Objective: The aim of this study was to assess the clinical outcomes of modified MIS-TLIF for the treatment of isthmic lumbar spondylolisthesis.

Methods: Sixty cases diagnosed with Meyerding grade I or⁺isthmic spondylolisthesis were included in this study. Thirty-two patients (group A) were treated with MIS-TLIF, twenty-eight patients (group

B) underwent traditional open TLIF. The surgical procedures for MIS-TLIF included the implantation of pedicle screws via the Wiltse approach, under working channel, microscopic decompression, and interbody fusion. The visual analog scale (VAS) for low back pain (LBP), the VAS for leg pain, and the Oswestry disability index (ODI) were used as follow- up clinical outcomes. According to the imaging data, the slip rate, intervertebral space height and slip angle of the two groups before and 12 months (last follow-up) were compared. All statistical analyses were performed with SPSS 22.0, and the results were presented as mean ± standard deviation (SD).

Results: The preoperative scores for the ODI, VAS for LBP, and VAS for leg pain were not statistically different between the 2 groups (P > 0.05). The estimated blood loss, and 1-day and 7-day incision pain were significantly higher in group B than in group A (P < 0.05). The mean operative time were not statistically different between the 2 groups (P > 0.05). No differences were found between the 2 groups in ODI, leg pain VAS score. The VAS for back pain was better in group A than in group B (P < 0.05). At the last follow-up, the slip rate, slip angle and intervertebral space height were significantly improved in the same group(P<0.05), but there was no significant difference between two groups(P>0.05).

Conclusion: Both methods are effective in the treatment of isthmic spondylolisthesis. MIS-TLIF can reduce surgical trauma, facilitate rapid postoperative recovery and reduce the occurrence of injury to the dura and nerve root during decompression and the interbody fusion procedure.