Introduction: Lumbar fusion for spondylolisthesis, which includes ALIF (anterior lumbar interbody fusion), PLIF (posterior lumbar interbody fusion), and TLIF (transforaminal lumbar interbody fusion) are commonly used for symptomatic spondylolisthesis with failed conservative treatment. PLIF and TLIF is powerful in reduction and decompression but is blamed for postoperative axial back pain and the possible dura and nerve root injury [1-3]. ALIF limits the postoperative axial back pain by sparing the exposure of posterior structures, provides excellent exposure to discectomy and the implantation of a large, lordotic device, which restores intervertebral height, resulting excellent realignment of the lumbar spine. In the past, stand-alone ALIF was not stable without pedicle screws, and often used as a complementary fusion after posterior reduction and decompression in spondylolisthesis [4-7]. However, combined anterior-posterior surgery was highly traumatic and costly. Besides, there were few comparisons between stand-alone ALIF and TLIF in spondylolisthesis. In this study, we retrospectively compared cases of single-level grade spondylolisthesis that were treated with stand-alone ALIF with self-anchored cages and TLIF, in which clinical and radiologic outcomes are presented.

Methods: Sixty-eight patients with L4 lumbar degenerative spondylolisthesis I° underwent surgery between January 2014 and January 2016 were included. Among them, 32 patients were treated with ALIF and 36 were treated with TLIF. All patients received follow-up for at least 5 years. Data of patient demographics, intraoperative parameters, perioperative complications were collected. Clinical outcomes included visual analog scale (VAS) of leg and back pain, Oswestry disability index (ODI) and radiological outcomes included fusion, lumbar lordosis (LL), disc height (DH) and lordotic angle of the surgical segments (SLA), and slip percentage (Slip%) were also evaluated.

Results: All cases achieved fusion at the final follow-up. No major vascular injury and other approach-related complications were found. The Average blood loss and operation time in ALIF group were significantly lower than TLIF group (P<0.05). Significant improvements were observed with respect to the VAS and ODI scores postoperatively. There was no significant difference on postoperative VAS and ODI score at each time points between the two groups. Radiologically, significant improvements in DH, LL, SLA and Slip% were found postoperatively. There was no significant difference in postoperative Slip% at each time points between the two groups. The postoperative DH, LL, and SLA at each time point were significantly higher in ALIF group than the ones in TLIF group(p<0.05). Five cases (15.6%) in ALIF group subsided postoperatively. There was no major complication of neurological deficit, visceral organ injury, fixation or implant failure in both groups. There was one case of external iliac vein tear and one intraoperative peritoneal injury in ALIF group which were both repaired without postoperative symptoms. There was one dura tear in TLIF group, who was successful treated with prolong drainage until the incision of the skin was healed at the 12th day after surgery.

Discussion: ALIF alone achieved excellent clinical and radiological results in Grade Ⅰ lumbar degenerative spondylolisthesis in L4 with 5 year follow up, making it an alternative treatment option  in selected patients.