Abstract / Summary
This study investigated plan–execution mismatch in single-level L4–5 oblique lumbar interbody fusion (OLIF) by evaluating whether a planned anterior-to-psoas approach could be maintained, identifying imaging factors associated with intraoperative conversion, and characterizing intraoperative process features and early postoperative outcomes in converted cases. This retrospective cohort study categorized 180 single-level L4–5 OLIF patients into: maintained anterior-to-psoas approach (A-A, n = 100), converted anterior-to-psoas-to-modified OLIF (A-M, n = 40), and maintained modified OLIF (M-M, n = 40). Primary analysis focused on the 140 patients initially planned for the anterior-to-psoas approach. Compared with A-A, A-M had a smaller oblique corridor, greater anterior migration of the psoas major, and higher proportions of unfavorable vascular position and teardrop-shaped psoas major. Multivariable analysis showed that smaller oblique corridor width (OR = 0.72, 95% CI 0.62–0.85; P < 0.001), greater anterior migration distance of the psoas major (OR = 1.15, 95% CI 1.02–1.29; P = 0.022), and unfavorable vascular position (OR = 3.27, 95% CI 1.22–8.80; P = 0.019) were independently associated with conversion. The A-M group showed the most complex intraoperative process profile, including longer corridor establishment time, more adjustments, and more frequent unplanned additional psoas handling; these measures were interpreted descriptively rather than as effects caused by conversion. The A-M group also had more immediate postoperative psoas swelling and more early approach-related symptoms, whereas most M-M values were intermediate. Differences in leg pain were limited to 24 h and 1 week postoperatively. In L4-5 OLIF, a visible antepsoas corridor on preoperative imaging does not guarantee safe intraoperative maintenance. Among patients initially planned for an anterior-to-psoas approach, a narrow oblique corridor, greater anterior psoas migration, and unfavorable vascular position should prompt careful reassessment of intraoperative conversion risk. Surgeons should prepare for timely conversion when a stable corridor cannot be maintained. Not applicable.