Static Cage Morphology in Short-Segment Transforaminal Lumbar Interbody Fusions Is Associated With Alterations in Foraminal Height But Not Clinical Outcomes

• Published in: World neurosurgery 2022-03, Vol.159, p.e389-e398
• Main Authors: Toop, Nathaniel, Grossbach, Andrew, Gibbs, David, Akhter, Asad, Keister, Alexander, Maggio, Dominic, Oosten, James, Deistler, Kyle, Gilkey, Ty, Farhadi, H. Francis, Viljoen, Stephanus
• Format: Article
• Language: English
• Subjects: Disc height; Foraminal height; Humans; Lordosis - diagnostic imaging; Lordosis - etiology; Lordosis - surgery; Lumbar Vertebrae - diagnostic imaging; Lumbar Vertebrae - surgery; Retrospective Studies; Segmental lordosis; Spinal Fusion - adverse effects; Steerable “banana” cage; Straight “bullet” cage; TLIF; Treatment Outcome
• ISSN: 1878-8750; 1878-8769
• DOI: 10.1016/j.wneu.2021.12.066

Steerable “banana” cages have been posited to increase segmental lordosis in short-segment transforaminal lumbar interbody fusions (TLIF). The same is not necessarily true for straight “bullet” cages. Although increased lordosis is generally thought to be advantageous, a potential complication is decreased foraminal height. Here we evaluate for any association between cage type and change in foraminal height and clinical outcomes following short-segment TLIFs. We retrospectively reviewed consecutive 1- and 2-level TLIFs with bilateral facetectomies with minimum 1-year clinical and radiographic follow-up. Two cohorts were based on cage morphology: steerable “banana” cage or straight “bullet” cage. Patient reported outcome measures (PROMs), radiographic measurements, and revision rates were compared. A total of 46 patients with 53 straight and 95 patients with 131 steerable cage levels were included. Steerable cages showed increased segmental lordosis (9.1° vs. 13.5°, P < 0.001) and decreased foraminal height (20.3 vs. 18.5 mm, P < 0.001) after surgery. Straight cages demonstrated similar segmental lordosis (8.7° vs 8.1°, P = 0.30) and foraminal height (19.4 vs 20.0 mm, P < 0.065). Both cohorts showed improved PROMs at last follow-up (P ≤ 0.005). Subanalysis comparing patients who had increased or decreased foraminal height revealed similarly improved PROMs between cohorts. Revision rates at 1 year were similar between cohorts (4.3% for straight and 3.2% for steerable group, P = 0.72). Although the increased segmental lordosis afforded by placement of steerable cages may decrease foraminal height after short segment TLIF, clinical outcomes are not negatively affected by this association.