The History of and Controversy over Kambin's Triangle: A Historical Analysis of the Lumbar Transforaminal Corridor for Endoscopic and Surgical Approaches.

The transforaminal corridor in the lumbar spine allows access to the traversing and exiting nerve roots, the thecal sac, and the intervertebral disc space. Surgeons performing midline and minimally invasive approaches for lumbar interbody fusion access the disc space within the boundaries created by the exiting root of a segment and the traversing root after a complete facetectomy and removal of the pars interarticularis and lamina. Endoscopic surgeons and interventional pain management physicians approach the lumbar segment through a similar corridor, but with the bony anatomy intact. Although the boundaries of the corridor may seem the same, the angle of the trajectory and the bone work between the two differ. The overlap between these 2 distinct access corridors has led to an openhanded application of the term Kambin's triangle. Initially described for endoscopic approaches to the lumbar spine for microdiscectomy, this working triangle has been grafted into the transforaminal lumbar interbody fusion literature. Given the similarities between these corridors, it is understandable how the lines of this nomenclature have blurred. The result has been an interchangeable application of the term Kambin's triangle for a variety of procedures in the spine literature. The objective of the current work is to add clarity to the various lumbar transforaminal corridors. The term Kambin's triangle should be limited to percutaneous access to the disc space for endoscopic procedures in the intact spine and should not be applied to transforaminal lumbar interbody fusion after laminectomy and facetectomy. Instead, the term expanded transforaminal corridor should be applied.