Transforaminal lumbar interbody fusion using banana-shaped and straight cages: meta-analysis of clinical and radiological outcomes

Purpose Transforaminal lumbar interbody fusion (TLIF) surgery rate increased over the last decade. There is no consensus about the better shape of cage to use in TLIF. This meta-analysis was conducted to compare the shape focusing on bony union, lordosis restoration as well as perioperative complications. Methods PubMed, Cochrane, and Google Scholar (page 1–20) were searched till September 2022. The clinical outcomes consisted of the bony union, segmental and lumbar lordosis restoration, quality of life, and operation-related outcomes. Results Only 5 studies were included in this meta-analysis. Straight-shaped cages tended to have a lower subsidence rate compared to banana-shaped cages ( p = 0.10), had a better restoration of segmental lordosis ( p < 0.0001), better disc height restoration ( p = 0.01), as well as a higher Oswestry Disability Index decrease ( p = 0.0002). Conclusion Straight-shaped cages had a better restoration of lumbar lordosis, disc height, and a lower subsidence rate when compared to banana-shaped cages. This may be explained by the absence of the optimal placement of the curved cages, which is at the most anterior part of the disc space. Better conducted randomized controlled trial could strengthen these findings.