Does the hip positioning matter for oblique lumbar interbody fusion approach? A morphometric study.

PURPOSE: To evaluate whether left hip positioning widened the access corridor using oblique lateral interbody fusion (OLIF) approach during right lateral decubitus (RLD). METHODS: Ten healthy adult volunteers underwent a T2 lumbosacral MRI (1.5 T) in the supine position, RLD position with left hip in extension and then in flexion. L2-L3 to L5-S1 disc spaces were identified. At each level, left psoas surface (in cm2), access corridor (in mm) and vessel movement were calculated in the three positions. Paired t test was used for comparison. RESULTS: The mean surface of the left psoas ranged from 7.83 to 17.19 cm2 in the three positions (p > 0.05). From L2-3 to L4-5, in RLD, when the left hip shifted from extension to flexion, nor the access corridor nor vessel movements were significantly different. When the volunteers shifted from supine to RLD position with hip in extension, arteries moved 3.66-5.61 mm to the right (p < 0.05 at L2-3, L3-4 and L5-S1), while the venous structures moved 0.92-4.96 mm (p < 0.05 at L2-3) to the right. When the position shifted from supine to RLD with hip in flexion, the arterial structures moved 0.47-4.88 mm (p < 0.05 at L2-3 and L3-4) to the right, while the venous structures moved - 0.94 to 4.13 mm (p < 0.05 at L2-3 and L3-4) to the right. CONCLUSION: Hip positioning was not associated with a significant widening of the surgical corridor. To perform OLIF, we advocate for RLD position with left hip in extension to move away the vascular structures and reduce the psoas volume. These slides can be retrieved under Electronic Supplementary Material.