Accuracy study of cervical pedicle screw placement assisted by O-arm combined with CT 3D navigation system

English Keywords:O-arm navigation  Pedicle screw  Lateral mass screw  Accuracy of screw placement

English Abstract:

  【Abstract】 Objectives: To investigate the accuracy of cervical pedicle screw placement assisted by O-arm combined with CT 3D navigation system, and to compare with lateral mass screw fixation. Methods: 54 patients who underwent posterior cervical fixation in our hospital from March 2017 to February 2021 were included in this study, which included 44 males and 10 females, aged 42-79 years(58.3±9.3 years). They were divided into two groups: O-arm navigation assisted C3-C7 pedicle screw placement group(group A) and freehand C3-C6 lateral mass screw placement and C7 pedicle screw placement group(group B). There were no significant differences in gender and age between the two groups(P>0.05). The amount of intraoperative blood loss, operative time and perioperative complications (posterior cervical hematoma, severe infection, vascular and nerve injury, etc.) were compared between the two groups. Plain CT scan was performed after removal of drainage tube, and according to the penetration degree of pedicle cortex by screw, the screw placement accuracy was classified into four grades: Grade 0, the screw was placed in the pedicle without penetration; Grade 1, penetration<2mm or less than 50% of the screw diameter; Grade 2, 2mm≤penetration<4mm or penetration>50% of the screw diameter; Grade 3, penetration≥4mm or screw penetrated cortex and entered into spinal canal or vertebral artery foramen. Also, the placement accuracy of lateral mass screw was recorded with reference to the above grading standard on the basis of penetration degree of lateral mass by screw. Grades 0 and 1 were evaluated as satisfactory placement, and grades 2 and 3 were evaluated as screw misplacement, and the misplacement rate(number of misplacement screws/total number of screws×100%) was calculated. The screw placement of both groups was analyzed, and the accuracy of C7 pedicle screw placement was compared between the two groups. Results: There were no significant differences in operative time (251±59min and 235±56min) and intraoperative blood loss(521±200ml and 448±213ml) between group A and group B(P>0.05). In group A, a total of 247 pedicle screws were placed, including 239 screws of grades 0 and 1 and 8 screws of grades 2 and 3, with a total misplacement rate of 3.2%. In group B, a total of 209 screws were inserted, including 157 C3-C6 lateral mass screws, and of which 144 screws were of grades 0 and 1 and 3 screws of grades 2 and 3, with a total misplacement rate of 1.9%; and 52 cervical pedicle screws, of which 50 screws were of grades 0 and 1 and 2 screws of grades 2 and 3, with a total misplacement rate of 3.8%. The placement accuracy of C7 pedicle screw between the two groups showed no statistical significance(P>0.05). There were no vascular of neurological complications related to screw placement, no serious wound infection, iatrogenic neurovascular injury, posterior cervical hematoma, screw removal and other perioperative complications in both groups. Conclusions: It is safe and effective to use O-arm combined with CT 3D navigation system in assisting cervical pedicle screw placement, with a placement accuracy of 96.8%. Comparing with conventional lateral mass screw, none of the operative time, intraoperative blood loss, or perioperative screw related complications is significantly increased.