An optimal cortical bone trajectory technique to prevent early surgical complications

Background: Cortical bone trajectory (CBT) technique has a theoretical benefit for patients with osteoporosis, and leads to reduce screw loosening. However, there are no reports of complications and outcomes of CBT. Methods: Consecutive patients (n = 34) with degenerative lumbar spines who underwent PLIF between December 2013 and December 2015 and were followed up for at least six months were analyzed in this study. Bone mineral density, fusion rate, cage subsidence, C-arm, screw loosening, screw violation, trajectory angle of the screw, Hounsfield unit and extent of facetectomy were examined. Outcome assessments were obtained in all patients preoperatively and postoperatively. Results: There were 34 patients and 73 screw levels. After the surgery with cortical screw fixation and PLIF, patients had good clinical outcomes. However, ten of the 34 patients had problems with cortical screw fixation such as screw loosening or cage migration. In the patients with screw loosening, two underwent revision surgery due to cage migration, and one had an infection. Incorrect trajectory angles of the screw were significantly related with screw loosening. Low BMD and HU at screw fixation level were associated with screw loosening. Cage subsidence was statistically related with clinical outcomes. Conclusion: The cortical screw offers improved clinical outcomes since it requires minimal muscle dissection. However, we have experienced some early complications using this technique. To reduce complications such as screw loosening, an exact insertion angle of the screw and osteoporotic bone quality should be considered carefully.