[Effects of cortical bone trajectory screw in adjacent-segment disease after posterior lumbar interbody fusion]

Objective: To investigate the effect of the cortical bone trajectory (CBT) screw fixation combined with midline lumbar fusion (MIDLF) for adjacent spondylopathy after posterior lumbar interbody fusion. Methods: A retrospective analysis was conducted in 16 patients, including 9 males and 7 females, with a mean age of (68±6) years, who underwent revision surgery for adjacent spondylopathy after posterior lumbar fusion surgery using CBT combined with MIDLF technology in Sir Run Run Shaw Hospital, Zhejiang University from May 2013 to August 2019. The reasons for revision were radiculalgia in 4 cases, intermittent claudication in 10 cases and protrusive dissociate in 2 cases. Eleven cases had 1 segment fused in the first operation, while the other 5 cases received fusion in 2 segments. The average interval time between the first operation and the revision operation was (7.5±2.0) years. For the levels underwent revision, 1 case was L_2/3, 6 cases were L_3/4, 7 cases were L_4/5 and 2 cases were L₅/S₁. Before the operation, all the patients took X-rays scans of the thoracic and lumbar spine. CT and MRI scans were also performed. The operation time, intraoperative bleeding, surgical complications, visual analog scale (VAS) of low back and leg pain before the operation and at each follow-up were all recorded. Oswestry disability index (ODI) questionnaire was used to evaluate the functional improvement of patients after the operation. Results: All operations were completed successfully. The operation time was 120-240 (170±30) mins, intraoperative bleeding was 100-280 (220±45) ml. One case had a slight split in the isthmus, and the screw was inserted smoothly after adjusting the insertion point. In one case, the cerebrospinal fluid leaked during the operation and was successfully treated with conservative methods including no pillow supine treatment and strengthened anti-infection. The average follow-up time was of (19.5±1.3) months. The VAS of low back pain was 2.9±1.7 before the operation and it was 1.8±0.5 at the last follow-up, and the difference was statistically significant (P<0.01). The VAS of leg pain was 5.9±1.5 before the operation and it was 1.5±0.4 at the last the follow-up (P<0.01). The ODI score was 34.5±3.2 preoperatively and it decreased to 12.6±4.2 at the last follow-up, the difference was statistically significant (P<0.01). Conclusion: CBT technique combined with MIDLF for the adjacent-segment disease after posterior lumbar interbody fusion is minimally invasive and convenient, with good clinical effects. This technique can be used as an option for the revision of adjacent spondylopathy.