Santoni et al. were the first one to report the cortical bone trajectory (CBT), in which screws follow a lateral path in the axial plane and caudocephalad path in the sagittal plane. In contrast to conventional pedicle screw fixation, CBT screws do not penetrate the vertebral body trabecular space 1).
Several biomechanical studies have demonstrated the favorable mechanical properties of the cortical bone trajectory (CBT) screw. However, no reports have examined surgical outcomes of posterior lumbar interbody fusion (PLIF) with CBT screw fixation for lumbar degenerative spondylolisthesis (DS) compared with those after PLIF using traditional pedicle screw (PS) fixation. The purposes of this study were thus to elucidate surgical outcomes after PLIF with CBT screw fixation for DS and to compare these results with those after PLIF using traditional PS fixation.
Ninety-five consecutive patients underwent PLIF with CBT screw fixation for DS (CBT group; mean followup 35 months). A historical control group consisted of 82 consecutive patients who underwent PLIF with traditional PS fixation (PS group; mean follow-up 40 months). Clinical status was assessed using the Japanese Orthopaedic Association (JOA) scale score. Fusion status was assessed by dynamic plain radiographs and CT. The need for additional surgery and surgery-related complications was also evaluated. RESULTS The mean JOA score improved significantly from 13.7 points before surgery to 23.3 points at the latest follow-up in the CBT group (mean recovery rate 64.4%), compared with 14.4 points preoperatively to 22.7 points at final follow-up in the PS group (mean recovery rate 55.8%; p < 0.05). Solid spinal fusion was achieved in 84 patients from the CBT group (88.4%) and in 79 patients from the PS group (96.3%, p > 0.05). Symptomatic adjacent-segment disease developed in 3 patients from the CBT group (3.2%) compared with 9 patients from the PS group (11.0%, p < 0.05).
PLIF with CBT screw fixation for DS provided comparable improvement of clinical symptoms with PLIF using traditional PS fixation. However, the successful fusion rate tended to be lower in the CBT group than in the PS group, although the difference was not statistically significant between the 2 groups 2).