[Comparison of the effectiveness of oblique lumbar interbody fusion and posterior lumbar interbody fusion for treatment of Cage dislodgement after lumbar surgery].

Objective: To compare the clinical and radiological effectiveness of oblique lumbar interbody fusion (OLIF) and posterior lumbar interbody fusion (PLIF) in the treatment of Cage dislodgement after lumbar surgery.
Methods: The clinical data of 40 patients who underwent revision surgery due to Cage dislodgement after lumbar surgery betweem April 2013 and March 2017 were retrospectively analyzed. Among them, 18 patients underwent OLIF (OLIF group) and 22 patients underwent PLIF (PLIF group) for revision. There was no significant difference between the two groups in age, gender, body mass index, intervals between primary surgery and revision surgery, number of primary fused levels, disc spaces of Cage dislodgement, and visual analogue scale (VAS) scores of low back pain and leg pain, Oswestry disability index (ODI), the segmental lordosis (SL) and disc height (DH) of the disc space of Cage dislodgement, and the lumbar lordosis (LL) before revision ( P >0.05). The operation time, intraoperative blood loss, hospital stay, and complications of the two groups were recorded and compared. The VAS scores of low back pain and leg pain were evaluated at 3 days, 3, 6, and 12 months after operation, and the ODI scores were evaluated at 3, 6, and 12 months after operation. The SL and DH of the disc space of Cage dislodgement and LL were measured at 12 months after operation and compared with those before operation. CT examination was performed at 12 months after operation, and the fusion of the disc space implanted with new Cage was judged by Bridwell grading standard.
Results: The intraoperative blood loss in the OLIF group was significantly less than that in the PLIF group ( t =-12.425, P =0.000); there was no significant difference between the two groups in the operation time and hospital stay ( P >0.05). Both groups were followed up 12-30 months, with an average of 18 months. In the OLIF group, 2 patients (11.1%) had thigh numbness and 1 patient (5.6%) had hip flexor weakness after operation; 2 patients (9.1%) in the PLIF group had intraoperative dural sac tear. The other patients' incisions healed by first intention without early postoperative complications. There was no significant difference in the incidence of complications between the two groups ( χ ² =0.519, P =0.642). The VAS scores of low back pain and leg pain, and the ODI score of the two groups at each time point after operation were significantly improved when compared with those before operation ( P <0.05); there was no significant difference between the two groups at each time point after operation ( P >0.05). At 12 months after operation, SL, LL, and DH in the two groups were significantly increased when compared with preoperative ones ( P <0.05); SL and DH in the OLIF group were significantly improved when compared with those in the PLIF group ( P <0.05), and there was no significant difference in LL between the two groups ( P >0.05). CT examination at 12 months after operation showed that all the operated disc spaces achieved bony fusion. According to the Bridwell grading standard, 12 cases were grade Ⅰ and 6 cases were grade Ⅱ in the OLIF group, and 13 cases were grade Ⅰ and 9 cases were grade Ⅱ in the PLIF group; there was no significant difference between the two groups ( Z =-0.486, P =0.627). During follow-up, neither re-displacement or sinking of Cage, nor loosening or fracture of internal fixation occurred.
Conclusion: OLIF and PLIF can achieve similar effectiveness in the treatment of Cage dislodgement after lumbar surgery. OLIF can further reduce intraoperative blood loss and restore the SL and DH of the disc space of Cage dislodgement better.