Analysis of the Fusion and Graft Resorption Rates, as Measured by Computed Tomography, 1 Year After Posterior Cervical Fusion Using a Cervical Pedicle Screw

BACKGROUND: We previously showed that cervical pedicle screw (CPS) placement is safe even with the freehand technique. The posterolateral fusion rate 1 year after CPS placement, as measured by computed tomography (CT), is reported here. The graft resorption rates when different graft materials were used were also analyzed. METHODS: Between 2012 and 2015, 93 patients underwent posterior cervical fusion surgery with the CPS from C2 to C7. Of these patients, 56 consented to CT scans immediately and 1 year after surgery. These patients formed the present study group. The patients were categorized according to whether the graft material was local bone, allograft, or a mixture. Graft volume was measured at both CT scans. Graft resorption rate was determined by comparing the 2 scans. Radiologic fusion was assessed on the 1 year postoperative CT scan and radiography. RESULTS: The reason for surgery was trauma (n =19), degenerative disease (n = 35), tumor (n = 1), and spondylitis (n = 1). Surgery was performed with CPS fixation and decompression. Even although iliac bone grafting was not performed, the overall fusion rate was 98.2% (55/56). The single fusion failure case received a mixture of local bone and allograft. Although the allograft group showed the greatest graft resorption rate (91.5%), all patients in this group had a bony bridge that crossed the facet joint on the 1 year CT scan. CONCLUSIONS: CPS placement yielded a posterolateral cervical fusion rate of 98.2%. Despite the high resorption rate of allograft only, this material yielded fusion rates that were similar to those of the other materials. Thus, the strong fixation power of CPS might compensate for the delayed fusion and high resorption rates of allograft bone chips.