When the safe triangle is unsafe: volumetric magnetic resonance imaging root mapping for patient-specific assessment of Kambin's triangle before transforaminal lumbar disc procedures.
13 affiliations
- 1RIWO Spine Center of Excellence, Department of Neurosurgery, Foundation Hospital Centro Médico Campinas, Campinas, Brazil.
- 2Division of Personalized Pain Research and Education, Center for Advanced Spine Care of Southern Arizona, Tucson, AZ, USA.
- 3Department of Orthopaedics, Fundación Universitaria Sanitas, Bogotá D.C., Colombia.
- 4Department of Orthopedics, Hospital Universitário Gaffrée e Guinle, Universidade Federal do Estado do Rio de Janeiro, Rio de Janeiro, Brazil.
- 5Department of Orthopedic Surgery, University of Arizona Tucson Campus, Tucson, AZ, USA.
- 6Centre for Musculoskeletal Surgery (CMSC), Berlin, Germany.
- 7Klinik für Unfall-, Hand- und Wiederherstellungschirurgie, Universitätsklinikum des Saarlandes, Homburg, Germany.
- 8Próton Radiologia, Hospital Centro Médico Campinas, Campinas, Brazil.
- 9Department of Orthopaedic Surgery & Sports Medicine, Lewis Katz School of Medicine at Temple University, Philadelphia, PA, USA.
- 10Latin American Endoscopic Spine Surgeons LESS Invasiva Academy, Bogotá D.C., Colombia.
- 11Grupo de Investigación en Ortopedia y Traumatología, Departamento de Ortopedia y Traumatología, Clínica Colsanitas S.A., Bogotá D.C., Colombia.
- 12Programa de Ortopedia y Traumatología, Facultad de Medicina, Fundación Universitaria Sanitas, Bogotá D.C., Colombia.
- 13Unidad de Investigación, Fundación Universitaria Sanitas, Bogotá D.C., Colombia.
Abstract
Kambin's triangle is a useful geometric model for lumbar transforaminal access, but the clinically usable corridor is patient specific because the exiting nerve root, dorsal root ganglion (DRG), traversing neural structures, anatomic variants, and disease-related displacement may alter the contemplated path. We evaluated volumetric magnetic resonance imaging (MRI) root mapping as a method for characterizing nerve-root anatomy relevant to patient-specific transforaminal trajectory planning. This retrospective descriptive MRI-anatomy study analyzed 76 selected patients who underwent volumetric 3D T2-weighted MRI root mapping between March 1, 2022 and March 12, 2026 during evaluation of symptomatic lumbar levels before contemplated transforaminal or percutaneous disc access. Sixteen earlier contrast-assisted cases are mentioned only as historical technique-development context and were not included in the MRI analysis. Multiplanar, oblique, and curved reconstructions were reviewed collaboratively by a radiologist with musculoskeletal/spine imaging involvement and the operating surgeon/radiology team. Trajectory assessment distinguished anatomically favorable, borderline, and unfavorable/high-risk relationships, including dimensional incompatibility and direct neural trajectory conflict. Nine of the 76 patients (11.8%) demonstrated one of the two predefined nerve-root findings relevant to the intended transforaminal trajectory. Four unique patients had double or variant nerve roots occupying the intended Kambin corridor. Five additional unique patients had displacement of the exiting nerve root into the planned cannula trajectory; three were considered unfavorable/high-risk and two borderline. The two groups did not overlap. The abnormalities were identified at L4-5 in five patients, L5-S1 in three, and L3-4 in one. The remaining 67 patients did not demonstrate either predefined finding and are not interpreted as a validated safe comparator group. None of the nine relevant cases generated a material disagreement regarding the root-course abnormality or its relationship to the contemplated trajectory. Volumetric MRI may identify patient-specific neural anatomy relevant to transforaminal trajectory and route planning. Its contribution is trajectory-oriented visualization rather than proof of procedural safety or diagnostic superiority over routine MRI. The observed frequency in this selected symptomatic-level cohort is descriptive and should not be interpreted as the population prevalence of aberrant nerve-root anatomy.
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BibTeX
@article{vargas2026when,
title = {{When the safe triangle is unsafe: volumetric magnetic resonance imaging root mapping for patient-specific assessment of Kambin's triangle before transforaminal lumbar disc procedures.}},
author = {Antonio Roth Vargas and Kai-Uwe Lewandrowski and Alexandre Borges and Celine C Akta and Theresa J C Pazionis and Tom Folkerts and Matthias Pumberger and Jorge Felipe Ramírez León},
journal = {Journal of spine surgery (Hong Kong)},
year = {2026},
month = oct,
doi = {10.21037/jss-2026-0180},
url = {https://europepmc.org/article/MED/42996268},
note = {CC BY-NC-ND},
}
RIS
TY - JOUR
TI - When the safe triangle is unsafe: volumetric magnetic resonance imaging root mapping for patient-specific assessment of Kambin's triangle before transforaminal lumbar disc procedures.
AU - Antonio Roth Vargas
AU - Kai-Uwe Lewandrowski
AU - Alexandre Borges
AU - Celine C Akta
AU - Theresa J C Pazionis
AU - Tom Folkerts
AU - Matthias Pumberger
AU - Jorge Felipe Ramírez León
PY - 2026
DA - 2026/10/23
JO - Journal of spine surgery (Hong Kong)
DO - 10.21037/jss-2026-0180
UR - https://europepmc.org/article/MED/42996268
AB - Kambin's triangle is a useful geometric model for lumbar transforaminal access, but the clinically usable corridor is patient specific because the exiting nerve root, dorsal root ganglion (DRG), traversing neural structures, anatomic variants, and disease-related displacement may alter the contemplated path. We evaluated volumetric magnetic resonance imaging (MRI) root mapping as a method for characterizing nerve-root anatomy relevant to patient-specific transforaminal trajectory planning. This retrospective descriptive MRI-anatomy study analyzed 76 selected patients who underwent volumetric 3D T2-weighted MRI root mapping between March 1, 2022 and March 12, 2026 during evaluation of symptomatic lumbar levels before contemplated transforaminal or percutaneous disc access. Sixteen earlier contrast-assisted cases are mentioned only as historical technique-development context and were not included in the MRI analysis. Multiplanar, oblique, and curved reconstructions were reviewed collaboratively by a radiologist with musculoskeletal/spine imaging involvement and the operating surgeon/radiology team. Trajectory assessment distinguished anatomically favorable, borderline, and unfavorable/high-risk relationships, including dimensional incompatibility and direct neural trajectory conflict. Nine of the 76 patients (11.8%) demonstrated one of the two predefined nerve-root findings relevant to the intended transforaminal trajectory. Four unique patients had double or variant nerve roots occupying the intended Kambin corridor. Five additional unique patients had displacement of the exiting nerve root into the planned cannula trajectory; three were considered unfavorable/high-risk and two borderline. The two groups did not overlap. The abnormalities were identified at L4-5 in five patients, L5-S1 in three, and L3-4 in one. The remaining 67 patients did not demonstrate either predefined finding and are not interpreted as a validated safe comparator group. None of the nine relevant cases generated a material disagreement regarding the root-course abnormality or its relationship to the contemplated trajectory. Volumetric MRI may identify patient-specific neural anatomy relevant to transforaminal trajectory and route planning. Its contribution is trajectory-oriented visualization rather than proof of procedural safety or diagnostic superiority over routine MRI. The observed frequency in this selected symptomatic-level cohort is descriptive and should not be interpreted as the population prevalence of aberrant nerve-root anatomy.
SN - 2414-469X
SN - 2414-4630
ER -