Preliminary study of the use of a CBT screw to treat lumbar adjacent segment degeneration

Objective: To investigate the feasibility of using the cortical bone trajectory (CBT) screw in revision surgery for lumbar adjacent segment degeneration (LASD) and to provide a reference for clinical practice.Methods:The computed tomography (CT) scans of the lumbar spine of 40 patients in our hospital were used. Three-dimensional (3D) reconstruction was performed using Mimics 19.0 software, screws with appropriate sizes were selected for the L1 to L5 vertebral segments, and the traditional pedicle (TP) screws were placed using the standard method. After the completion of screw placement, the simulated placement of CBT screws with appropriate sizes was performed separately. During screw placement, the site and the direction were adjusted accordingly to complete the screw placement as much as possible. Under the premise of safe and feasible placement, penetration of the screw through the CBT and overlap between the TP and CBT screws should be avoided. If these requirements are met, screw placement is considered successful. Otherwise, the screw placement is considered failed. After all simulated screw placements were complete, the success rate of the screw placement in each segment of the lumbar vertebra was calculated from the statistical results. Finally, the pedicle trajectory reference width (TRW) was used for grouping to investigate the correlation between the TRW and sucess rate of screw placement. Results: Four hundred simulated screw placements (80 in each pedicle) were performed in the L1-L5 pedicles. The overall success rate of CBT screw placement in the lumbar spine was 57.00%. The success rates in the L1 to L5 segments were 47.50%, 62.50%, 57.50%, 70.00%, and 47.50%, respectively. The success rate in L4 was greater than in L2 and L3, while the lowest success rates were observed in L1 and L5. The groups were established based on the TRW. The success rate of CBT screw placement increased as the TRW increased.Conclusions: CBT screws are not suitable treatments for all cases of LASD. The success rate of screw placement varies in different lumbar segments. A preoperative measurement of TRW has important reference value for evaluating the feasibility of CBT screw placement in revision surgery for LASD.