**6. Conclusions**

Disc height, smoking, diabetes mellitus (DM), subligamentous extrusion (SE) type, and Modic change were identified as risk factors for recurrent lumbar disc herniation after FED-IL. The procedure selected to treat recurrent lumbar disc herniation mostly depends on the surgeon's preference. Revision FED-IL is the first choice for the recurrent herniation in terms of minimizing surgical burden, whereas fusion surgery offers the advantage that discectomy can be performed through unscarred tissues. FED-IL is recommended for recurrent herniation within 2 weeks before adhesion progress.

**Author Contributions:** Conceptualization, K.O. (Koichiro Ono); methodology, K.O. (Koichiro Ono); Supervision, K.O. (Kazuo Ohmori) and T.M.; Visualization, R.Y. and O.M.; writing—original draft preparation, K.O. (Koichiro Ono); writing—review and editing, K.O. (Koichiro Ono); supervision, K.O. (Kazuo Ohmori) and T.M. All authors have read and agreed to the published version of the manuscript.

**Funding:** No funding was received for this study. No benefits in any form have been or will be received from a commercial party related directly or indirectly to the subject of this paper.

**Institutional Review Board Statement:** The study was conducted according to the guidelines of the Declaration of Helsinki, approved by the Nippon Koukan Hospital Ethics Committee (202115, 4 January 2022).

**Informed Consent Statement:** Informed consent was obtained in the form of opt-out on the website.

**Data Availability Statement:** The data used to support the funding of this study are available from the corresponding author upon request.

**Conflicts of Interest:** The authors declare that there is no conflict of interest regarding the publication of this paper.
