The study subjects were 20 consecutive patients who had XLIF after November 2014 (X group: 10 males and 10 females; mean age, 69.9 years) and 20 patients who had mini-open TLIF before November 2014, all of whom underwent the same clinical and radiological evaluations as the patients who received XLIF (T group: seven males and 13 females; mean age, 66.2 years).Preoperative neurological symptoms were neurogenic claudication and radiculopathy in both groups (X group: nine cases and 11 cases, respectively and T group: 10 cases and 10 cases, respectively) (
Table 1). During clinical assessment, patients in both the X and T groups showed significant improvement in terms of with their respective preoperative scores in all domains at 12 months after surgery (
Fig. 3). No significant differences were observed between the two groups in terms of the JOABPEQ scores obtained before surgery and those obtained at 12 months after surgery (
Table 2). In the assessment of surgery invasiveness, there was no significant difference in the mean surgery time (X group, 131.1±23.2 minutes; T group, 148.1±39.5 minutes); however, the X group showed a significant decrease in the mean volume of blood loss (X group, 36.1±15.3 mL; T group, 225.7±215.9 mL;
p<0.001). The hospitalization period was not significantly different between the two groups (X group, 14.6±7.5 days; T group, 13.7±3.9 days) (
Table 3). Perioperative complications in the T group included dural tear in one patient (5%), transient pain in the legs of two patients (10%), and deep infection in one patient (5%); no reoperations were performed. In the X group, thigh symptoms on the approach side were observed in eight patients (40%), all of which resolved within 3 months after surgery, and pain in the contralateral thigh, probably due to hematoma and cage placement failure, was observed in two patients (10%), which were relieved by conservative therapy. Serious complications were not observed in either group. One patient (5%) in the X group required additional posterior decompression due to no improvement in symptoms (
Table 4). As for the image measurements over time, the DA was significantly increased after surgery in the X group (from 5.1° to 8.5° to 8.3° and was maintained even after 1 year; however, the improvement was not significant in the T group (from 3.7° to 5.8° to 5.0°). The DH was significantly increased after surgery in the X group (from 8.3 to 11.4 to 10.1 mm) and was maintained until after 1 year; however, in the T group, although significant increase in DH was observed after surgery (from 6.4 to 8.6 to 7.1 mm), there was no significant difference when the values determined before surgery and those determined at 1 year after surgery are compared. For SL, significant postoperative restoration was observed in both groups (from −5.5 to −3.1 to −2.8 mm in the X group and from −8.0 to −5.5 to −6.0 mm in the T group), which was maintained until after 1 year. CSA was significantly larger after surgery in both groups (from 26.4 to 55.4 mm
2 in the X group, and from 33.3 to 131.1 mm
2 in the T group) (
Fig. 4). When compared in terms of changes, significant differences were observed between the two groups in terms of DH, SL, and CSA measured before surgery, but no such difference was observed in DA. With regard to postoperative change, the change in DH at 12 months after surgery increased significantly in the X group than in the T group (X group, 1.8 mm; T group, 0.7 mm;
p<0.05), and the changes in DA and SL were not significantly different between the two groups. The change in CSA was significantly greater in the T group (X group, 29 mm
2; T group, 97.7 mm
2;
p<0.001) (
Table 5).