The Effect of Straight or Lordotic Rods on Cervical Subaxial Alignment While Fusing C1-C2

The C1 lateral mass and C2 pedicle screw with rod fixation system has been used commonly in recent years. Despite the numerous reports on this technique in the literature, there are no studies regarding the effect of the angle of the rod used. We investigated the effect of rod angle on subaxial lordosis, cervical sagittal balance, and pain scores.

Clinical records and radiologic images of 58 patients who underwent procedures between 2011 and 2016 at our clinic were assessed retrospectively. We recorded clinical findings, visual analog scale (VAS) scores, angles of cervical and segmental lordosis, and the distance between the C2 sagittal vertical axis (SVA) and the C7 posterior-superior corner.

A total of 36 male and 22 female patients were enrolled. A negative correlation was found between the C1-C2 lordosis angle and the C2-C7 lordosis angle irrespective of surgical technique. In patients who were operated on using 30°-angled rods, there was a postoperative increase in C1-C2 lordosis degree and an improvement in C2 cervical SVA values. Postoperative month 6 VAS scores were significantly better in the patients who were operated on with angled rods compared with those who received straight rods.

We believe this is because of the positive effect of the angled rod on sagittal balance. Nevertheless, prospective case-control studies should be conducted with larger groups of subjects. Furthermore, every patient should be evaluated considering the whole spinal sagittal balance.