Introducing V-Line as a New Strategy to Choose Surgical Corridor in Oblique Lumbar Interbody Fusion at the L5-S1 Segment

Purpose A retrospective imaging study assessing the availability of oblique lumbar interbody fusion at the level of L5-S1 (OLIF51) and to choose ideal surgical corridor in OLIF51 by introducing V-line.Methods The axial views through the center of L5-S1 disc were reviewed. We adopt 18 mm as the width of the simulated surgical corridor. The midline of the surgical corridor is at the center of L5-S1 disc. According to the traction distance of the left iliac vein (LCIV) and psoas major (PM), we defined all the subjects as V (+) (traction-difficultly LCIV), V (-) (traction-friendly LCIV), P (+) (traction-difficultly PM), and P (-) (traction-friendly PM). V-line was defined as a straight line dividing equally the simulated surgical corridor. All cases were divided into 2 groups: The V-line (+) group, more than half of the LCIV region, is located in the ventral part of V-line; the V-line (-) group, more than half of the LCIV region, is located in the dorsal part of V-line. Multiple variables regressive analysis was conducted to analyze the independent risk factors of V-line (+).Results V-line (+) was found in 36 (38.7%) patients and V-line (-) in 57 (61.3%). Incidence of V (+) and P (+) was 35.4% (33/93) and 30.1% (28/93), respectively. 16.1% (15/93) subjects processed V (+) and P (+) at the same time. The independent risk factor of V-line (+) were gender of male ( P = 0.034, OR: 12.152) and medial position of LCIV ( P < 0.001, OR: 265.085). High iliac crest was a significant independent protective factor ( P = 0.001, OR: 0.750).Conclusions Most patients were suitable for OLIF51. V-line could assess the injury risk of LCIV. For patients who are V-line (+), mainly among males having the LCIV near the midline or the iliac crest relatively low, a surgical corridor external to the LCIV should be taken into consideration.