Midline lumbar fusion with cortical bone trajectory as first line treatment in a selected series of patients with lumbar instability

Comparison of Affected-Vertebra Fixation of Cortical Bone Trajectory Screw and Pedicle Screw for Lumbar Tuberculosis: A Minimum 3-Year Follow-Up

Purpose

This study is aimed at comparing the clinical efficacy of cortical bone trajectory (CBT) screw fixation and pedicle screw (PS) fixation of the affected vertebrae in lumbar tuberculosis.

Methods

We retrospectively analyzed the outcomes in 52 patients (27 cases in the CBT group, 25 cases in the PS group) with lumbar TB who underwent posterior affected-vertebra fixation combined with anterior debridement and bone grafting. The intraoperative blood loss, operative time, visual analog scale (VAS) scores for incision pain and leg pain, Japanese Orthopedic Association (JOA) score, bone grafting fusion, and complications were recorded.

Results

All patients were followed up for 35-52 months and achieved good clinical outcomes. There were no differences between the two groups in the operative time, intraoperative blood loss, JOA score, bone grafting fusion, and complications. However, there was a significant difference between the two groups in VAS scores for incision pain on the 1st day and 3rd day after surgery. At the last follow-up, JOA scores were significantly improved in both groups compared to the preoperation.

Conclusion

This retrospective study confirmed that both the affected-vertebra CBT screw fixation and PS fixation for lumbar TB via posterior and anterior approaches could achieve satisfactory outcomes, while the former resulted in better improvement for postoperative VAS scores.

Cortical bone trajectory fixation cause low compression force in anterior vertebral column

Background

The cortical bone trajectory (CBT) screws follow a caudocephalad and lateral path from the pedicle to the vertebral body. The bone fusion rate of CBT fixation is equal to or lower than conventional pedicle screw fixation. It remains unclear whether or not CVT screws exert equally compressive forces across the vertebral column. In this study, we intraoperatively examined the insertional torque of CBT screws, and investigated the compression loading and pressure distribution in conventional and CBT fixation using pig bones.

Methods

The insertional torque was measured for a total of 115 CBT screws. Detailed positions of these screws were retrospectively confirmed using CT scans. Screw loosening and interbody fusion were examined 1 year after surgery. In the experiment using pig bones, we inserted screws by conventional trajectory (n = 3) and CBT (n = 4).

Results

Multiple regression analysis showed that the total screw length, the distance from the screw to the medial border of the pedicle and the distance from the superior endplate of the vertebrae were significant independent factors affecting the insertional torque. There was no significant association between the insertional torque and the radiographic bone fusion rate 12 months after surgery. The average pressure and the compression loading in the anterior column were significantly lower in CBT group.

Conclusion

These results suggested that the long CBT screws as close to the endplate had high insertional torque, but the anterior column in CBT fixation showed low compression force leading to the insufficient holding intervertebral cage. CBT screws may cause the micromotion of cages, which lowers the bone fusion rate.