D reconstruction to evaluate the illness situation, to confirm shortest fixation volumes, and to collect the parameters of aim pedicle screw insertion.

RESULTS

The time of insertion for each screw was (392 +/- 62) seconds. It was found that one pedicle was clausura (1.25%, 1/80) and five pedicle diameters in coronal view were less than 3 mm (6.25%, 5/80), which all were not fit for screw insertion. A total of 74 screws were placed successfully. One-time success rate of screw insertion was 95.95% (71/74). The total accuracy rate was 91.89% (68/74). Six screws penetrated (8.11%). According to the Richter penetrating classification: grade one was 6.76% (5/74) and grade two was 1.35% (1/74). There were significant differences (P < 0.05) in penetrated rate between our study and anatomic landmark localization (47.37%), Miller methods (25.00%), and there was no significant difference (P > 0.05) when compared with Abumi method (6.70%), hopper method (7.10%), pipeline depopulation method (5.20%) and navigation technique (11.30%). In clinical 28 cases, 121 screws were inserted; one pedicle was clausura and one was fissure fracture, which all were unfit for insert screw in preoperative plan, the surgery project was adjusted. After operation, 17 patients (76 screws) were given MSCT scanning again. A total of 67 screws (88.16%) were placed successfully. Nine screws (11.84%) penetrated, grade one was 7.89% (6/76) and grade two was 3.95% (3/76).

CONCLUSION

It is accurate to apply MSCT 3D reconstruction techniques to measure the ideal screw canal in preoperative individualized plan. Strictly following individual quantitative data, the safety and accuracy of the surgery can be improved. And it is feasible and available to use MSCT MPR imaging to evaluate the accuracy of pedicle screw insertion.