Letter to the Editor: Concerning Using Lordotic Cages at the L5–S1 Level Does Not Guarantee the Improvement of Sagittarius Alignment in Patients Who Underwent Posterior Lumbar Interbody Fusion

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Asian Spine J. 2023;17(4):803-804
Publication date (electronic) : 2023 August 21
doi : https://doi.org/10.31616/asj.2023.0176.r1
Department of Orthopedic Surgery, Faculty of Medicine, Saga University, Nabeshima, Japan
Corresponding author: Tadatsugu Morimoto Department of Orthopedic Surgery, Faculty of Medicine, Saga University, 5-1-1 Nabeshima, Saga, Japan Tel: +81-955-72-5111, Fax: +81-955-73-9530, E-mail: sakiyuki0830@gmail.com
Received 2023 May 31; Accepted 2023 June 11.

We were intrigued by the article by Cho et al. [1], which concluded that clinical and radiological outcomes did not markedly differ based on the lordotic angle of cages. However, we still have some concerns about this paper.

First, while the potential for improved spinal alignment has been discussed in relation to the anterior placement of cages, such placement in the L5/S1 region may increase the risk of anterior dislocation. This is due, in part, to the anatomical features of the L5–S region, where the anterior longitudinal ligament is particularly thin, and the shape of the S1 vertebral body is typically trapezoidal. In addition, the pelvis is tilted at the superior plate margin of S1, which is thought to be a contributing factor to cage deviation [2,3].

Given these potential risks, it may be worthwhile to consider alternative measures to address spinal alignment. For example, increasing the intrinsic angle of the cage to ≥8° may offer a viable alternative to anterior placement.

We would also like to know how placing lordotic cages in the anterior region of the spine improved the clinical outcomes compared to posterior placement.

We would appreciate further information regarding the statistical methods employed, as detailed information is not provided in the manuscript. It should be noted that the absence of statistical significance does not necessarily indicate a lack of difference between the two groups, as certain statistical methods may not directly prove the absence of a difference.

To improve our understanding of your excellent research, we look forward to hearing from you regarding our submission. We would be glad to respond to any further questions and comments that you may have as well.


Conflict of Interest

No potential conflict of interest relevant to this article was reported.

Author Contributions

All authors provided the same amount of effort for the preparation of this commentary.


1. Cho JH, Hwang CJ, Lee DH, Lee CS. Using lordotic cages at the L5-S1 level does not guarantee the improvement of sagittal alignment in patients who underwent posterior lumbar interbody fusion. Asian Spine J 2023;17:477–84.
2. Xu Z, Zheng Y. Anterior dislocation of fusion cage after minimal invasive transforaminal lumbar interbody fusion (MI-TLIF): a case report. Biomed Res 2017;28:7834–6.
3. Maeno T, Okuda S, Haku T, et al. Anterior migration of an interbody graft in posterior lumbar interbody fusion: report of three cases without removal of the migrated graft. J Orthop Sci 2019;24:742–5.

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