C-arm assessment of cervical pedicle screw: screw coaxial fluoroscopy and oblique view.

STUDY DESIGN

Oblique view and screw coaxial fluoroscopy were used to assess cervical pedicle screw position in human cadaveric spine, results of which were compared with those of direct visual inspection by an anatomist.

OBJECTIVES

To determine whether clinicians can detect misplaced cervical pedicle screws with accurate sensitivity and specificity using conventional C-arm equipment.

SUMMARY OF BACKGROUND DATA

In the cervical region, pedicle screws have not been used so popularly as in lumbar or in thoracic regions. The reasons are related to the risk of inserting screw in small pedicle. So far, no method has been studied to assess the position of cervical pedicle screw during the operation.

METHODS

Ten human cadavers were prepared for this study. Headed and nonheaded pedicle screws were inserted bilaterally from C3-C7. Using C-arm oblique and screw coaxial fluoroscopy, the depth of penetration was recorded in 2-dimension scale (superoinferior and mediolateral direction) by 6 different observers. The vertebrae were all harvested, and the penetration depth was recorded by an anatomist under direct visualization. The accuracy of C-arm measurements was analyzed. The results of nonheaded and headed screws also were compared.

RESULTS

A total of 98 pedicle screw positions were finally enrolled into the study. The oblique view can verify screw position with the sensitivity of 86.1% and specificity of 64.5%. Coaxial fluoroscopy had a sensitivity of 89.8% and a specificity of 56.9% in superoinferior direction. Mediolaterally coaxial fluoroscopy had a sensitivity of 70.0% and a specificity of 51.3%.

CONCLUSION

C-arm assessment of pedicle position has acceptable accuracy. With C-arm swing motion of the coaxial fluoroscopy, headed screws were also inspected without any difference as nonheaded screws. Measurements for superoinferior direction showed better sensitivity than those for mediolateral direction, which are supposed to be related to be elliptical shape and thin lateral margin of cervical pedicle.