Morphologic Changes of Lumbar Foramen and Segmental Lordosis Related to Cage Position in Transforaminal Lumbar Interbody Fusion

Abstract

Objectives: To evaluate the influence of the positioning of cages on segmental lumbar lordosis and height of the intervertebral foramen when performing transforaminal interbody fusion. Method: cages of 8, 10 and 12 mm were inserted into the disc spaces of the L3-L4, L4-L5 and L5-S1 segments of three human cadavers. Cages were positioned in the anterior, middle and posterior part of the disc space. The transforaminal interbody fusion technique was performed using: unilateral facetectomy, bilateral facetectomy and facetectomy with resection of the adjacent lamina, spinous process and yellow ligament (posterior column osteotomy). The lordosis of the lumbar segment and the height of the intervertebral foramen were measured before and after placement of the cages. Results: The placement of cages in the anterior and middle portion of the disc space produced an increase in segmental lordosis and placement in the posterior portion reduced segmental lordosis. The height of the intervertebral foramen increased with the placement of cages in the posterior portion and a reduction in height with the placement of the interbody spacer in the anterior and middle portion of the disc space. Conclusion: The positioning of the interbody spacer in transforaminal interbody arthrodesis influences segmental lumbar lordosis and the height of the intervertebral foramen. Level of Evidence III; Experimental study.