Medial-caudal first access strategy for safe disc-side corridor creation in unilateral biportal endoscopic surgery...

Lateral lumbar disc herniation presents a technical challenge because the herniated fragment may elevate the exiting nerve root and dorsal root ganglion within the narrow foraminal-extraforaminal corridor. During unilateral biportal endoscopy (UBE), limited depth perception in the early stages of decompression may increase the risk of premature neural contact and postoperative dysesthesia. We developed a medial-caudal first access strategy supported by O-arm navigation to establish a safe disc-side working corridor before direct neural exposure. Four patients with symptomatic lateral lumbar disc herniation underwent decompression using an anatomy-based strategy. Preoperative computed tomography/magnetic resonance imaging fusion imaging was used to identify a reproducible medial-caudal disc-side corridor according to the anatomical relationship between the disc fragment, pedicle, facet complex, iliac crest, and exiting nerve root. Portal placement was planned to reproduce this corridor, and O-arm navigation was used as an adjunct to facilitate the reproduction of the planned trajectory and portal geometry during surgery. The planned medial-caudal corridor was successfully reproduced in all four patients. Sufficient disc-side working space was established before direct exposure of the exiting nerve root, allowing gradual cranial and lateral decompression under continuous endoscopic observation. Adequate decompression was achieved without neurological complications, postoperative dysesthesia, or conversion to open surgery. Postoperative imaging confirmed sufficient decompression with limited medial bone removal. The proposed strategy may provide a practical and reproducible workflow for UBE treatment of lateral lumbar disc herniation. By prioritizing the creation of a limited disc-side working corridor before neural exposure, this technique may improve early depth control, reduce unnecessary neural manipulation, and preserve the surrounding bony structures. O-arm navigation serves as an adjunct to reproduce the preplanned surgical corridor, rather than as the primary objective of the procedure.