Surgical anatomy of minimally invasive lateral approaches to the thoracolumbar junction.

Objective: The thoracolumbar (TL) junction spanning T11 to L2 is difficult to access because of the convergence of multiple anatomical structures and tissue planes. Earlier studies have described different approaches and anatomical structures relevant to the TL junction. This anatomical study aims to build a conceptual framework for selecting and executing a minimally invasive lateral approach to the spine for interbody fusion at any level of the TL junction with appropriate adjustments for local anatomical variations.

Methods: The authors reviewed anatomical dissections from 9 fresh-frozen cadaveric specimens as well as clinical case examples to denote key anatomical relationships and considerations for approach selection.

Results: The retroperitoneal and retropleural spaces reside within the same extracoelomic cavity and are separated from each other by the lateral attachments of the diaphragm to the rib and the L1 transverse process. If the lateral diaphragmatic attachments are dissected and the diaphragm is retracted anteriorly, the retroperitoneal and retropleural spaces will be in direct continuity, allowing full access to the TL junction. The T12-L2 disc spaces can be reached by a conventional lateral retroperitoneal exposure with the rostral displacement of the 11th and 12th ribs. With caudally displaced ribs, or to expose T12-L1 disc spaces, the diaphragm can be freed from its lateral attachments to perform a retrodiaphragmatic approach. The T11-12 disc space can be accessed purely through a retropleural approach without significant mobilization of the diaphragm.

Conclusions: The entirety of the TL junction can be accessed through a minimally invasive extracoelomic approach, with or without manipulation of the diaphragm. Approach selection is determined by the region of interest, degree of diaphragmatic mobilization required, and rib anatomy.