400 - Suggestion of Optimal Cortical Bone Trajectory Technique to Prevent Ea...

General Session: MIS-2

Presented by: S. Yi - View Audio/Video Presentation (Members Only)


C.K. Lee(1), D.S. Kim(2), S. Yi(2)

(1) Keimyung University Dongsan Medical Center, Daegu, Korea, Republic of
(2) Yonsei University Severance Hospital, Seoul, Korea, Republic of


Study Design: Retrospective study.

Objective: To report on our early experience using cortical screw technique in patients who underwent posterior lumbar interbody fusion (PLIF).

Methods: Consecutive patients (n=34) with degenerative lumbar spine who underwent PLIF between December 2013 and December 2015 were followed up for at least six month were analyzed in this study. Standing plain films and CT of the lumbar spine were obtained preoperatively and postoperatively. Body mass index, bone mineral density, fusion rate, cage subsidence, C-arm, screw loosening, screw violation, trajectory angle of screw, and degree of facetectomy were checked. Outcome assessments (Visual Analog Scale [VAS], Oswestry Disability Index [ODI], Physical component score [PCS], and Mental component score [MCS] on SF-36) were obtained in all patients preoperatively and postoperatively.

Results: The mean age was 62.1 years. Mean follow-up duration was 10.4 months. 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 34 patients had problems with cortical screw fixation such as screw loosening or cage migration. On screw loosening, two had underwent revision surgery due to cage migration, and one had infection. Low trajectory sagittal and high trajectory axial angles of screw were significantly related with screw loosening, respectively (p=0.014; p=0.003). Low BMD and HU at screw fixation level were associated with screw loosening (p=0.001; p=0.327). Cage subsidence was related with clinical outcome statistically (VAS; p < 0.001, ODI; p < 0.001, SF-36 [PCS]; p = 0.004, SF-36 [MCS]; p= 0.012).

Conclusion: The cortical screw offers improved clinical outcomes due to requiring minimal muscle dissection. However, we have experienced some early complications. To reduce the complication like screw loosening, exact insertion angle of screw and osteoporotic bone quality should be considered carefully. Long term follow-up studies will be necessary to totally understand the efficacy of cortical screw.