Inside-Out Versus Outside-In Transforaminal Endoscopic Lumbar Discectomy: A Structured Debate and International Practice Patterns

Transforaminal endoscopic lumbar discectomy (TELD) is performed by 2 techniques that differ in where the working corridor is first established: inside-out docks within the disc and works outward; outside-in establishes the corridor in the foramen, typically by foraminoplasty, and enters the disc last. This review tested each technique’s arguments against the literature and described current expert opinion. The literature component was a narrative, nonsystematic structured debate across 7 domains, with one author arguing each position and a joint reconciliation assigning verdicts from a predefined taxonomy. A single-round structured international expert-opinion survey of 78 endoscopic spine surgeons from 23 countries was analyzed against a prespecified 70% agreement threshold. Seven domains yielded 8 verdicts because clinical outcomes were judged separately at short and long term: 2 resolved as mixed, 2 as context-dependent, 1 conditional on patient phenotype, and 3 unresolved for lack of comparative studies. The panel was imbalanced: 57.1% practiced predominantly outside-in and 6.5% predominantly inside-out. Ten statements met the threshold: acceptance of outside-in (85.9%; inside-out 43.6%), its preference in all 4 case scenarios and for foraminal or bony access, migrated fragments, annulus and nucleus preservation, and exiting-nerve safety, and neutrality on cost-effectiveness. Case 1 reached 70.1% among 77 decided respondents but 69.2% of the full panel of 78. Current evidence does not support a general recommendation for either technique, and the survey describes the preferences of a predominantly outside-in panel rather than establishing superiority. Selection should follow pathology, foraminal anatomy, and surgeon expertise.

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Publication Details

Journal
Neurospine
Published
2026-10-29
DOI
https://doi.org/10.14245/ns.26521602.0801
Citations
1
Primary Topic
Spine and Intervertebral Disc Pathology
Type
article
Field-Weighted Citation Impact
4.57

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article

Inside-Out Versus Outside-In Transforaminal Endoscopic Lumbar Discectomy: A Structured Debate and International Practice Patterns

Nicolás Prada Ramírez, Jae‐Joong Kim, Mazda Farshad, Facundo Van Isseldyk et al.
1 citations
Neurospine
Spine and Intervertebral Disc Pathology
4.57
article

Inside-Out Versus Outside-In Transforaminal Endoscopic Lumbar Discectomy: A Structured Debate and International Practice Patterns

Nicolás Prada Ramírez, Jae‐Joong Kim, Mazda Farshad, Facundo Van Isseldyk, Siravich Suvithayasiri, Il Saing Choi, Adimilson dos Santos Delgado, Muhammed Assous, Yi Jiang, Hyun‐Jin Park, Syed Ifthekar, Georgios Vastardis, Christoph Johannes Laux, Woo‐Keun Kwon, Salvatore Russo, Zhongliang Deng, Junseok Bae, José Gabriel Rugeles Ortíz, Henri‐Arthur Leroy, James Joseph Yue, Surachat Jaroenwareekul, Saqib Hasan, Maria Pedraza, Xuexiao Ma
article en
1 citations

Abstract

Transforaminal endoscopic lumbar discectomy (TELD) is performed by 2 techniques that differ in where the working corridor is first established: inside-out docks within the disc and works outward; outside-in establishes the corridor in the foramen, typically by foraminoplasty, and enters the disc last. This review tested each technique’s arguments against the literature and described current expert opinion. The literature component was a narrative, nonsystematic structured debate across 7 domains, with one author arguing each position and a joint reconciliation assigning verdicts from a predefined taxonomy. A single-round structured international expert-opinion survey of 78 endoscopic spine surgeons from 23 countries was analyzed against a prespecified 70% agreement threshold. Seven domains yielded 8 verdicts because clinical outcomes were judged separately at short and long term: 2 resolved as mixed, 2 as context-dependent, 1 conditional on patient phenotype, and 3 unresolved for lack of comparative studies. The panel was imbalanced: 57.1% practiced predominantly outside-in and 6.5% predominantly inside-out. Ten statements met the threshold: acceptance of outside-in (85.9%; inside-out 43.6%), its preference in all 4 case scenarios and for foraminal or bony access, migrated fragments, annulus and nucleus preservation, and exiting-nerve safety, and neutrality on cost-effectiveness. Case 1 reached 70.1% among 77 decided respondents but 69.2% of the full panel of 78. Current evidence does not support a general recommendation for either technique, and the survey describes the preferences of a predominantly outside-in panel rather than establishing superiority. Selection should follow pathology, foraminal anatomy, and surgeon expertise.

NeurospineVol. 23(4)
Hallym University (KR), Chulalongkorn University (TH), Universidade de São Paulo (BR), University of Washington (US), University of Zurich (CH), King Chulalongkorn Memorial Hospital (TH), Centre Hospitalier Universitaire de Lille (FR), Wooridul Hospital (KR), Hallym University Kangnam Sacred Heart Hospital (KR), Xi'an Honghui Hospital (CN), Chulabhorn Hospital (TH), Affiliated Hospital of Qingdao University (CN), Universitätsklinik Balgrist (CH), Beijing Aerospace General Hospital (CN), IASO General Hospital (GR), Hallym University Dongtan Sacred Heart Hospital (KR), Foscal Hospital (CO), The Catholic University of Korea Seoul St. Mary's Hospital (KR), Quinnipiac University (US), All India Institute of Medical Sciences Bibinagar (IN), Chulabhorn Royal Academy (TH), Korea University Guro Hospital (KR), Thonburi Hospital (TH), Catholic University of Korea (KR), Xi'an Jiaotong University (CN)
ZonMw, Leids Universitair Medisch Centrum
Good health and well-being
Openalex Percentile: Top 4%
Spine and Intervertebral Disc Pathology
4.57
DOIOpen Access PDFOpenAlex
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