The Konakondla-Telfeian-Shen (KTS) Pyramid: a safe entry zone for ventral thoracic pathologies.

BACKGROUND: Transforaminal (TF) endoscopic access to the lumbar spine has long relied on Kambin's triangle as a posterolateral safe zone. As endoscopic indications expand, there are fundamental differences in thoracic anatomy that Kambin's triangle does not account for, including smaller foraminal dimensions, the presence of the spinal cord, cranio-caudal pedicle angulation, and the rib head-costovertebral complex. To date, no formal anatomic framework exists to standardize thoracic TF planning. The objective of this study is to define and describe a three-dimensional thoracic TF working corridor, the Konakondla-Telfeian-Shen (KTS) Thoracic Pyramid, and to propose a standardized anatomic language and preoperative planning framework for endoscopic access to ventral thoracic pathology. METHODS: The thoracic TF corridor is conceptualized as a six-faced three-dimensional volume. Level-dependent anatomic constraints, including the rib head-costovertebral complex, pedicle morphology, spinal cord position, and segmental vascular anatomy, are incorporated. Variations due to degeneration, fusion, prior surgery, and vascular anatomy are discussed within this geometric framework. RESULTS: The KTS Pyramid defines a reproducible, level-specific posterolateral access corridor to the ventral thoracic canal. The corridor predictably narrows from T12 to T1 as the rib head and costovertebral joint migrate cranially toward the disc plane and pedicle angulation increases. This framework identifies which anatomic "face" of the pyramid limits access at each thoracic level. CONCLUSIONS: The KTS Pyramid provides a formal geometric and anatomic description of a thoracic TF working corridor. By standardizing thoracic endoscopic planning with level-specific boundaries and terminology, this framework supports safer access to ventral thoracic pathology, shortens the learning curve, and enables consistent communication, training, and future comparative research in thoracic endoscopic spine surgery.