ObjectiveTo compare the effectiveness of modified transforaminal lumbar interbody fusion (modified-TLIF) and posterior lumbar interbody fusion (PLIF) for mild to moderate lumbar spondylolisthesis in middle-aged and elderly patients.MethodsThe clinical data of 106 patients with mild to moderate lumbar spondylolisthesis (Meyerding classification≤Ⅱ degree) who met the selection criteria between January 2015 and January 2017 were retrospectively analysed. All patients were divided into modified-TLIF group (54 cases) and PLIF group (52 cases) according to the different surgical methods. There was no significant difference in preoperative clinical data of gender, age, disease duration, sliding vertebra, Meyerding grade, and slippage type between the two groups (P>0.05). The intraoperative blood loss, operation time, postoperative drainage volume, postoperative bed time, hospital stay, and complications of the two groups were recorded and compared. The improvement of pain and function were evaluated by the visual analogue scale (VAS) score and Japanese Orthopedic Association (JOA) score at preoperation, 1 week, and 1, 6, 12 months after operation, and last follow-up, respectively. The effect of slip correction was evaluated by slip angle and intervertebral altitude at preoperation and last follow-up, and the effectiveness of fusion was evaluated according to Suk criteria.ResultsAll patients were followed up, the modified-TLIF group was followed up 25-36 months (mean, 32.7 months), the PLIF group was followed up 24-38 months (mean, 33.3 months). The intraoperative blood loss, operation time, postoperative drainage volume, postoperative bed time, and hospital stay of the modified-TLIF group were significantly less than those of the PLIF group (P<0.05). The VAS score and JOA score of both groups were significantly improved at each time point after operation (P<0.05); the scores of the modified-TLIF group were significantly better than those of the PLIF group at 1 and 6 months after operation (P<0.05). The slip angle and intervertebral altitude of both groups were obviously improved at last follow-up (P<0.05), and there was no significant difference between the two groups at preoperation and last follow-up (P>0.05). At last follow-up, the fusion rate of the modified-TLIF group and the PLIF group was 96.3% (52/54) and 98.1% (51/52), respectively, and no significant difference was found between the two groups (χ2=0.000, P=1.000). About complications, there was no significant difference between the two groups in nerve injury on the opposite side within a week, incision infection, and pulmonary infection (P>0.05). No case of nerve injury on the operation side within a week or dural laceration occurred in the modified-TLIF group, while 8 cases (15.4%, P=0.002) and 4 cases (7.7%, P=0.054) occurred in the PLIF group respectively.ConclusionModified-TLIF and PLIF are effective in the treatment of mild to moderate lumbar spondylolisthesis in middle-aged and elderly patients. However, modified-TLIF has relatively less trauma, lower blood loss, lower drainage volume, lower incidence of dural laceration and nerve injury, which promotes enhanced recovery after surgery.